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This study reports a SiN x channel optical waveguide on a SiO2-covered bulk Si platform. The waveguide shows a low propagation loss of ∼0.6 dB/cm at 1550 and 1310 nm wavelengths. The SiN x film is deposited by reactive sputtering and is free from N–H species, which cause optical absorption loss at ∼1520 nm. No post-deposition high-temperature annealing is required as an increase in sputtering temperature, from room temperature to a moderate temperature of 200 °C, is effective for low-loss propagation. Based on chemical and optical analyses, the quality of the sputtered film at 200 °C is comparable to that prepared by low-pressure chemical vapor deposition at a high temperature of 820 °C. Fabricated fundamental passive optical devices (a multi-mode interferometer splitter and a directional coupler) reveal reasonable device function. A ring resonator shows a thermally stable operation because of the small thermo-optic coefficient for the SiN x , on the order of 10−5 K−1. The results indicate that the SiN x film by reactive sputtering at 200 °C can be favorably applied for photonic integration concerning CMOS back-end processing and hybrid-integration processing with non-CMOS materials. A Si-on-insulator wafer is not necessarily used as the platform, but a low-cost bulk Si wafer is replaced depending on the application. The reduction in the SiO2 under-cladding thickness, as thin as 1.0 µm, is examined regarding the potential in multilayered interconnects.

In this study, influence of magnetron sputtering on indium gallium zinc oxide (IGZO) ceramic target was studied to improve its performance and utilization. Results indicated that state of the target such as target grain uniformity, micro defects, C element pollution, and secondary phase showed significant influence on magnetron sputtering process. Atoms located in small grains were easily bombarded out of IGZO target, and grains with slow sputtering rate protruded from target surface. Porous microstructure of IGZO ceramic created abnormal electric field of the target during sputtering, resulting in the poisoning of target. Moreover, more indium atoms were sputtered from the target, and the proportion of In after sputtering decreased by 0.62–0.97%. The difference in sputtering rates between secondary phase and main phase led to the formation of IGZO cladding layer with poor conductivity under the combined action of sputtering and re-sputtering. In sum, these findings may provide strong guidance for further improvement and performance enhancement of IGZO sputtering target.

Ta-doped Bi3.25La0.75Ti3O12(BLTT)/ZnO films were fabricated on Pt(111)/Ti/SiO2/Si substrates by a magnetron sputtering method. Firstly, ZnO crystal thin films were grown on the substrates by a reactive sputtering method. Then, BLTT thin films were deposited on the ZnO layers at room temperature and post-annealed at 600 °C. The micromorphology, ferroelectric and dielectric properties of BLTT/ZnO films were analyzed. The XRD analysis shows that ZnO buffer layer significantly reduces the crystallization temperature of BLTT thin film. The TEM results show that lamellar BLTT grains are grown on ZnO layer at a certain angle with few elements diffusion at the interface of ZnO phase and Bi4Ti3O12 phase. The ferroelectric properties indicate that BLTT/ZnO films exhibit different remanent polarization and coercive fields under electric field with different directions. The novel mechanism of tailoring ferroelectric properties may open new possibilities for designing special ferroelectric devices.

SiCN ceramics show large potential in high temperature pressure sensors with excellent stability up to 1000 °C, as it is changeling for the most of the existing pressure sensors to work stably at a temperature above 600 °C. However, bulk SiCN ceramics are not compatible to microelectronic processing and exhibit slow response due to viscoelasticity, it is necessary to propose alternative method to prepare SiCN functional structures. In this work, SiCN piezoresistive thin films are prepared by magnetron sputtering, and the influence of sputtering power on their piezoresistive properties and interfacial strengths are studied. The gauge factors of SiCN films range from 2786 to 4714 at various sputtering powers, which are significantly higher than the range from 46 to 1105 for existing piezoresistive thin films. Upon an optimal sputtering power of 75 W for silicon nitride target, the obtained SiCN sample show the largest gauge factors in a large range from 0.5 to 3.4 MPa. Furthermore, the SiCN thin films present high critical loads up to 36.5 N in scratch tests and indicate strong interfacial adhesion with substrate. This work provides an important reference for developing SiCN-based MEMS pressure sensors.

The production of O2 at TiO2 surface during the photoelectrochemical water splitting is the bottleneck of the reaction process indicating the need for surface engineering of TiO2. Here, 1-D TiO2 was coated with the defect tuned SnO2 nanolayer (via sputtering) for enhanced solar water splitting activity. The sputtering strategy allows oxygen vacancy tuning of SnO2 with complete coverage on TiO2. Importantly, the optimized SnO2/TiO2 system exhibited the record photocurrent of 1.85 mA cm−2 at 1.23 V vs. RHE, incident photon to current efficiency of 95% at 350 nm, and H2 and O2 production with ∼90% of faradaic efficiency. Band structure analysis indicated a decrease in work function along with an upward shift of Fermi level and conduction band at the electrolyte interface after SnO2 coating. The present study demonstrates the utilization of oxygen vacancy in SnO2 for the surface engineered electrodes for facile O2 production during solar water splitting.

Ag has been incorporated into the CZTS film through post-doping by magnetron sputtering to decrease the CuZn anti-site defect. Efforts have been dedicated to optimize the Ag sputtering time and 60 s will be the best as surveyed from the SEM, XRD and Raman spectra. Then the broad-band self-driven heterostructure photodetector has been manufactured by combining the CZTS and inverted pyramid n-Si (IP n-Si). The device represents the first-rank property under the irradiation of 5 mW, 780 nm LED with 0 V bias with the responsivity and detectivity of 7.2 mA/W and 4.98 × 1010 Jones respectively. The device can persist excellent linearity when enduring a 40 mW-80 mW, 980 nm NIR laser with 0 V bias. The comprehensive performance becomes the best under the irradiation of a 50 mW laser. The responsivity and detectivity are 1.22 mA/W and 1.98 × 1010 Jones. The device can also work stably as the laser changes from 1 Hz to 15 kHz. The rise time and decay time are 93.3 μs and 141.0 μs respectively. These results open up an innovative application for CZTS to build a broad-band self-driven photodetector as a window-layer.

