Ion deposition in a crossed E×B field system with vacuum arc plasma sources

The system with crossed magnetic and electric fields and vacuum arc plasma sources for ion deposition and low-voltage plasma treatment and plasma immersion ion implantation has been investigated. The use of crossed E×B fields provides intense gas ionization and suppresses sheath expansion. Maximum deposition rate of about 1 μm min⁻¹ was obtained on the target surface located under the area where intense ionization of reactive gas occurs (circular area of about 40 mm wide around the target). Without magnetic field the maximum rate of only 0.15 μm min⁻¹ can be achieved. In the crossed E×B fields, high-quality dense TiN coating was obtained. High ion current density to the target surface reaches 500 A m⁻², provides effective cleaning of the target surface and heating of the growing film. The ratio of metal plasma current and reactive gas ion current reaches 2.1 and can be easily changed by adjusting the magnetic field strength, without changing the vacuum arc gun current. The uniform film deposition around circumference of the target is provided as a result of ion magnetization in the crossed field zone. The uniform film deposition along the entire target length can be provided by moving magnetic field up and down.     

Adequacy of the methods used to approximate the volt-ampere characteristics of dc electric-arc plasma generators

The adequacy of power approximation of volt-ampere characteristics of a dc electric-arc generator is estimated. Using Fisher's ratio for the variances of the inadequacy and random error, it is shown that this approximation is acceptable. It is also shown that the power source has a slight effect on the characteristics of the arc.Notation A constant - G gas flow rate through the discharge channel of the plasma generator - I current - u voltage across the arc - F Fisher's ratio for variances Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 5, pp. 815–819, September–October, 1995.     

Effects of the O2 flow rate and post-deposition thermal annealing on the optical absorption spectra of Ga-doped ZnO films

The optical absorption spectra of polycrystalline Ga-doped ZnO (GZO) thin films deposited by ion plating with direct current arc discharge have been studied. The GZO films that were deficient in oxygen showed absorption in the visible wavelength range. The intensity of the absorption band decreased with increasing O₂ flow rate during the deposition. Post-deposition thermal annealing in air and in a N₂ gas atmosphere also decreased the intensity of the absorption band. The intensity of the absorption band showed a slight correlation with carrier concentrations in the GZO films. The absorption intensity decreased with the decrease of the carrier concentration and diminished at a carrier concentration of around 7 × 10²⁰ cm^− 3. The contribution of carriers from native donors to transport in GZO films is discussed.     

Time and energy resolved ion mass spectroscopy studies of the ion flux during high power pulsed magnetron sputtering of Cr in Ar and Ar/N2 atmospheres

Mass spectroscopy was used to analyze the energy and composition of the ion flux during high power pulsed magnetron sputtering (HIPIMS/HPPMS) of a Cr target in an industrial deposition system. The ion energy distribution functions were recorded in the time-averaged and time-resolved mode for Ar⁺, Ar²⁺, Cr⁺, Cr²⁺, N₂⁺ and N⁺ ions. In the metallic mode the dependence on pulse energy (equivalent of peak target current) was studied. In the case of reactive sputtering in an Ar/N₂ atmosphere, variations in ion flux composition were investigated for varying N₂-to-Ar flow ratio at constant pressure and HIPIMS power settings. The number of doubly charged Cr ions is found to increase linearly with increasing pulse energy. An intense flux of energetic N⁺ ions was observed during deposition in the reactive mode. The time evolution of ion flux composition is analyzed in detail and related to the film growth process. The ionization of working gas mixture is hampered during the most energetic phase of discharge by a high flux of sputter-ejected species entering the plasma, causing both gas rarefaction and quenching of the electron energy distribution function. It is suggested that the properties (composition and energy) of the ion flux incident on the substrate can be intentionally adjusted not only by varying the pulse energy (discharge peak current), but also by taking advantage of the observed time variations in the composition of ion flux.     

Elimination of stagnant particles from a N-valve with side aeration in circulating fluidized bed

The existence of stagnant particle layer in the conventional non-mechanical valves limits their utilization in CFB with the feedstock of caking particles. A new N-valve consisted of a fluidized weir chamber with bottom aeration and a moving-bed angled standpipe with side aeration was developed to eliminate the stagnant particle layer and reach high solids circulation rate G_s in CFBs. The particle flow behavior and its control in the N-valve were studied experimentally. By combining the bottom aeration for weir chamber and the side aeration for angled standpipe the G_s over 270 kg/(m² s) was achieved, and the stagnant particle layer completely disappeared. The G_s increased with increasing the side aeration gas flow rate Q_sa, and this loosing gas flow was optimally injected from the bend between the downcomer and the angled standpipe. At a constant but enough high Q_sa, the increase in the bottom aeration gas flow rate Q_ba elevated G_s linearly.     

