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Aluminum nitride (AlN), which belongs to the family of the III-V semiconductors, is a material of great interest in the microelectronics industry due to its high decomposition temperature, good chemical stability, wide bandgap and CMOS compatibility. Moreover, AlN is known by its Pockels coefficients, which makes it very suitable for various non-linear optical devices. In this work, a study of a design space exploration of fundamental mode polarization in an AlN pedestal waveguide is proposed. The current work performs a dispersion analysis of this type of waveguide by varying the dimensions of the core and the pedestal. Lastly, electrode design for phase shifting analysis is also proposed. The data obtained with the exhibited work will allow the device designer to have a design space with light polarization control to stimulate the adequate electro-optic coefficient, with potential applications in modulators, switches, multiplexers, phase shifters, among others. A feasibility study will also be provided.

Photonic crystal (PhC) slabs with a lower-index material surrounding the core layer are an attractive choice to circumvent the drawbacks in the fabrication of membranes suspended in air. In this chapter, we summarize and expand a numerical study performing a design protocol for nanophotonic devices based on an oxide-cladding aluminum nitride PhC slab. We show the design of an ideal structure and analyze the effects of material dispersion based on a first-order correction perturbation theory approach, in which the dielectric functions obtained by experimental measurements of the thin film materials were employed. This bulk PhC slab was then used as a host medium for the study of an optimized nanocavity, as well as for the development of a slow light waveguide that can compose a Mach–Zehnder electro-optic modulator. The study also includes modeling and analysis of the effects of fabrication-induced disorder, such as deviation in sizes and positions of holes, in the performance of the photonic devices. The results show that the oxide-cladding AlN PhC can be a promising platform for the development of integrated photonic devices.

Slow light propagation throughout photonic crystal slab waveguides have great potential to reduce the size and power consumption of active silicon photonic devices. A great effort has been done to understand the slow light mechanisms and their relations with the waveguide geometrical parameters. In this way, it is expected to control the waveguide dispersion characteristics and exploit the effects produced when slowing down light propagation speed, but avoiding, at the same time, the high group velocity dispersion (GVD) level drawbacks such as pulse broadening and distortion. Here, we present a concise methodology to perform an efficient near-zero GVD slow light photonic crystal waveguide oriented-design. We use a slow light flatness parameter for enabling a systematic comparison of slow light waveguide structures regarding their average group velocity and group index slope within a limited bandwidth. The results show the feasibility of obtain near-zero GVD slow light photonic crystal waveguide structures with slowdown factors up to 40, normalized delay-bandwidth products over 0.2, and dispersion lengths at the millimeter scale.

In this work, we present a numerical design of a pedestal waveguide as a suitable alternative for coupling between few-mode fibers and integrated devices. The proposed waveguide has a cylindrical core deposited over a pedestal base. Numerical simulations are performed to show that modes propagating in pedestal waveguides possess an electric field profile similar to the LP modes in few-mode fibers. The power coupling between these two devices can reach values up to than 96% (-0.18 dB). Besides this, the pedestal waveguide has low insertion loss (IL) and the return loss is around 8 dB. This approach is a suitable alternative in the study of multimode integrated devices in order to work alongside few-mode fibers.

In this work, the non-linear refractive index (n 2 ) of silicon oxynitride (SiO x N y ) is determined, obtaining a value for this material of n 2 = 2.11×10-19 m2/W. The results demonstrate that this material has interesting properties for the development of non-linear optical devices. The paper presents in detail the waveguide fabrication process using the pedestal technique, which allows using different materials since it does not require etching to define the sidewalls of the waveguides. We show the results of the measurement of the n2 employing the non-linear optical phenomena of Self-Phase Modulation (SPM).

Made available in DSpace on 2020-12-12T01:10:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work, we investigate a pedestal tantalum oxide (Ta2O5) material platform for integrated nonlinear optics (NLO). In order to achieve low propagation losses with this material, pedestal waveguides with Ta2O5 cores were designed. The nonlinear refractive index n2 of this new platform was obtained by measuring the amount of spectral broadening due to self-phase modulation (SPM) of 23 fs optical pulses at 785 nm propagating through the waveguides. In this manner, a nonlinear index of (5.8 ± 2.0) × 10−19 m2W−1 was found for this material, which is in good agreement with values reported in related works where strip waveguides were used for a similar purpose. Furthermore, due to the pedestal configuration, propagation losses as low as 1.6 dB·cm−1 for narrow waveguides and 0.1 dB·cm−1 for large waveguides were obtained. Finite element method (FEM) mode analysis was performed to calculate the mode characteristics, as well as the effective areas of the waveguides. The high nonlinear and linear refractive indices, wide bandgap and low propagation losses make this platform ideal for applications extending from the visible into the mid-IR regions of the optical spectrum. Due the large gap, Ta2O5 should have low two photon absorption at the near-IR as well. Polytechnic School University of São Paulo (USP) Center for Lasers and Applications IPEN-CNEN/SP Telecommunications Department São Paulo State University (UNESP) Telecommunications Department São Paulo State University (UNESP) CNPq: 305447/2017-3 CNPq: 32088/2018-0

