Deposition Pressure Research Articles

Optimization of electrical properties and radio frequency applications of GeTe thin film

GeTe belongs to a chalcogenide phase change material, which can dynamically achieve reversible switching between the crystalline state of low resistivity and the amorphous state of high resistivity by utilizing the thermally induced phase change characteristics. The GeTe is an important functional material in the fields of memristors and nonvolatile radio frequency (RF) switches. For RF switch applications, this paper focuses on optimizing the electrical performance of GeTe thin films prepared by magnetron sputtering. By comprehensively analyzing the effects of substrate materials, sputtering conditions, and annealing conditions on the resistivity of crystalline GeTe films, effective conditions for preparing low resistivity GeTe films are explored. Fig. (a) shows that compared with the GeTe film on a SiO<sub>2</sub> substrate, the film on an Al<sub>2</sub>O<sub>3</sub> substrate can obtain higher crystallinity and lower resistivity. For the deposition power and pressure shown in Fig. (b), the combination of medium power (50–80 W) and low pressure (2–3 mTorr) is beneficial for low crystalline resistivity of GeTe film. Additionally, Fig. (c) shows that higher annealing temperature (350–400 ℃) can realize lower film resistivity. Finally, the experimental results show that the lowest crystalline resistivity of the prepared GeTe thin film reaches 3.6×10<sup>–6</sup> Ω·m, and the resistance ratio is more than 10<sup>6</sup>. Based on rectangular chips of GeTe film, a parallel millimeter-wave switch with zero static power is also constructed. As shown in Fig. (d), the insertion loss is less than 2.4 dB, and the isolation is greater than 19 dB in a 1–40 GHz frequency band, demonstrating the potential application of GeTe thin films in the field of broadband high-performance discrete nonvolatile RF switches.

The Zn Deposition Mechanism and Pressure Effects for Aqueous Zn Batteries: A Combined Theoretical and Experimental Study

AbstractA new reactive force field based on quantum mechanical data for describing formation of the Zn electrode‐electrolyte interface (EEI) chemistry in aqueous zinc‐ion batteries (ZIBs) is developed. This is the first demonstration in which Reactive Molecular Dynamics (RMD) simulation is used to follow the Zn reduction and anode structural evolution at the EEI. It is found that under axial pressure, Zn dendrite formation is inhibited. This is associated with accelerated ion transport and reduction while increasing preference towards horizontal (002) plane growth. Pressure‐induced desolvation of Zn ions within the electric double layer, which promotes faster reduction kinetics is observed. It is found that axial pressure stabilizes adatoms on the (002) plane by decreasing axial atom stress during nucleation and by increasing favorable lateral adatom diffusion, which reduces atomic scale dendrite formation. Finally, these are confirmed results by experimental characterization and electrochemical tests.

Tracking anthropogenic microparticles in wildlife of an alpine insular environment

Despite the isolation of remote natural regions, it has been discovered that they are experiencing the accumulation of anthropogenic microparticles (i.e., microplastics or natural or semisynthetic cellulosic particles). Teide National Park (Canary Islands, Spain) is a high-mountain protected area known for its rich biodiversity. This study aims to assess the occurrence of coloured anthropogenic particles in the faecal matter of wild mammals, specifically rabbits and mouflons, residing in the park. With this purpose, faeces were collected from 68 systematically distributed sampling points. A stereomicroscopy-guided grinding process allowed a chemical-free and quick visual inspection of 616 individual excreta, revealing that 96% were particle-free. However, 37 anthropogenic particles were found, which correspond to 0.79 ± 0.20 items per gram of dry faecal matter. The archetypical particle was a cellulosic blue microfibre of 2721 ± 407 µm, though poly(ethylene-vinyl acetate) and polypropylene were also identified via micro Fourier-transform infrared spectroscopic analysis. Atmospheric deposition and touristic pressure may be the sources of the anthropogenic particles, as they were randomly found in 36% of the sampling points. These findings represent the first evidence of anthropogenic particle ingestion by wild rabbits and mouflons, signifying the introduction of microplastics into terrestrial food chains in a remote high-mountain environment.

