Effects Of Ar Pressure Research Articles

Effect of Ar pressure on phase transition characteristics and charge transport mechanism in VO2 films grown by RF sputtering of V2O5

In this study, we report the growth and characterization of VO2 films deposited on YSZ (001) substrate employing RF magnetron sputtering of vanadium pentoxide (V2O5) target in pure Ar gas ambient. The VO2 film growth has been carried out at ∼700 °C for ∼15 min at ∼100 W RF power with a flow rate of ∼20 sccm at Ar gas deposition pressure of ∼3, ∼6, ∼20, and ∼40 mTorr. x-ray diffractometry and Raman spectroscopy show that the nearly pure VO2 phase achieved at lower Ar pressure, e.g., ∼3 and ∼6 mTorr transform into a multiphase V-O system at ∼20 and ∼40 mTorr. This pattern is also supported by the electrical transport measurements through the occurrence of hysteretic IMT in films grown at ∼3 and ∼6 mTorr and the absence of this signature in these films deposited at ∼20 and ∼40 mtorr Ar pressure. The most pronounced with the strongest hysteresis is seen in the Y6 film, and therefore, the optimum growth pressure in the present study is ∼6 mTorr. The suppression of IMT in Y20 and Y40 is attributed to the appearance of other V-O phases, which smear out the phase transition. The activation energy of the insulating phase is estimated from the Arrhenius fit to the ρ-T data is found to be ∼0.223 eV at ∼3 mTorr Ar pressure which increases to ∼0.311 eV for ∼6 mTorr film in the cooling cycle. The low temperature (120K≤T≤300K) transport conduction in all VO2 films is governed by Efros-Shklovskii’s variable range hopping (ES-VRH) mechanism with a systematic relation between growth conditions and phase transition characteristics. Thus, Argon gas pressure plays a critical role in growth and brings out the feasibility of VO2 films growth by RF sputtering of oxide V2O5 target under Argon ambient only.

Effect of Ar pressure on the wettability of copper droplet on graphite substrate by molecular dynamics simulation

Effect of Ar pressure on the wettability of copper droplet on graphite substrate by molecular dynamics simulation

Direct Regulation of O/W Stoichiometric Ratio and Microstructure in Tungsten Oxide Electrochromic Films by Ar Pressure Using Oxide Target Sputtering

Herein, amorphous tungsten oxide electrochromic (EC) films are successfully prepared by radiofrequency (RF) magnetron sputtering in pure Ar atmosphere using an oxide target. The effect of Ar pressure on the apparent color, deposition rate, crystal structure, O/W ratio, surface morphology, and EC properties of the as‐deposited tungsten oxide films is systematically investigated using spectroscopic ellipsometry, X‐ray photoelectron spectroscopy, X‐ray diffraction, scanning electron microscopy, and cyclic voltammetry. Interestingly, the Ar gas pressure plays a key role in regulating the O/W ratio, microstructure, and EC properties of the obtained tungsten oxide films. The films are all substoichiometric, and the O/W ratio changes from 2.79 to 2.89 with the increase in Ar pressure. In addition, the loose surface microstructure is shown as Ar pressure increases. The tungsten oxide films deposited at the Ar gas pressure of 1.2 Pa reaches the deposition rate of 13.0 nm min−1, the largest optical modulation of 71.2% at 550 nm, and the EC efficiency of 51.3 cm2 C−1. This film also reveals excellent electrochemical stability and sustains more than 200 cycles. These results provide a simple solution for preparing high‐quality tungsten oxide EC films using oxide ceramic targets in pure Ar atmosphere.

Low-temperature fabrication of sputtered high-k HfO2 gate dielectric for flexible a-IGZO thin film transistors

In this work, low temperature fabrication of a sputtered high-k HfO2 gate dielectric for flexible a-IGZO thin film transistors (TFTs) on polyimide substrates was investigated. The effects of Ar-pressure during the sputtering process and then especially the post-annealing treatments at low temperature (≤200 °C) for HfO2 on reducing the density of defects in the bulk and on the surface were systematically studied. X-ray reflectivity, UV-vis and X-ray photoelectron spectroscopy, and micro-wave photoconductivity decay measurements were carried out and indicated that the high quality of optimized HfO2 film and its high dielectric properties contributed to the low concentration of structural defects and shallow localized defects such as oxygen vacancies. As a result, the well-structured HfO2 gate dielectric exhibited a high density of 9.7 g/cm3, a high dielectric constant of 28.5, a wide optical bandgap of 4.75 eV, and relatively low leakage current. The corresponding flexible a-IGZO TFT on polyimide exhibited an optimal device performance with a saturation mobility of 10.3 cm2 V−1 s−1, an Ion/Ioff ratio of 4.3 × 107, a SS value of 0.28 V dec−1, and a threshold voltage (Vth) of 1.1 V, as well as favorable stability under NBS/PBS gate bias and bending stress.