The present work reports the fabrication, passive and active characterization of Yb3+/Er3+ codoped GeO2–PbO pedestal waveguides. We show the advances obtained in pedestal fabrication by comparing waveguides obtained under different processes parameters. The thin films were deposited on previously oxidized silicon wafers in Ar plasma at 5 mTorr; pedestal waveguides, with 1–100 μm width range were defined by conventional lithography procedure, followed by reactive ion etching (RIE). A comparison between the results of propagation losses and internal gain is presented in order to show that the improvement of fabrication process contributed to enhance the performance of the pedestal waveguides. Reduction of about 50% was observed for the propagation losses at 632 and 1068 nm, whereas enhancement of approximately 50% was obtained for the internal gain at 1530 nm (4 and 6 dB/cm, for 70 μm waveguide width), under 980 nm excitation. The present results demonstrate the possibility of using Yb3+/Er3+ codoped GeO2–PbO as pedestal waveguide amplifiers.

This paper presents the design and post-process of a CMOS-MEMS IR emitter device implemented in standard AMS 0.35μm CMOS process. The IR emitter is based on thermal heating of a chain of tungsten vias implemented on the Back-End-Of-Line. This heating element is protected from oxidation with a SiO 2 film and is thermally isolated from the substrate. The IR light emitted from the heating element is directed through a waveguide made of SiO 2 and air, used as core and cladding layers, respectively. The optical waveguide is connected to a photodiode used as detector, implemented in the Front-End-Of-Line. The post-process used to isolate the thermal emitter and create the waveguide was done through a maskless post-process that selectively etched the SiO 2 layers and used the aluminum film as a sacrificial material. The release of both emitter and optical waveguide was confirmed by visual inspection using optical and electronic microscopes.

In this work we present the details regarding the fabrication process of pedestal based optical waveguides, using different materials with large optical nonlinearities as core layer. With the pedestal fabrication process it is possible to use novel materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, since this technique does not require etching of the core material itself. Lateral confinement of light is performed through the fabrication of pedestals by Reactive Ion Etching (RIE) on the lower cladding. The last step in the fabrication process is the deposition of the core layer and, for this reason, etching this layer is no longer necessary. The materials used as core layer are Aluminum Nitride and Titanium oxynitride films, due to the fact that these materials present a great potential for the fabrication of Nonlinear Optics integrated devices.

Made available in DSpace on 2019-10-04T11:55:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Institute of Photonics (INCT de Fotonica) This work reports the signal enhancement of Yb3+/Er3+ codoped PbO-GeO2 pedestal waveguides due to gold nanoparticles deposited over the core layer. The pedestal structure was obtained by conventional photolithography and plasma etching with a new procedure that does not use metallic hard-masks that normally introduce roughness, leading to light scattering. This new procedure brings advantages that benefit light guiding, reducing the propagation losses. Yb (3+)/Er3+ codoped PbO-GeO2 thin film was obtained by RF Magnetron Sputtering deposition and was used as core layer (410 nm height). In order to cover the core with gold nanoparticles the sputtering technique was used, followed by annealing at 400 degrees C during 1 h. The minimum propagation losses obtained were of 1.0 dB/cm at 1068 nm. Scanning Electron Microscopy (SEM) was employed for the waveguides structure inspection and transmission electronic microscopy (TEM) was used to verify the presence of gold nanoparticles on the waveguides. It was observed an enhancement of 180% for the relative gain that reached 7.8 dB/cm at 1530 nm, for an optical waveguide with 6 pm core width, under 980 nm excitation (pump power of 60 mW), attributed to the local field enhancement in the vicinity of the gold nanoparticles. The new fabrication process presented in this work opens possibilities for optical amplifiers with low propagation losses based on different metal dielectric composites, as well as other waveguide-based devices. Univ Sao Paulo, Escola Politecn, BR-05508010 Sao Paulo, SP, Brazil Fac Tecnol Sao Paulo, Lab Tecnol Mat Foton & Optoeletron, BR-01124060 Sao Paulo, SP, Brazil Univ Estadual Paulista, BR-13876750 Sao Joao Da Boa Vista, SP, Brazil Univ Estadual Campinas, Inst Fis Gleb Wataghin, Dept Fis Aplicada, BR-13083859 Campinas, SP, Brazil Univ Estadual Paulista, BR-13876750 Sao Joao Da Boa Vista, SP, Brazil CNPq: 303548/2015-0 National Institute of Photonics (INCT de Fotonica): 465763/2014-6