Effect of Nb and V doped elements on the mechanical and tribological properties of CrYN coatings

One of the most promising approaches to enhancing the tribological properties of engineering coatings is to add transition elements to the structure. In this study, Nb-doped CrYN and V-doped CrYN thin films were deposited by pulsed DC reactive sputtering in a closed-field unbalanced magnetron sputtering (CFUBMS) system. The deposition parameters examined were target current (1, 1.5 and 2 A), deposition pressure (0.15, 0.25 and 0.35 Pa), pulse frequency (100, 200 and 350 kHz) and duty cycle (85 %, 70 % and 50 %). A Taguchi L9 orthogonal design was used to define the deposition process parameters for each doped film. The Nb and V-doped CrYN thin films were characterized in terms of their microstructure, thickness, composition, hardness and tribological properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), nanohardness and pin-on-disc testing, respectively. The bond strength between the substrate and the films (adhesion) was analyzed by scratch testing. For the Nb-doped thin films, a maximum hardness value of 21.4 GPa and the lowest friction coefficient of 0.36 were obtained. On the other hand, in the V-doped thin films, the maximum hardness value was 16.1 GPa, while the lowest friction coefficient obtained was 0.11. In addition, Nb-doped and V-doped CrYN thin films exhibited extraordinary adhesion properties. The effect of the selected deposition parameters (target current, pulse frequency, and duty cycle) in relation to the film thickness, hardness, and coefficient of friction properties of the Nb and V-doped CrYN thin films were investigated using the Taguchi approach and optimum operating conditions were identified and confirmed.

Tribological and Corrosion Performance of CrAlN/CrN Coatings in Artificial Seawater under Varied Nitrogen Pressures

This study employed arc ion plating technology to deposit CrAlN/CrN coatings on stainless steel substrates, adjusting deposition pressures ranging from 1.0 Pa to 4.0 Pa. A detailed analysis of the coatings’ microstructure, wear, and corrosion features was performed using X-ray diffraction, scanning electron microscopy, nanoindentation, tribometers, profilometers, and electrochemical workstations. The study revealed that the crystalline structure of the CrAlN/CrN coatings primarily consists of cubic crystals of AlN, (Cr, Al)N, and CrN. Diffraction peak intensity analysis revealed preferential orientation in the CrAlN coatings along the (111) and (200) crystal planes. As the pressure increased to 3.0 Pa, the content of Al elements peaked, and the columnar structure became denser; at this point, the H/E* ratio reached a maximum of 0.079, indicating excellent delamination and fracture resistance of the CrAlN/CrN coating at this pressure. Tests in artificial seawater environments showed that with the increase in nitrogen pressure, the friction coefficient gradually decreased, reaching its lowest at 3 Pa, approximately 0.19. The wear rate trend aligned with the friction coefficient, recorded at a mere 2.20 × 10−7 mm3/Nm. Electrochemical polarization curve tests revealed that at 3 Pa pressure, the CrAlN/CrN coating had a corrosion potential of −0.04 V, a polarization resistance of 9.28 × 105 Ω·cm2, and a very low corrosion current of 4.81 × 10−8 A/cm2, demonstrating excellent corrosion resistance.

Electrochemical Performance of Biocompatible TiC Films Deposited through Nonreactive RF Magnetron Sputtering for Neural Interfacing.

The efficacy of neural electrode stimulation and recording hinges significantly on the choice of a neural electrode interface material. Transition metal carbides (TMCs), particularly titanium carbide (TiC), have demonstrated exceptional chemical stability and high electrical conductivity. Yet, the fabrication of TiC thin films and their potential application as neural electrode interfaces remains relatively unexplored. Herein, we present a systematic examination of TiC thin films synthesized through nonreactive radio frequency (RF) magnetron sputtering. TiC films were optimized toward high areal capacitance, low impedance, and stable electrochemical cyclability. We varied the RF power and deposition pressure to pinpoint the optimal properties, focusing on the deposition rate, surface roughness, crystallinity, and elemental composition to achieve high areal capacitance and low impedance. The best-performing TiC film showed an areal capacitance of 475 μF/cm2 with a capacitance retention of 93% after 5000 cycles. In addition, the electrochemical performance of the optimum film under varying scanning rates demonstrated a stable electrochemical performance even under dynamic and fast-changing stimulation conditions. Furthermore, the in vitro cell culture for 3 weeks revealed excellent biocompatibility, promoting cell growth compared with a control substrate. This work presents a novel contribution, highlighting the potential of sputtered TiC thin films as robust neural electrode interface materials.