We describe the design of a new ion source that combines a hot filament hollow cathode source with a sputtering source. This combination makes it possible to provide ion beams of a wider range that previously could not be used due to respective high melting points and low vapor pressure of the needed elements. We demonstrate the sources viability for molybdenum, cobalt, niobium and the rare-earth element gadolinium. An implantation current of 20–900 nA on the sample, depending on the element, could be achieved. Moreover, we experimentally prove that these ion beams are suitable for ultra-low energy implantation into 2D materials like graphene and transition metal dichalcogenides (TMDs). Furthermore, computational studies were conducted to investigate the ion trajectories within the source and ion implantation into 2D materials. RBS and PIXE measurements were performed to quantitative investigate the implanted samples.

In environment air quality monitoring, toxic and flammable gas detection plays an important role. Due to the extreme concern for safety standards in industrial and residential applications, real-time observation of toxic gas and notification of inadvertent leaks is necessary. This paper delves into a simple and cost-effective way for fabricating extremely sensitive zinc oxide (ZnO) thin film gas sensors for the detection of Liquefied Petroleum Gas (LPG) at low concentrations. Sol-gel method is used to fabricate the ZnO thin films. Platinum (Pt) nanoparticles have been placed on the semiconducting material to behave as catalysts in order to enhance sensing performance. The platinum doping is done via the RF Sputtering technique. For different concentration of LPG, the variation in electrical resistance of a semiconductor material was evaluated. Sensor characterization was carried out using XRD, and FESEM. ZnO thin films are optimized at different thickness varying from 70 nm to 550 nm. Then annealing of thin films of ZnO is carried out at temperatures range from 450 °C to 675 °C. LPG shows a maximum response for thin film of 170 nm annealed at 625 °C, at operating temperature of 150 °C, for 1000 ppm concentration. Sensing response for ZnO thin film has been enhanced to 2.586 post doping which was 1.896 for annealed bare ZnO thin film. Comparing to bare ZnO thin films, there had been a significant improvement in sensor response with platinum doped ZnO thin films.

Sputter grown copper (Cu) and titanium dioxide (TiO2) based transparent solar heat rejecting film has been developed on glass substrates at room temperature for energy saving smart window applications. The performance of as-deposited ultra-thin TiO2/Cu/TiO2 multilayers was elucidated, wherein the visible transmittance of the multilayer significantly depends on the crystal quality of TiO2 layers. In-situ nanocrystal engineering of TiO2 films with optimized sputtering power improves crystallinity of nano-TiO2 domains. The transparent heat regulation (THR) coating with an average transmittance of ∼70% over the visible spectral regime and infra-red reflectance of ∼60% at 1200 nm was developed at room temperature. Optical characterization, X-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) have been utilized to analyze the crystallinity of TiO2 and quality of the multilayered structure. TiO2/Cu/TiO2 based prototype device has been demonstrated for the energy saving smart windows application.

This work describes the development of an acoustic sensor based on piezoelectric ZnO thin film to be utilized for aero-acoustic measurements. The design of the device was carried out through CAD tool Coventorware. The backside of the device consists of the microtunnel and diaphragm structures. The Si-diaphragm thickness of the device was optimized for high sound pressure level (SPL) (upto 180 dB) using Coventorware. A microtunnel connects the cavity, created after diaphragm formation to the outside environment. The designed device has been fabricated using standard Si-fabrication technology. Microtunnel and diaphragm structures have been fabricated in a single step using wet etching technique which results in reduced cost as well as fewer number of process steps and increased yield of the device. The front side consists of a piezoelectric sensing layer of ZnO sandwiched between two sputter deposited electrode layers of Au covered with PECVD oxide on a thermally oxidized Si-diaphragm. The low cut-off frequency, bandwidth, resonance frequency and flat band sensitivity of the device have been found to be 35.2 Hz, 15 kHz, 78 kHz and 136.5 μV/Pa respectively. The fabricated device can be used for the SPL measurement in aircrafts, aerospace and similar applications.

Atomic layer deposition (ALD) has been studied extensively to employ oxide semiconductor thin film transistor (TFT) including both active layer and gate insulator (GI). Herein, we developed an ALD sandwich structure, which deposits both semiconductor and GI by ALD. In contrast to the previous results using sputter In-Ga-Zn-O (IGZO), ALD sandwich structure IGZO TFT exhibited severe deterioration in its electrical performance when the Al₂O₃ was adopted for both buffer layer and GI application. Through measurement of hydrogen permeability of ALD insulators and secondary ion mass spectroscopy of each sandwich structure after annealing, we found a hydrogen accumulation effect between Al₂O₃ and ALD IGZO interface layer, which caused deterioration of electrical performance. In contrast, TFTs with ALD SiO₂, which has proper hydrogen diffusivity, chosen as the buffer and GI had favorable electric properties of 28.17 cm²/V·s, 0.20 V/dec, 0.96, and 0.12 V for the mobility, $V_{th}$ , subthreshold swing (SS), and hysteresis. In this regard, an optimized GI structure via the ALD SiO₂ and Al₂O₃ in situ process based on excellent interface formation with the semiconductor and hydrogen barrier performance, respectively, was developed. This functional GI structure consisting of SiO₂ and Al₂O₃ exhibited excellent TFT characteristics (27.52 cm²/V·s, 0.24 V/dec, and 1.07 V for the mobility, SS, and $V_{th}$ , respectively) with improved stability even after hydrogen annealing, which was used to examine the resistance to external hydrogen, showing a threshold voltage shift of -0.15 V and a SS shift of 0.01 V/dec.

In this work, vertical micromirrors that are fabricated using deep etching of silicon followed by metal sputtering are studied. Physical parameter extraction methodology, image processing, machine learning and discrete element analysis are used to extend the easy-to-take scanning electron microscope images into 3-D topographical information, that are usually obtained using atomic force microscope and transmission electron microscope. The experimental results show that vertical micromirrors surface quality has a granular nature showing degraded performance and a different optical response with respect to the bulk metal. A physical model is developed and validated by comparing the measured reflectivity of the fabricated micromirrors with a multi-layer reflectivity optical model based on the effective medium theory fed by the extracted physical parameters. In agreement with the experimental results, the model predicts a reflectivity of about 60 % for a sputtered aluminum thickness of 50 nm, compared to 97.5% reflectivity predicted by the bulk metal model. [2021-0154]

Indium tin oxide (ITO) films were grown by radio frequency (RF) sputtering on plain and textured glass substrates that are kept at room temperature. Periodical texturing on the substrate surface wa...

