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International audience; In this paper, we present the design and fabrication of a 11-layer notch filter for photovoltaic applications. Thickness modulation has been done on a starting quarter-wave design to obtain a 11-layer final structure. For our design parameters, we considered materials with indices of 2.09 and 1.51 as high and low refractive index materials, respectively. Since this filter aims for photovoltaic applications, we defined the substrate as silicon. The design shows a reflection peak of around 73% from 350 to 467 nm with a FWHM of 79 nm along with less than 10% reflection for longer wavelengths of the remaining high transmission region of 300-1200 nm. For fabrication, we used silicon nitride and silicon oxynitride as alternating high and low refractive index materials on a silicon substrate. Layers of silicon nitride and oxynitride were deposited with an electron cyclotron resonance plasma-enhanced chemical vapor deposition reactor and characterized with variable angle spectroscopic ellipsometry and spectrophotometry.

Silicon carbonitride (SiCN) thin films are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another scope of study of SiCN thin films is as the low dielectric constant (LKC) materials, which are desired for replacing silicon oxide (SiO2) in integrated circuits (IC). SiCN owes the interest shown to being an intermediate compound between silicon nitride (Si3N4) which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with excellent mechanical performance. In this study we present the optical and electrical properties of SiCN:H thin films fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) by using a mixture of acetylene (C2H2) or methane (CH4), silane (SiH4), argon (Ar), and nitrogen (N2) gas precursors. Samples fabricated with two different carbon sources were analyzed and compared regarding their chemical composition as well as their electrical and optical properties. The atomic composition of Si, C, N, O, and H were determined by Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analysis and the chemical bonds formed in SiCN:H were analyzed through Fourier transform infrared spectroscopy (FTIR). Optical bandgap, index of refraction and extinction coefficient were analyzed by variable angle spectroscopic ellipsometry (VASE) and will be presented for different deposition conditions. The dielectric constants and dielectric breakdown voltages of the thin films were determined through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Lastly, the hardness properties are explained due to varying C and H concentrations.

International audience; We describe work to quantify the effects of structured dielectric thin films, such as SiNx, at the surface of III-V semiconductors, in terms of strain engineering with applications to photonic components such as waveguides and lasers. We show that the strain in the semiconductor can be engineered by controlling the stress in the dielectric thin film by tuning its deposition process. In the first part of this study, we describe how we can control the amount of this built-in mechanical stress, in the case of SiNx, over a large range, from highly tensile (300 MPa) to highly compressive (-800 MPa), using two different kinds of plasma-enhanced chemical vapor deposition reactors: a standard capacitively-coupled reactor with radio-frequency excitation and an electron cyclotron resonance reactor with microwave excitation. We focused on characterizing and understanding these thin films' optical and chemical bonding properties through spectroscopic ellipsometry and Fourier transform infrared spectroscopy. We have also studied their mechanical properties experimentally using the wafer curvature measurement technique, microstructure fabrication, and nano-indentation measurements. In the second part, we show accurate

Silicon carbon nitride (SiCN) ternary compounds present remarkable mechanical strength, bandgap tunability, optical responsivity in the UV region, and dielectric performance in microelectronics due to the combined features of silicon nitride (SiN), silicon carbide (SiC), and carbonitride (CN) [1]. The SiCN compounds can be formed using fabrication methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and chemical synthesis. Successful SiCN thin films fabricated with different techniques and their characteristics have been reported extensively in the literature; however, the influence of hydrocarbon gas precursors has not drawn the same amount of attention for SiCN. Chemical, physical, and mechanical properties of thin films are determined by the growth parameters and the choice of sources used, like the organic single-molecule (methylsilazanes) or highly pure individual gas precursors [2,3]. The chemical vapor deposition systems mainly affect the energy of bombarding ions. Plasma-enhanced CVD has been commonly used for thin-film depositions since it provides low deposition temperature, high purity, good step coverage, and easy control of reaction parameters. Our work focuses on the electron-cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method to fabricate SiCN thin films. This method differs from other PECVD methods because it can generate a dense, highly ionized plasma (1011 ions/cm3) and ion impingement energies on the substrate as low as 20 eV [4]. A combination of argon diluted silane (SiH4) and molecular nitrogen (N2) are utilized. For carbon incorporation, we explored the influence of methane (CH4), acetylene (C2H2), and ethane (C2H6) hydrocarbon gas precursors on SiCN thin film properties. The stoichiometry, density of the thin film, optical constants, and the bonding structure of SiCN thin films as a function of hydrocarbon carbon flow rates are presented. Due to the hydrogen-containing precursors used, the silicon carbonitride films deposited by CVD methods contain a significant amount of hydrogen (H), lowest for C2H2 and highest for C2H6. Nearly stoichiometric silicon nitride and silicon carbide thin films were also prepared to interpret the measurements further. From Rutherford backscattering spectrometry (RBS) and elastic recoil detection (ERD) analysis, quantitative elemental composition distributions including H were found for films deposited with both carbon sources. For further investigation of the bonding structure of SiCN, Fourier Transform Infrared (FTIR) Spectroscopy was performed. Furthermore, we studied the hardness and Young’s modulus by nanoindentation, and optical constants were measured by variable angle spectroscopic ellipsometry (VASE). [1] C.W. Chen, C.C. Huang, Y.Y. Lin, L.C. Chen, K.H. Chen, W.F. Su, Optical prop- erties and photoconductivity of amorphous silicon carbon nitride thin film and its application for UV detection, Diamond Relat. Mater. 14 (3-7) (2005) 1010–1013. [2] Schwarz-Selinger, T., Von Keudell, A., & Jacob, W. (1999). Plasma chemical vapor deposition of hydrocarbon films: The influence of hydrocarbon source gas on the film properties. Journal of Applied Physics, 86(7), 3988-3996. [3] V.I. Ivashchenko, A.O. Kozak, O.K. Porada, L.A. Ivashchenko, O.K. Sinelnichenko, O.S. Lytvyn, T.V. Tomila, V.J. Malakhov, Characterization of SiCN thin films: experimental and theoretical investigations, Thin Solid Films 569 (2014) 57–63. [4] M. G. Boudreau, "SiOxNy Waveguides Deposited by ECR-PECVD", M.Eng. thesis, McMaster University, 1993.

Silicon carbonitride (SiCN) is a wide bandgap semiconductor material that has drawn significant interest over the past few decades due to its excellent optical, electrical, and mechanical properties[1]. Rare earth doping in wide bandgap semiconductors has several prospective applications in the field of photoelectric devices, solid-state lasers, flat panel displays, and high-energy radiation detectors [2]. Among the various rare earth materials, europium (Eu) is particularly interesting due to its optically active divalent and trivalent states capable of emitting in different visible spectral ranges [3]. In this work, Eu-doped SiCN thin films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) with integrated magnetron sputtering [4] on p-type 3” Si (100) substrates. Silane (diluted in 90% argon), nitrogen (diluted in 90% argon) and ethane (C2H6) were used as precursor gases, and a 99.9% pure Eu sputtering target was used as a sputtering source. To understand the effect of C incorporation in the Eu-doped SiCN matrix, we have prepared a set of samples without C. The as-deposited samples were annealed over a wide range of temperatures from 600 to 1100° C in an internet N2 environment. Rutherford backscattering spectrometry (RBS) was performed to determine the atomic concentration of the constituents. Variable angle spectroscopic ellipsometry (VASE) analysis was performed to investigate the optical properties of the films. The room temperature photoluminescence (PL) experiments were carried out with a laser diode excitation source, operating at a wavelength of 375nm. Finally, we performed nanoindentation measurements to understand the deformation behavior of SiCN films as a function of the incorporation of C. The indentation hardness and Young’s modulus of the films were investigated for different Eu and C concentrations. References: [1] Q. Li, Y. Wang, X. Shan, X. Wang, and W. Zhao, “Preparation and optical properties of SiCN thin films deposited by reactive magnetron sputtering,” J. Mater. Sci. Mater. Electron., vol. 28, no. 9, pp. 6769–6781, 2017. [2] Z. Ma, J. Zhou, Z. Chen, and E. Xie, “Luminescence properties of terbium-doped SiCN thin films by rf magnetron reactive sputtering,” Diam. Relat. Mater., vol. 20, no. 4, pp. 475–479, 2011. [3] X. Zhang, D. Yang, D. Li, and M. Wang, “Intense photoluminescence from Eu-doped silicon-rich silicon oxide films prepared by electron beam evaporation,” IEEE Int. Conf. Gr. IV Photonics GFP, pp. 66–68, 2009. [4] J. W. Miller, Z. Khatami, J. Wojcik, J. D. B. Bradley, and P. Mascher, “Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials,” Surf. Coatings Technol., vol. 336, pp. 99–105, 2018.

