Increasing Sputtering Pressure Research Articles

The impact of oxygen vacancy defect density on the nonlinearity and short-term plasticity of TiO2-based exponential selector

The readout margin of the one selector-one RRAM crossbar array architecture is strongly dependent on the nonlinearity of the selector device. In this work, we demonstrated that the nonlinearity of Pt/TiO2/Pt exponential selectors increases with decreasing oxygen vacancy defect density. The defect density is controlled by modulating the sputtering pressure in the oxide deposition process. Our results reveal that the dominant conduction mechanisms of the Pt/TiO2/Pt structure transit from Schottky emission to Poole–Frenkel emission with the increase of sputtering pressure. Such transition is attributed to the rise of oxygen vacancy concentration. In addition, the short-term plasticity feature of the Pt/TiO2/Pt selector is shown to be enhanced with a lower defect density. These results suggest that low defect density is necessary for improved exponential selector performances.

Impedance spectroscopy analysis of Al/100-plane AlN/p-Si MIS prepared by HiPIMS method for tailoring dielectric properties

The effects of variation of sputtering pressure of AlN HiPIMS deposition on Si substrate to the structure and electrical properties were investigated through XRD, AFM and impedance spectroscopy method. The strong preferred 100-plane AlN was observed for all samples from XRD pattern. The AlN thin film thickness was observed decrease with the increase of sputtering pressure. AFM analysis shows the lowest surface roughness at 0.84 nm for 5 mTorr sputtering pressure. Impedance spectroscopy analysis of Al/100-plane AlN/Si MIS structure shows the electrical conductivity of AlN was directly proportional to the sputtering pressure and stable with temperature ranging from room temperature (299 K) to 353 K. Good dielectric stability was achieved at 3 mTorr sputtering pressure for all variation temperature and the dielectric constant calculated at average 3.5.

Understanding the effect of sputtering pressures on the thermoelectric properties of GeTe films

In this work, we study the effect of sputtering pressures on the thermoelectric properties of GeTe films. The working pressures were differentiated from 3 to 30 mTorr, and the as-deposited films were annealed at 623 K for 10 min in Ar atmosphere. The results show that the working pressure has a significant effect on the Ge content and crystalline size. The turning trend of the Seebeck coefficient with different sputtering pressures corresponds to the Ge content. The surface morphology of annealed film will change from cracks to voids with increasing sputtering pressure. This behavior can be explained by the growth mechanisms model. The voids and relatively low crystalline size of GeTe films affect to the reduction of the electrical conductivity. In addition, the void content decreased as film thickness was increased. Therefore, controlling the working pressures in the sputtering process and film thickness is important for the thermoelectric performance of GeTe thin film. In our work, we prove that the thermoelectric properties of GeTe films could be optimized effectively by simply tuning different sputtering conditions.

Effect of sputtering pressure on the optical and electrical properties of ITO film on fluorphlogopite substrate

The van der Waals forces between the layers of fluorphlogopite make it flexible, and its stability under strong acid, strong alkali, and high temperature conditions has potential applications as a new base material for flexible electronics. In this article, using magnetron sputtering technology, the focus is on the influence of the change of sputtering pressure on the photoelectric properties of the prepared ITO thin film. In this study, indium tin oxide (ITO) film samples were prepared on a fluorphlogopite substrate using the magnetron sputtering technique and adjusting the sputtering pressure from 0.6 Pa to 11 Pa at room temperature. The film was characterized using SEM, XRD, four-probe tester, and ultraviolet–visible spectrophotometer to understand its microstructure and photoelectric properties. The number of bending times of the sample's square resistance around the steel cylinder characterized its flexibility. The results showed that the sample crystal grains decreased significantly with the increase in pressure. Further, it can be seen from SEM images that all samples contained extremely uniform particles. The light transmittance and resistivity of the sample synthesized below 3 Pa increased sharply with the increase of sputtering pressure, and the change above 3 Pa tended to be stable. The average transmittance of visible light in the wavelength range of 400–800 nm ​​is higher than 86%, the highest being 92.7%; the sputtering pressure of 0.6 Pa yielded a sample with the lowest resistivity of 1.51 × 10−3 Ωcm. All the samples were bent 1200 times around a steel cylinder with a radius of 3.65 mm, and the change in sheet resistance did not exceed 5%.