The semiconductor material of ternary alloy of Indium and Aluminum nitride (InxAl1-xN) has interesting properties for potential optoelectronic applications and solar cells as well. In the present research, layers of In0.63Al0.37 N were synthesized using the DC reactive sputtering magnetron technique, on p-type silicon substrates (100), ITO/PET, and ITO/Glass. The reason why an intermediate layer of ITO was placed on the PET and Glass substrates is that possibly in an InAlN thin-layer solar cell, the ITO would fulfill the role of Conductive Transparent Oxide (CTO). This CTO would be located between the window layer and the transparent substrate. On the other hand, in the case of a hetero-union solar cell, InAlN-n would be located on the Si-p material, in order to form the p–n junction. Therefore, the present work allowed us to study subsystems in which the InAlN would be part of the window layer in three different types of solar cells.

X-ray photoelectron spectroscopy (XPS) confirmed that RF magnetron sputtering of h-BN onto unheated substrates produced a-BOxNy films under all of the sputtering conditions studied. The surface roughness improved and pinholes were eliminated as the deposition pressure increased. Analysis of the current density dependence on the electric field of the a-BOxNy films suggests field-enhanced Schottky emission and/or Frenkel-Poole emission transport mechanisms. The highest breakdown strength obtained was 8 MV cm−1. A bandgap of 3.9 eV was confirmed by spectroscopic ellipsometry and UV–Vis spectroscopy. An interface trap concentration (Nit) of 7.3 × 1010 cm−2 and interface state density (Nss) of 7.5 × 1012 eV−1 cm−2 were measured for transparent ITO/a-BOxNy/ZnO metal–insulator-semiconductor (MIS) structures. Approximately, 2 V was required to switch the a-BOxNy/ZnO interface from accumulation to inversion.

In this work, ZnO films are deposited by magnetron sputtering [using direct current (DC)], on polished silicon substrate Si(100) (non-etched), etched for 1 min, 5 min, 10 min and 15 min. The effect of etched silicon substrate on structural, morphological, and optical properties of ZnO films has been investigated. A new nanostructure can be obtained by mean of modification in morphology of substrate. The etching of the substrate was effectuated by means of dry plasma at different time and they compared with non-etched substrates. AFM and SEM images have been used to investigate the morphology behaviors of ZnO films growth on etched and non-etched silicon substrates. Optical properties were studied in details, photoluminescence (PL) showed that the intensity of ZnO films have been increased by increasing the substrate etching time from 0 to 15 min, which were associated with the crystallographic properties [for (002) orientation] using X-ray diffraction (XRD). That may be related to the decrease of grain size and roughness morphology increasing with the etching time. FTIR and MicroRaman spectra of films show vibrational modes characteristic of ZnO materials and they were related with morphology and structural of the films. In addition, the variation of ethylene glycol contact angle data (ECA) related to roughness of the ZnO films deposited on etched Si substrate at different times were studied. The ZnO films on etched substrate were interesting in optoelectronic purpose as well as for gas sensor in future work of our team.

The results of ellipsometric, x-ray, and spectral studies of In2O3 films deposited by dc-magnetron sputtering on Al2O3 (012) substrates are presented. The experimental data are interpreted in terms of a three-layer model of the fi lm. It is assumed that large particles of the material are formed on the surface of the substrate at the beginning of the deposition process. The size of the crystallites then decreases, and they fill the gaps between the larger particles, after which the film formation goes into the stationary mode. It was shown that there is a transition layer with a band gap of 1.39 eV, a refractive index of ~3, and thickness of 25 nm at the interface between the film and the substrate. The properties of this layer do not depend on the deposition time.

The doping of two-dimensional materials provides them with tunable physical properties and broadens their application. In this study, the doping of tungsten disulfide with metallic Sn atoms via a co-sputtering technique was demonstrated. In particular, WS2 was deposited by radio frequency (RF) magnetron sputtering, while Sn atoms deposited by DC sputtering become substitutional dopants. It was revealed that the metallic tungsten atom, and in some cases sulfur vacancies, in the WS2 atomic layer created by RF magnetron sputtering were partially filled/substituted by metallic Sn atoms. The Sn-doped WS2 layers exhibited n-type doping behavior with remarkable opto-electronic properties (bandgap 2.09 eV, mobility 7.84 cm2/V·s and resistivity 2.81 × 103 Ω-cm for 1 min Sn doping) suitable for photovoltaic applications. Overall, this technique facilitates better control of the dopant distribution than the traditional approach.

In this work, the mechanism of reliability of high resistance state (HRS) in AlOxNy-based resistive random access memory (RRAM) has been studied. The Ta/AlOxNy/Pt devices with high quality of the Schottky contact in the Ta/AlOxNy interface show excellent HRS reliability and low power consumption characteristics. We propose that the resistive switching (RS) process is caused by the migration of oxygen ions in the AlOxNy-based RRAM device, and the quality of the metal–semiconductor Schottky contact directly determines HRS reliability in AlOxNy-based RRAM.

SiCN thin film is one of the most attractive silicon-based materials due to its excellent electrical, mechanical and optical properties. In this study, SiCN thin films have been prepared by the radio frequency reactive magnetron sputtering method under different sputtering power, pressure, and substrate temperature. The microstructure, morphology, and the optical and field emission properties of SiCN thin films were performed. The results indicated that the high-quality SiCN thin films have been successfully prepared and it is proved that these properties can be tailored by the preparation conditions. A main near ultraviolet light emission line at around 370 nm in SiCN thin films makes it suitable for the development of optoelectronic devices. This study can provide novel guidance for the controlled preparation of high-quality SiCN thin films by magnetron sputtering.