Effects of Ar pressure on magnetic and magnetocaloric properties of sputtered Er–Co thin films

The magnetic and magnetocaloric properties of Er–Co thin films fabricated by sputtering under an Ar pressure (PAr) varying from 2 to 10mTorr in steps of 2mTorr are investigated. The content of Co in the sputtered thin films decreases slightly as the PAr increases from 2 to 10mTorr, resulting in a film composition varying from ErCo1.07 to ErCo0.93. Extensive changes in the magnetic and magnetocaloric properties are observed. As the PAr increases, the compensation temperature increases substantially from 83 to 141K, as well as the temperature at which the maximum change in the magnetic entropy occurs, particularly in the low PAr range. Considering the small change observed in the composition of the thin films as a function of PAr, the changes in the magnetic and magnetocaloric properties are extensive, indicating that the PAr plays an important role in affecting the aforementioned properties in amorphous magnetic thin films.

Synthesis of yttrium silicates by annealing r.f. sputtered glassy coatings

In this work, the composition evolution of yttrium silicate coatings was investigated during r.f. sputtering from a γ-Y2Si2O7 compound target, focusing on the effect of Ar pressure, target-substrate distance and r.f. power. By controlling the number of collisions between Ar gas and target species, glassy coatings with the stoichiometry of Y2SiO5 and Y2Si2O7 were obtained. Finally, the formation of X2-Y2SiO5 on SiC substrates was observed after annealing the glassy coatings in air at 1250 °C. After annealing at 1550 °C γ-Y2Si2O7 crystallized with high quality and grain boundaries appeared to be crack-free.

Influence of working gas pressure on the performance of W/Si multilayers

The effect of Ar pressure on the performance of W/Si multilayers is investigated. W/Si multilayers were deposited by a high vacuum DC magnetron sputtering system. The Ar pressure was changed from 1.0 to 5.0 mTorr with an interval of 1.0 mTorr during the deposition process. Electron probe microanalysis and Rutherford backscattering are performed to determine the Ar content incorporated within these multilayers. The results demonstrate that less Ar is incorporated within the sample when more Ar is used in the plasma, which could be explained by the increase of the collision probability and the decrease in the kinetic energy of Ar ions arriving at the substrate when more Ar exists. The grazing incident X-ray reflectivity (GIXR) at 0.154 nm is used to determine the structural parameters of the layers. The results show that the structures of these multilayers prepared at different Ar pressure are very similar and that the interface roughness increases quickly when the Ar pressure is higher than 3.0 mTorr. The measurements of the extreme ultraviolet (EUV) reflectivity indicate that the reflectivity decreases when Ar pressure increases. The fitting results of GIXR and EUV reflectivity curves indicate that with an increase of Ar pressure, the density and decrement of the refractive index are increased for W and decreased for Si, which is mainly due to (1) the decrease in Ar content incorporated within these multilayers which affects their performance and (2) the increase of collision probability for sputtered W and Si, the decrease of their average kinetic energy arriving at the substrate, and thus the loosing of their layers.

The study of conductance in magnetic tunnel junctions with a thin MgO barrier: The effect of Ar pressure on tunnel magnetoresistance and resistance area product

The thickness dependence of tunnel magnetoresistance and resistance area product in Co40Fe40B20/MgO wedge/Co40Fe40B20 magnetic tunnel junctions (MTJs) has been studied for multiple Ar partial pressure (PAr) values during MgO sputtering. The extension of the simple equivalent circuit model [B. Oliver et al., J. Appl. Phys. 91, 4348 (2002)] has been suggested in order to include different transport mechanism contributions to the overall conductance of the MTJ as a function of the MgO barrier thickness. Parameters of the model, used for quantitative description of the conductivity of unpatterned MTJ stacks, have been analyzed as a function of PAr.