In this work we review the recent advances and demonstrate possible future perspectives regarding pedestal waveguide fabrication technology. The optical waveguides produced using this technology represent a new platform to study novel optical materials that could not be explored differently as this fabrication process does not require etching of the core material itself. Thus, novel materials that are highly inert to chemical etchants, such as those composed of heavy metal elements, can be used with this new architecture that allows the fabrication of integrated optical devices. Lower propagation losses with pedestal waveguides when compared to rib waveguides are reviewed. The possibility to construct Mach-Zehnder interferometer structures using the pedestal waveguide technology is shown. The optical amplifiers with high gain are demonstrated using this pedestal process. Furthermore, using the pedestal architecture, it is presented the possibility to produce rare earth ions doped waveguides with gold nanoparticles, which demonstrated gain enhancement attributed to the efficient luminescence due to gold nanoparticles, thus opening possibilities for potential applications in integrated photonics. Finally, another research field that could benefit greatly in the near future from this new architecture is the integrated nonlinear optics as the pedestal waveguide fabrication technology opens up the possibility of using novel materials with high optical nonlinear susceptibilities.

Group III-nitride materials such as GaN and AlN have attracted a great attention in researches on photonic devices that operate at short light wavelengths. The large band gaps of these materials turn them suitable for nanophotonic devices that operate in light ranges from visible to deep ultraviolet. The physical properties of wurtzite GaN and AlN such as their second and third order nonlinear susceptibilities, and their thermal and piezoelectric coefficients, also make them excellent candidates for integrate photonic devices with electronics, microelectromechanics, microfluidics and general sensing applications. Using a plane wave expansion method (PWE) the photonic band gap maps of 36 different two-dimensional photonic crystal lattices in wurtzite GaN and AlN were obtained and analyzed. The wavelength dependence and the effects of the material anisotropy on the position of the photonic band gaps are also discussed. The results show regions with slow group velocity at the edges of a complete photonic band gap in the M–K direction of the triangular lattices with circular, hexagonal, and rhombic air holes. Was also found a very interesting disposition of the photonic band gaps in the lattices composed of rhombic air holes.

In this work we review and summarize the recent developments regarding pedestal waveguide fabrication technology and demonstrate the applicability of this type of structure for Nonlinear Optics (NLO) integrated devices. Pedestals show great potential as a platform for exploring new optical materials. The fabrication process of this type of waveguide does not require etching of the core material itself, making it possible to explore materials that are highly inert to chemical etchants or alloys composed of heavy metal elements, which would not be usually suitable for this purpose otherwise. Lower propagation losses can be achieved with pedestal waveguide when compared to rib waveguides fabricated with different materials. Since the pedestal process allows the exploitation of novel materials, optical amplifiers with higher gain have been demonstrated using this procedure. We show that pedestals could also greatly benefit the field of nonlinear optics, where novel materials with high nonlinearities could be explored as well.

Made available in DSpace on 2018-12-11T16:47:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work we investigate the principles of an alternative method for defining sidewall in optical waveguides fabricated using planar technology. The efficiency of this method is demonstrated through simulations and experimental results regarding propagation losses of a solid core ARROW waveguide fabricated on silicon substrate. It is well known that waveguides fabricated using sidewalls etched via Reactive Ion Etching (RIE) can present high sidewall roughness, especially if metallic hard-masks are used. This is largely responsible for the undesirable losses observed in these waveguides. The basic strategy of the proposed method is to do the etching step, in the fabrication of the waveguides, before the deposition of the core, so as to have the lower cladding layer and part of the silicon substrate etched away. Only after this, is the core of the waveguide deposited. This results in a waveguide sustained by a silicon pedestal. With this process, losses as low as 0.45 dB cm-1 for multimode and 0.84 dB cm-1 for single mode waveguides are obtained. The numerical simulations demonstrate that roughness in sidewalls implicates in propagation losses which are at least five times larger that those in the bulk of the material, thus corroborating the idea behind the proposed method. Escola Politécnica University of São Paulo (USP) São Paulo State University (UNESP) São Paulo State University (UNESP) FAPESP: 2007/00775-1 FAPESP: 2007/0860-9 CNPq: 307349/2014-4 CNPq: 477214/2007-0

The production and characterization of pedestal waveguides based on PbO-GeO 2 amorphous thin films codoped with Tm 3+ /Yb 3+ , with and without gold nanoparticles (NPs), are reported. Pedestal structure was obtained by conventional photolithography and plasma etching. Tm 3+ /Yb 3+ codoped PGO amorphous thin film was obtained by RF Magnetron Sputtering deposition and used as core layer in the pedestal optical waveguide. The minimum propagation losses in the waveguide were 3.6 dB/cm at 1068 nm. The internal gain at 805 nm was enhanced and increased to 8.67 dB due to the presence of gold NPs. These results demonstrate for the first time that Tm 3+ /Yb 3+ codoped PbO-GeO 2 waveguides are promising for first telecom window and integrated photonics, especially for applications on fiber network at short distances.