Silicon-based materials are useful components in microelectronics owing to their tunable electronic properties [1]. However, they are not high-quality photonics candidates for light applications due to indirect band gap nature of silicon. To enhance the light emission properties of silicon, one solution is doping with rare earth elements (RE) because of their allowed 4f transition, and sharp well-defined emission peaks [2]. RE related luminescence has attracted attention for greenhouse applications due to their efficient emissions in the photosynthetically active radiation (PAR) regions of 380 to 480 and 600 to 700 nm. The europium trivalent emission (Eu3+) is associated with $^5\mathrm{D}_{0}\rightarrow^{7}\mathrm{F}_{2}$ transitions (red emission at 613 nm), which is of significant interest to drive plant photosynthesis [3].

We report on the design of subwavelength grating metamaterial waveguides coated with tellurium oxide on a silicon-on-insulator platform. We discuss our design optimization that led to substantial improvements of modal overlap with the optically active cladding., 2021 Photonics North (PN), May 31 - June 2, 2021, Toronto, ON, Canada

Dielectric thin films deposited by plasma enhanced chemical vapor deposition (PECVD) have been extensively studied over the last decades due to their interesting optical and electrical properties besides their many applications in microelectronic and optoelectronic devices. Recently published studies have shown the impact of the mechanical properties of amorphous dielectric films on semiconductor substrates [1]. In strain engineering, stressed films are used to control on demand the physical properties of semiconductors at the surface such as bandgap energy, dielectric constant, and refractive index. We aim to study in this work how to control the distribution of the strain field beneath a dielectric film and how the changing of the residual stress affects the physical properties of the dielectric film itself. We deposited hydrogenated amorphous silicon nitride a-SiN:H films on Si, InP, and GaAs substrates using a capacitively coupled plasma reactor CCP-PECVD with a radiofrequency (RF) power at 13.56 MHz.The a-SiN:H films were deposited at 280 °C, with a thickness of approximatively 500 nm, using a SiH4/NH3/N2/Ar precursor mixture. The RF power injected into the plasma allows a tunable residual stress and a wide range of built-in stress, from tensile (+ 300 MPa) to compressive (– 400 MPa). To evaluate the residual stress in our deposited thin films, we used the standard method of wafer curvature measurements. The thickness and the refractive index were characterized by variable angle spectroscopic ellipsometry (VASE). The determination of Young’s modulus and hardness of the a-SiN:H films was performed by nanoindentation. We noticed that the adjustment of the residual stress leads to the modification of the film in terms of optical and mechanical properties. In order to investigate the deformation induced in the semiconductor, an understanding of the semiconductor mechanical behavior on a microscopic scale is required. Thus, we performed a detailed investigation of the effect of strain on the degree of polarization (DOP) of the photoluminescence signal on direct bandgap substrates [2]. After examining the DOP profiles beneath the film, it is interesting to note that the anisotropic deformation extends to significant depths (~ 8 µm), as illustrated in figure 1, while the horizontal distribution of the stress can propagate beyond the edge of the sample by a few microns (see figure 2). The confinement of light in some photonic devices such as photoelastic planar waveguides can be achieved by a photo-elastic effect in semiconductor using stressed dielectric films [3]. [1] S. Gérard et al., “Photoluminescence mapping of the strain induced in InP and GaAs substrates by SiNx stripes etched from thin films grown under controlled mechanical stress,” Thin Solid Films, vol. 706, p. 138079, Jul. 2020, doi: 10.1016/j.tsf.2020.138079. [2] D. T. Cassidy, C. K. Hall, O. Rehioui, and L. Bechou, “Strain estimation in III-V materials by analysis of the degree of polarization of luminescence,” Microelectron. Reliab., vol. 50, no. 4, pp. 462–466, Apr. 2010, doi: 10.1016/j.microrel.2009.11.003. [3] P. A. Kirkby, P. R. Selway, and L. D. Westbrook, “Photoelastic waveguides and their effect on stripe-geometry GaAs/Ga 1-xAlxAs lasers,” J. Appl. Phys., vol. 50, no. 7, pp. 4567–4579, Jul. 1979, doi: 10.1063/1.326563. Figure 1

The use of electric vehicles (EVs) can reduce greenhouse gas emissions, air pollution, dependency on fossil fuels, and their adverse health effects on humans. But, we can only utilize the full environmental benefits of EVs when they are charged with renewable energy sources with zero or low carbon emissions. As a solution, Mobarak et al. [1] suggested integrating low-cost, flexible, and thin-film copper indium gallium selenide (CIGS) solar cells directly onto the steel of all the upward-facing body parts of the vehicles. But, this integration of solar cells comes with an aesthetic drawback. Previously, colorful photovoltaics (PVs) have been designed with one-dimensional (1D) photonic crystals or various 1D and 2D metallic nanostructures for aesthetic building-integrated photovoltaics (BIPVs) [2, 3]. However, the functionality of our application differs from that of BIPV as we need maximum absorption of the solar spectrum to obtain maximum conversion efficiency. Thus, we propose replacing the anti-reflective coating (ARC) present in the solar cells with a notch filter (a narrow high-reflection region in the visible range along with high transmission for the rest of the solar spectrum) to obtain colors. High-performance notch filters with a narrow and ultra-steep notch are well known in literature [4, 5]. Generally, high-performance notch filters are designed with a minimum of 45 layers. It is challenging to use filters with many layers on solar cells due to fabrication and thickness complexities. Thus, we created designs with a maximum of 27 layers for possible integration with photovoltaics. We used OptiLayer [6] to simulate our designs and the gradual evolution technique was used to optimize the designs. We performed our simulations with a multilayer structure of alternating high and low refractive indices of 2.09 and 1.45, respectively, on top of a silicon substrate. We optimized this multilayer structure for three reference wavelengths (400 nm, 550 nm, and 700 nm) resembling three colors. Our designs have notch widths of less than 100 nm for all the reference wavelengths with an average of 70% reflection in the high-reflection region and less than 20% reflection in the high-transmission area. To fabricate our designs, we need materials that are transparent to the solar spectrum targeted by the active material of the solar cells. The materials also need to have refractive indices closer to our simulation. Thus, we chose the combination of silicon nitride and silicon dioxide as our high and low refractive index material, respectively [7, 8]. To better understand our designs’ optical characteristics, we fabricated a scaled-down version of our structure with 5-10 layers. We used electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) to deposit the multilayer structure on silicon wafers. To obtain the silicon nitride and silicon dioxide layers, we used a SiH4/N2/O2/Ar precursor mixture. By tuning the gas flow rate in the reactor chamber, we tuned the stoichiometry and obtained the required refractive index for each layer. To characterize the refractive index and thickness for each layer, we used variable angle spectroscopic ellipsometry (VASE). We made a detailed comparison of our simulation and fabrication results. References [1] M. H. Mobarak, R. N. Kleiman, J. Bauman, Solar-charged electric vehicles: A comprehensive analysis of grid, driver, and environmental benefits, IEEE Transactions on Transportation Electrification 7 (2021) 579–603. doi:10.1109/TTE.2020.2996363. [2] G. Y. Yoo, et al., Multiple-color-generating cu(in,ga)(s,se)2 thin-film solar cells via dichroic film incorporation for power-generating window applications, ACS Applied Materials & Interfaces 9 (2017) 14817–14826. doi:10.1021/acsami.7b01416, pMID: 28406026. [3] K. T. Lee, et al., Colored dual-functional photovoltaic cells, Journal of Optics 18 (2016) 064003. [4] U. Schallenberg, et al., Design and manufacturing of high-performance notch filters, volume 7739, International Society for Optics and Photonics, SPIE, 2010, pp. 720 – 728. doi:10.1117/12.856580. [5] J. Zhang, et al., Design and fabrication of ultra-steep notch filters, Opt. Express 21 (2013) 21523–21529. doi:10.1364/OE.21.021523. [6] OptiLayer, 1994. URL: https://www.optilayer.com/support/faq, accessed: 2021-12-06. [7] A. Z. Subramanian, et al., Low-loss singlemode pecvd silicon nitride photonic wire waveguides for 532–900 nm wavelength window fabricated within a cmos pilot line, IEEE Photonics Journal 5 (2013) 2202809–2202809. doi:10.1109/JPHOT.2013.2292698. [8] W. D. Sacher, et al., Visible-light silicon nitride waveguide devices and implantable neurophotonic probes on thinned 200 mm silicon wafers, Opt. Express 27 (2019) 37400–37418. doi:10.1364/OE.27.037400