Experimental and Theoretical Investigation of Gadolinium Oxyhydride (GdHO) Thin Films: Optical, Photocatalytic, and Electronic Properties.

Oxyhydrides of rare-earth metals (REMOHs) exhibit notable photochromic behaviors. Among these, yttrium oxyhydride (YHO) stands out for its impressive transparency and swift UV-responsive color change, positioning it as an optimal material for self-cleaning window applications. Although semiconductor photocatalysis holds potential solutions for critical environmental issues, optimizing the photocatalytic efficacy of photochromic substances has not been adequately addressed. This research advances the study of REMOHs, focusing on the properties of gadolinium oxyhydride (GdHO) both theoretically and experimentally. The electronic and structural characteristics of GdHO, vital for ceramic technology, are thoroughly examined. Explicitly determined work functions for GdH2, GdHO, and Gd2O3 stand at 3.4 eV, 3.0 eV, and 4.3 eV, respectively. Bader charge analysis showcases GdHO's intricate bonding attributes, whereas its electron localization function majorly presents an ionic nature. The charge neutrality level is situated about 0.33 eV below the top valence band, highlighting these materials' inclination for acceptor-dominant electrical conductivity. Remarkably, this research unveils GdHO films' photocatalytic capabilities for the first time. Even with their restricted surface due to thinness, these films follow the Langmuir-Hinshelwood degradation kinetics, ensuring total degradation of methylene blue in a day. It was observed that GdHO's work function diminishes with reduced deposition pressure, and UV exposure further decreases it by 0.2 eV-a change that reverts post-UV exposure. The persistent stability of GdHO films, hinting at feasible recyclability, enhances their potential efficiency, underlining their viability in practical applications. Overall, this study accentuates GdHO's pivotal role in electronics and photocatalysis, representing a landmark advancement in the domain.

Modeling of sputter-based atomic layer deposition with altered parameters

Computational modeling of the sputtering process forming atomic layers of some technologically significant materials was performed based on sputter rate relation. Bismuth atomic layer deposition at different polar angles and ion fluence were shown. The atomic layers getting deposited were studied as a function of incident Argon ion energy at different pressure and a curve analogous to the Bragg curve was obtained. The sputtering parameters were varied to get different atomic layers of TiOx films and the variation of coverage with sticking coefficient was shown. The rate of change of partial sputtering yield with coverage was depicted in the sputter-based deposition of TiN films. The deposition pressure and time were varied to get films of different thicknesses. All the simulated results were correlated with experimental findings with features like variation of reactive gas pressure, electron aided momentum transfer in Bi, multilayer anatase and rutile formation in TiO2 and effect of process parameters on TiN.

Growth and defect formation mechanism of CVD-prepared SiC coatings based on cross-scale simulation

The high quality and efficient production of third-generation semiconductor materials has recently been a hot research topic. At the same time, the substrate material properties could significantly influence the MOCVD quality. In this study, the CVD SiC process on graphite substrate was efficiently controlled by molecular dynamics (MD)-finite volume (FVM) cross-scale simulations. The key deposition parameters such as MTS-H2 flow rate, deposition pressure, and reaction source nMTS:nH2 were first simulated by MD. Subsequently, the results obtained from the MD simulations were input into the FVM software, and CFD simulations were performed in a home-made reactor. The cross-scale simulation results from microscopic chemical reactions and crystal structures to macroscopic airflow fields and deposition rate distributions were obtained. The defects of CVD SiC were optimized by visualizing the simulation process. The tests showed that the graphite substrate was effectively protected by the SiC coating on the surface. The optimal deposition parameters for CVD SiC coatings were finally obtained. This study laid the foundation for the mass production of high-quality semiconductor materials.