While single target sputter deposition appears very attractive to prepare kesterite Cu2ZnSnS4 (CZTS) thin films for photovoltaic applications, the growth of secondary phases arising as a consequence of stoichiometric deviation stemming from variation in sputter yield of elements must be prevented. Here, we demonstrate growth of phase pure kesterite CZTS thin films by RF magnetron sputtering of a single target by intuitively manipulating the target composition and post-sulfurization process carried out in a quasi-open environment using sulfur flakes. The influencing mechanism of post-sulfurization process was elucidated from systematic variation in the dwell time, temperature and the sulfur amount. A high temperature or a shorter dwell time yielded a small-grained microstructure associated with the presence of secondary phases. Phase pure CZTS films with better microstructural features were obtained for sulfurization at 500 °C for 60 min with 1.0 g of sulfur flakes. This film exhibited an optical bandgap of ∼1.58 eV indicating its photovoltaic potential. A device in the Mo/CZTS/Ag configuration showed typical features of a Schottky junction. The obtained current–voltage characteristic was analyzed to estimate saturation current, ideality factor and series resistance in correlation with the properties of the CZTS film.

Surface acoustic wave (SAW) can be used as passive wireless sensors in high temperature environments. For such applications, protective layers are crucial and important for the SAW sensors. In this paper, ultra-thin Al2O3 layers prepared by atomic layer deposition (ALD) and RF magnetron sputtering were used to protect SAW devices with platinum (Pt) electrodes and their temperature stability was studied systematically. The devices were thermally treated up to 1150 °C in air, the real-time resistance of Pt resistive tracks with a sputtering Al2O3 protective layer showed much better and improved thermal stability than those without or with an ALD Al2O3 protective layer. Microstructure characterizations showed that the superior temperature stability is attributed to its mixture of amorphous and nano-crystalline nature of the Al2O3 layer deposited by sputtering and full recrystallization at high temperatures. SAW devices with a sputtering Al2O3 protective layer after 1150 °C treatment maintained almost unchanged properties, while those with an ALD Al2O3 protective layer failed to work. Investigation also indicated there exists an optimal thickness for the sputtering Al2O3 layer to achieve best performance and thermal-stability for the SAW devices. Besides, the deposition rate of Al2O3 layer by sputtering is 10 times faster than that by ALD. All the results demonstrate that the sputtering Al2O3 protective layer is more suitable for high temperature SAW device applications owing to its lower cost, higher deposition rate and temperature stability.

High operating temperature and low response restrict the application of H2S sensors. Due to the strong chemical affinity of CuO to H2S and the large band gap and high stability of β-In2S3, CuO nanotube/In2S3 nanosheet p/n heterostructures have been delicately designed for binder-free gas sensors by a facile method consisting of sputtering, chemical etching, and annealing. A switching effect of H2S concentration on the response of CuO/In2S3 gas sensors has been observed. When exposed to low-concentration H2S (1-10 ppm), the response is less than 0.10 and dominated by the surface-type adsorption-desorption process between CuO and H2S. When exposed to high-concentration H2S, the sensor exhibits a superior response of 3511 toward 50 ppm H2S, considerable selectivity, and long-term stability at room temperature. This dramatically enhanced response can be explained by the transformed junction from the CuO/In2S3 heterojunction to the CuS/In2S3 Schottky junction. These results suggest that the binder-free ceramic tube-type CuO/In2S3 gas sensor with considerable performance will have promising potential for H2S gas detection. Moreover, this method provides an effective strategy to fabricate other binder-free gas sensors.

The present work addresses the changing microstructure, bulk optoelectronic, and surface electrical properties of sputter deposited Cu(In,Ga)Se2 (CIGS) films on the soda lime glass (SLG) substrates as a function of altered film thickness. To this end, these films were deposited by varying the deposition time from 180 to 540 min in radio frequency (RF) magnetron sputtering and by using a low substrate temperature of 523 K. A range of experimental techniques were then used to investigate the microstructure, bulk optoelectronic, and surface electrical properties of these films. All these films are found to grow in single phase, chalcopyrite crystal structure, and with dominant (112) orientation, though the overall composition of these films is found to slightly alter. Moreover, a semimetallic to semiconductor transition in the thickening CIGS film is seen, which is then correlated with their hole concentration. Based on these observations and the positions of the Fermi energy, a possible theory regarding the presence of the types, quantities, and positions of the electronic defect states and their variations by thickening the CIGS film is discussed. Both the transport and optical band gaps (Eg) are found to follow the same trend, which could also be related with the compositional variation in these films. Moreover, CIGS film deposited for 540 min is found to yield a film thickness of about 2.85 μm, with hole concentration of 2.17 × 1017 cm−3 and optical band gap of 1.16 eV; optoelectronic properties appropriate for an absorber layer in photovoltaic application.

The future of the industry development depends greatly on the permanently ensured energy needs and can be achieved only through the use of a variety of sustainable energy sources where the solar energy, which gains its optimal exploitation directly by linking it to the properties of solar cells and in particular to the crystallographic quality of the used semiconductor substrates, is one of them. Many growth processes are used to obtain a high quality of semiconductor formation and deposition, among them the DC sputtering. In this work, based on the Monte-Carlo method, a 3D DC sputtering simulation of the CZTS {\mathrm{CZTS}} , Si {\mathrm{Si}} and CIGS {\mathrm{CIGS}} semiconductors thin film formation is proposed by considering Argon as vacuum chamber bombardment gas. We extrapolate firstly the best sputtering yield possible of the semiconductors CZTS {\mathrm{CZTS}} and Silicon represented by their chemical formulas Cu 2 ⁢ ZnSnS 4 {\mathrm{Cu}_{2}\mathrm{Zn}\mathrm{Sn}\mathrm{S}_{4}} and Si {\mathrm{Si}} , respectively, by the application of different energies and incidence angles. From the obtained results, firstly we deduce that the best sputtering angle is 85 ∘ {85^{\circ}} ; in the same time, CZTS {\mathrm{CZTS}} is more efficient comparing to the Si {\mathrm{Si}} . Secondly, with the application of this angle ( 85 ∘ {85^{\circ}} ) in the sputtering process for the CZTS {\mathrm{CZTS}} ( Cu 2 ⁢ ZnSnS 4 {\mathrm{Cu}_{2}\mathrm{Zn}\mathrm{Sn}\mathrm{S}_{4}} ) and CIGS {\mathrm{CIGS}} represented by its chemical formula CuIn x ⁢ Ga ( 1 - x ) ⁢ Se 2 {\mathrm{Cu}\mathrm{In}_{x}\mathrm{Ga}_{(1-x)}\mathrm{Se}_{2}} , and the variation of the bombardment energy in order to find the total ejected atoms from each element of these two materials, we deduce that the sulfide ( S 4 {\mathrm{S}_{4}} ) and selenide ( Se 2 {\mathrm{Se}_{2}} ) elements give the majority of the sputtering yield amount obtained.