Effect of sputtering pressure on the structure and properties of SiO 2 films prepared by magnetron sputtering

The effects of sputtering pressure on the O/Si ratio, microstructure, surface morphology and optical properties within 300–1100 nm of SiO2 film via radio frequency magnetron sputtering were investigated. The results showed that the molar ratio of O/Si in the film increased from 1.96 to 2.03, from silicon rich to oxygen rich, with the sputtering pressure increase from 0.3 to 1.3 Pa. The SiO2 films deposited at different pressure were all amorphous. There were many ditches with a length of about 50 nm on the surface of the film deposited at lower pressure. The increase of sputtering pressure could reduce the number of ditches, and make the surface denser and more uniform. The refractive index increased first, then decreased and finally increased with the increase of sputtering pressure, and the maximum and minimum values were obtained at 0.7 and 1.1 Pa, respectively. The change of absorptivity was approximately the same as that of the refractive index, while the change of the average transmittance of coated quartz glass was exactly the opposite of refractive index. The minimum value of the average transmittance 92.6% and the maximum value 93.1% were obtained at 0.7 and 1.1 Pa, respectively.

A comprehensive study on Cu2SnS3 prepared by sulfurization of Cu–Sn sputtered precursor for thin-film solar cell applications

In this work, a comprehensive study on the influences of the various synthesizing parameters of monoclinic Cu2SnS3 using the RF sputtering method, followed by the sulfurization process, is investigated. In particular, the impact of sputtering power and pressure on multi-material target Cu–Sn (compositional ratio Cu:Sn of 52:48%) was examined. All samples exhibited a monoclinic structure with similar split bandgaps around 0.9 eV. Increasing sputtering power showed direct effects on the sputtered Cu/Sn atoms ratio and the secondary phases obtained. The increase of sputtering pressure causes gas droplets and blistering on the film surfaces. The effects of changing the sulfurization temperature and the sulfur powder amount were also studied. The increase in the sulfurization temperature reduces the surface roughness, increases film crystallinity, and minimizes Cu-based secondary phases. The sulfur amount used during the sulfurization process showed a vital impact on film formation. Using a small amount of sulfur produced a partially sulfurized film that exhibited a poor performance solar cell. A power conversion efficiency of 1.94% is achieved with the optimized condition for the bare Cu2SnS3 without doping or heat treatment for the fabricated cell.

The Properties of Cd1−xZnxTe Films Prepared by RF Magnetron Sputtering

Cd1−xZnxTe films were prepared on borosilicate glass substrate using RF magnetron sputtering in this work. The effects of sputtering power, sputtering pressure and substrate temperature on the properties of the films were investigated in detail. The films were annealed in CdCl2 atmosphere for 2 h at 200 °C, 300 °C, and 400 °C, respectively. The effects of annealing treatment on the properties of the films were also investigated. The properties of the films were investigated by x-ray diffraction, atomic force microscopy, and current–voltage (I–V) characterization. The results indicate that crystalline quality and the average grain size of the films increases with the increases of sputtering power. The grain size of the films becomes larger as the substrate temperature increases. The Zn concentration of the films rises as the sputtering pressure increases. After annealing, the grain size of the films becomes larger, furthermore, the resistivity decreases.

Sputtering pressure influenced structural, electrical and optical properties of RF magnetron sputtered MoO3 films

Abstract MoO3 films were deposited by RF magnetron sputtering technique on glass and silicon substrates held at 473 K by sputtering of metallic molybdenum target at an oxygen partial pressure of 4 × 10−2 Pa and at different sputtering pressures in the range of 2 Pa to 6 Pa. The influence of sputtering pressure on the structure and surface morphology, electrical and optical properties of the MoO3 thin films was studied. X-ray diffraction studies suggest that the films deposited at a sputtering pressure of 2 Pa were polycrystalline in nature with mixed phase of α- and β-phase MoO3, while those formed at sputtering pressure of 4 Pa and above were of α-phase MoO3. Scanning electron micrographs showed a decrement in the size of the particles and their shapes changed from needle like structure to dense films with the increase of sputtering pressure. Fourier transform infrared spectroscopic studies confirmed the presence of characteristic vibration modes of Mo=O, Mo–O and Mo–O–Mo related to MoO3. Electrical resistivity of the MoO3 films decreased from 6.0 × 104 Ω cm to 2 × 104 Ω cm with an increase of sputtering pressure from 2 Pa to 6 Pa, respectively. Optical band gap of the films decreased from 3.12 eV to 2.86 eV with the increase of sputtering pressure from 2 Pa to 6 Pa, respectively.

