New leak element using sintered stainless steel filter for in-situ calibration of ionization gauges and quadrupole mass spectrometers

A new leak element using a sintered stainless steel filter with a pore size of less than 1 μm has been developed for in-situ calibrations of ionization gauges (IGs) and quadruple mass spectrometers (QMSs). The gas flow through this leak element realizes molecular flow at an upstream pressure of less than 10⁴ Pa. This new leak element, which is a kind of open-type standard leak, has four advantages. (1) Calibrations for various gas species are available only with this single leak element because the conductance is easily compensated for gas species by molecular mass. (2) Calibrations with multiple pressure points are easily available because the conductance is constant against changing upstream pressure. (3) Calibrations for a gas mixture are available because the interference effect between gas molecules in a gas mixture is negligible. (4) The dependence of flow rate on temperature is small and is compensated theoretically. These advantages were experimentally demonstrated. The stability and uncertainty of the leak element were also evaluated. The changes in the conductance of this leak element were less than 3% over one year. Since the conductance is typically 10⁻¹⁰ · m³/s, the reference gas flow in the range from 10⁻⁸ Pa · m³/s to 10⁻⁶ Pa m³ is obtained by changing the upstream pressure from 10² Pa to 10⁴ Pa with an uncertainty of approximately 6%.     

Stability tests of ionization gauges using two-stage flow-dividing system

Stability tests of four ionization gauges (a BA gauge, an extractor gauge, an AT gauge, and a BA gauge with a heating electrode) were performed using a two-stage flow-dividing system from four viewpoints: (1) the fluctuation and drift of pressure readings, (2) the repeatability of pressure readings, (3) the change in sensitivity owing to prior conditions of use and (4) long-term stability. These tests were performed at pressures from 8 × 10⁻⁶ Pa to 8 × 10⁻⁴ Pa using N₂ gas under tightly controlled conditions.The fluctuation and drift of the four IGs were within 1% over 1 h. Their repeatability was also within 1% during eight cycles with an interval of 1 h between each cycle. Although changes in sensitivity of several percent owing to prior conditions of use were observed, the sensitivity was recovered to within 1% of its original values after operation in ultrahigh vacuum for one day. The result of a long-term stability test over a year showed that the sensitivity of the four IGs tended to decrease by 2.6-5.4% due to aging, depending on the gauge.     

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.     

Effect of base and oxygen partial pressures on the electrical and optical properties of indium molybdenum oxide thin films

Indium molybdenum oxide thin films were RF sputtered at room temperature on glass substrates with a reference base pressure of 7.5 × 10^− 4 Pa. The electrical and optical properties of the films were studied as a function of oxygen partial pressures (OPP) ranging from 1.5 × 10^− 3 Pa to 3.5 × 10^− 3 Pa. The obtained data show that the bulk resistivity of the films increased by about 4 orders of magnitude (from 7.9 × 10^− 3 to 7.6 × 10¹ Ω-cm) when the OPP increased from 1.5 × 10⁻³ to 3.5 × 10^− 3 Pa, and the carrier concentration decreased by about 4 orders (from 1.77 × 10²⁰ to 2.31 × 10¹⁶ cm^− 3). On the other hand, the average visible transmittance of 30.54% of the films (brown colour; OPP = 1.5 × 10^− 3 Pa) was increased with increasing OPP to a maximum of 80.47% (OPP = 3.5 × 10^− 3 Pa). The optical band gap calculated from the absorption edge of the transmittance spectra ranges from 3.77 to 3.88 eV. Further, the optical and electrical properties of the films differ from those deposited at similar conditions but with a base pressure lower than 7.5 × 10^− 4 Pa.     

Chemical vapor deposition of phase-rich WC thin films on silicon and carbon substrates

Chemical vapor deposition was used to deposit tungsten carbide from a mixture of WCl₆, H₂ and C₃H₈ at 750-1050 °C on silicon and carbon substrates. The phase composition of the films was correlated with substrate temperature, substrate position in the reactor, and total flow rates. X-ray diffraction and X-ray photoelectron spectroscopy were employed to investigate the surface and bulk properties of the thin films. Thick, adherent films of phase-rich hexagonal WC were deposited using 1.3 × 10³ Pa total pressure, 1050 °C substrate temperature, and reactant flow rates of H₂/C₃H₈/Ar/WCl₆ = 1.8 × 10^− 2/3.6 × 10^− 3/8.9 × 10^− 4/1.8 × 10^− 4 mol/min, where Ar is the carrier gas. The surface composition was oxygen and carbon rich as compared with the bulk.     