Thick epitaxial BaTiO3 films ranging from 120 nm to 1 μm were grown by off-axis RF magnetron sputtering on SrTiO3-templated silicon-on-insulator (SOI) substrates for use in electro-optic applications, where such large thicknesses are necessary. The films are of high quality, rivaling those grown by molecular beam epitaxy (MBE) in crystalline quality, but can be grown 10 times faster. Extraction of lattice parameters from geometric phase analysis of atomic-resolution scanning transmission electron microscopy images revealed how the in-plane and out-of-plane lattice spacings of sputtered BaTiO3 changes as a function of layer position within a thick film. Our results indicate that compared to molecular beam epitaxy, sputtered films retain their out-of-plane polarization (c-axis) orientation for larger thicknesses. We also find an unusual re-transition from in-plane polarization (a-axis) to out-of-plane polarization (c-axis), along with an anomalous lattice expansion, near the surface. We also studied a method of achieving 100% a-axis-oriented films using a two-step process involving amorphous growth and recrystallization of a seed layer followed by normal high temperature growth. While this method is successful in achieving full a-axis orientation even at low thicknesses, the resulting film has a large number of voids and misoriented grains. Electro-optic measurement using a transmission setup of a sputtered BTO film grown using the optimized conditions yields an effective Pockels coefficient as high as 183 pm/V. A Mach–Zehnder modulator fabricated on such films exhibits phase shifting with an equivalent Pockels coefficient of 157 pm/V. These results demonstrate that sputtered BTO thick films can be used for integrated electro-optic modulators for Si photonics.

The ion-sensitive field-effect transistor (ISFET) is a popular technology utilized for pH sensing applications. In this work, we have presented the fabrication, characterization, and electrochemical modeling of an aluminum oxide (Al2O3)-gate ISFET-based pH sensor. The sensor is fabricated using well-established metal–oxide–semiconductor (MOS) unit processes with five steps of photolithography, and the sensing film is patterned using the lift-off process. The Al2O3 sensing film is deposited over the gate area using pulsed-DC magnetron-assisted reactive sputtering technique in order to improve the sensor performance. The material characterization of sensing film has been done using x-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray photoelectron spectroscopy techniques. The sensor has been packaged using thick-film technology and encapsulated by a dam-and-fill approach. The packaged device has been tested in various pH buffer solutions, and a sensitivity of nearly 42.1 mV/pH has been achieved. A simulation program with integrated circuit emphasis (SPICE) macromodel of the Al2O3-gate ISFET is empirically derived from the experimental results, and the extracted electrochemical parameters have been reported. The drift and hysteresis characteristics of the Al2O3-gate ISFET were also studied, and the obtained drift rates for different pH buffer solutions of 4, 7, and 10 are 0.136 μA/min, 0.124 μA/min, and 0.108 μA/min, respectively. A hysteresis of nearly 5.806 μA has been obtained. The developed sensor has high sensitivity along with low drift and hysteresis.

TiN films with different thicknesses (17.9–102.8 nm) were prepared using rf magnetron sputtering to study the effect thickness on the plasmonic, electrical, and optical properties. X-ray diffraction revealed the amorphous-like structure for thinner films with thicknesses lower than 50.3 nm, whereas polycrystalline of face-centered cubic TiN structure was observed for thicker films. Scanning electron microscopy observations revealed rounded nano-crystallites morphology for TiN films. The EDAX depicted oxygen in the TiN films which attributed to the residual oxygen inside the sputtering chamber and to the partial surface oxidation resulted from the exposure to atmospheric air. As the thickness increased from 17.9 to 102.8 nm, the carrier concentration increases from 1.47 × 1022 to 3.51 × 1022 cm−3 and the carrier mobility increased from 0.091 to 0.489 cm2/V.s, which resulted in a resistivity decrease from 4.65 × 10–3 to 3.64 × 10–4 Ω cm. Two absorption bands around 250 and 1000 nm were observed. The band around 1000 nm was ascribed to the localized surface plasmon resonance (LSPR) and increased with increasing the film thickness. The optical band gap and refractive index values decreased monotonically with increasing the film thickness. It is also inferred that the thickness has a strong influence on the values of real and imaginary parts of the dielectric function. Applying various figures of merit indicated that the prepared TiN films are probably not practical for LSPR device fabrication however they are probably suitable for practical transformation optics and superlens device applications.

We report a highly efficient quantum dot light emitting diode (QLEDs) with a radio frequency (RF) sputtered ZnO thin film as an electron transport layer (ETL) instead of the conventional ZnO nanoparticles (NPs) by solution process. ZnO NPs have been used as a key material to improve the performance of QLEDs, but the charge imbalance in ZnO NPs resulting from fast electron injection, and their limited uniformity are significant disadvantages. In this study, ZnO layers were deposited by RF sputtering with various O2 partial pressures. All of the ZnO films showed preferential growth along the (002) direction, smooth morphology, and good optical transmittance. To test their feasibility for QLEDs, we fabricated devices with RF sputtered ZnO layers as an ETL, which has the inverted structure of ITO/RF sputtered ZnO/QDs/CBP/MoO3/Al. The optical/electrical characteristics of two devices, comprised of RF sputtered ZnO and ZnO NPs, were compared with each other. QLEDs with the sputtered ZnO ETL achieved a current efficiency of 11.32 cd/A, which was higher than the 8.23 cd/A of the QLEDs with ZnO NPs ETL. Next, to find the optimum ZnO thin film for highly efficient QLEDs, deposition conditions with various O2 partial pressures were tested, and device performance was investigated. The maximum current efficiency was 13.33 cd/A when the ratio of Ar/O2 was 4:3. Additional oxygen gas reduced the O vacancies in the ZnO thin film, which resulted in a decrease in electrical conductivity, thereby improving charge balance in the emission layer of the QLEDs. As a result, we provide a way to control the ZnO ETL properties and to improve device performance by controlling O2 partial pressure.