Defect photoluminescence and structure properties of undoping (InxGa1-x)2O3 films and their dependence on sputtering pressure

The (InxGa1-x)2O3 thin films were deposited on sapphire substrates by radio frequency magnetron sputtering with increasing sputtering pressure from 0.6 Pa to 1.6 Pa. X-ray diffraction analysis indicated In composition of (InxGa1-x)2O3 thin films maintained constant with the increase of sputtering pressure and In content and bandgaps of (InxGa1-x)2O3 thin films were estimated to be 6% and 4.78 eV by Vegard’s law, respectively. The influence of sputtering pressure on structural and optical properties was discussed in detail. Especially, the origin of different emission of (InxGa1-x)2O3 thin films was investigated. The role of VGa defects on the green emission centered at about 550 nm had been clarified. The energy band diagram of (InxGa1-x)2O3 thin film was also proposed with intrinsic defect levels.

Insight of the doping mechanism of F and Al co-doped ZnO transparent conductive films

Transparent conductive oxide (TCO) films, as transparent electrodes, are widely used in thin-film solar cells. The performance of TCO film has a significant influence on the conversion efficiency of the film solar cell fabricated byusing it. Although the conductivity can be improved by increasing the carrier concentration, the transmittance in the long wave will be sacrificed. Therefore, the only feasible method is to increase the carrier mobility within a certain carrier concentration range, rather than increase the mobility by reducing carrier concentration. In this paper, the F and Al co-doped ZnO (FAZO) films are deposited on glass substrates (Corning XG) by an RF magnetron sputtering technique with using a small amount of ZnF<sub>2</sub> (1 wt.%) and Al<sub>2</sub>O<sub>3</sub> (1 wt.%) dopant. The influences of sputtering pressure on the structure, morphology and photoelectric characteristics of the films are respectively investigated by X-ray diffraction analysis, scanning electron microscope, Hall effect measurement, and ultraviolet–visible–near infrared spectrophotometry. All the thin films show typical wurtzite structure with the <i>c</i> axis preferentially oriented perpendicular to the substrate. With the increase of sputtering pressure, the deposition rate of FAZO film decreases, the crystallization quality is deteriorated, surface topography changes gradually from “crater-like” to co-existent “crater-like” and “granular-like”, and the surface roughness increases. The FAZO film deposited at 0.5 Pa presents the optimal performance with a mobility of 40.03 cm<sup>2</sup>/V·s, carrier concentration of 3.92 × 10<sup>20</sup> cm<sup>–3</sup>, resistivity of 3.98 × 10<sup>–4</sup> Ω·cm, and about 90% average transmittance in a range of 380－1200 nm. The theoretical result shows that the co-doping of F and Al takes the advantages of single F and Al doped ZnO films, and overcomes the shortcoming of metal elements doping, which donates the carriers just from doped metal elements. Furthermore, the co-doping of F and Al not only increases the carriers but also reduces the scatterings caused by the inter-orbital interaction of doped atoms. The doped F 2p electron orbitals repel the O 2p and Zn 4s electron orbitals, making them move down and donate electrons. At the same time, the orbitals of Al 3s and Al 3p also make a contribution to the conductivity. After co-doping of F and Al, both the carrier concentration and conductivity increase significantly.

Structural and luminescence studies on TiO2-MoO3 thin films

Thin films of MoO3 and TiO2-MoO3 were deposited on quartz glass and Silicon (100) substrates by dc magnetron sputtering at two substrate temperatures of 300 K and 600 K and at two sputtering pressure of 5 Pa and 10 Pa and sputtering power of 50 W respectively. The deposited films were characterized by X-ray Photo Electron Spectroscopy (XPS), Raman and photoluminescence spectra. The pure MoO3 films deposited at 300 K exhibited the Raman bands at 242 cm−1 and 974 cm−1 indicating the absorption of water molecules and formation of alpha MoO3-H2O. With increasing Ti content the bands are shifted to 224 cm−1 and 960 cm−1 that correspond to h-MoO3 and absorption of water molecules. For Ti at. % of 2.4 the bands were observed only at low frequencies but at high temperatures, a single peak noticed at 954 cm−1 corresponds to α – MoO3 H2O. The Photo-luminescence spectrum reveals that the MoO3 films deposited at 5 Pa and 300 K exhibits Near Band Edge (NBE) transition at 324 nm. The intensity of NBE increases further and with corresponding shift towards higher wavelength with TiO2 doping. The TiO2 doping also introduces Deep Level (DL) emission in TiO2-MoO3 composite film. With increase of deposition temperature the intensity of emission due to NBE in MoO3 films decrease introducing DL emission. The TiO2 doping enhances the intensity of both NBE and DL emission with a shift in emission wavelength towards higher value. The intensity of these NBE and DL emissions are further increasing with increasing sputtering pressure (10 Pa) and deposition temperature (600 K) of MoO3 and TiO2-MoO3.