Effect of Ar pressure on grain size of magnetron sputter-deposited Cu thin films

Copper (Cu) thin films with thicknesses ranging from 300 to 425 nm were prepared at various argon (Ar) pressures on p-type silicon substrates by direct current magnetron sputtering deposition. X-ray diffraction (XRD) and Karl Suss four-point probe were employed to study the film crystallinity and conductivity, respectively, as a function of Ar pressure in the deposition process. Detailed analysis on the XRD patterns shows that low Ar pressure enhances the Cu film crystallinity with larger grain size, which was deduced using Scherrer's formula. The behaviour of the electrical property of the Cu films complies with the trend of the grain size with Ar pressure, in which the film conductivity decreases with increasing Ar pressure. The authors attribute these phenomena to the degraded surface diffusion mechanism of the adatom on the growing surface, with increasing Ar pressure during the sputtering deposition process.

Microstructure and optical properties of nanocrystalline CaWO 4 thin films deposited by pulsed laser ablation in room temperature

Nanocrystalline CaWO 4 films were successfully deposited by pulsed laser ablation at various background Ar gas pressures (10–100 Pa) without substrate heating or after annealing treatment. The effects of Ar pressure on microstructure, surface morphology, chemical composition and optical properties were investigated by XRD, HR-TEM, FE-SEM, XPS, UV–vis and PL analyses. The crystallite size of CaWO 4 films increased with increasing Ar pressure, which was associated with a change of surface morphology. Reduced tungsten states [W 5+] or [W 4+] caused by oxygen vacancies were observed at 10 Pa. However, over 50 Pa, the atomic concentration of all the constituent elements was almost constant, especially [Ca]/[W] ratio, which was nearly unity. The optical energy band-gap of CaWO 4 films was strongly dependent on the Ar pressure, i.e., decreased from 4.9 to 4.5 eV with the increase of Ar pressure from 50 to 100 Pa. The photoluminescence (PL) spectra was positioned in a blue-shifted region around 378 nm compared with emission at 420 nm of bulk CaWO 4 target, which clearly demonstrates the optical band-gap widening phenomena induced by quantum-size effect.

DC-sputtered Pt 3(Co 1− xNi x) ( x=0.4) alloy films at different ultra-high Ar pressure with perpendicular anisotropy

The effect of Ar pressure upon the structure, magnetic and magneto-optical properties was studied in Pt 3(Co 1− x Ni x ) ( x=0.4) alloy films with a Curie temperature T c of 200°C. The experimental data indicated that 20 Pa was the most suitable Ar pressure for obtaining 100% remanence, high coercivity and the largest Kerr rotation angle θ k (0.435°) during the blue-wave range. X-Ray studies showed that the 〈111〉 texture was not the source of perpendicular magnetic anisotropy in the studied films. Atomic force microscopy results showed that the average roughness of the films may greatly affect the saturated magnetization and, consequently, affect the shape anisotropy. The incremental inclination of H c could be explained by the extended Kronmuller formula in the range of Ar pressures from 3 to 20 Pa.

High-coercivity CoPt alloy films prepared at ultra-high Ar pressure

Large coercivity of 4.8 KOe with fine grains and smooth surface was obtained in Co 0.27Pt 0.73 alloy film deposited directly on heated glass by sputtering an alloy target at ultrahigh Ar pressure of 20 Pa. The effect of Ar pressure on the microscopic structure and magnetic anisotropy was investigated. The increase of the coercivity with the sputtering pressure was attributed to the increase of the perpendicular magnetic anisotropy but not the change of microscopic structure. The similarity of Kerr hysteresis loops of a film on and without substrate showed clearly that the perpendicular magnetic anisotropy did not result from external strain. Strong evidence is shown that there was Co-rich phase segregation in the films with strong perpendicular magnetic anisotropy.

Effects of Ar pressure during CoCrPt sputter-deposition on read/write and related properties of CoCrPt/Cr magnetic recording media formed at low temperatures

Structures, magnetic properties and read/write properties were studied for low-temperature-growth CoCrPt/Cr magnetic recording media, of which CoCrPt films were sputter-deposited under various Ar pressures. Increase of Ar pressure causes both isolation enhancement and size decrease of CoCrPt grains, which are epitaxially grown on Cr grains. Coercivity increases as Ar pressure increases upto 20–30 mTorr. With an increase of Ar pressure, fluctuation field increases more rapidly than the case when the magnetic film thickness is decreased. Consequently, an increase of Ar pressure for sputter deposition significantly decreases medium noise with a slight decrease of output signal. The highest signal-to-noise ratio of 26.4 dB for 75 kFCI recording was obtained with the Ar pressure of 30 mTorr. This fabrication technique, which requires neither a thick Cr underlayer nor a Cr underlayer deposited under high Ar pressure, is especially suitable for the media with plastic substrates.