Gas release of the dielectric coating of an anode and its effect on the characteristics of an ion diode with electron flux insulation by a radial magnetic field

Generation of an ion beam by an ion diode is accompanied by the release of gas from the surface of the dielectric coating of the anode. The magnitude of the pulse pressure of gas in the vacuum chamber depends on the type of the dielectric used and can reach 6 × 10^–4–2 × 10^–3 mm Hg. The magnitude of the limit vacuum chamber pressure at which ion beam parameters remain constant has been found. Characteristics of the ion beam current in the vacuum chamber pressure range of 2 × 10^–4–1.3 × 10^–3 mm Hg are presented.     

Prussian blue modified Fe3O4 nanoparticles for Cs detoxification

Fe₃O₄ nanoparticles were surface modified with Prussian blue (PB) and the nanoparticles were used for the removal of cesium (Cs) ion. The attachment of PB with the Fe₃O₄ and their morphology were explained based on the studies by transmission electron microscope and BET measurements. The Cs ion adsorption studies have shown that the Cs removal efficiency reached maximum within 120 min. The adsorption kinetics studies using Lagergren pseudo-first-order kinetic model suggest the values of the amount of metal ion adsorbed at equilibrium (q _e) and adsorption rate constant (k ₁) as 22 mg/g and 0.015 min^?1, respectively. The capture efficiency of the prepared nanoparticles was studied by varying the flow channel diameter, applied magnetic field, and the fluid flow velocity. The study suggests that PB-Fe₃O₄ nanoparticles could be used for the detoxification of Cs where the flow velocity is in the range of few tens of cm/s.     

Deposition of titanium nitride films onto silicon by an ion beam assisted deposition method

Titanium nitride (TiN) films were deposited onto silicon wafers using an ion beam assisted deposition (IBAD) method with an electron cyclotron resonance (ECR) ion source for ionizing the nitrogen (N₂) gas under a condition of high nitrogen ion to titanium neutral ratio. The deposition rate of the TiN films was strongly dependent on the evaporation rate, d_Ti, of Ti metal and decreased with increasing nitrogen ion current. The deposition rate can be approximated as d=βd_Ti?_N2/{1/k+?_N2}−αI, where β, k and α are proportional constants, ?_N2 is the sum rate of neutral and ionized nitrogen impinging onto the substrate, and I is the nitrogen ion current.     

Experimental study of the effect of process parameters on plasma-enhanced chemical vapour deposition of silicon nitride film

The effect of plasma-enhanced chemical vapour deposition parameters on refractive index and deposition rate of silicon nitride films is investigated. Usually, this kind of study is performed in a laboratory system. In the present work, a horizontal batch system for the simultaneous coating of 100 silicon wafers is used. Using a gas mixture of silane and ammonia as the reactant-gas sources, the effects of the gas flow rate ratio (R = NH3/SiH4 with the total flow rate constant), pressure, power and temperature on the refractive index and deposition rate were studied and the experimental results are presented and discussed.     

Experimental study of the effect of process parameters on plasma-enhanced chemical vapour deposition of silicon nitride film

The effect of plasma-enhanced chemical vapour deposition parameters on refractive index and deposition rate of silicon nitride films is investigated. Usually, this kind of study is performed in a laboratory system. In the present work, a horizontal batch system for the simultaneous coating of 100 silicon wafers is used. Using a gas mixture of silane and ammonia as the reactant-gas sources, the effects of the gas flow rate ratio (R = NH3/SiH4 with the total flow rate constant), pressure, power and temperature on the refractive index and deposition rate were studied and the experimental results are presented and discussed.     

Development of a dedicated ion injector for accelerator-based nanoprobe facilities

The paper discusses possible ways of increasing beam brightness in ion injectors. The argon/helium ion injector comprising a newly designed RF ion source and, a Wien filter has been designed for use in accelerator-based nanoprobe facilities. The phase set degradation due to aberrations in the injector ion-optic system was simulated with allowance for multipole and fringing fields. The RF ion sources with different permanent magnet systems were tested. Experiments were performed with argon and helium. A plasma density of up to 3×10¹¹ cm⁻³ and beam brightness of ∼100 A/(m² rad² eV) were obtained. The ion current density inside an extracting electrode in the source was 10 mA/cm² for an emission hole diameter of 0.6 mm. Measurements of the current value and emittance were performed with ion source testing equipment permitting measurements of the ion beam current, emittance, mass composition, and RF power input into the plasma.     

Mugti-frequency Superconducting Cavity Stabilized Oscillators (SCSO) for Quantum-Gas Measurements and Gravitational Physics

We report on the development of a superconducting cavity stabilized oscillator (SCSO) for use as a high-stability frequency source and for precision measurements. The SCSO system in its optimized condition has a potential frequency stability of parts in 10¹⁷ to 10¹⁸ over short measurement times (up to 10³ s). It can also operate in two resonant modes, which provides useful diagnostics of sources of frequency instability. This paper describes the progress of applying our SCSO to precise measurements of the equation of state of ⁴He gas near T _λ and the concepts of using SCSO in conjunction with other ground and space clocks to perform tests of gravitational and relativistic physics.     

