In situ study of film stress and kinetics of platinum silicide formation on silicon

In situ measurements of the film stress and the film reflectivity were carried out when samples of platinum film on silicon were sintered in an inert gas ambient. The reflectivity of the film dropped in two stages when the reaction between platinum and silicon transformed the platinum film to a Pt₂Si film and then to a PtSi film. The kinetics of the silicide formations were studied by monitoring the film reflectivity in situ while the reaction was progressing. The activation energies for the Pt₂Si phase and the PtSi phase formations were derived to be 1.2 eV and 1.7 eV respectively. The stress of the as-deposited platinum films is 1 × 10⁸ Pa. The room temperature stress of the final PtSi film is 1.5 × 10⁹ Pa in which the thermal stress component is far greater than the intrinsic component.     

Effects of oxygen pressure on the microstructural,ferroelectric and magnetic properties of BiFe0.95Mn0.05O3 thin films grown on Si substrates

We have investigated the effects of oxygen pressure on the microstructure, leakage current, ferroelectric and magnetic properties of BiFe_0.95Mn_0.05O₃ (BFMO) thin films epitaxially grown on SrRuO₃, SrTiO₃, and TiN-buffered (001)-oriented Si substrates. X-ray diffraction θ?2θ scans and scanning electron microscope images reveal that the epitaxy and microstructures of the BFMO films were strongly dependent on oxygen pressure during film deposition. Epitaxial BFMO films can be obtained in a low oxygen pressure of 2 Pa while polycrystalline BFMO films were obtained in a relatively high oxygen pressure of 15 Pa. Furthermore, the oxygen pressure strongly influences the ferroelectric properties of the BFMO films grown on Si. The remnant polarization (2P _r) of approximately 107 μC/cm² and coercive field (2E _c) of approximately 580 kV/cm were observed for the epitaxial BFMO films grown in a low oxygen pressure of 2 Pa. The saturation magnetization of the BFMO films decreases with increasing oxygen pressure while the magnetic coercive field remains unchanged.     

Pulsed laser deposition of cobalt ferrite in a reactive O2:N2 atmosphere: effect of the deposition pressure and temperature

Thin films of CoFe₂O₄ have been fabricated by pulsed laser ablation of a metallic CoFe₂ target at two different temperatures (200 and 400 °C) and in various O₂:N₂, 20:80 pressures [from 0.7 Pa (5×10^-3 Torr) up to 26.7 Pa (2×10^-1 Torr)]. Too low pressures resulted in an insufficient oxidation of the deposited material and an antiferromagnetic (Fe,Co)O phase is observed together with CoFe₂O₄. A minimum pressure of 6.7 Pa was found necessary to obtain pure CoFe₂O₄ films with magnetic properties close to the bulk. The higher the pressure and the temperature, the larger was the roughness of the films. The optimum deposition temperature and pressure to obtain flat (3 nm rms roughness) CoFe₂O₄ films were, respectively, 200 °C and 6.7 Pa.     

Stress tuning in AIN thin films

Aluminium nitride films were deposited on fused silica by reactive dc magnetron sputtering from an Al-target in an Ar/N₂ atmosphere. In-situ measurements during deposition provided data concerning mechanical stresses inherent to the growing thin films. By variation of both the gas composition (Ar, N₂) and the total gas flow in the vacuum chamber, the occuring intrinsic stresses could be shifted in magnitude and direction. Stress values of the AIN films ranged from ?0.9 GPa (compressive) to +1.2 GPa (tensile) when the Ar/N₂ ratio was varied between 3:1 and 1:3 for the different total gas flows of 50 sccm, 100 sccm, and 200 sccm (corresponding to total gas pressures of approximately 2 × 10^?1 Pa, 4 × 10^?1 Pa, and 8 × 10^?1 Pa respectively). Investigations of optical and structural film properties were carried out and the results were related to the observed film stress.     