Pumping performance analysis on turbomolecular pump

The pumping speed, conductance, and throughput of turbomolecular pump are investigated by both experiment and numerical simulation. The mass flow rates varying from 0.2 to 19.2 sccm (standard cubic centimeter per minute) for various inlet pressures are conducted in experiment. The experimental and analytic pumping speeds versus the inlet pressures of turbomolecular pump for N₂ were revealed. The pumping speeds obtained from experimental and simulation analysis are consistent at inlet pressures ranged from 5 × 10⁻² to 8 × 10⁻² Pa. When the inlet pressure is below 10³ Pa, the conductance decreases because the flow enters the transition flow region. Finally, the influence of inlet pressure on the throughput is also reported.     

Ultra-thin zinc oxide film on Mo(100)

Zinc oxide films on a single crystal Mo(100) substrate were fabricated by annealing the pre-deposited metal Zn films in 10^− 5-10^− 4 Pa O₂ ambience at 300-525 K, and were characterized by in situ Auger electron spectroscopy, electron energy loss spectroscopy, low energy electron diffraction and high-resolution electron energy loss spectroscopy. The results show that the atomic ratio of oxygen to zinc in zinc oxide film is significantly dependent on sample annealing temperature and O₂ pressure. A stoichiometric zinc oxide film has been obtained under ∼10^− 4 Pa O₂ at about 400 K. A redshift of Fuchs-Kliewer phonon energy correlated with surface oxygen deficiency is observed.     

Chemical diffusion coefficient of lithium ion in Li3V2(PO4)3 cathode material

The kinetic properties of monoclinic lithium vanadium phosphate were investigated by potential step chronoamperometry (PSCA) and electrochemical impedance spectroscopy (EIS) method. The PSCA results show that there exists a linear relationship between the current and the square root of the time. The D?_Li values of lithium ion in Li_3-xV₂(PO₄)₃ under various initial potentials of 3.41, 3.67, 3.91 and 4.07 V (vs Li/Li⁺) obtained from PSCA are 1.26 × 10^− 9, 2.38 × 10^− 9, 2.27 × 10^− 9 and 2.22 × 10^− 9 cm²·s^− 1, respectively. Over the measuring temperature range 15-65 °C, the diffusion coefficient increased from 2.67 × 10^− 8 cm²·s^− 1 (at 15 °C) to 1.80 × 10^− 7 cm²·s^− 1 (at 65 °C) as the measuring temperature increased.     

Hot-wire chemical vapor deposition of silicon nanoparticles on fused silica

Silicon nanoparticles on fused silica have potential as recombination centers in infrared detectors due quantum confinement effects that result in a size dependent band gap. Growth on fused silica was realized by etching in HF, annealing under vacuum at 700-750 °C, and cooling to ambient temperature before ramping to the growth temperature of 600 °C. Silicon particles could not be grown in a thermal chemical vapor deposition (CVD) process with adequate size uniformity and density. Seeding fused silica with Si adatoms in a hot-wire chemical vapor deposition (HWCVD) process at a disilane pressure of 1.1 × 10^− 5 Pa followed by thermal CVD at a disilane pressure of 1.3 × 10^− 2 Pa, or direct HWCVD at a disilane pressure of 2.1 × 10^− 5 Pa led to acceptable size uniformity and density. Dangling bonds at the surface of the as-grown nanoparticle were passivated using atomic H formed by cracking H₂ over the HWCVD filament.     

Optical response and surface morphology of crystalline Nd-doped fluoride films grown on monocrystalline LiYF4 substrates by pulsed laser deposition

The realization of crystalline films of Nd³⁺:YF₃ and Nd³⁺:LiYF₄ on a monocrystalline LiYF₄ substrate by pulsed laser deposition is reported. The films were obtained by laser ablation with 355 nm photons of a bulk LiYF₄ crystal doped with Nd³⁺ ions at 1.5% atomic concentration in the presence of different ablation/deposition parameters. The films optical characteristics, analyzed via laser induced polarized fluorescence spectroscopy upon IR excitation, are presented. Lifetime measurements of the fundamental Nd³⁺ ion transition in the film were also performed. All these results were compared with those obtained in the Nd³⁺:LiYF₄ bulk crystal. The surface morphology of the depositions was analyzed via a scanning electron microscope. When the production of the deposition took place in high vacuum (1 × 10^− 4 Pa) and the substrate temperature was 750 °C, the grown film was Nd³⁺:YF₃. A 1 Pa controlled atmosphere of He in the ablation chamber and a substrate temperature of 650 °C favoured the growth of a Nd³⁺:LiYF₄ film. In the latter case the film showed also a smoother surface.     