Threatened European butterflies concentrate in areas of strong climatic change and atmospheric deposition pressure

Land use change, as a result of many local-scale decisions scaling up to large spatial extents, is considered the main threat to European butterflies. The impact of large-scale pressures, such as atmospheric nitrogen deposition or climate change, is less understood or less documented, respectively. However, it is acknowledged that they might reinforce the pressure on already threatened species. To evaluate the additional threat exerted by these pressures we compared their geographical pattern to those of threatened butterflies across Europe. We therefore derived range maps of 383 butterfly species and used two species-specific threat assessments derived from national and European Red Lists. We then used Spearman rank-correlations and beta-regressions to compare two metrics of species threat per 10 × 10 km raster cells with geographical patterns of cumulative nitrogen depositions from 1980 to 2015, as well as the magnitude of change in precipitation sums and temperature means between the decades 1979–1988 and 2004–2013. We found that threatened species tend to concentrate in areas with high nitrogen depositions and pronounced summer temperature changes. In particular, parts of central and eastern Europe were both hotspots of threatened butterflies and hotspots of climatic pressure. This spatial coincidence of the distribution of threatened butterfly species with large-scale patterns of nitrogen depositions and recent climate warming indicates an already considerable risk of regional to continental extinctions that will likely increase further in the future as climate change will most likely intensify. Consequences for area-based conservation measures are discussed.

Effect of substrate temperature on structural, morphological, and optical properties of Gallium Oxide thin films deposited by RF-Sputtering

In this paper, gallium oxide thin films at different substrate temperatures were deposited on Indium TinOxide (ITO), glass and p-type silicon wafers by radio-frequency magnetron sputtering (RFMS). The effect of substrate temperature at 8 mTorr deposition pressure on the structural, morphological and optical properties of films was investigated. X-ray diffraction (XRD) analysis of thin films deposited on p-Si substrate suggests that crystal structure characteristics of synthesized thin films depend on the substrate temperature. From SEM analyzes of Ga2O3 thin films grown on p-type silicon substrate, It was observed that when the temperature increased, a porous structure appeared and the particle size changed depending on the substrate temperature. Morover, optained results from the absorption measurements, the band gap energy of the Gallium Oxide thin films deposited on the p-Si substrate decreased with increasing substrate temperature.

A temperature study of methanol interstellar ice analogues

Methanol ice has been studied in the field of astrochemistry for many years. As a simple organic compound, CH3OH is extremely interesting in the study of ice formation and evolution. There are three forms of methanol ice – amorphous, α-crystalline, and β-crystalline. Although there are studies focused on the comparison of crystalline and amorphous phases in terms of chemical properties, there is a lack of systematic studies on phase transition. Factors such as pressure, temperature, and rate of ice formation have an influence on the process of phase transition. In this study, the influence of temperature on the vibrational properties of methanol ice is considered. For the experimental section, a Portable Astrochemistry Chamber (PAC) with the ability to control deposition pressure and temperature was used. The temperature of phase transition was experimentally determined at 103 K and for analysis of the ice structure, two vibrational modes were chosen – OH stretch and CH3 in-plane rocking. Moreover, depositions at higher temperatures were performed with the result of different vibrational properties depending on ice formation conditions. This study presents the temperature-dependant properties of methanol ice in the mid-infrared spectrum and considers the possibility of thermal history determination.

Deposition of Ti[sbnd]Zr alloy films using Ti and Zr dual-cathode high-power impulse magnetron co-sputtering

In this study, titanium–zirconium binary alloy films were deposited using heterogeneous dual-cathode high-power impulse magnetron sputtering with a closed magnetron field. For both Ti and Zr cathodes, the discharge voltage pulses were synchronized with an equal pulse width. In addition, we investigated the effects of the average discharge power ratios of the two cathode materials, deposition pressure, and substrate bias voltage on the mechanical strength and microstructure of the deposited films. The results revealed that the film composition could be controlled by the average power ratio of the two cathodes at a constant deposition pressure; however, the deposition rate of each element varied with the deposition pressure. At a constant average power ratio at the two cathodes, the Zr content in the films decreased with decreasing the deposition pressure. Decreasing the deposition pressure can smoothen the film surface, but the dependence of the film composition on two cathode powers also changes. An adequate enhancement of the negative substrate bias can further increase the film hardness and reduce the film elastic modulus, yielding only a moderate loss in the film deposition rate and marginal variations in the film composition. However, the magnitudes of the increase in hardness and the decrease in elastic modulus brought by enhancing negative substrate bias varies with the film composition, and will be minimized when the atomic fractions of Ti and Zr are near equal. Notably, with adjusting the negative substrate bias, adding Zr can change the film hardness from 4.8 to 10.6 GPa, and the film elastic modulus from 100 to 162 GPa. Overall, the advantageous mechanical and structural properties of the TiZr alloy films deposited using HiPIMS might be useful in tools, biomedical devices, wearable equipment applications.