A Double-Primary Dead-Weight Tester for Pressures (35–175) kPa in Gage Mode

Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also been used. Recent advances in technology on two fronts i) the fabrication of large-diameter pistons and cylinders with good geometry; and ii) the ability to measure the dimensions of these components, have allowed some dead-weight testers at NIST to approach total relative uncertainties (k = 2) in dimensionally-derived effective areas near 5 × 10⁻⁶. This paper describes a single piston/cylinder assembly (NIST-PG201WC/WC) that serves as both a primary gage in which both piston and cylinder are measured dimensionally and a controlled-clearance primary gage (employing the Heydemann-Welch method). Thus it allows some previous assumptions about the modeling of dead-weight testers to be checked. For the gage described in this paper the piston/cylinder clearance obtained from the two analyses have relative differences of 4 × 10⁻⁶ to 7 × 10⁻⁶ over the pressure range 35 kPa to 175 kPa. Some implications of these results will be discussed. From the dimensional characterizations and auxiliary measurements we have determined that the effective area for this gauge at 20 °C is: A_eff,20 = 1961.0659mm²(1 + 3.75 × 10^?12P/Pa + 3.05 × 10^?12P_J/Pa), where P is the system pressure and P_J is a control pressure. The estimated relative uncertainty in effective area is 8.2 × 10⁻⁶ +1.4 × 10⁻¹¹ P/Pa (k = 2). The temperature coefficient for the area was measured and found to be (9.06 ± 0.04) × 10⁻⁶/K. Thus using the gage at a reference temperature of 23 °C yields an effective area: A_eff,23 = 1961.1192mm²(1 + 3.75 × 10^?12P/Pa + 3.05 × 10^?12P_J/Pa), with almost no increase in the uncertainty over that at 20 °C.     

Magnetic properties of sputtered multilayers of Mo/Ni

We have studied the d.c. magnetization of Mo/Ni artificial superlattices in the temperature range 5–300 K and in magnetic fields of up to 10⁷/4πAm^-1 (10kG). The saturation magnetization and the Curie temperature behavior are consistent with expectations based on thin film effects. However, there are indications of ferromagnetic coupling across the normal metal and the coercive field shows an unexpected peak at a layer thickness of 25 Å.     

Effect of temperature on the properties of Al:ZnO films deposited by magnetron sputtering with inborn surface texture

Al:ZnO (AZO) films were deposited on glass substrate with inborn surface texture by magnetron sputtering at a power density as high as 7 W/cm². The sputtering parameters, such as argon working pressure and substrate temperature were varied from 1.0 to 6.0 Pa and from room temperature to 500 °C, respectively. All the films exhibited perfect (002) orientations with very weak (004) peaks measured by X-ray diffraction. A linear relationship between the growth rate of AZO film and working pressure was found. The AZO film with best electrical properties of all films obtained at room temperature was deposited at working pressure of 2.0 Pa. And the root-mean-square roughness tested by atomic force microscopy was 37.50 nm, which indicated that surface texture was successfully fabricated without further etching process. For higher substrate temperature a decrease in the resistivity was observed due to an increase in the mobility and the carrier concentration. Resistivity low as 9.044 × 10⁻⁴ ohm/cm was obtained at 500 °C and 2.0 Pa, the corresponding mobility and carrier concentration were 20.45 m²/Vs and 3.379 × 10²⁰/cm³, respectively. The grain size and the surface texture size tested by scanning electron microscopy also peaked at 500 °C. All the films showed a relatively high transmittance about 80%.     

Modeling breakage and motion of black pepper seeds in cryogenic mill

The present investigation aims to represent three-dimensional motion and breakage phenomena of black pepper seeds in the cryogenic mill (hammer mill) using discrete element method (DEM). In DEM modeling, bonded particle model was coupled with Hertz-Mindlin contact model. Calibration method was used to select appropriate model (bond) parameters. The calibrated set of bond parameters includes 3.12?×?10¹¹?Pa?m^?1 normal stiffness; 1.56?×?10¹¹?Pa?m^?1 shear stiffness; 3.88?×?10⁸?Pa critical normal stiffness; 1.94?×?10⁸?Pa critical shear stiffness. Besides, the validity of calibrated parameters was tested in the hammer mill. The observed qualitative and quantitative results (breakage and flow pattern) of numerical and experimental approaches were in good agreement. Based on these results, a few prefatory suggestions were provided to improve the design aspects of the mill. Overall, DEM modeling offered a better understanding of particle breakage and flow pattern in the mill.     