Effects of H2O partial pressure on the crystallinity of ZnO thin film and electrical characteristics of film bulk acoustic wave resonators

We have improved electrical characteristics of a film bulk acoustic wave (BAW) resonator that features the injection of H₂O gas into a process chamber. The preferred crystallinity of piezoelectric ZnO film was obtained by RF sputtering at a high H₂O partial pressure 1.5×10⁻⁴ Pa. The effective electromechanical coupling coefficient () of the BAW resonator remarkably goes up from 1.8% to 4.7% for which the corresponding H₂O partial pressures are 2.7×10⁻⁵ and 1.5×10⁻⁴ Pa. Injection of H₂O during the deposition process contributes to the improvement of crystallinity of ZnO thin film and the electrical characteristics of the BAW resonator.     

Production of high density and large volume plasma by using a polyphase AC voltage source

Production of high density and large volume plasma for a plasma source ion implantation has been studied. Plasma is produced by a polyphase AC voltage source with maximum voltage and power of 2 kV and 12 kVA, respectively. Produced N₂ plasma had a small ripple frequency of 720 Hz and a ripple ratio of 20% though frequency of the AC voltage source was 60 Hz. At output voltage of 600 V and N₂ gas pressure of 5 Pa, plasma density in 6-phase operation and 12-phase operation were 8×10⁸ cm⁻³ and 4×10⁹ cm⁻³, respectively. The plasma density in 12-phase operation was about five times larger than that in 6-phase operation. Electron temperature of 0.9 eV was obtained in both operations. The uniform plasma was produced in the inner region of the ring basket electrode which had a radius of 20 cm and length 80 cm at 12-phase operation. The plasma density was increased in proportion to the N₂ gas pressure and output voltage of the AC voltage source. When line-cusp magnets were attached to the process chamber wall, the plasma density increased about 2.5 times.     

Polycrystalline films of tungsten-doped indium oxide prepared by d.c. magnetron sputtering

Electrical and optical properties of polycrystalline films of W-doped indium oxide (IWO) were investigated. These films were deposited on glass substrate at 300 °C by d.c. magnetron sputtering using ceramic targets. The W-doping in the sputter-deposited indium oxide film effectively increased the carrier density and the mobility and decreased the resistivity. A minimum resistivity of 1.8 × 10^− 4 Ω cm was obtained at 3.3 at.% W-doping using the In₂O₃ ceramic targets containing 7.0 wt.% WO₃. The 2.2 at.% W-doped films obtained from the targets containing 5.0 wt.% WO₃, showed the high Hall mobility of 73 cm² V^− 1 s^− 1 and relatively low carrier density of 2.9 × 10²⁰ cm^− 3. Such properties resulted in novel characteristics of both low resistivity (3.0 × 10^− 4 Ω cm) and high transmittance in the near-infrared region.     

AC plasma induced modifications in β-In2S3 thin films prepared by spray pyrolysis

β-In₂S₃ thin films, deposited by spray pyrolysis, were treated in N₂ and air plasmas at 240 and 400 Pa. X-ray diffraction, SEM, and EDS analysis, and optical and electrical studies have been used to characterize the as-prepared and plasma treated thin films. The post-deposition plasma treatments affect the morphology and the optoelectronic properties of the In₂S₃ thin films. The In₂S₃ thin films treated with N₂ plasma at 240 Pa showed an optical band gap, E_g, of 2.16 eV and an electrical conductivity of 2 × 10^− 2 (Ω cm)^− 1.     

Composition, structural and electrical properties of thin films prepared by laser ablation of neodymium-doped potassium gadolinium tungstate

Thin films were grown on (001) SiO₂, SiO₂/(100) Si or (100) MgO substrates by laser ablation of neodymium-doped potassium gadolinium tungstate (Nd:KGW) single crystal target. The films were deposited at temperatures between room temperature and 750 °C and pressures between 1 × 10^− 4 Pa and 50 Pa of oxygen ambient. The influence of the deposition conditions on the composition, structure, morphology and electrical properties of the films was investigated. Special attention was paid to the films deposited in vacuum (1 × 10^− 4 Pa) or at very low oxygen pressures. Under such conditions, the potassium (K), gadolinium (Gd) and oxygen (O) content decreased strongly as the temperature was increased. At room temperature, the films were K and O stoichiometric, in contrast with Gd, which showed a concentration twice higher. The films were polycrystalline, with the exception of those deposited at temperatures below 500 °C, which were amorphous. However, all were smooth and dense. The films grown in vacuum and at temperatures between 500 and 700 °C consist mainly of “â-tungsten” - tungsten oxide (W₃O) phase. The films grown on SiO₂/Si possessed the best surface quality with nano-size relief. The resistivity measurements as a function of the temperature showed that the films produced in vacuum and at temperatures below 500 °C were highly insulating, whereas at 600 °C they exhibited semiconducting behavior or a metallic one at 700 °C. This behavior can be attributed to the existence of various valence states for tungsten below W⁶⁺ in the films and to their crystal structure.     