Silicon nitride (SiN) based films deposited by plasma-enhanced chemical vapor deposition (PECVD) have interesting optical, mechanical, and chemical properties. They are used for applications such as anti-reflective coatings and surface passivation layers in solar cells. Amorphous SiN-based films also are frequently used to create multilayer structures of alternatingly high-index and low-index films. This approach is very promising to fabricate narrow-bandwidth notch filters on photovoltaic cells to reflect on demand a wide variety of colors over the entire visible spectrum [1]. However, these multilayer structures need to be highly durable and mechanically stable since the lifecycle of photovoltaic cells in some applications [2] is very long, and the coated surfaces are very large. To satisfy these specific functional requirements, we need to adjust the films' optical and mechanical properties by changing the deposition parameters of a PECVD reactor. For instance, it is possible to strongly influence the chemical composition of amorphous SiN-based films, such as their stoichiometry, by tuning the gas flows [3]. This work investigates the effect of the deposition pressure, power, and source gas ratio on SiN-based monolayers during plasma deposition. We have deposited SiN and silicon oxynitride (SiON) films in an electron cyclotron resonance (ECR) PECVD reactor using a SiH4/N2/O2/Ar precursor mixture. We have measured the refractive index and the absorption of the films using a variable angle spectroscopic ellipsometry (VASE) to assess their optical quality. The mechanical properties of the films, such as residual stress and coefficient of thermal expansion, were measured ex-situ on a KLA-Tencor FLX-2320 film stress measurement system. The Young's modulus and hardness of the films were evaluated using nanoindentation. After studying the properties of monolayers, we have made numerical simulations and further characterizations to optimize the design of multilayer structures considering both the optical and mechanical properties. Through this discussion, we try to better understand the interactions taking place when amorphous SiN-based films with different structural properties and compositions are stacked on top of each other. Finally, we suggest methods to predict and control the residual stress in multilayer structures without affecting the optical properties. References: [1] S. Lee et al., "RGB-Colored Cu(In,Ga)(S,Se) 2 Thin-Film Solar Cells with Minimal Efficiency Loss Using Narrow-Bandwidth Stopband Nano-Multilayered Filters," ACS Appl. Mater. Interfaces, vol. 11, no. 10, pp. 9994–10003, Mar. 2019. [2] G. Ban-Weiss, C. Wray, W. Delp, P. Ly, H. Akbari, and R. Levinson, "Electricity production and cooling energy savings from the installation of a building-integrated photovoltaic roof on an office building," Energy Build., vol. 56, pp. 210–220, 2013. [3] D. B. Bonneville, J. W. Miller, C. Smyth, P. Mascher, and J. D. B. Bradley, "Low-temperature and low-pressure silicon nitride deposition by ecr-pecvd for optical waveguides," Appl. Sci., vol. 11, no. 5, pp. 1–11, 2021.

Light emission from silicon-based systems has gained significant interest over the past few decades with the vision of developing an optoelectronic platform that can be integrated with the existing metal-oxide-semiconductor (MOS) technology [1]. Rare earth doping of silicon-based materials is a promising approach to fabricating efficient light emitting devices because of their excellent luminescence properties and their chemical stability [2]. Europium (Eu) ions are attractive dopants for silicon photonic applications due to their intense emission in the visible spectral region. The efficiency of such photonic devices can be influenced by the mechanical properties of the Eu-doped films. Thus, the integration of these films in photonic devices requires an understanding of their mechanical properties as well. In this work, we discuss the relationship between the photoluminescence (PL) behavior and the elasticity and hardness of Eu doped silicon oxynitride (SiON) thin films. We have fabricated thin films using an electron cyclotron resonance plasma-enhanced chemical vapor deposition system with integrated magnetron sputtering system [3] on p-type 3” Si (100) substrates. Silane (diluted in 90% argon) and nitrogen (diluted in 90% argon) were used as precursor gases, while a 99.9% pure Eu sputtering target was used as a sputtering source. Different sets of samples were fabricated by changing the sputtering power and argon flow rate to understand the effect of deposition parameters on the dopant concentration and the optical and mechanical properties. Post-deposition annealing in nitrogen and a mixture of nitrogen with hydrogen (5%) were performed over a wide range of temperatures from 600° to 1100° C. The effect of hydrogen passivation was studied as well. The atomic concentration of the constituents was identified by Rutherford backscattering spectrometry. Optical properties were investigated by variable angle spectroscopic ellipsometry (VASE) analysis. The PL spectra were obtained at room temperature with a laser diode excitation source, operating at a wavelength of 375nm. Finally, we performed nanoindentation measurements to understand the deformation behavior of SiON films with the incorporation of Eu. The indentation hardness and Young’s modulus of the films were investigated, respectively, for different Eu concentrations and different deposition parameters. Reference [1] A. Moadhen, H. Elhouichet, M. Oueslati, and M. Férid, “Photoluminescence properties of europium-doped porous silicon nanocomposites,” J. Lumin., vol. 99, no. 1, pp. 13–17, 2002, doi: 10.1016/S0022-2313(02)00322-8. [2] Z. Lin R. Huang, H. Wang, Y. Wang, Y. Zhang, Y. Gao, J. Song, C. Song, H. Li, “Dense nanosized europium silicate clusters induced light emission enhancement in Eu-doped silicon oxycarbide films,” J. Alloys Compd., vol. 694, pp. 946–951, 2017, doi: 10.1016/j.jallcom.2016.10.132. [3] J. W. Miller, Z. Khatami, J. Wojcik, J. D. B. Bradley, and P. Mascher, “Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials,” Surf. Coatings Technol., vol. 336, pp. 99–105, 2018, doi: 10.1016/j.surfcoat.2017.08.051.

This paper reports tunable emission of trivalent (Eu3+) and divalent (Eu2+) europium (Eu) from SiOxNy films fabricated by integrated electron cyclotron plasma enhanced chemical vapor deposition and magnetron sputtering. The photoluminescence (PL) spectra of intense red emission from Eu3+ around 600 nm and blue (cyan) broadband emission from 400 to 750 nm of Eu2+ are observed under daylight conditions with the naked eye. The spectra reveal a strong dependency of the PL on the atomic concentration of the dopant and the silicon/nitrogen ratio. The atomic composition of the films is investigated by Rutherford backscattering spectrometry and elastic recoil detection analysis. Values of the refractive indices are obtained by variable angle spectroscopic ellipsometry. To confirm the presence of crystalline phases of europium silicate Eu4.67(SiO4)3O [Eu2(Si2O7)] and europium silicon oxynitride (EuSi2N2O2) distributed in the amorphous host matrix of SiOxNy, high-resolution x-ray diffraction is used. The findings of this work are promising toward the realization of europium-doped Si-based materials for photonics and lighting technologies.

We have designed blue organic light emitting diodes (OLEDs) consisting of fluorescent and phosphorescent emitters whose phosphorescent emitting layers have three step-controlled doping profiles of 0, 4 and 8%. The different doping profiles determined the characteristics of electroluminescent and fluorescent intensity variation under various voltages. Also, it was found that emission channels separated by the non-doped region enhanced fluorescent emission. The phosphorescent doping concentration adjacent to the fluorescent emitting layer is strongly related to device efficiency and the location of the non-doped region, particularly, affected the electrical and optical characteristics of the blue OLEDs due to the hole transport type of the host material. Placing the region on the anode side had the effect of widening the hole transport region, leading to higher current density. Based on this effect, the device with the regularly stepwise doping concentration (0-4-8%) showed high current density and luminance but the phosphorescent emission was dominant. The lowest efficiency roll-off was observed from the device containing the separated emission channels for fluorescence and phosphorescence by the non-doped region, which gave rise to relatively stronger fluorescent emission.

We studied a sample of Tb-doped a-Si3N4:H prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD). The sample has an optical gap E04 = 4.7 ± 0.3 eV and refractive index n (at 632 nm) = 1.81 ± 0.01. Room temperature photoluminescence was measured under sub-gap excitation. Both characteristic a-Si3N4:H and Tb3+ photoluminescence peaks were detected in the sample as deposited. Annealing at 300 °C maximizes the Tb3+ photoluminescence lines. At higher annealing temperatures the Tb3+ photoluminescence decreases while the host photoluminescence increases. The Tb3+ photoluminescence is inversely correlated with the density of Si-H bonds in the sample. The results indicate that silicon dangling bonds are involved in the excitation of the Tb3+ ions. We propose a new efficient non-radiative recombination path to the static disorder model that explains the luminescence of amorphous silicon and alloys: the Auger excitation of a rare earth ion near a silicon dangling bond. The model provides a very good explanation of the excitation and does not require the presence of nanostructures.