Fabrication and optical characterization of Tm 3+ /Yb 3+ codoped PbO–GeO 2 (PGO) pedestal-type waveguides are investigated in this work. It is important to mention that, to the best of authors’ knowledge, the use of PGO pedestal-type waveguide has not been studied before. PGO thin films codoped with Tm 3+ and Yb 3+ were obtained through RF magnetron sputtering technique. The pedestal profile was obtained using conventional optical lithography procedures, followed by plasma etching and sputtering deposition. The profile of Tm 3+ /Yb 3+ codoped PGO waveguides was observed by means of Scanning Electron Microscopy (SEM) measurements. Also the infrared and infrared-to-visible frequency upconversion luminescences of Tm 3+ ions were measured exciting the samples with a cw 980 nm diode laser. Propagation losses around 11 dB/cm and 9 dB/cm were obtained at 630 and 1050 nm, respectively, for waveguides in the 20–100 μm width range. Single-mode propagation was observed for waveguides width up to 12 μm and 7 μm, at 1050 nm and 630 nm, respectively; larger waveguides width provided multi-mode propagation. The present results corroborate the possibility of using Tm 3+ /Yb 3+ codoped PGO thin films as active waveguide for photonic applications.

Light sources are used in optofluidic devices for real-time system control and quantitative analysis of important process parameters. In this work, we present a random laser source using a hollow-core antiresonant reflecting optical waveguide (HC-ARROW) containing the gain media inside a reservoir to reduce dye bleaching, which is connected to microchannel waveguides to increase beam directionality. The device is pumped externally and emits a highly coherent and collimated laser beam.

Made available in DSpace on 2018-12-11T16:40:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-14 Photonic crystal slabs with a lower-index material surrounding the core layer are an attractive choice to circumvent the drawbacks in the fabrication of membranes suspended in air. In this work we propose a photonic crystal (PhC) slab structure composed of a triangular pattern of air holes in a multilayer thin film of aluminum nitride embedded in silicon dioxide layers designed for operating around 450 nm wavelengths. We show the design of an ideal structure and analyze the effects of material dispersion based on a first-order correction perturbation theory approach using dielectric functions obtained by experimental measurements of the thin film materials. Numerical methods were used to investigate the effects of fabrication induced disorder of typical nanofabrication processes on the bandgap size and spectral response of the proposed device. Deviation in holes radii and positions were introduced in the proposed PhC slab model with a Gaussian distribution profile. Impacts of slope in holes sidewalls that might result from the dry etching of AlN were also evaluated. The results show that for operation at the midgap frequency, slope in holes sidewalls is more critical than displacements in holes sizes and positions. Electronic Systems Engineering Department University of São Paulo UNESP-São Paulo State University Department of Physics Federal University of Minas Gerais UNESP-São Paulo State University

We use numerical simulations and optical characterizations of Pedestal waveguides to show that it leads to lower propagation losses than rib or strip waveguides, due essentially to the smaller sidewall roughness in these waveguides.

A comparison in the behavior of highly c-axis oriented and amorphous Aluminum Nitride (AlN) films as core layer in self-aligned pedestal (SAP) optical waveguides is presented, aiming to study the influence of AlN crystallinity in waveguiding.

We study the effects of slow light in the performance parameters of a Mach-Zehnder electro-optic modulator based on oxide-cladding AlN photonic crystal. A sub-1V modulation voltage can be obtained for modulation lengths of few micrometers.

The simulation, fabrication and characterization of ARROW waveguides using dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and Sputtering techniques, are presented in this work. Amorphous titanium oxide (TiO2) films were used as first cladding layer and silicon oxynitride (SiOxNy) films, as core layer. Furthermore, homemade routines based in two computational methods were used, for numerical simulations: Transfer Matrix Method (TMM) for the determination of the optimum thickness values of the Fabry-Perot layers, and the Finite Difference Method (FDM) for 2D design and determination of the maximum width that allows single-mode operation. The utilization of thermally grown silicon oxide as second anti-resonant layer, along with improvements in the Reactive Ion Etching conditions for the definition of sidewalls of the optical waveguides were responsible for diminishing optical attenuations. Optimization of the waveguide rib height was done both through FDM simulations and experimentally. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The simulation, fabrication and characterization of ARROW waveguides using dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and Sputtering techniques, are presented in this work. Amorphous titanium oxide (TiO2) films were used as first cladding layer and silicon oxynitride (SiOxNy) films, as core and second cladding layers. Furthermore, homemade routines based in two computational methods were developed, for numerical simulations: Transfer Matrix Method (TMM) for the determination of the optimum thickness values of the Fabry-Perot layers, and the Finite Difference Method (FDM) for 2D design and determination of the maximum width that allows single-mode operation. The utilization of titanium oxide as first anti-resonant layer resulted in low optical attenuations, since high interlayer refractive index differences can be obtained.