Surface morphology and growth mechanisms for sputtered amorphous silicon nitride thin films

Evolution of surface of sputter-deposited amorphous Si₃N₄ films growth on Si (100) substrates was investigated using atomic force microscopy (AFM). The scaling behaviors of the AFM topographical profiles were analyzed using the one-dimensional power spectral density. The results of root-mean-square surface height variation showed that there is a power law relationship between the surface roughness and deposition time. It is interesting to note that the growth exponent can be divided into one region and two regions, respectively, when Si₃N₄ films are deposited at different working pressures. A very low growth exponent of β = 0.07 ± 0.01 was found when Si₃N₄ films were deposited at a working pressure of 1.6 × 10^− 1 Pa. However, the growth exponent β can be divided into two regions, which is β₁ = 0.09 ± 0.01, β₂ = 0.24 ± 0.03 and β₁ = 0.09 ± 0.01, β₂ = 0.33 ± 0.04, when the films were deposited at a working pressure of 2.1 × 10^− 1 Pa and 2.7 × 10^− 1 Pa, respectively. The mechanisms of anomalous dynamic scaling exponents of Si₃N₄ films deposited at different working pressures were discussed.     

DC sputter deposition of amorphous indium-gallium-zinc-oxide (a-IGZO) films with H2O introduction

Amorphous indium-gallium-zinc-oxide (a-IGZO) films were deposited by dc magnetron sputtering with H₂O introduction and how the H₂O partial pressure (P_H2O) during the deposition affects the electrical properties of the films was investigated in detail. Resistivity of the a-IGZO films increased dramatically to over 2 × 10⁵ Ωcm with increasing P_H2O to 2.7 × 10^− 2 Pa while the hydrogen concentration in the films increased to 2.0 × 10²¹ cm^− 3. TFTs using a-IGZO channels deposited under P_H2O at 1.6-8.6 × 10^− 2 Pa exhibited a field-effect mobility of 1.4-3.0 cm²/Vs, subthreshold swing of 1.0-1.6 V/decade and on-off current ratio of 3.9 × 10⁷-1.0 × 10⁸.     

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.     

Electrochromic properties of nickel oxide based thin films sputter deposited in the presence of water vapor

Electrochromic nickel oxide based thin films were prepared by reactive RF magnetron sputtering from metallic nickel in the presence of Ar, O₂ and H₂O. The water vapor led to enhanced optical modulation and charge capacity. At a wavelength of 550 nm the bleached state transmittance was 0.73 and the transmittance for the colored state was 0.28 and 0.15 for water partial pressures of p_H2O < 10⁻³ Pa and p_H2O ~ 7 × 10⁻² Pa, respectively. The charge densities were 14 and 25 mC/cm² for p_H2O < 10⁻³ Pa and p_H2O ~ 7 × 10⁻² Pa, respectively. The coloration efficiency was decreased with increased water partial pressure, from about 0.07 to 0.06 cm²/mC. Preliminary results show that the H₂O promotes an amorphous structure and makes the films increasingly hydrous.     

The effect of deposition parameters on the properties of SrCu2O2 films fabricated by pulsed laser deposition

SrCu₂O₂ (SCO) thin films have been fabricated by pulsed laser deposition at oxygen partial pressures between 5 × 10^− 5-5 × 10^− 2 mbar and substrate temperatures from 300 °C to 500 °C. All films were single-phase SrCu₂O₂, p-type materials. Films deposited at a substrate temperature of 300 °C and oxygen pressure 5 × 10^− 4 mbar exhibited the highest transparency (∼ 80%), having conductivity 10^− 3 S/cm and carrier concentration around 10¹³ cm^− 3. Films deposited at oxygen partial pressure higher than 10^− 3 mbar exhibited higher conductivity and carrier concentration but lower transmittance. Depositions at substrate temperatures higher than 300 °C gave films of high crystallinity and transmittance even for films as thick as 800 nm. The energy gap of SrCu₂O₂ thin films was found to be around 3.3 eV.