Hybrid-type thin-film transistors were fabricated using amorphous oxide and colloidal quantum dots. To prevent damage to the quantum dots, amorphous SIZO, which can be processed at low temperatures, was deposited by RF sputtering. In the case of a general hybrid type device, it is known that the characteristics of a multilayer material are significantly lower than that of a single material, and this is greatly affected by the interface characteristics between each material. The electrical characteristics of a single SIZO TFT, such as threshold voltage, field-effect mobility, on/off current ratio, and subthreshold slope, have been observed as −0.15 V, 9.54 cm2/Vs, 2.9 × 108, and 0.34 V/dec, respectively while electrical characteristics of hybrid-type OQO TFT were observed as 1.39 V, 9.19 cm2/Vs, 3.9 × 108, and 0.35 V/dec, respectively. As a result, it was confirmed that the electrical characteristics did not change significantly when the single SIZO TFT and the hybrid type OQO TFT have been compared in this experiment. Its electrical properties are mainly driven by the upper and lower a-SIZO layers. a-SIZO which has amorphous properties, can provide excellent surface properties because it can completely cover the spherical QD when it comes into contact with the QD. These results are expected to be applicable to many important applications.

This letter presents a new strategy for the formation of continuous Cu seed layer in high aspect ratio (HAR) through-silicon-vias (TSVs) with large depth based on sequential sputtering and electroless plating. The deposited seed layer is continuous and dense even at the bottom of the TSVs, which is difficult to achieve by individual sputtering or electroless plating. Combined with the spin coating of polyimide (PI) liner, atomic layer deposition (ALD) of TiN barrier layer, and electroplating of Cu conductor, TSVs with diameter of $9~\mu \text{m}$ and depth of $141~\mu \text{m}$ are successfully fabricated, and the aspect ratio is 15.5. The TSVs are fully filled without cracks or voids, proving the good quality of seed layers. Electrical measurements show that the minimum capacitance of a single TSV is around 145 fF, and the leakage current is about 3.4 pA at 20 V, indicating good electrical properties of the fabricated TSVs and the feasibility of the proposed fabrication flow in deep HAR TSV applications.

Spectral control of light for efficient absorption and emission in the targeted wavelength region attracted considerable attention in recent years to attain high photothermal conversion efficiency. In this connection, a highly selective tandem absorber with wide-angular absorptance has been developed in the configuration of low emissive metallic layer by sputtering, absorber and anti-reflective layers by simple wet-chemical methods. The developed tandem absorber has a highly reflective Molybdenum (Mo) layer over on the glass substrate with emittance (e) of 0.04 and tri-transition metal precursors-based absorber on Mo layer to improve the solar absorptance. The coatings are annealed in a vacuum environment and the resultant nanocomposite absorber coating enhanced the solar absorptance from 0.36 to 0.90. The SiO2 nanoparticles-based anti-reflective layer over on nanocomposite absorber has been developed to enhance the optical properties and the final configured tandem absorber exhibited absorptance of 0.96, the emittance of 0.12 and selectivity of 8. The tandem absorber has also exhibited a good wide-angular absorptance with a net improvement of 3.7–10.8% from an angle of incidence 10–70° respectively. Hence, the developed tandem absorber may aid in achieving high photothermal conversion efficiency for solar thermal applications.

In this work, ferroelectric properties with a coercive field of 1.6 MV/cm and a remanent polarization of 17.9 μC/cm2 were achieved in Y-doped HfO2 thin films prepared by ion beam assisted RF magnetron sputtering without any heating and annealing. Systematic grazing incidence X-ray diffraction and polarization hysteresis measurements revealed that the structural and electrical properties of the films were strongly dependent on the applied ion beam energy. A model of phase transition kinetics during deposition was introduced to explain the variations in the crystal structure and electric properties with various ion beam energies. It was found that the bombardment of the Ar ion beam provided extra energy to the sputtering particles, therefore conducive to the increased atomic diffusion and overcoming the potential barriers of the phase transition. The current processing method provides great potential for ferroelectric device applications that cannot be addressed with heating and annealing.

In recent years, Cu2ZnSnS4 (CZTS) semiconductor materials have received intensive attention in the field of thin-film solar cells owing to its non-toxic and low-cost elements. In this work, double-pressure sputtering technology is applied to obtain highly efficient and ultra-thin (~450 nm) pure Cu2ZnSnS4 (CZTS) solar cell. Using mixed materials with sulfides and copper powder as a quaternary target via spark plasma sintering (SPS) method and adopting double-layer sputtering (high + low pressure), a highly adhesive and large-grained CZTS thin film is achieved. As a result, the damage to the surface of Mo contact is decreased so that the reflectivity of incident light can be improved. Moreover, the composition of CZTS film was more uniform and the secondary phase separation at the Mo interface was reduced. Therefore, the interface defect state and deep level defect density in corresponding device with double-pressure is reduced and the ratio of depletion thickness to absorption layer thickness can reached to 0.58, which promoted the collection of photogenerated carriers. Finally, an efficiency of 9.3% for ultra-thin (~450 nm) CZTS film solar cell is obtained.