In this work, we present the simulation, fabrication and characterization of a tunable Bragg filter employing amorphous dielectric films deposited by plasma enhanced chemical vapor deposition technique on a crystalline silicon substrate. The optical device was built using conventional microelectronic processes and consisted of fifteen periodic intervals of Si 3 N 4 layers separated by air with appropriated thickness and lengths to produce transmittance attenuation peaks in the visible region. For this, previous simulations were realized based in the optical parameters of the dielectric film, which were extracted from ellipsometry and profilometry techniques. For the characterization of the optical interferential filter, a 633 nm monochromatic light was injected on the filter, and then the transmitted output light was collected and conducted to a detector through an optical waveguide made also of amorphous dielectric layers. Afterwards, the optical filter was mounted on a Peltier thermoelectric device in order to control the temperature of the optical device. When the temperature of filter changes, a refractive index variation is originated in the dielectric film due to the thermo-optic effect, producing a shift of attenuation peak, which can be well predicted by numerical simulations. This characteristic allows this device to be used as a thermo-optic sensor.

In this work, we propose the integration of optical waveguides with a simple light source device. Light is emitted from an incandescent chromium micro-resistor embedded in a self-supported region of silicon oxynitride (SiOxNy) film. The waveguide structure is fabricated on a (1 0 0) silicon substrate using silicon oxynitride as the core and cladding layers. Bulk micromachining of the silicon substrate in KOH solution is used to free from the substrate the embedded micro-resistor, reducing the thermal dissipation of that region, allowing the resistor to heat up to incandescent temperatures. A comparison between a theoretical calculation and the experimental data indicate that the microlamp reaches 1160 K before failure. After a microannealing process realized on the microlamp structure, it is possible to couple light into the waveguide and control the output power by adjusting the current that flows through the microlamp.

The development and fabrication of a thermo-electro-optic sensor using a Mach–Zehnder interferometer and a resistive micro-heater placed in one of the device’s arms is presented. The Mach–Zehnder structure was fabricated on a single crystal silicon substrate using silicon oxynitride and amorphous hydrogenated silicon carbide films to form an anti-resonant reflective optical waveguide. The materials were deposited by Plasma enhanced chemical vapor deposition technique at low temperatures (∼320 °C). To optimize the heat transfer and increase the device response with current variation, part of the Mach–Zehnder sensor arm was suspended through front-side bulk micromachining of the silicon substrate in a KOH solution. With the temperature variation caused by the micro-heater, the refractive index of the core layer of the optical waveguide changes due to the thermo-optic effect. Since this variation occurs only in one of the Mach–Zehnder’s arm, a phase difference between the arms is produced, leading to electromagnetic interference. In this way, the current applied to the micro-resistor can control the device output optical power. Further, reactive ion etching technique was used in this work to define the device’s geometry, and a study of SF 6 based etching rates on different composition of silicon oxynitride films is also presented.

of a Tunable Bragg Reflector based on dielectric silicon oxide and silicon nitride films deposited over corning-glass substrates by Plasma Enhanced Chemical Vapor Deposition at low temperatures (320 oC). The device consists of consecutive layers of silicon oxide and silicon nitride films with appropriated refractive indices and thickness to function as an interferential filter in the visible region. The optical results of these devices are comparable to the numerical simulations previously realized, showing an attenuation peak in the transmittance curve at approximately 680 nm. Also, when an angular variation between the incident light beam and the optical filter is produced, a shift in the attenuation peak is observed, which is due to a difference in the optical path of the incident beam. This behavior agrees with simulated results. When a change in temperature is applied to the optical device, a shift in the attenuation peak is also observed, which is related to the thermo-optic effect (TOE) of this kind of material. These results demonstrate that it is possible to control the optical output power of the device through the adequate control of the angle of the incident beam and/or temperature of the device.

In this work, the fabrication and operation of micro-incandescent lamps is presented. Two types of microlamps are fabricated using micro-cantilevers and micro-bridges of silicon oxynitride (SiOxNy) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at low temperatures (320{degree sign}C) with embedded chromium thin film resistors. In both cases, the chromium resistor is sandwiched between layers of SiOxNy that isolates it from the atmosphere, while electric current heats the resistor to incandescent temperatures. Front-side bulk micromachining of the silicon substrate in KOH solution is used to fabricate the cantilevers and bridges that thermally isolate the resistors from the substrate, thus reducing the heat transfer and current required to light the lamp. Finally, arrays of bridges are used to fabricate arrays of microlamps that can be polarized as a micro-display.

We report experimental results on pedestal waveguides produced with Yb3+ /Er3+ codoped PbO-GeO 2 thin films deposited by RF Sputtering for photonic applications. Losses around 2.5 dB/cm and 1.5 dB/cm were obtained at 632 and 1068 nm, respectively, for waveguides in the 20–100 µm width range. Internal gain of 6.0 dB and 4.0 dB, at 1530 nm, under 980 nm excitation, were measured for waveguides width of 80 and 14 µm, respectively. The present results show the possibility of using Yb3+/Er3+ codoped PbO-GeO 2 pedestal waveguide for optical amplifiers.