The effects of thermal annealing on the visible luminescence of hydrogenated silicon carbonitride (SiCxNy:Hz) thin films were investigated. Thin films of a-SiC1.2N0.7:H1.4 were grown using electron cyclotron resonance plasma enhanced chemical vapor deposition and subsequently were annealed between 400 and 1200 °C for 1 h in nitrogen gas. The samples exhibited a broad luminescence band, covering the visible range with two dominant peaks at ~ 470 and 550 nm, which appeared “white” to the naked eye. This white light emission could be deconvoluted into four photoluminescence (PL) bands. To understand the origin of PL from this complex material, two fairly well-studied submatrices, SiC:H1.3 and SiN1.3:H0.3, were also investigated. Our findings showed that the intensity of the PL emission of a-SiC1.2N0.7:H1.4 was higher than that of the binary matrices and was achieved at an optimized annealing temperature of 500 °C. Carbon-related silicon defect centers were suggested as the sources of the luminescence of the a-SiCxNy:Hz thin films. The observed visible emission was strongly correlated with different Si-C bonding configurations.

We report on a novel hybrid deposition technique to dope silicon-based materials with optically active elements in a plasma enhanced chemical vapor deposition (PECVD) process using a magnetron sputtering source. This approach is in contrast to traditional methods of rare-earth doping of PECVD films that utilise a metal organic precursor to introduce the rare earth species into the host matrix. We investigated the influence of the sputtering power applied to the rare earth metal target, in this case terbium, and the argon (Ar) partial pressure on the optical properties and composition of terbium-doped silicon oxide (SiOx:Tb3+) thin films. The film morphology was determined using high-resolution transmission electron microscopy, Rutherford backscattering spectrometry, and elastic recoil detection. We demonstrated that employing this novel technique provides a wider range of control of the doping level, yet delivers a similar rare earth (terbium) content to that which can be achieved using a traditional metal organic process. While the terbium concentration was strongly influenced by the sputtering power, it was only slightly affected by the Ar partial pressure. The refractive index was calculated from variable angle spectroscopic ellipsometry analysis and shows a direct relationship with the sputtering power whereas the film thickness shows an inverse relationship. The optically active Tb3+ ions were successfully excited within the silicon dioxide host matrix and the green Tb3+ emission was visible by the naked eye.

Silicon carbonitride (SiCxNy) materials, inspired by their outstanding multifunctional properties, are finding increasing applications in a variety of fields, including as next generation solar cells and hard coatings. Hydrogenated SiCxNy thin films, along with binary submatrices of stoichiometric SiC and SiN3 as a reference, were deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition. We described a comparative study of the effects of post-deposition thermal annealing, from 300 to 1200 °C, on the evolution of hydrogen-rich a-SiC1.2N0.7:H1.4 thin films. Concurrently, two featured annealing temperatures (500 and 900 °C) were found to have the significant influence on the morphology, optical, and microstructural properties of the films. During annealing the amorphous phase of SiC1.2N0.7:H1.4 thin films was fully maintained according to the transmission electron microscopy and X-ray diffraction analyses. The hydrogen density was quantitatively analyzed employing two different experimental techniques, elastic recoil detection and Fourier transform infrared spectroscopy, showing the associate annealing temperatures of hydrogen desorption, breaking of all hydrogen-terminated bonds, and depletion of all hydrogen content. The refractive indices and optical band gap of the films were calculated using variable angle spectroscopic ellipsometer. Thermal annealing resulted in hydrogen desorption and consequently layer densification along with an increase in the refractive index. During the annealing process, first the optical band gap widened, and then narrowed due to hydrogen out-diffusion or chemical bond restructuring, depending on the annealing temperature. In addition, Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy were performed. These findings are discussed in the context of the interdependency of the hydrogen desorption and thermally induced changes in chemical bonds, mass density, and optical properties.

We report on the design, fabrication and characterization of subwavelength grating metamaterial waveguides coated with tellurium oxide. The structures are first fabricated using a standard CMOS compatible process on a silicon-on-insulator platform. Amorphous tellurium oxide top cladding material is then deposited via post-process RF magnetron sputtering. The photonic bandstructure is controlled by adjustment of the device geometry, opening a wide range of operating regimes, including subwavelength propagation, slow light and the photonic bandgap, for various wavelength bands within the 1550 nm telecommunications window. Propagation loss of 1.0 ± 0.1 dB/mm is reported for the tellurium oxide-cladded device, compared to 1.5 ± 0.1 dB/mm propagation loss reported for the silicon dioxide-cladded reference structure. This is the first time that a high-index (n > 2) oxide cladding has been demonstrated for subwavelength grating metamaterial waveguides, thus introducing a new material platform for on-chip integrated optics.

We report wideband photoluminescent emission from cerium-doped silicon oxynitride (Ce-doped SiOxNy) thin films deposited using electron cyclotron resonance plasma enhanced chemical-vapor deposition (ECR-PECVD). The in situ doping with Cerium (Ce) was performed using a volatile metal organic powder, (Ce[tmhd]4). Oxygen was gradually substituted by nitrogen to produce SiOxNy thin films with varying nitrogen to oxygen ratio, to explore the effect of nitrogen on the photoluminescence (PL) of the thin films. Thin film composition and optical constants were determined using Rutherford back scattering and ellipsometry techniques, respectively. Samples subjected to post-deposition thermal annealing yielded considerably stronger blue/white PL emission than as-deposited ones, due to the formation of Ce-containing clusters at a temperature of 1000 °C and above. X-ray diffraction (XRD) revealed no crystalline structure in samples annealed at elevated temperatures. The optimum layer composition and annealing condition to produce SiOxNy thin films with maximized Ce3+ emission was determined. Besides, hydrogen fluoride etching along with hydrogen passivation demonstrated the enhancement of the PL emission of the thin films.

Luminescent silicon (Si) based structures that are compatible with the existing complementary metal oxide semiconductor industry has drawn significant interest with the vision of developing an integrated optoelectronic platform on monolithic Si [1]. Such luminescent structures find several applications in inter- and intra-chip optical interconnects, microdisplay, biological detections, and solid-state lighting [2, 3]. The outstanding optical properties and chemical stability of rare earth materials make doping Si with rare earths a promising approach to obtain bright emission from Si-based structures [4]. In this work, we have investigated the influence of sputtering power and argon (Ar) partial pressure on the optical properties and the composition of europium (Eu) doped silicon oxide (SiOx) thin films. For this purpose, the thin films were fabricated by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) with in-situ magnetron sputtering on a p-type 3" Si (100) substrate. Silane (SiH4) and oxygen (O2) were used as precursor gases, and a solid 99.9% pure Eu as the sputtering target. Ar was used as the sputtering gas and brought into the chamber through a gas injection ring. A set of samples was prepared by changing the Ar flow rate ranging from 10 to 40 cubic centimeters per minute at standard temperature and pressure (sccm) in steps of 10 sccm. Another set of samples was fabricated by varying the sputtering power from 20 to 30W in steps of 5W. Post-deposition annealing was performed at a higher temperature from 900°C to 1200°C in ambient nitrogen and a mixture of nitrogen (95%) and hydrogen (5%) atmosphere. The effect of hydrogen passivation has also been studied in this work. The compositional analysis was performed by Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA). We found that the doping concentration was strongly influenced by the sputtering power, and it is slightly affected by the Ar partial pressure. The thickness, refractive index, and absorption coefficient of the thin films were obtained from variable angle spectroscopic ellipsometry (VASE) analysis. The dependency of the thickness and the optical parameters on sputtering power and Ar partial pressure was also analyzed. In addition, the luminescence properties of Eu doped SiOx films have been investigated. A bright white emission was observed due to the transition between 4f65d and 4f7energy levels of Eu2+ ion from all the films, which can be seen by the naked eye under daylight conditions. The relation between intensity and doping concentration was also discussed. [1] Lin, R. Huang, H. Wang, Y. Wang, Y. Zhang, Y. Guo, ... and H. Li, “Dense nanosized europium silicate clusters induced light emission enhancement in Eu-doped silicon oxycarbide films,” J. Alloys Compd., vol. 694, pp. 946–951, 2017, doi: 10.1016/j.jallcom.2016.10.132. [2] D. Thomson, A. Zilkie, J. E. Bowers, T. Komljenovic, G. T. Reed, L. Vivien, ... and J. M. Hartmann, , “Roadmap on silicon photonics,” J. Opt. (United Kingdom), vol. 18, no. 7, pp. 1–20, 2016, doi: 10.1088/2040-8978/18/7/073003. [3] H. Jeong, S. Lee, G. Y. Sung, and J. H. Shin, “Design and fabrication of Tb3+-doped silicon oxy-nitride microdisk for biosensor applications,” IEEE Photonics Technol. Lett., vol. 23, no. 2, pp. 88–90, 2011, doi: 10.1109/LPT.2010.2091268. [4] L. Li, J. Zheng, Y. Zuo, B. Cheng, and Q. Wang, “Strong Eu2+ light emission in Eu silicate through Eu3+ reduction in Eu2O3/Si multilayer deposited on Si substrates,” Nanoscale Res. Lett., vol. 8, no. 1, p. 194, 2013, doi: 10.1186/1556-276x-8-194.