The influence of Ar pressure on the structure and optical properties of non-hydrogenated a-Si thin films grown by rf magnetron sputtering onto room-temperature glass substrates

Seven 1.1–1.4-μm-thick hydrogen-free amorphous‑silicon (a-Si) thin films were deposited at high rates (larger than 10 Å/s), by rf magnetron sputtering (RFMS) onto room-temperature glass substrates. The influence of argon-gas pressure on the structural and optical properties of these amorphous films has been systematically studied. We have used the Wemple-DiDomenico (WD) single-effective-oscillator model, n2(ℏω) − 1 = EdE0/(E02 − (ℏω)2), in order to determine the WD parameters oscillator strength or dispersion energy, Ed, and oscillator energy, E0. The amorphous-to-crystalline mass-density ratio, ρa/ρx, in the empirical expression for Ed, proposed by Wemple, is the key factor in understanding the refractive-index behaviour of the RFMS-a-Si thin films. The value of the static refractive index, n(0), which is related to both the atomic structure and mass density, remains approximately constant up to a threshold Ar-gas pressure of nearly 1 Pa, and then it starts dropping rather abruptly. The decrease found in the Urbach energy, EU, as well as the increase observed in the Tauc gap and slope, Eg and B respectively, for Ar-gas pressures higher than the voided-structure threshold sputtering pressure, clearly suggests that the amount of intermediate-range order present within the RFMS-a-Si layers under study, is increasing in direct response to the increase in the Ar-gas pressure, during the deposition process. This is independently corroborated by the decreasing values of the Raman-intensity ratio, ITA/ITO, as the sputtering pressure increases, in the case of high Ar pressure a-Si films.

Friction and wear properties of amorphous and nanocrystalline Ta-Ag films at elevated temperatures as function of working pressure

Ta-Ag immiscible alloy film shows potential application as a protective coating during sliding contact at high temperatures. In this study, Ta-Ag films were deposited on carbon steel by DC magnetron sputtering at the ambient temperature. The microstructures of Ta-Ag films were adjusted by controlling working pressures (0.2–0.8 Pa) and sputtering powers of tantalum (90 W–100 W). The nano-crystalline α-Ta is deposited at the working pressure of 0.2 and 0.4 Pa while the amorphous Ta is produced at 0.6 and 0.8 Pa for Ta90-Ag8 films. The hardness and elastic of Ta-Ag films decreases with the increase of sputtering pressure. The friction coefficients of nanocrystalline Ta90-Ag8 films deposited at 0.2 and 0.4 Pa are lower than that of amorphous films deposited at 0.6 and 0.8 Pa from RT to 600 °C. A friction coefficient of about 0.32 and low wear rate (1.6 × 10−5 mm3/Nm) is obtained for the Ta90-Ag8 film deposited at 0.2 Pa at 700 °C.

Effects of sputtering pressure on microstructure and mechanical properties of ZrN films deposited by magnetron sputtering

Zirconium nitride films can act as one of the coating materials for important components due to their excellent mechanical properties. Here, we reported a room-temperature magnetron sputtering to deposit ZrN films onto zirconium alloy substrates. The results of sputtering pressure on microstructure and mechanical properties of ZrN films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), atomic force microscope (AFM) and nanoindentation. The results showed that the crystallinity trend of ZrN films increased first and then decreased with the increase of sputtering pressure at room temperature. The variations of surface roughness, the hardness, elastic and modulus of ZrN films were consistent with the crystallinity trend of ZrN films. Finally, we obtained the best mechanical properties of the nanocrystalline ZrN films at a sputtering pressure of 0.7 Pa. The surface roughness was 11.20 nm, the hardness and elastic modulus were 16.022 GPa and 193.518 GPa, respectively.

Sputtering based synthesis of CuO nanoparticles and their structural, thermal and optical studies

In the current research, we report the synthesis of CuO nanoparticles using dc reactive magnetron sputtering technique at various sputtering pressure (10, 20, 30, 40 and 50mTorr) and their structural, thermal and optical properties. The characterization of the synthesized CuO nanoparticles was carried using powder XRD, Raman spectroscopy, FT-IR, FE-SEM, EDX, TEM, TGA and UV–vis DRS. XRD results exhibited the monoclinic phase of CuO nanoparticles and the crystallite size increases with increase in sputtering pressure. The EDX and Raman analysis confirm the formation of high purity CuO nanoparticles. The particle size of synthesized nanoparticles was calculated using TEM analysis. The FE-SEM and TEM results show spherical morphology in aggregated form. TGA results reveal that nanoparticles are purely hydrous and weight loss was inversely correlated to the particle size. UV-DRS results indicated that the band gap energy decreased with increase of sputtering pressure due to increase in particle size.