In this work, we report studies on the residual stress and structure of silicon oxynitride films deposited by PECVD with nitrogen atomic percent varying from 24 to 55. The stress response to thermal annealing at different temperatures is analyzed and correlated with Rutherford backscattering spectroscopy, ellipsometry, Fourier transform infrared spectroscopy, small-angle X-ray scattering spectroscopy and X-ray near edge absorption spectroscopy at the Si–K edge measurements. The results show that the stress varies from compressive to tensile for the as-deposited samples. The annealing process increased the stress value in samples that had a tensile behavior as-deposited, while decreased its value in samples with compressive stress as-grown. It is observed that the stress shifts with annealing in a way that can be correlated with the volume density of voids, also depending on the composition and structure of the films.

In this work, we report on the optimization of all process steps for the fabrication of optical waveguides with high index contrast by using as core and cladding layers silicon oxynitride films deposited by plasma enhanced chemical vapor deposition at low temperatures. The main advantage of using this material, besides allowing the integration of optical and microelectronic devices, is the possibility of controlling accurately the refractive index over a wide range ( n = 1.46–2) allowing in this way a precise control of the index contrast and favoring a high integration density and relatively small dimensions in optical integrated circuits.

This work reports on the growth of silicon clusters within silicon oxynitride (SiO x N y ) matrices, at low temperatures, by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. The films were characterized by Fourier transform infrared spectroscopy (FTIR), soft X-ray absorption spectroscopy (XANES) measurements at the Si K-edge and photoluminescence, before and after thermal annealing at various temperatures. The XANES spectra demonstrate the presence of silicon aggregates in as-deposited and annealed films. A correlation between the presence of silicon clusters in the as-deposited samples and the intensity of the photoluminescence emission is observed.

We have investigated the SiO x N y films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperature using nitrous oxide (N 2 O), nitrogen (N 2 ) and silane (SiH 4 ) as precursor gases. Controlling the gas flow ratio during film deposition, it was possible to vary the material stoichiometry from silicon dioxide to silicon nitride. The structure of the films was investigated by X-ray absorption near-edge spectroscopy (XANES) at the Si K, N K and O K edges, Rutherford backscattering spectroscopy (RBS) was utilized to characterize the material composition. The results show the possibility of obtaining a chemical composition varying continuously from SiO 2 to Si 3 N 4 . The Si K edge absorption spectra indicate that the basic structural element of the network is a tetrahedron with a central Si atom connected to N and O, consistent with a random bonding model. Analysis at the N K edge shows the presence of two distinct edges, which are attributed to the different nitrogen neighborhoods in this material, nitrogen in a Si 3 N 4 matrix and nitrogen substituting O in a SiO 2 type matrix.

In this work we present the results of studies on the deposition and characterization of silicon oxynitride films deposited by plasma enhanced chemical vapor deposition technique using N 2 , N 2 O and SiH 4 gaseous mixtures at low temperatures. Rutherford backscattering spectroscopy and refractive index measurements demonstrate that it is possible to transit from silicon dioxide to stoichiometric silicon nitride by varying the N 2 /N 2 O ratio in the precursor gaseous mixture. Stress measurements and plasma etching experiments show that both the internal stress and the etching rate are very sensitive to the films chemical composition and for specific deposition conditions it is possible to obtain films with very low stress and with high plasma etching rate. These results are very promising for application in low-cost, compact integrated optical devices.

In this work metal/oxide/silicon (MOS) capacitors using SiOxNy and SiO2 films with different nitrogen concentrations as gate dielectrics were deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique, fabricated and characterized. These films were obtained through the variation of the N2O/SiH4 flow ratio (R) at low temperatures (∼320 °C). The refractive index results show that by varying the N2O/SiH4 flow ratio it is possible to obtain a precise control of this parameter in the 1.46–1.57 range. From the low- and high-frequency C–V curves, the interface state density (Dit), the effective charge density (Nss), dielectric constant (k), among others were extracted. Optimized properties were found for the capacitor with a low nitrogen concentration (∼8%) SiOxNy gate dielectric.

The results of the fabrication and characterization of silicon oxynitride films deposited by the plasma-enhanced chemical vapor deposition (PECVD) technique at low temperature and from N 2 , N 2 O and SiH 4 gaseous mixtures are reported herein. It is shown that high nitrogen concentration films with characteristics close to stoichiometric silicon nitride (Si 3 N 4 ) can be obtained. In previous experiments utilizing N 2 O and SiH 4 as precursor gases, it was demonstrated that precise control of the refractive index for silicon dioxide-like oxynitride SiO x N y ( x + y =2) material in the 1.46 (SiO 2 ) to 1.57 range can be attained. In this study, nitrogen gas (N 2 ) was added to the previously studied gaseous mixture. In this way, it was possible to control the refractive index from 1.46 (SiO 2 ) to ∼2 (Si 3 N 4 ) through the appropriate choice of the deposition parameters. The films were characterized by profilometry, ellipsometry, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared spectroscopy (FTIR).