Hydrogenated amorphous silicon nitride (a-SiN:H) and silicon carbonitride (a-SiCN:H) films grown by plasma enhanced chemical vapor deposition (PECVD) are widely investigated for their interesting optical and electrical properties [1]. In this work, we discuss the effect of the deposition power on SiN-based films during plasma deposition. The influence on the optical and mechanical properties of the films was investigated. In order to study this issue on a broader basis, two types of plasmas were applied to deposit 0.5 to 1.5 μm a-SiN:H and a-SiCN:H films. First, a-SiN:H and a-SiCN:H films were deposited by electron cyclotron resonance (ECR) PECVD using the same deposition parameters for all films. During the deposition process, the carbon content in the a-SiCN:H thin films was introduced into the chamber through a pure CH4 gas source to avoid any perturbation on the deposition pressure. Second, a-SiN:H films were deposited by a capacitively coupled plasma reactor CCP PECVD using a SiH4/NH3/N2/Ar precursor mixture. In both deposition processes, the ion bombardment energy was tuned only by the deposition power. The mechanical properties of the films were determined ex-situ by profilometry to evaluate the residual stress using the wafer curvature method and by nanoindentation to determine Young’s modulus and hardness of the films. The thickness and the refractive index were measured by variable angle spectroscopic ellipsometry (VASE). It was observed that the evolution of the residual stress according to the deposition power in the ECR PECVD was different from the CCP PECVD. Besides, we notice a slight increase in the refractive index when the residual stress becomes more compressive as illustrated in figure 1 for a-SiN:H and a-SiCN:H films. Through this discussion, we try to have a better understanding of the different interactions taking place when the deposition power increases in terms of ion bombardment energy. Then, we will study the effect of ion bombardment on the film structure based on the composition and structure of the films and the hydrogen bond concentration measured by Fourier transmission infrared spectroscopy (FTIR). In addition, we have also investigated the influence of carbon incorporation on a-SiN:H thin film properties. We notice a decrease in the refractive index and an increase in the compressive residual stress caused by the carbon incorporation. [1] A. Abdelal, Z. Khatami, and P. Mascher, “Optical and Electrical Properties of ECR-PECVD Grown SiCN Thin Films,” ECS Meet. Abstr., vol. MA2018-01, no. 17, p. 1189, Apr. 2018, doi: 10.1149/ma2018-01/17/1189. Figure 1

Silicon carbonitride (SiCN) thin films have drawn considerable interest among the ternary compounds due to the combination of unique properties such as high hardness, wide band gap, high photosensitivity in the ultraviolet (UV) region and low dielectric coefficient (k). In the last few decades various fabrication methods including reactive sputtering and plasma-enhanced chemical vapour deposition (PECVD) have been intensively studied to achieve SiCN thin films having attractive mechanical, tribological and optoelectronic features. Applications range from hard, wear-resistant coatings, low-k interconnects, UV photodetectors to gas separation membranes [1]. The properties of thin films are not only influenced by the deposition method, which mainly determines the energy of bombarding ions, but also the choice of source gas [2]. In PECVD processes, silicon (Si), carbon (C) and nitrogen (N) can either be introduced separately as silane (SiH4), methane (CH4), and molecular nitrogen (N2) or ammonia (NH3), or alternatively using organic single precursors such as methylsilazanes [3]. In this work we deposited our thin films with the electron cyclotron resonance (ECR) PECVD method, which differs from other PECVD methods due to it is capability of generating a dense, highly ionized plasma (1011 ions/cm3) and ion impingement energies on the substrate as low as 20 eV [4]. We present the compositional and mechanical properties of hydrogenated SiCN (SiCN:H) thin films which were deposited with two different C precursors, acetylene (C2H2) and ethane (C2H6). The stoichiometry, density of the thin film, optical constants, and the bonding structure of SiCN:H thin films as a function of hydrocarbon carbon gas source have been explored. Due to the hydrogen-containing precursors used, the silicon carbonitride films deposited by CVD methods contain a significant amount of hydrogen (H). From Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD) analysis, quantitative elemental composition distributions including H were found for films deposited with both carbon sources. For further investigation of bonding structure of SiCN:H, Fourier Transform Infrared (FTIR) Spectroscopy and X-ray Photoelectron Spectroscopy (XPS) measurements were performed. Furthermore, we studied the hardness and Young’s modulus by nanoindentation, and variable angle spectroscopic ellipsometry (VASE) measurements were performed to extract optical constants. To interpret the measurements further, nearly stoichiometric silicon nitride and silicon carbide thin films were also prepared. [1] C.W. Chen, C.C. Huang, Y.Y. Lin, L.C. Chen, K.H. Chen, W.F. Su, Optical prop- erties and photoconductivity of amorphous silicon carbon nitride thin film and its application for UV detection, Diamond Relat. Mater. 14 (3-7) (2005) 1010–1013. [2] Schwarz-Selinger, T., Von Keudell, A., & Jacob, W. (1999). Plasma chemical vapor deposition of hydrocarbon films: The influence of hydrocarbon source gas on the film properties. Journal of Applied Physics, 86(7), 3988-3996. [3] V.I. Ivashchenko, A.O. Kozak, O.K. Porada, L.A. Ivashchenko, O.K. Sinelnichenko, O.S. Lytvyn, T.V. Tomila, V.J. Malakhov, Characterization of SiCN thin films: experimental and theoretical investigations, Thin Solid Films 569 (2014) 57–63. [4] M. G. Boudreau, "SiOxNy Waveguides Deposited by ECR-PECVD", M.Eng. thesis, McMaster University, 1993.

Silicon carbonitride (SiCN), an intermediate structure between silicon carbide and silicon nitride, has emerged as a material of interest to increase the performance of silicon-based visible luminescence. In this work, thin films of SiCN were deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition using silane, nitrogen, and methane as the gas precursors. The microstructure, composition, and optical properties of the SiCN layers were determined by elastic recoil detection, Rutherford backscattering spectrometry, ultraviolet–visible spectroscopy, variable angle spectroscopic ellipsometry, photoluminescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction spectroscopy techniques. The optical and electrical characteristics were linked with the structural properties to investigate the effect of carbon incorporation on the nature of SiCN thin films. Successive increases in the carbon content from 0 to 41.6 at.% resulted in an increase in refractive index and growth rate of the films, while band gap narrowing occurred. Structural studies showed that carbon preferred to form bonds with silicon rather than nitrogen in SiCN thin layers. The produced films contained mainly amorphous silicon nitride and silicon carbide structures and small amounts of an amorphous SiCN network. Photoluminescence emission showed two peaks centred at 475 and 550 nm. The observed link between the photoluminescence behavior and the composition and structure of SiCN layers revealed the details of the most luminescent SiCN thin film. Silicon nitride (carbon-free) thin films exhibited lower emission intensities indicating that the presence of carbon in the silicon nitride matrix enhanced the visible light emission.

Terbium-doped silicon-rich silicon oxide films were deposited and hydrogenated at elevated temperatures. The influence of hydrogenation on defects-mediated non-radiative recombination of excited Tb 3+ ions was investigated by means of photoluminescence and photoluminescence decay measurements. An increase in photoluminescence intensity and photoluminescence decay time was observed upon hydrogenation for the main 5 D 4 – 7 F 5 transition of Tb 3+ ions. This observation was ascribed to saturation of non-radiative recombination defect centers with hydrogen. It was found that the number of emitted photons increases upon passivation as a result of two effects: (1) a reduction of the non-radiative recombination rate, and (2) optical activation of new Tb 3+ emitters. Based on the obtained results and literature data, Forster energy-transfer was suggested as the interaction responsible for the non-radiative coupling between Tb 3+ ions and defects.