Comprehensive investigation of sputtering deposition pressure effects on a-InGaZnO Schottky diodes

The effects of Ar sputtering deposition pressure on the optical, structural, morphological, and electrical properties of amorphous InGaZnO thin films were investigated. The InGaZnO thin films, which have amorphous structures determined by grazing incidence x-ray diffraction, contained In, Ga, Zn, and O confirmed by secondary ion mass spectrometry method. Additionally, when the thicknesses of the deposited thin films are examined, it was seen that the profilometer measurement results of the crater formed by secondary ion mass spectrometer and scanning electron microscope measurement results are nearly similar, and it is approximately 100 nm. The surface roughness, obtained from Atomic Force Microscopy results, show that decreased up to a particular value with the increase of the working pressure, and then the surface roughness increased. The optical band gaps of the films were obtained in the range of 3.50 eV−3.58 eV via Tauc relation by using the Ultraviolet-Visible measurements carried out in the wavelength range of 200 nm−1100 nm. It was seen that the optical band gap was decreased with the increase in Ar pressure. The electrical properties of InGaZnO thin film-based Schottky diodes, such as the barrier height, ideality factor, saturation current, series resistance, and shunt resistance, have also been studied comprehensively. The electrical results showed that diode properties change with increasing deposition pressure.

Permeation of oxygen and water into a plasma-enhanced chemical vapor deposited silicon nitride film as function of deposition pressure

In this work, we demonstrate that the permeability of a SiNx thin film (prepared by plasma-enhanced chemical vapor deposition) to water and oxygen is closely related to the deposition pressure. By dynamic secondary ion mass spectrometry, we confirmed that water penetration occurs into the SiNx film only in the oxidized layer. Furthermore, positron annihilation lifetime spectroscopy indicated that a SiNx film with a lower deposition pressure provides a smaller pore (free volume hole) radius, which is more effective in terms of blocking ambient molecular diffusion or penetration. The SiNx films were also applied as an encapsulation layer for organic light-emitting diodes; SiNx films with a lower deposition pressure exhibited higher encapsulation properties.

Characterization of PECVD Si3N4 thin film in multiple oxide–nitride stack for 3D-NAND flash memory

3D-NAND flash memory is currently essential in the semiconductor industry due to the interference issue between memory cells of the conventional planar type. In order to vertically stack the memory, an oxide–nitride stack structure is formed using plasma enhanced chemical vapor deposition (PECVD) equipment. Thereafter, part of the silicon nitride (Si3N4) layer is removed by wet etching using phosphoric acid (H3PO4) to make space for the memory cell. At this time, it is important to selectively wet etch only the Si3N4 film while protecting the silicon oxide (SiO2). Therefore, in this study, the process parameters that affect the etch rate in PECVD were derived, and the correlation with the hydrogen content, surface roughness, and thin film density, which are the thin film characteristics that the parameters affect, were investigated. Through the experimental results, we confirmed that hydrogen content increases according to the deposition pressure, affects the surface roughness, and can be an important factor in improving the wet etching rate.