スパッタ法でＡｌ‐Ｍｇ合金基板上に成膜したＡｌＮ薄膜の防食特性および皮膜構造に与える成膜時のＡｒガス圧の影響

A series of AlN thin films was synthesized on Al-25mass%Mg substrate under different Ar pressures from 007 to 1.3Pa using rf magnetron sputtering. The effects of Ar pressure on the corrosion protection in a 5mass%NaCl solution and structural properties were studied. As Ar pressure was increased above 027Pa, the corrosion resistance of the AlN-coated Al-Mg alloy was significantly improved. Residual film stress was compressive under low Ar pressures, which decreased as Ar pressure increased and turned tensile at high Ar pressures. An obvious correlation was observed between the corrosion protection property and residual stress. A coating with low residual stress was superior in corrosion protection to a coating with high compressive residual stress. The change of the corrosion protection property is discussed in connection with the residual stress of the sputtered film. The origin of the residual stress in the AlN coating is also discussed from the viewpoint of the energy change in sputtered particles.

Damaged depth in GaAs processed by Ar plasma etching

The damaged depths in GaAs processed by Ar plasma etching under various applied radio-frequency (RF) voltages and Ar pressures in a parallel-plate type apparatus were studied. The damaged depth was evaluated in terms of the chemically etched thickness at which the photoluminescence intensity recovers. The damaged depth decreased as the applied radio frequency peak voltage was decreased. The depth was extraordinarily deep in the lower radio frequency voltage region. The effect of Ar pressure on damaged depth was small in the range from 1 to 10 Pa.

Effects of Ar Pressure and Substrate Bias on TbCo Sputtered Films

The effect of Ar pressure on the magnetic characteristics and structure of TbCo sputtered film was studied using bias voltages of 0, -50, and -100 V as parameters. In zero bias films, varying the Ar pressure caused different types of stress (tensile or compressive) as well as structural changes in these films. The Tb atomic density in the films made while alternating the bias voltage between 0 and -100 V was modulated, and these modulated films had perpendicular magnetization characteristics.

Influence of Sputtering Conditions on Perpendicular Magnetic Anisotropy in GdTbCo Amorphous Films

The effects of Ar pressure on GdTbCo film characteristics without bias voltage were studied. Sample films demonstrated a large perpendicular anisotropy (K u ) which increased with the Tb contraction. In GdCo films, K u became less negative as the Ar pressure increased, but K u decreased in films containing Tb. Other results indicated that GdTbCo disks will be easy to manufacture.

Structure and Magnetic Properties of Sputtered (Gd,Tb)-(Fe,Co) Films

The effect of Ar pressure on internal stress and magnetic characteristics of various rare-earth transition metal (Gd or Tb)-(Co or Fe) films were studied. Increasing the Ar pressure changed the internal stress of all of the films tested from compressive to tensile. The authors suggest that Ar pressure affects internal stress and fractured the cross-sectional structure because the pressure affects the mean free path of the particles.

Effects of Air pressure and substrate bias on magnetic properties and microstructure in amorphous TbCo sputtered films

Effects of Ar pressure and negative substrate bias voltage on magnetic properties and micro-structure in amorphous TbCo sputtered films are investigated. Magnetic properties, especially perpendicular anisotropy, depend strongly on Ar pressure and substrate bias. A perpendicular anisotropy of the order of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> erg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> with a rectangular hysteresis loop is induced in the films deposited at 10 mTorr of Ar pressure without bias or in the films deposited with 100-150 V negative bias. In these films, the ordered fiber structure developed perpendicular to the film plane is observed, which is due to the moderate bombardment of energetic species. The large perpendicular anisotropy is associated with the ordered fiber structure.

Rotatable Anisotropy and Property Control of CoZr Sputtered Films

To clarify the origin of rotatable anisotropy observed in CoZr sputtered films, the effects of Ar pressure and other conditions during RF sputtering of samples on glass were studied. Increases in Ar pressure give rise to sharp jumps in film coercivity Hc and anisotropic field Hk; films with a rotatable anisotropy, as determined from magnetization curves and domain observations, had extremely high Hc and Hk values. If the film magnetostriction is positive-valued, tensile stresses in the film due to high Ar pressures will give rise to an anisotropy with the easy axis within the plane of the film.