Ternary compound thin films have drawn interest since intermediate forms can be developed for materials with tunable properties. Among them, thin films of silicon carbonitride (SiCN) are widely used for protective hard coatings due to their superior mechanical and chemical properties such as high wear resistance, chemical and thermal stability at high temperatures, and hardness. Another area of application of SiCN thin films is as low dielectric constant materials, which are desired for replacing silicon oxide (SiO2) or silicon nitride (Si3N4) in integrated circuits (IC) and charge trapping capacitors. In general, SiCN is an intermediate compound between Si3N4 which is a highly transparent, wide band gap (5 eV) dielectric, and silicon carbide (SiC) with high mechanical durability [1]. One of the most common techniques for the fabrication of SiCN thin films is plasma enhanced chemical vapour deposition (PECVD) with alkylsilazane precursors for high composition control [2]. Recently, we reported the compositional and mechanical properties of SiCN:H thin films, which were deposited using electron cyclotron resonance (ECR) PECVD with two different hydrocarbon precursors, acetylene (C2H2) and methane (CH4) [3, 4]. In the present work, we explore how film composition affects the electrical behaviour of the thin films. More specifically, we investigate the dielectric properties of SiCN:H thin films and the charge transportation and trapping mechanisms for different stoichiometries and film densities, as a function of the hydrocarbon precursor. Metal-insulator-semiconductor (MIS) capacitor type structures were formed on p-type (100) silicon substrates. Following the deposition, aluminum (Al) gate electrodes were sputtered for current-voltage (I-V) and capacitance-voltage (C-V) measurements operated at 1 MHz. The results were correlated with composition and density of SiCN:H thin films obtained from Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD), and variable angle spectroscopic ellipsometry (VASE) measurements. Finally, finite element modeling was performed by COMSOL to compare the capacitance characteristics in MIS structures of the thin films. [1] L.C Chen, C.K. Chen, S.L Wei, D.M Bhusari, K.H. Chen, Y.F. Chen, Y.C. Jong and Y.S. Huang. Crystalline silicon carbon nitride: A wide band gap semiconductor. Applied Physics Letters, 72(19), pp.2463-2465 (1998). [2] S. Bulou, L. Le Brizoual, P. Miska, L. de Poucques, R. Hugon, M. Belmahi, J. Bougdira. The influence of CH4 addition on composition, structure and optical characteristics of SiCN thin films deposited in a CH4/N2/Ar/hexamethyldisilazane microwave plasma. Thin Solid Films, 520(1), 245-250 (2011). [3] A. Abdelal, Z. Khatami and P. Mascher. Influence of Different Carbon Precursors on Optical and Electrical Properties of Silicon Carbonitride Thin Films. ECS Transactions, 97(2), 59 (2020). [4] Z. Khatami, G. B. F. Bosco, J. Wojcik, T. R. Tessler, P. Mascher. Influence of Deposition Conditions on the Characteristics of Luminescent Silicon Carbonitride Thin Films. ECS Journal of Solid-State Science and Technology, 7(2), N7 (2018).

Over the last decades, silicon-based materials have exhibited outstanding electronic properties and been used in photovoltaic and electrical devices such as transistors [1]. However, due to their indirect band gap nature and poor light emitting properties, they are not satisfying candidates when it comes to photonics. One way through which this poor performance is sorted out is doping of rare earth (RE) elements into the silicon nanostructure thin film to enhance the light emission. The reason for the use of RE elements in silicon-based materials is the fact that they showed well-defined emission peaks and 4f electron shielding making them independence of the host matrix [2]. In this study, luminescence properties of Europium (Eu) doped oxygen rich silicon oxide (ORSO) materials using two fabrication techniques are discussed as well as controlling of the Eu concentration, argon partial pressure and sputtering power. In addition, the effect of different annealing atmospheres is observed as here pure nitrogen (N2) and forming gas (N2+5% H2) are tested at a variety of deposition temperatures ranging between 300 °C and 1350 °C. In particular, samples subjected to the higher annealing temperatures of 1200 °C and 1350 °C behave differently in comparison with lower annealing temperatures where their structural and photoluminescence (PL) properties are investigated in more details. The introducing of Eu into ORSO host matrix was performed by two different deposition methods with the first one being the conventional method of metal organic powders where RE elements are introduced using electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) system. The second method involves the use of a novel and custom-made integration of ECR-PECVD and magnetron sputtering [3]. The investigation of a variation of optical and structural properties of the samples made with similar deposition parameters using these two different techniques resulted in insignificant light emission of the ones fabricated with metal organic precursor and remarkable emission of the samples produced using the integrated ECR-PECVD and sputtering method. Variable angle spectroscopic ellipsometry (VASE) measurements are carried to comprehend the refractive index and thin films thicknesses, and their dependence on the deposition parameters such as the sputtering power. Rutherford backscattering spectrometry (RBS) measurements provide the film composition and verify a good control of the Eu concentration using the second deposition method (integrated ECR-PECVD and sputtering). X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) confirm the formation of nanostructures in the Eu-ORSO thin films following post-deposition annealing beyond 1200 °C. The PL studies are performed to study the light emission properties of Eu-ORSO thin films and the changes introduced by the hydrogen passivation. Figure 1 shows the influence of hydrogen passivation on one of the Eu-ORSO thin films containing 0.1 ± 0.01 at. % of Eu. The sample is annealed at 1200 °C and 1350 °C using N2 and N2+H2 atmospheres for 1 hour in the quartz tube furnace. The hydrogen passivation enhances the PL emission by one order of magnitude possibly due to the passivation of the defects and dangling bonds. References: 1-Priolo, F., Gregorkiewicz, T., Galli, M., & Krauss, T. F. (2014). Silicon nanostructures for photonics and photovoltaics. Nature Nanotechnology, 9(1), 19–32. https://doi.org/10.1038/nnano.2013.271 2- Kenyon, A. J. (2002). Recent developments in rare-earth doped materials for optoelectronics. In Progress in Quantum Electronics (Vol. 26). https://doi.org/10.1016/S0079-6727(02)00014-9 3- Miller, J. W., Khatami, Z., Wojcik, J., Bradley, J. D. B., & Mascher, P. (2018). Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials. Surface and Coatings Technology, 336, 99–105. https://doi.org/10.1016/j.surfcoat.2017.08.051 Figure 1

We report low optical loss germanium oxide (GeO2) thin films which have been deposited by low pressure ion-assisted alternating current dual magnetron sputtering of germanium targets in an oxygen plasma environment. The germanium oxide films ranging from 0.7- to 1.0-µm-thick were fabricated at low temperature and high deposition rates of 6–38 nm/min on silicon and thermally oxidized silicon substrates. The refractive index of the films was determined through variable angle spectroscopic ellipsometry and found to be 1.6051 on average at a wavelength of 638 nm. The films were shown to be near stoichiometric through Rutherford backscattering spectroscopy analysis and displayed sub-nanometer roughness when measured with atomic force microscopy. High peak-to-valley uniformity on a 3-inch substrate with relative deviation of 0.8% was achieved. We characterized the attenuation of the GeO2 thin films from visible to near-infrared wavelengths and observed it to be as low as 0.1 dB/cm at 638 nm for deposition rates of 8 nm/min. This deposition technique provides complementary metal-oxide-semiconductor compatible GeO2 thin films suitable for integrated photonics applications and is promising for the fabrication of other dielectric waveguide materials.

The compatibility of Si-based light sources with mainstream metal-oxide semiconductor technology has become very interesting over the past decades due to their potential in integrated optoelectronics circuits of monolithic Si [1]. A very promising approach to improve the light emission from silicon-based materials is doping silicon with rare earth elements, and numerous research is involved in this field [1]. However, there are only a few works on europium (Eu) doped silicon-based matrix. In this work, Eu doped silicon oxide, silicon oxynitride, and silicon nitride thin films were deposited on P (100) Si substrates using integrated electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) and magnetron sputtering. Silane (SiH4), oxygen (O2), and Nitrogen(N2) gases were used as precursors and solid Eu as the sputtering target. The integrated ECR-PECVD and sputtering system allows tunable and highly consistent Eu doping concentration, better control of the layer stoichiometry along with less hydrogen incorporation in the deposited film compared to conventional CVD systems [2]. Several thin films were investigated using room temperature photoluminescence (PL) and X-ray diffraction (XRD). A detailed investigation of the effect of annealing on the PL was performed. The annealing temperature was varied from 500 OC to 1200 OC in nitrogen and a mixture of nitrogen and hydrogen atmospheres. It was observed that the intensity of the PL spectra increased with increasing annealing temperature. Besides, the hydrogen passivation effect has been studied in this work, which shows that hydrogen passivation increases the intensity of the peak. Based on the XRD measurements, we have found that the amorphous silicon oxide structure changes to a crystalline structure by adding nitrogen in the film. Interestingly silicon oxynitride and silicon nitride films do not show any luminescence at room temperature. The influence of the precursors' gases in the atomic percentage of the thin films was analyzed by Rutherford Backscattering spectrometry (RBS). In addition to it, the thickness and the index of refraction were characterized by variable angle spectroscopic ellipsometry (VASE). Reference: 1. Lin, Z., Huang, R., Wang, H., Wang, Y., Zhang, Y., Guo, Y., ... & Li, H. (2017). Dense nanosized europium silicate clusters induced light emission enhancement in Eu-doped silicon oxycarbide films. Journal of Alloys and Compounds, 694, 946-951. 2. Miller, J. W., Khatami, Z., Wojcik, J., Bradley, J. D. B., & Mascher, P. (2018). Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials. Surface and Coatings Technology, 336, 99-105.