Effect of nitrogen pressure on the fabrication of AlCrFeCoNiCu0.5 high entropy nitride thin films via cathodic arc deposition

In the past two decades, high entropy alloy (HEA) coatings have attracted great attention due to their superior mechanical properties, outstanding corrosion and oxidation resistance, and exceptionally high thermal stability. In comparison to HEA thin films, high entropy nitrides (HENs) exhibit higher mechanical strength and chemical inertness. In this work, AlCrFeCoNiCu0.5 HEA and HEN thin films were fabricated using a filtered cathodic arc. By regulating the deposition pressure from 0.0005 Pa (HEA thin film) to 0.05 Pa, the nitrogen concentration in each thin film was precisely controlled to tune the mechanical properties. Scanning transmission electron microscopy-energy dispersive spectroscopy revealed that the nitrogen concentration of the films was up to 21.2 at. % at the pressure of 0.05 Pa. The reduced effect of preferential sputtering increased aluminum concentration from 8.3 ± 1.5 to 12.9 ± 2.2 at. % as pressure increased up to 0.05 Pa. X-ray photoelectron spectroscopy further confirmed the formation of AlN and CrN at pressures of 0.01–0.05 Pa. The highest hardness and elastic modulus of the HEN film were 12.4 ± 0.6 and 347.3 ± 17.7 GPa, respectively, which were 84.8% and 131.4% higher than those of the HEA thin film.

Soft deposition of TCOs by pulsed laser for high-quality ultra-thin poly-Si passivating contacts

In this work, the applicability of pulsed laser deposition (PLD) of transparent conductive oxides (TCOs) on high-quality ultra-thin poly-Si based passivating contacts is explored. Parasitic absorption caused by poly-Si layers can be minimized by reducing the poly-Si layer thickness. However, TCO deposition on poly-Si contacts, commonly by sputtering, results in severe deposition-induced damage and further aggravates the surface passivation for thinner poly-Si layers (<20 nm). Although a thermal treatment at elevated temperature (∼350 °C) can be used to partially repair the surface passivation quality, the contact resistivity severely increases due to the formation of a parasitic oxide layer at the poly-Si/ITO interface. Alternatively, we show that PLD TCOs can be used to mitigate the damage on ultra-thin (∼10 nm) poly-Si layers. Further improvement in poly-Si contact passivation can be achieved by increasing the deposition pressure while low contact resistivities (∼45 mΩ cm2) and good thermal stability (up to 350 °C) are achieved with a PLD indium-doped tin oxide (ITO) layer on high-quality ultra-thin poly-Si(n+) contacts. This allows for the application of a highly transparent front side contact by combining the excellent opto-electrical properties of a PLD ITO film with a 10 nm thin poly-Si contact.

Computational tool for analyzing stress in thin films

A computational model has been developed to analyze calculations of residual stress in thin films determined from in-situ wafer curvature measurements. The model is based on several physical mechanisms that have been proposed to control the stress, including the effect of growth kinetics, grain growth and energetic particle bombardment. From a set of data, the program determines a set of kinetic parameters that can be used to understand the processes controlling stress. These parameters can be used to estimate the stress that will develop under different processing conditions in order to obtain a desired stress state. Several examples are described that illustrate the program's capabilities, including the effects of growth rate, growth temperature and particle energy (via chamber pressure in sputter deposition). Interested researchers may obtain the program and associated documentation to use the program to analyze their own data.

Regulating Deposition Pressures During Rapid Thermal Evaporation Processes to Enable Efficient Sb2 Se3 Solar Cells.

Sb2 Se3 solar cells deposited by rapid thermal evaporation (RTE) have drawn extensive attention owing to their compatibility with the commercial production line of CdTe solar cells and can be used to fabricate high-quality Sb2 Se3 films with high reproducibility. However, the deposition pressure during the RTE process has not been clearly explored, although it has a significant effect on the Sb2 Se3 film quality. A novel two-step deposition strategy is proposed that finely regulates the deposition pressure to improve the quality of Sb2 Se3 absorber layers, thereby improving the device performance of Sb2 Se3 solar cells. This novel method includes a rapid deposition process under a low pressure (5 mTorr) and an in situ annealing process under a relatively high pressure (200Torr). The maximum power conversion efficiency (PCE) of Sb2 Se3 solar cells fabricated by two-step deposited approach is up to 8.12%. The PCE enhancement is attributed to the increased grain size, reduced grain boundaries, modified surface Fermi level gradient of the absorber layer, and improved defect performance. This innovative deposition technique is expected to benefit other low-melting-point metal sulfoselenides for solar cell applications.