Cu2ZnSnS4 films with different preferred orientations prepared by pulsed DC magnetron sputtering from a quaternary ceramic target

Cu2ZnSnS4 (CZTS) films applicable to an absorber material in thin film solar cells were prepared at room temperature by pulsed DC magnetron sputtering from a CZTS ceramic target, and the effects of sputtering pressure on the phase, preferred orientation and composition of the deposited CZTS films were investigated. The results indicated that the dominant phase in the deposited films was Kesterite structure, only having the trace impurity phase of Cu2−xS. The preferred orientation was gradually converted from (2 2 0) to (1 1 2) with increasing sputtering pressure. Moreover, the composition of the deposited films was also affected by the sputtering pressures.

Effect of Sputtering Pressure on Surface Roughness, Oxygen Vacancy and Electrical Properties of a-IGZO Thin Films

Thin films of amorphous indium gallium zinc oxide amorphous indium-gallium-zinc-oxide (a-IGZO) were fabricated by DC magnetron sputtering. The influence of sputtering pressure on the microstructures and the electronic properties were investigated. AFM characterization on surface morphology demonstrates that the surface roughness increases with higher sputtering pressure. The oxygen vacancies of the a-IGZO films change considerably and are reduced significantly with increasing sputtering pressure, as disclosed by X-ray photoelectron spectroscopy. Both the increased surface roughness and reduced oxygen vacancy are detrimental to the performance of a-IGZO TFTs. From this point of view, the sputtering should be done at a proper pressure of 0.06 Pa in order to ensure the enhanced performance. The electron saturation mobility ( μ sat ) and the threshold voltage ( V TH ) of the a-IGZO TFTs are 3.32 cm 2 /(V·s) and 24.6 V at such a sputtering condition, respectively.

Effect of sputtering pressure on crystalline quality and residual stress of AlN films deposited at 823 K on nitrided sapphire substrates by pulsed DC reactive sputtering

Aluminum nitride (AlN) is a promising material for use in applications such as deep-ultraviolet light-emitting diodes (UV-LEDs) and surface acoustic wave (SAW) devices. In the present study, the effect of sputtering pressure on the surface morphology, crystalline quality, and residual stress of AlN films deposited at 823 K on nitrided a-plane sapphire substrates, which have high-crystalline-quality c-plane AlN thin layers, by pulsed DC reactive sputtering was investigated. The c-axis-oriented AlN films were homoepitaxially grown on nitrided sapphire substrates at sputtering pressures of 0.4–1.5 Pa. Surface damage of the AlN sputtered films increased with increasing sputtering pressure because of arcing (abnormal electrical discharge) during sputtering. The sputtering pressure affected the crystalline quality and residual stress of AlN sputtered films because of a change in the number and energy of Ar+ ions and Al sputtered atoms. The crystalline quality of AlN films was improved by deposition with lower sputtering pressure.

Composition and optoelectrical properties of sputtering MoSex films

Influence of sputtering pressure on composition, optical and electrical properties of amorphous MoSex films has been systematically investigated. The highest Se concentration and nearly stoichiometric ratio Se/Mo in MoSex films were observed at a sputtering pressure of 0.3 Pa. When the sputtering pressure is increased, the binding energies of Mo 3d and Se 3d peaks of the MoSex films increase, the blue shift of optical transmission edge is observed and the optical band gap decreases from 0.92 to 0.78 eV. Additionally, Hall mobility decreases first and then increases slightly, the resistivity of the films decreases, whereas the carrier concentration of the films increases with an increase in sputtering pressure. The MoSex films deposited at 0.3 Pa have larger Hall mobility (6.45 cm2 V− 1 s− 1) and higher optical band gap (0.92 eV) because of lower Se vacancy defect concentration.

Evaluation of residual stress in sputtered tantalum thin-film

The influence of deposition conditions on the residual stress of sputtered tantalum thin-film has been evaluated in the present study. Films have been deposited by DC magnetron sputtering and curvature measurement method has been employed to calculate the residual stress of the films. Transitions of tantalum film stress from compressive to tensile state have been observed as the sputtering pressure increases. Also, the effect of annealing process at temperature range of 90–300°C in oxygen ambient on the residual stress of the films has been studied. The results demonstrate that the residual stress of the films that have been deposited at lower sputtering pressure has become more compressive when annealed at 300°C. Furthermore, the impact of exposure to atmospheric ambient on the tantalum film stress has been investigated by monitoring the variation of the residual stress of both annealed and unannealed films over time. The as-deposited films have been exposed to pure Argon energy bombardment and as result, a high compressive stress has been developed in the films.