Rare earth doped silicon-based thin films can be used for light emitting applications, where the control of dopant type and concentration plays a significant role in the enhancement of optical functionalities [1]. In this work, nanostructured terbium (Tb) doped oxygen-rich silicon oxide (ORSO) samples were fabricated using a novel fabrication technique: integrated sputtering and plasma enhanced chemical vapor deposition (PECVD) [2]. The Tb dopant concentration in the ORSO host matrix was varied from 0.5 at. % to 17 at. % and post-deposition thermal annealing was performed in a wide range of temperatures in a N2 atmosphere. In addition, the presence of defects, one of the general physical problems limiting the emission efficiency of rare earth doped silicon-based materials, was investigated using a combination of photoluminescence measurements and positron annihilation spectroscopy (PAS). We discuss the influence of the Tb dopant concentration on the silicon nanocrystal growth and the formation of Tb silicate nanocrystals. A precipitation mechanism as a function Tb content and annealing temperature is proposed and tested using X-ray diffraction, photoluminescence, and microscopy techniques. Following post-deposition annealing at 1200 °C, all Tb ions agglomerate and form large nanocrystals with diameters reaching 50 nm (Fig. 1). Scanning transmission electron microscopy (STEM) analysis shows that these large nanocrystals are composed of Tb, silicon, and oxygen, however, no Tb remains in the amorphous regions of the silicon oxide matrix. Despite the oxygen-rich content, small silicon nanocrystals (Si-ncs) are formed in the matrix with a size distribution between 2 and 5 nm. The influence of hydrogen passivation and the contribution of trap states to the luminescence mechanism is discussed using the interdependency of the photoluminescence emission for the dominant Tb excited state (5D4 to 7F5) and the values of the S-parameter obtained from PAS. The values of the S- and W-parameters identify the traps at the interface between the amorphous silicon oxide host matrix and embedded nanocrystals. Finally, the solubility level of Tb ions is extended using this novel processing method and an optimized Tb concentration for the most luminescent matrix is suggested. High-temperature annealing promoted the formation of a different Tb silicate crystal phase than the phases observed in samples with lower Tb content. A fiber texture with no preferred orientation in the plane but growth direction of is observed [Fig. 2]; however, samples with lower Tb content are fully random and show no distinct texture. The correlation between the nanostructure and emission properties is an important step to fabricating Tb-doped silicon oxide materials which can be potentially used in a variety of light emitting applications such as displays, solar cells, optical communications, and other silicon optoelectronic devices. Fig. 1 High-resolution transmission electron microscopy (HR-TEM) image of a focused ion beam (FIB) prepared Tb-doped ORSO thin film annealed at 1200 ℃ for 1 hour in N2 atmosphere. Fig. 2 A fiber texture is evident by the ring of intensity shown in the pole figure and no preferred orientation in plane is observed. References: Li, O. Zalloum, T. Roschuk, C. Heng, J. Wojcik, P. Mascher “The formation of light emitting cerium silicates in cerium-doped silicon oxides”, Appl. Phys. Lett. 94, 011112 (2009). W. Miller, Z. Khatami, J. Wojcik, J. D. B. Bradley, P. Mascher “Integrated ECR-PECVD and magnetron sputtering system for rare-earth-doped Si-based materials”, Surf. Coat. Techn., 336, 99-105 (2018). Figure 1

In this work, we propose a new type of silicon-based electroluminescent device. The thin film emitting layers of the device were deposited using Electron-Cyclotron-Resonance Plasma Enhanced Chemical-Vapor Deposition (ECR-PECVD) with in-situ Ce3+ doping on a P-type silicon substrate. Oxygen was gradually substituted by nitrogen to produce silicon oxynitride thin films with different layer compositions. Refractive indices extracted from variable-angle spectroscopic ellipsometry (VASE) measurements classified the thin films into two main groups, silicon oxide (SiOx) and silicon oxynitride (SiOxNy). The thin film composition was studied by Rutherford Backscattering Spectrometry (RBS), verifying the gradual increase in oxygen content. Photoluminescence (PL) spectroscopy of the emitting layer was obtained using a 375 nm laser as an excitation source. All samples were subjected to the post-deposition annealing treatment for 1 hour at different temperatures varying from 600 to 1200°C in 95% N2 and 5% H2 ambient gas environment, yielding considerably stronger blue PL emission than as-deposited ones. PL intensity of SiOx showed a sudden increase due to the formation of Ce2Si2O7 clusters when annealed at 1200°C. Internal Quantum Efficiency (IQE) and External Quantum Efficiency (EQE) were measured using an integrating sphere and a UV-Vis-NIR spectrometer. The optimum layer composition and annealing condition to produce SiOxNy thin films with maximized Ce3+ excitation efficiency were obtained. To further investigate the electrical performance of the produced samples, the thin films were coated with indium tin oxide (ITO) and aluminum (Al) on the top and bottom side of the thin film respectively. Current-Voltage (I-V) measurements showed improved charge injections in SiOxNy compared to SiOx, due to the reduction of the bandgap upon the incorporation of nitrogen.

Synchrotron-based experiments in combination with optical measurements were used to explore the potential of a photovoltaic material based on silicon carbonitride (SiCN) thin films, in particular for the use in space solar cells. The large bandgap, SiCN films were fabricated using electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) followed by low-temperature annealing processes. X-ray absorption near edge structure (XANES) with excitations at the carbon, nitrogen, and silicon K-edges verifies that the presence of nitrogen tends to disrupt Si–C networks. This results in the enhancement of light absorption and bandgap widening, which is desirable for front emitters in all-silicon tandem solar cells. The ternary structure of SiCN allows bandgap engineering and tuning of the light absorption and refractive index through careful design of the composition. XANES showed that the thermal annealing at a medium temperature (500 °C) using N2 ambient promoted the formation of Si–Si and C–N sp2 bonds before disappearing in higher annealing temperatures. In our opinion unlocking the potential of robust SiC mixed with nitrogen in SiCN matrix has appeal in radiation-resistant solar cells, where it can serve as the top emitter layer in all-silicon tandem solar cells and at the same time benefits the antireflection properties.

Silicon-rich silicon oxide films, with various Si concentrations, were deposited by plasma enhanced chemical vapor deposition and annealed at 1100 °C in order to form silicon nanocrystals. For these films, it has been found that the absorption edge shifts as a function of the nanocrystal size due to the quantum confinement of exciton. This result showed that the size-related effects are present in the investigated films. Next, we examined the influence of the nanocrystal size on the vibrational modes. In this case, the Raman line related to silicon nanocrystals significantly down-shifts as a function of the nanocrystal size, which is against the predictions of the phonon confinement model. It has been shown that this effect is due to stress exerted on the nanocrystals. It has been also found that this stress changes from compressive to tensile, and the stress character depends on the film stoichiometry.

We demonstrate blue organic light-emitting diodes (OLEDs) based on a host-dopant system with a dual emitting layer (EML) configuration consisting of variable concentration of fluorescent doped and fixed concentration of phosphorescent doped emitting materials. We also introduce two different device designs by switching the position of the fluorescent and phosphorescent EMLs. Because 4,4'-Bis(2,2-diphenylvinyl)-1,1'-biphenyl (BCzVBi), which is the blue fluorescent dopant, exhibits the highest occupied molecular orbital (HOMO) energy level compared to the neighboring layers, the fluorescent dopant is shown to strongly correlate with hole transport in the fabricated blue OLEDs. In this study, we show how the electrical and optical properties of devices are affected by different doping concentrations due to the hole-transport-related properties of dopant molecules.