In recent years, the integration of optical and microelectronic devices has been of great interest, motivating studies related to the production of photoluminescent material compatible with present silicon technology. In this context, silicon clusters embedded in a SiO2 matrix are ideal candidates for these applications, mainly due to the intense emission that these new structures present, being promising for the production of devices such as lasers and photodiodes. In this work, we report the fabrication and characterization of silicon-rich SiOxNy deposited by plasma-enhanced chemical vapor deposition (PECVD) technique at low temperatures. These films were annealed at different temperatures, in N2 ambient. Fourier transform infrared spectroscopy (FTIR) and Raman scattering results showed phase segregation and crystallization in the clusters induced by heat treatment. Photoluminescence measurements showed visible emission peaks, compatible with variable size cluster distribution.

In this work results on the study of the physical and optical properties of silicon rich SiOxNy thin films are presented. The films were deposited by the plasma enhanced chemical vapor deposition technique at low temperature (≈320 °C) using nitrous oxide and silane as precursor gases. The films were thermally annealed at 750 and 1000 °C, at low pressures (10−2 Pa) and in N2 ambient for different annealing times. The samples were characterized through Fourier-transform infrared spectroscopy, Raman scattering and photoluminescence (PL). Raman spectra for all samples show a band approximately at 480 cm−1, related to amorphous silicon. The spectrum for the sample with the highest silicon content, heat treated at 1000 °C also presents a band at 520 cm−1, related to microcrystalline silicon. Finally, PL experiments showed the presence of visible luminescence for the as-deposited samples in the region between 1.5 and 2 eV, attributed to defects (at higher energies) and to the presence of small variable size amorphous silicon clusters embedded in the dielectric matrix. High temperature annealing substantially decreases the PL intensity, result attributed to increased cluster size and crystallization.

In this work we study the structural properties and mechanical stress of silicon oxynitride (SiO x N y ) films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures (320 °C) and report the feasibility of using this material for the fabrication of large area self-sustained grids. The films were obtained at different deposition conditions, varying the gas flow ratio between the precursor gases (N 2 O and SiH 4 ) and maintaining all the other deposition parameters constant. The films were characterized by ellipsometry, by Fourier transform infrared (FT-IR) spectroscopy and by optically levered laser technique to measure the total mechanical stress. The results demonstrate that for appropriated deposition conditions, it is possible to obtain SiO x N y with very low mechanical stress, a necessary condition for the fabrication of mechanically stable thick films (up to ∼10 μm). Since this material (SiO x N y ) is very resistant to KOH wet chemical etching it can be utilized to fabricate, by silicon substrate bulk micromachining, very large self-sustained grids and membranes, with areas up to ∼1 cm 2 and with thickness in the 2–6 μm range. These results allied with the compatibility of the PECVD SiO x N y films deposition with the standard silicon based microelectronic processing technology makes this material promising for micro electro mechanical system (MEMS) fabrication.

This work reports on the local structure and bonds of amorphous silicon oxynitride thin films, deposited by plasma enhanced chemical vapor deposition. The dependence of the structural properties and chemical bonds with the film's composition was investigated. The used analytical techniques were X-ray absorption at the Si K-edge and Fourier transform infrared spectroscopies. The coordination numbers, interatomic distances and Debye–Waller disorder factors of the Si first shell and, the bond types and the concentration of hydrogen in the films were obtained. All the analyzed data support the formation of a material's homogeneous network with a random distribution of SiO and SiN bonds. The basic structural element of the network is a tetrahedron with a central Si atom connected to N and O, consistent with a random bonding model. As the nitrogen content in the solid phase decreases the SiON 3 , SiO 2 N 2 tetrahedral units gradually change to SiO 4 , keeping the quantity of SiO 3 N tetrahedrons almost unchanged, approximately 40%. The amount of SiO 4 units is 100% for films with high oxygen content. The nitrogen is preferentially bonded to silicon and hydrogen, while the hydrogen is mostly bonded to nitrogen.

GaN and AlN have attracted a great attention in the photonics researches. The large band gaps of these materials turn them suitable for nanophotonic devices that operate in light ranges from visible to deep ultraviolet. The photonic band gap maps obtained from plane wave calculations of common structures in wurtzite GaN and also in AlN were presented and analyzed. A complete photonic band gap with flat bands in the M - K direction was observed in the triangular lattice of air holes in dielectric medium.

The antiresonant reflecting optical waveguide (ARROW) with hollow core and liquid core are one of the most promising technologies in Lab-on-a-Chips and optofluidic research. Motivated by this, in this paper we present the design, simulation and fabrication processes of hollow core ARROW built in Corning glass substrates and utilizing Si 3 N 4 /SiO 2 PECVD antiresonant reflecting multilayer films on the channel wall. Details about the TMM/FDM methodology developed for the simple and fast design of ARROW waveguides built with multilayer dielectric thin films deposited over rounded microchannels in glass substrates are exhibited. The preliminary results confirm the light confinement in the hollow core region of the fabricated waveguide structure but further experiment are needed to fully characterize the devices.