15 kV class high-voltage electrical vacuum feedthrough

In the feeder system of the Experimental Advanced Superconducting Tokamak (EAST), the high-voltage (HV) electrical vacuum feedthrough plays an important role in transmitting the voltage signals from one vacuum environment to anther vacuum environment under cryogenic temperature. Due to no commercial solutions, the feedthroughs for EAST were developed in the Institute of Plasma Physics, Chinese Academy of Sciences. In this paper, the structural design, electrical analysis, structural analysis and experiments involving thermal cycle, helium gas tightness, HV-leakage current and Paschen discharge are presented. The experimental result indicates that the leak rate of the developed feedthroughs was less than 1 × 10⁻⁹ Pa·m³·s⁻¹. After the 5 thermal cycles from room temperature (RT) to 77 K, the HV-leakage current experiment under 10⁻³ Pa vacuum environment and the Paschen discharge experiments of feedthroughs were performed, the leakage current under 15 kV DC is lower than the allowable value 5 µA, and the leakage currents in helium gas and nitrogen gas from 1 Pa to 50 kPa are lower than the allowable value 10 µA.     

Distillation recovery of AsCl<Subscript>3</Subscript> from AsCl<Subscript>3</Subscript>-HCl-H<Subscript>2</Subscript>O solutions

The distillation recovery of arsenic trichloride from saturated solutions in concentrated hydrochloric acid has been studied experimentally at a pressure of 1.013 × 10⁵ Pa and temperatures from 60 to 75°C, and the optimal process temperature has been determined.     

The mechanical properties of PVC under high pressure

The deformation properties of PVC have been studied under high pressure. Craze initiation and yield criteria have been proposed. The brittle-to-ductile transition was observed between 1×10⁷ and 2×10⁷ Pa, which is a relatively low transition pressure compared to polystyrene. Deformation in the post-yield region occurred by neck formation and subsequent drawing to produce chain orientation. When PVC was exposed to the pressure-transmitting fluid, silicon oil, a strong environmental stress cracking effect was observed.     

The conversion of para to orthohydrogen in a gamma-ray and neutron radiation field

The radiation-induced conversion of para to orthohydrogen was investigated at pressures between 1 to 15 × 10⁶ Pa at three temperatures: 77 K (LN₂), 200 K (dry ice), and 300 K (ambient). The radiation dose levels were studied: gamma rays only at 8 × 106 rads and a combination of 5 × 10¹² n mm^?2, E > 1 MeV, plus gamma rays at 8 × 10⁵ rads. The conversion at LN₂ temperature was nearly zero in all cases.     

Calibration of ultrahigh vacuum gauge from 10−9 Pa to 10−5 Pa by the two-stage flow-dividing system

A new two-stage flow-dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂. This system is designed based on the techniques for our previously developed calibration system in the range from 10⁻⁷ Pa to 10⁻² Pa. Three modifications were performed to extend the calibration pressure to a lower range. The relative standard uncertainty of the generated pressure (k = 1) is in the range from 2.3% to 2.6%, from 10⁻⁹ Pa to 10⁻⁵ Pa. The characteristics of ultrahigh vacuum gauges were also examined by using this system. The stabilities of the pressure reading, the linearity, the temperature dependence, and the long-term stability were examined. These results show that the calibration of ultrahigh vacuum gauges is possible in the range from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂ with the uncertainty of about 6.0% (k = 2) by this new system.     

Effects of annealing on the formation of Mg2Si film prepared by resistive thermal evaporation method

The effects of annealing time and temperature on the formation and structure of magnesium silicide (Mg₂Si) films were investigated. Magnesium films of 380 nm thickness were deposited on Si (111) substrates using resistive thermal evaporation method. The films were then annealed in an annealing furnace under a low vacuum atmosphere of 10^?1–10^?2 Pa. The results showed that the crystallization quality of Mg₂Si films was strongly affected by the annealing time and temperature. Annealing at 400 °C for 4 h was the optimal preparation conditions for Mg₂Si films.     

Structural and optical studies on dc reactive magnetron sputtered Cu2O films

Cuprous oxide (Cu₂O) thin films were deposited by dc reactive magnetron sputtering technique onto glass substrates by sputtering of pure copper target in a mixture of argon and oxygen gases under various oxygen partial pressures in the range 8 × 10^− 3–1 × 10^− 1 Pa at a constant substrate temperature of 473 K and a sputtering pressure of 4 Pa. The dependence of cathode potential on the oxygen partial pressure was explained in terms of cathode poisoning effect. The influence of oxygen partial pressure on the structural and optical properties of Cu₂O films was systematically studied. Single phase films of Cu₂O were obtained at an oxygen partial pressure of 2 × 10^− 2 Pa. The films formed at an oxygen partial pressure of 2 × 10^− 2 Pa were polycrystalline with cubic structure and exhibited an optical band gap of 2.04 eV.     