Plasma cleaning of extreme ultra-violet (EUV) optics for the semiconductor industry requires atomic-level precision. Low-energy ions and neutrals can be highly beneficial for this purpose. However, ion energies in many industrial capacitively or inductively coupled plasmas may be too high for atomic precision processing so that ions can cause sputtering and re-deposition of materials and produce vacuum system contamination. We discuss two sources that create low-energy ions: a capacitively coupled (CCP) plasma source operating at several tens of MHz and an electron beam gas ionization source. The goal here is to minimize the contamination by limiting the ion impact energy to a few tens of electron-volts. Ion energy and flux measurements on a grounded surface are characterized with a compact retarding field ion spectrometer. Plasma-induced contamination is quantified using X-ray photo-electron spectroscopy (XPS). Low ion energy plasma sources introducing little surface contamination may be interesting for cleaning and accelerated testing in EUV lithography (EUVL)-related research and for cleaning of front-end optical mirrors in fusion reactor diagnostics.

The development of niobium oxide (Nb2O5) thin films is an important work as a result of wide applications of this oxide in the field of material science and thin-film applications. In this study, thin-film microstructures of aluminum (Al)-doped Nb2O5 were prepared by DC plasma sputtering on glasses substrate. The ratio of doping was (0.5, 1, and 1.5) wt. % Al. The obtained samples were thermally treated at 450 °C. Characterized and analyzed the physical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and UV-Visible spectroscopy for optical properties investigation. Results showed that the average crystalline size of Nb2O5:0.5%Al film was found at 26.47 nm and the structure was a monoclinic phase for all samples. The distribution of grain size was found lower than 36.3 nm and uninformed particles on the surface. The analyzed optical properties showed the absorption decreased from 0.46 to 0.05 with increasing the wavelength and Low energy gap values decreased from 3.10 eV for Nb2O5 samples to 2.84 eV for 1.5%Al samples. In general, the doping by aluminum improved the physical properties of Nb2O5 films.

Reduced graphene oxide (rGO) is among only a few p-type transparent conductors. This article describes the use of pre-decoration of gold nanoparticles (AuNPs) to tune the optoelectronic properties of rGO film. High-purity Au is sputtered on GO film before the thermal reduction process at 825°C in a H2/CH4 environment. For the optimum 30 s Au sputtering, a high-temperature process transformed the Au nanoballs into nanowires. These conditions resulted in the maximum hole mobility of 158.99 cm2 V−1 s−1 and the minimum sheet resistance of 325.82 Ω□−1. The degree of reduction for the rGO-Au(30s) sample was the highest, since it had the lowest optical transmittance of 0.871 and the lowest bandgap of 3.75 eV. It thus represents the best p-type transparent conductor, with a figure of merit σdc/σop of approximately 8.11. The deconvoluted Raman fit elaborates more on the elimination of defect components on the rGO samples. The integrated area ratio for several defect peaks over a pristine peak was the lowest for the rGO-Au(30s), at 3.98. The AuNPs intervened in the reduction process by repairing the lattice defects for the in-plane carbon sp2, edge, amorphous phase, and out-of-plane sp2–sp3. This was responsible for the great improvement in the carrier transport mechanism and the value of σdc/σop.

Meeting the evolving demands of plasmonics research requires increasingly precise control over surface plasmon properties, which necessitates extremely fine nanopatterning, complex geometries, and/or long-range order. Nanoplasmonic metasurfaces are representative of a modern research area requiring intricate, high-fidelity features reproduced over areas of several free-space wavelengths, making them one of the most challenging fabrication problems in the field today. This work presents a systematic study of the helium focused ion beam milling of gold for nanoplasmonic metasurface applications, using as its example a nanoplasmonic metasurface based on an array of nanometer-scale plasmonic-wire-loaded subwavelength apertures in a gold film. At each step, the pattern variations are compared to simulation to predict the experimental outcome. Our results show that even in a practical fabrication environment, helium ion beam milling can be used to reliably pattern 10 nm features into gold with 1:5 aspect ratio in complex geometries over a wide area.

The author reported the AlGaZnO photodetector characteristics with various AGO:ZnO co-sputtering power ratio. It was found the optimized on/off ratio and responsivity were about $3.64 \times 10^{5}$ and 0.15 A/W, respectively, at the 10 V applied bias, and with AGO:ZnO power ratio of 80 W:50 W. The UV to visible rejection ratio was $8.08 \times 10^{3}$ , indicated the significant response under UV illumination. The on/off ratio and responsivity could further be improved to $4.2 \times 10^{6}$ and 0.44 A/W, respectively, by annealed at 300°C for an hour, to decrease the defect in the AGZO film. Besides, the photoresponse of the AGZO photodetectors also showed a repeatable and stable switching characteristic. These results indicate the performance of AGZO photodetector were good, and can be a good candidate for low cost, fast fabricated solar-blind application.

A thin-film deposition system was developed for the surface coating of X-ray mirrors of up to 1 m in length. With two coating process areas and four sputtering cathodes, various combinations employing a single layer, multilayered, and co-sputtered thin films are possible. Furthermore, it is possible to correct and modify the mirror surface shape by controlling the speed of the substrate stage. In this study, to evaluate the performance of the proposed coating system, the static coating distribution was measured to check the vertical direction. In a 10 mm area, a 0.9% peak-to-valley error and 0.2% root mean square error occurred. A differential deposition test was also performed for the horizontal direction (stage scan direction). In this study, arbitrary shapes were deposited on 100-mm and 400-mm-long mirrors. After removing the measurement error, the deposition error was less than 1 nm (peak-to-valley). The results demonstrate that this system can correct the surface of an X-ray mirror with ultra-high precision.

High-efficiency Cu(In,Ga)Se2 (CIGSe) thin-film solar cells are typically fabricated by a multistage coevaporation process. The Cu-rich composition achieved during the second stage is known to favor the grain growth of the polycrystalline CIGSe film and has a beneficial effect on the solar cell performance. In this article, we analyze the effect of copper stoichiometry on the grain size of sputtered CIGSe absorbers and the efficiency of respective solar cells. CIGSe absorber layers were deposited on Mo-coated soda-lime glass substrates by pulsed hybrid reactive magnetron sputtering from Cu-poor and Cu-rich Cu-In-Ga targets and simultaneous Se evaporation. CIGSe films sputtered with the Cu-rich target show larger grain size and lead to better solar cell performance. Furthermore, we also introduce a two-stage process, which further increases the solar cell performance, consisting of an initial CIGSe layer deposited from the Cu-rich target followed by an indium-selenide postdeposition step. This two-stage process effectively eliminates the unwanted Cu2- x Se impurity phase and renders the otherwise required and toxic KCN etching unnecessary.