We report, for the first time to our knowledge, experimental results on pedestal waveguides produced with Yb 3+ /Er 3+ codoped Bi 2 O 3 –WO 3 –TeO 2 thin films deposited by RF Sputtering for photonic applications. Thin films were deposited using Ar/O 2 plasma at 5 mTorr pressure and RF power of 40 W on substrates of silicon wafers. The definition of the pedestal waveguide structure was made using conventional optical lithography followed by plasma etching. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm, respectively, for waveguides in the 20–100 μm width range. Single-mode propagation was measured for waveguides width up to 10 μm and 12 μm, at 633 nm and 1050 nm, respectively; for larger waveguides widths multi-mode propagation was obtained. Internal gain of 5.6 dB at 1530 nm, under 980 nm excitation, was measured for 1.5 cm waveguide length (∼3.7 dB/cm). The present results show the possibility of using Yb 3+ /Er 3+ codoped Bi 2 O 3 –WO 3 –TeO 2 pedestal waveguide for optical amplifiers.

We present the production and characterization of pedestal type optical waveguides with TeO 2 –WO 3 –Bi 2 O 3 thin films to be used as core layer for applications in optical devices such as the Mach–Zehnder Interferometer (MZI). The optical waveguides and MZI structure were fabricated from pedestal type obtained using conventional optical lithography procedures, followed by plasma etching and Magnetron Sputtering deposition. Optical measurements were performed to characterize the waveguides and MZI. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm respectively. Single-mode propagation at 633 nm wavelength was observed for waveguide width up to 5 μm; larger waveguide width provided multi-mode propagation. Also, preliminary characterizations of the pedestal MZI structure presented multi-mode propagation for waveguide width of 30 μm.

Silicon oxynitride films (SiOxNy) are of great importance for opto-electronic applications and are promising for the development of microelectromechanical systems (MEMS). This work presents a theoretical model to determine the modulus of elasticity, the thermal expansion coefficient, and the thermal conductivity of rf-plasma enhanced CVD SiOxNy films using suspended micromachined beams. The model predicts the occurrence of well-defined deformations (buckling) of a fixed-end microbeam when this microbeam is subjected to controlled thermal compression forces. The mechanical and thermophysical properties are obtained through the measurement of the beam deflection. The results show that microbeams with a 20 μm width and a 1000 μm length readily exhibit observable buckling when electrical voltages in the range of 0.1–0.3 V are applied to the resistor. This confirms the feasibility of fabricating SiOxNy microbeams and the use of these microstructures for its mechanical and thermophysical characterization.

In this work we present the results on the fabrication of thick silicon oxynitride and dioxide films deposited by conventional r.f. direct plasma enhanced chemical vapor deposition (DPECVD), at temperature as low as 320°C and from (N2O+SiH4) gaseous mixtures. The samples were characterized by profile measurements, ellipsometry measurements, etching rate, Fourier transform infrared spectroscopy (FTIR), and by scanning electron microscopy (SEM). The results show that for appropriate N2O/SiH4 flow ratio and SiH4 flow, it is possible to obtain very thick SiO2 and SiOxNy films (up to ∼10 μm) at high deposition rates (∼3 μm/h) and preserving the compositional and structural properties of similar high quality thin films obtained in a previous work (I. Pereyra, M.I. Alayo, J. Non-Cryst. Solids 212 (1997) 225). These thick SiO2 and SiOxNy films, exhibit a very well controlled refractive index, in a short range between ∼1.43 and ∼1.53, which is very attractive to SiO2/SiOxNy based waveguide fabrication. Besides the large thickness, the results show that the films present an etching rate just twice the thermally grown SiO2 rate, therefore lower than the reported values for PECVD SiO2 by other authors (M.S. Haque, H.A. Naseem, W.D. Brown, J. Electrochem. Soc. 142 (1995) 3864). Also etching experiments were performed using reactive ion etching (RIE) equipment on thick silicon oxynitride film grown onto silicon substrates covered by a thick DPECVD SiO2 buffer layer, in order to simulate a waveguide structure (ridge type) fabrication. The results of these tests show that it is possible to define vertical walls in these thick SiOxNy films, which is very important for ridge type waveguides.

In this work we present the results on silicon dioxide films grown by the direct plasma enhanced chemical vapor deposition (DPECVD) technique at low temperature (

We present the production and characterization of TeO2-WO3-Bi2O3 thin films to be used as core layer in the fabrication of optical sensors based on Mach-Zehnder Interferometer (MZI) that has applications as pressure sensors, temperature sensors, chemical and biological sensors. The waveguides were fabricated from pedestal type obtained using conventional optical lithography procedures, followed by plasma etching and Sputtering deposition. Propagation losses around 2.0 dB/cm and 2.5 dB/cm were obtained at 633 and 1050 nm, respectively. Measurements were also performed to characterize the guide modes. Single-mode propagation at 630 and 1050 nm was observed for waveguides width up to 10 μm; larger waveguides width provided multi-mode propagation.