Calibration of ultrahigh vacuum gauge from 10 Pa to 10 Pa by the two-stage flow-dividing system

A new two-stage flow-dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂. This system is designed based on the techniques for our previously developed calibration system in the range from 10⁻⁷ Pa to 10⁻² Pa. Three modifications were performed to extend the calibration pressure to a lower range. The relative standard uncertainty of the generated pressure (k = 1) is in the range from 2.3% to 2.6%, from 10⁻⁹ Pa to 10⁻⁵ Pa. The characteristics of ultrahigh vacuum gauges were also examined by using this system. The stabilities of the pressure reading, the linearity, the temperature dependence, and the long-term stability were examined. These results show that the calibration of ultrahigh vacuum gauges is possible in the range from 10⁻⁹ Pa to 10⁻⁵ Pa for N₂, Ar, and H₂ with the uncertainty of about 6.0% (k = 2) by this new system.     

Stress dependent properties of Ga-doped ZnO thin films prepared by magnetron sputtering

Ga doped ZnO films have been prepared by radio frequency magnetron sputtering at room temperature. The (002) preferential orientation is observed for all the films. In plane lattice parameters of the films are obtained by X-ray diffraction θ–2θ scan with the samples tilted 61.63°. Intrinsic compressive stress is observed parallel to the film surface, varying from 410 to 3,000 MPa. Electrical properties of the films show a great dependence on the stress. Carrier concentration and mobility are both improved as the intrinsic compressive stress is reduced which is greatly affected by adjusting the deposition pressure. Therefore, the electrical resistivity is optimized to be 1.8 × 10^?3 Ω·cm for the film prepared at 8.0 Pa. In addition, the optical analysis reveals that the transmittance of the films is higher than 90 %. The band gap of the films increases from 3.11 to 3.38 eV with decreasing the stress due to the increase in the carrier concentration, which is related to Burstein–Moss effect.     

Spherical indentation of tooth enamel

Spherical indentation measurements were made on enamel surfaces of intact human teeth. From the load versus depth of indentation curve Young's modulus was found to be typically 8.3×10¹⁰ Pa and the yield stress to be 3.3×10⁸ Pa. Young's modulus was observed to vary with moisture content and with the orientation of the enamel surface. Viscoelastic behaviour was evident, also depending on the moisture content of the enamel.     

High vacuum tribology of polycrystalline diamond coatings

Polycrystalline diamond coatings have been grown on unpolished side of Si(100) wafers by hot filament chemical vapour deposition process. The morphology of the grown coatings has been varied from cauliflower morphology to faceted morphology by manipulation of the growth temperature from 700°C to 900°C and methane gas concentration from 3% to 1·5%. It is found that the coefficient of friction of the coatings under high vacuum of 133·32×10^?7 Pa (10^?7 torr) with nanocrystalline grains can be manipulated to 0·35 to enhance tribological behaviour of bare Si substrates.     

Tensile creep study of copper with alumina dispersions prepared by high rate physical vapour deposition

Mott has suggested that the ideal creep-resistant material will be one with a fine grain size in which the grain boundaries are filled with some substance, say a refractory oxide, to inhibit the motion of grain boundaries. Such a system, alumina-dispersed copper, was prepared by high rate physical vapour deposition. The process parameters and their effect on structure and texture have been studied. The room temperature mechanical properties have also been reported. This paper deals with a high temperature mechanical property, i.e. tensile creep. Tests were made on a constant-stress vacuum creep rig with a Ferrometic feedthrough to ensure a zero leakage rotary seal. A vacuum of 1.33 X 10^?3 Pa was maintained. The test temperatures were 500°C (0.57T_m) and 700°C (0.72T_m). The stresses applied were 2.07, 3.45, 4.14 and 6.89 X 10⁷ Nm^?2. Tests were made on as-deposited films and on cold-rolled condensates.Minimum creep rate curves showed the effect of the alumina content in raising the creep resistance of copper. Cold rolling also reduced the minimum creep rate markedly. Varying the temperature and stress affected the shape of these curves. Stress-rupture plots were used to summarize the data.Grain refinement together with a fine stable dispersion seem to give improved creep strength. The critical barrier of the Orowan stress was noted. The stress exponent for a low alumina deposit (0.21 vol.%) was about 8, and the apparent activation energy for creep was about 202 kJ mol^?1 (0.13 vol.%). There was an inverse relationship between the rupture life and the minimum creep rate, their product being constant (about 0.2).