In this paper, a new optical fiber corrosion sensor based on metallic bilayers is described. The detection region is located at a fiber end facet and we present simulations as well as experimental results in controlled lab conditions for Ti(10 nm)/Al(10 nm) and Ni(5 nm)/Al(5 nm) bilayers. We perform the characterization of the device by numerical simulations using the COMSOL Multiphysics software, and with an analytical model, which makes use of the Fresnel equations. According to the simulations, the change in the reflected optical signal over time is related to variations in the thickness of the metallic films by the corrosive process and, consequently, the corrosion rate in each metal of the bilayer can be obtained. Upon the simulation results, sensor devices were fabricated by depositing thin metallic films on the cleaved facet of the optical fiber using the sputtering method. We show that the use of a metallic bilayer as a transducer, instead of a monolayer, improves the sensor measuring interval (20 ± 1 nm) and provides information about the corrosion rate along the corrosion process.

To date, the deposition of AlGaN thin film using the co-sputtering technique at room temperature has not been reported yet. The use of AlGaN for electronic devices has been widely known because of its ultra-wide bandgap. However, to deposit the AlGaN thin film and achieved high quality of AlGaN films, higher temperature or extra time deposition are needed, which is not compatible with industrial fabrication process. Here, a co-sputtering technique between two power supplies of magnetron sputtering (which are RF and HiPIMS) is introduced to deposit the AlGaN thin films. The AlGaN thin films were deposited at various RF power to study their effect on structural properties and morphology of the thin films. AlGaN films were sputtered simultaneously on silicon (111) substrate for short time and at room temperature using GaN and Al target. Then, the films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and surface profiler to study their properties. XRD shows the GaN (101) and (013) plane for the AlGaN deposited at RF power of 30 W. Also there only GaN (101) for the AlGaN with 50 W RF power. Yet, the 70 W RF power shows the amorphous structure of AlGaN. The roughness and the grain size of AlGaN film from AFM analysis showed the trend of decreasing and increasing respectively. The roughness of the AlGaN films with 30 W power was 0.82 nm, 0.85 nm for 50 W, and 0.46 nm for 70 W RF power. The grain size of the AlGaN films was 30.06 nm, 32.10 nm, and 37.65 nm for RF power of 30 W, 50 W, and 70 W respectively. The profilometer found that the thickness of the AlGaN films was decreasing with increasing of RF power. This paper can demonstrate a successful co-sputtering technique of AlGaN. Despite AlGaN crystal structure was not able to found out in the XRD analysis, the effect of RF power has been studied to give significant effects on AlGaN thin film deposition.

Here, we report the fabrication of the p-n hetero-junction devices of p-Zn1-xSbxO/n-Si− grown by utilizing the radio-frequency sputtering technique. The fabricated devices were analyzed for morphological and structural modifications under atomic force microscopy (AFM) and X-Ray diffraction (XRD) techniques. The AFM studies reveal the growth of agglomerated nanoparticles like structures distributed throughout the surfaces of the deposited films, whereas, XRD studies reveal the significant change in crystallite size, lattice parameters, stress and strain with the incorporation of antimony (Sb) in ZnO matrix. The conduction behavior of charge carriers has been systematically analyzed in the fabricated hetero-junction devices. Current–Voltage (I–V) characteristics reveal a trap free space charge limiting current conduction in the fabricated devices. The room temperature mobility of charge carriers for the pristine ZnO, Zn0.97Sb0.03O and Zn0.95Sb0.05O thin film devices are found to be 8.06 × 10–2, 19.0 × 10–2 and 40.69 × 10–2 cm2/Vs, respectively.

In this study, we successfully deposit c-axis oriented aluminum nitride (AlN) piezoelectric films at low temperature (100 °C) via the DC sputtering method with tilt gun. The X-ray diffraction (XRD) observations prove that the deposited films have a c-axis preferred orientation. Effective d33 value of the proposed films is 5.92 pm/V, which is better than most of the reported data using DC sputtering or other processing methods. It is found that the gun placed at 25° helped the films to rearrange at low temperature and c-axis orientation AlN films were successfully grown at 100 °C. This temperature is much lower than the reported growing temperature. It means the piezoelectric films can be deposited at flexible substrate and the photoresist can be stable at this temperature. The cantilever beam type microelectromechanical systems (MEMS) piezoelectric accelerometers are then fabricated based on the proposed AlN films with a lift-off process. The results show that the responsivity of the proposed devices is 8.12 mV/g, and the resonance frequency is 460 Hz, which indicates they can be used for machine tools.

Introduction. It is important to decrease light and heavy impurities influxes towards the plasma volume during the high temperature plasma experiments in fusion devices. This is why the conditioning of the wall inner vacuumsurfaces is a basic part of the fusion device operation.Problem Statement. The conventional inner vacuum chamber surface conditioning methods has a significant drawback: sputtering materials in a vacuum chamber. The inner vacuum surfaces can be also conditioned with radio-frequency (RF) discharge plasma, but the conditioning effectiveness is limited by low ion energy.Purpose. The purpose of this research is to develop vacuum surface conditioning technology by the radio frequency plasma combined with DC discharge. Materials and Methods. The noncontact passive method of optical plasma spectroscopy has been used to estimate ion plasma composition. The stainless steel outgassing has been determined in situ with the thermodesorption probe method. The sputtering of the samples has been measured with the weight loss method.Results. The studies of combined discharge have shown that: the anode voltage of combined discharge is lower than in case of the glow discharge; the stainless steel 12Kh18N10T erosion coefficient is about 1.5 times less in thecase of combined discharge than in the glow one; the thermal desorption diagnostic of wall conditions in the DSM-1 has shown better efficiency with the combined discharge as compared with the glow discharge. Theproposed technology is an original one and has no analogs.Conclusions. The reported research results have shown good prospects for the combined discharge usage for plasma walls conditioning and opportunities for using the combined discharge technology for big fusion machines.