Silicon carbonitride (SiCN) thin films have recently emerged as the promising class of multifunctional materials because of their unique properties inherited from binary submatrices of silicon carbide, silicon nitride, and carbonitride. The luminescence mechanism of such ternary materials is complex and is influenced by slight changes in the film composition, deposition temperature, and post-deposition annealing temperature. This paper reports the temperature dependence of luminescent centres in SiCN thin films grown using the electron cyclotron plasma enhanced chemical vapour deposition (ECR PECVD) at different deposition temperatures, which are subsequently subjected to a wide range of annealing temperatures. With the increase of the deposition temperature, the photoluminescence (PL) sub-band positioned at around 1.8 eV (650 nm) intensifies. Following the annealing, the changes of the PL spectra at higher annealing temperatures are dominated by the emission related to this PL sub-band. The white luminescence of SiCN thin films observed under excitation by a 325 nm laser is explained in terms of the radiative defects at localized carbide- and nitride-related states. We assign the changes of the intensity and shape of the PL-sub bands mainly to the evolution of carbon-related defects. The observed variation of the PL emission of different samples was linked with the film restructuring and original growth temperature. We discuss how the post-deposition thermal annealing influences the emissions associated with the carbon and nitride states differently in the samples grown at different deposition temperatures, which have different compositions.

Amorphous hydrogenated silicon carbonitride (a-SiCN:H) thin films were grown using electron cyclotron resonance chemical vapour deposition using a mixture of methane, nitrogen, and silane as precursors. The origin of the variation of macroscopic properties such as hardness (H), elastic modulus (E), photoluminescence (PL), and the optical band gap was investigated through their correlation with the microscopic features of a-SiCN:H thin films as a function of the process parameters, including the deposition temperature and methane gas flow rate. From a microstructural perspective, the thin films were investigated using x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, elastic recoil detection, transmission electron microscopy, and x-ray diffraction. It is verified that an increase of the substrate temperature resulted in the substitution of hydrogen atoms mainly by carbon atoms, causing the density of the silicon carbide-related structures to increase in the amorphous structure of the a-SiCN:H thin films. Hardness and elastic modulus were found to increase with the deposition temperature and decreased with an increase of the methane gas flow during the deposition, resulting in higher carbon content in the films. The observed changes are ascribed to the reduced density of the weak hydrogen terminated bonds and the variation of the relative bond density of Si-C to Si-N bonds. In addition, the thin films were depth profiled using a slow positron beam to investigate the role of vacancies. The observed increase of the positronium formation with increasing deposition temperature was found to correlate with the variation of PL, where an enhancement of the visible emission originating from carbon-related defects was observed. A set of optimized process parameters to fabricate a-SiCN:H thin films with improved visible emission and hardness properties is suggested.

We investigated the optical properties of light emission based on the resonance energy transfer mechanism between two molecules in the host–dopant systems. For this purpose, we fabricated the organic light-emitting devices with the different doped emissive layers. The host matrices were made of 4,4′,4″-tris(carbasol-l-nyl)triphenylamine (TCTA) and 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) molecules and the doped molecules were 5,6,11,12-tetraphenylnaphtacene (Rubrene) and 4-(Dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB). The concentrations of the doped molecules were 0.1%, 0.3%, 0.5%, and 0.8%. Through spectroscopic analysis using multi-peak fits with a Gaussian function to the emission spectra, we obtained the relative light intensity of the two dopants according to the doping concentrations and examined the relations between the molecular excited energy states and the nature of energy transfer in the host and dopant systems. We show that the luminous efficiency of the devices has a strong correlation between the energy transfer owing to the individual molecular intrinsic properties and the electrical characteristics associated with the bulky properties in the devices.

We investigated the photoluminescence (PL) and electronic properties of both undoped and doped silicon carbonitride (SiCN) thin films, fabricated using electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD). The PL intensity of SiCN films is highly dependent on the annealing temperature and doping condition with rare-earth metals. Notably, Ce+3- and Tb+3-related luminescence were observed from doped samples after being annealed in nitrogen ambient at 1200°C for one hour. The electronic characteristics of these doped and un-doped films were analyzed using soft X-ray absorption near edge structure (XANES) and X-ray emission spectroscopy (XES) measurements, showing significant structural re-ordering occurs as the annealing temperatures were increased.

11 pags., 6 figs., For years bismuth (Bi) has appealed to a broad community of scientists due to its peculiar electronic, optical, and more recently plasmonic and photocatalytic properties, which enable both the understanding of basic science phenomena and the development of a wide range of applications. In spite of this interest, a comprehensive spectral analysis of the dielectric function (¿ = ¿1 + j¿2) of bulk Bi from the far infrared (IR) to the ultraviolet (UV) region is not available. So far, the data have been reported in limited spectral ranges and show a wide dispersion that is especially notorious for the IR region. In this work we report ¿ for Bi in a wide spectral range from 0.05 to 4.7 eV (24.8 to 0.3 ¿m, far IR to UV). ¿ is extracted from spectroscopic ellipsometry measurements of excellent quality (dense and smooth) Bi films by using the transfer matrix formalism and Kramers¿Kronig consistent analysis. The higher quality and accuracy of the obtained ¿ compared with the literature data is demonstrated. The analysis and use of this reference bulk dielectric function provides crucial information for the exploration and understanding of the optical, plasmonic, and photocatalytic properties of Bi nanostructures. From its analysis, it is evidenced that the optical properties of Bi in the mid wave IR-to-UV are driven only by interband transitions, which are responsible for the dominant absorption band peaking at about 0.8 eV. Therefore, the plasmonic behavior and the photocatalytic performance of Bi nanostructures in the visible and UV are likely driven by these interband transitions that make ¿1 turn negative in this region without the need of exciting free carriers. Furthermore, classical electrodynamic simulations using the obtained ¿ show a strong size dependence for the optical extinction of Bi nanospheres in the far IR-to-near IR with Mie-like resonances broadly tunable across this region., This research received funding from the European Community Seven Framework Programme (FP7-NMP-2010-EU-MEXICO) under Grant Agreement No. 263878. We also acknowledge funding from the Spanish Ministry for Economy and Competitiveness through and TEC2012-38901-C02-01 and TEC 2015-69916-C2-1-R projects. E.R. acknowledges funding from the Spanish Ministry for Economy and Competitiveness through a Ramón y Cajal Fellowship (RYC-2011-08069). In Canada, this work was supported by the Discovery Grants program of the Natural Science and Engineering Research Council (NSERC).

This paper uses the results of the characterization of amorphous semiconductor thin film transistors (TFTs) with the quasi-permanent memory structure referred to as silicon oxide nitride semiconductor (SONOS) gates, to model spiking neural circuits. SONOS gates were fabricated and characterized. In addition, MOSFETs using organic copper phthalocyanine (CuPc) were fabricated with these SONOS gates to demonstrate proof of concept performance. Analog spiking circuits were then modeled using these low performance TFTs to demonstrate the general suitability of organic TFTs in neural circuits. The basic circuit utilizes a standard comparator with charge and discharge circuits. A simple Hebbian learning circuit was added to charge and discharge the SONOS device. The use of these elements allows for the design and fabrication of high-density 3-dimensional circuits that can achieve the interconnect density of biological neural systems.

We combine X-ray absorption, electron spin resonance and Raman spectroscopies, X-ray diffraction and photoluminescence (PL) techniques to determine the structure and luminescence mechanisms in Si nanoclusters (Si-ncls) embedded within Si oxides at various intermediate formation stages. The Si-ncls/oxide systems are fabricated by thermally annealing plasma-enhanced chemical vapor deposited Si-rich Si-oxide films. The structural and chemical orders in the amorphous oxide matrix, the Si-ncls amorphous and crystalline volume fractions and sizes, the dangling bond density and PL spectra and decay rates are followed closely as a function of the annealing temperature. The results can be interpreted by a crystalline core/amorphous shell model for the Sincls. The important role of the shell, often ignored in the literature, is discussed. As the Si-ncls crystalline cores grow at the expense of thinning amorphous shells, the PL undergoes a transition from a regime dominated by disorder-induced effects to a situation where quantum confinement prevails. Fil: Borrero Gonzalez, Luis Jose. Universidade de São Paulo; Brasil Fil: Nunes, L. A. O.. Universidade de São Paulo; Brasil Fil: Guimaraes, F. E. G.. Universidade de São Paulo; Brasil Fil: Wojcik, J.. McMaster University; Canadá Fil: Mascher, P.. McMaster University; Canadá Fil: Gennaro, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Tirado, Monica Cecilia. Universidad Nacional de Tucumán; Argentina Fil: Comedi, David Mario. Universidad Nacional de Tucumán; Argentina