Extracting inert gases from water samples for analysis on a magnetic resonance mass spectrometer

A system for extracting and purifying inert gases from water samples has been developed that ensures the isolation of more than 90% of He and Ne dissolved in water. The system is linked to a magnetic resonance mass spectrometer (MRMS) that is used for determining the peaks of helium and neon isotopes and performing calibration measurements of reference gas mixtures. On this basis, the absolute amounts of ³He, ⁴He, and ²⁰Ne as well as the isotope ratios of ³He/⁴He and ⁴He/²⁰Ne in the sample are calculated with a good precision. The errors of determination depends on the amounts of isolated gases and the uncertainty of electrode potential adjustment in the ion source (for the MRMS operating in a double-beam mode); in the case of measurements on the static stage (for neon ions), an additional error component is related to the jumplike switching of the accelerating voltage.     

Cu2O thin films deposited by reactive direct current magnetron sputtering

The Cu₂O thin films were prepared on quartz substrate by reactive direct current magnetron sputtering. The influences of oxygen partial pressure and gas flow rate on the structures and properties of deposited films were investigated. Varying oxygen partial pressure leads to the synthesis of Cu₂O, Cu₄O₃ and CuO with different microstructures. At a constant oxygen partial pressure of 6.6 × 10^− 2 Pa, the single Cu₂O films can be obtained when the gas flow rate is below 80 sccm. The as-deposited Cu₂O thin films have a very high absorption in the visible region resulting in the visible-light induced photocatalytic activity.     

Effects of oxygen gas flow rate and ion beam plasma conditions on the opto-electronic properties of indium molybdenum oxide films fabricated by ion beam-assisted evaporation

The purpose of the present work is to experimentally study the effects of the oxygen gas flow rate and ion beam plasma conditions on the properties of indium molybdenum oxide (IMO) films deposited onto the polyethersulfone (PES) substrate. Crystal structure, surface morphology, and optoelectronic properties of IMO films are examined as a function of oxygen gas flow rate and ion beam discharge voltage.Experimental results show that the IMO films consist of a cubic bixbyite B-In₂O₃ single phase with its crystal preferred orientation alone B(222). Mo⁶⁺ ions are therefore considered to partially substitute In³⁺ sites in the deposit. Under-controlled ion bombardment during deposition enhances the reaction among those arriving oxygen and metal ion species to condense into IMO film and facilitates a decreased surface roughness of IMO film. The film with ultimate crystallinity and the lowest surface roughness is obtained when the oxygen flow rate of 3 sccm and the discharge voltage of 110 V are employed. This results in the lowest electrical resistivity due mainly to the increased Hall mobility and irrelevant to carrier concentration. The lowest electrical resistivity of 8.63 × 10^− 4 ohm-cm with a 84.63% transmittance at a wavelength of 550 nm can be obtained, which satisfies the requirement of a flexible transparent conductive polymer substrate.     

Synthesis of graphene flakes using a non-thermal plasma based on magnetically stabilized gliding arc discharge

Abstract

The use of non-thermal plasma at atmospheric pressure has emerged as a technique for the substrate-free, gas-phase synthesis of graphene nanoflakes (GNFs). In this paper, a non-thermal plasma based on magnetically stabilized gliding arc discharge (MSGAD) was employed to prepare GNFs. The effects of the carbon-containing precursor, plasma gas, and arc current on the GNFs synthesis were investigated. The technique produced GNFs with sizes of 50–200?nm and 1–20 layers, spherical carbon nanoparticles with 10–40?nm diameters, and graphitic particles. The results showed that the formation of GNFs depended on the selection of proper process parameters, such as precursors with a high H/C ratio, an Ar-N₂ plasma gas, a low arc current, a low precursor flow rate, and a suitable plasma gas flow rate. Correlations between the process parameters and the product morphology indicated that abundant H atoms and fewer polycyclic aromatic hydrocarbons were favorable for the formation of GNFs.     

High-pressure mass spectrometric investigations of ion-molecule reactions in hydrogen sulfide and ammonia mixtures

The positive ion-molecule reactions in the mixtures of hydrogen sulfide and ammonia have been examined by means of quadrupole mass spectrometer with high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. Mainly observed primary ions: NH₂⁺ (m/q=16), NH₃⁺ (m/q=17), S⁺ (m/q=32) and H₂S⁺ (m/q=34) were formed as the result of ionization and dissociative ionization by electrons with energy of 300 eV. For each mixture, major bimolecular ion-molecule reactions have been identified at total pressure from 0.5 to 33.3 Pa. The main secondary ions: NH₄⁺ (m/q=18), H₃S⁺ (m/q=35) and NH₃S⁺ (m/q=49) were observed.Relative intensities of ion currents for observed ions were determined as a function of total gas pressure inside ion source collision chamber, repeller potential and concentration of hydrogen sulfide in the mixture.     

Ion beam reactively sputtered silicon nitride coatings

An ion beam source was used to deposit silicon nitride films by reactive sputtering a silicon target with an Ar+N₂ beam. The nitrogen fraction in the sputtering gas was 0.05 to 0.80 at a total pressure of 6 to 20×10^?5 torr. The ion beam current was 50 mA at 500 V. A rate of deposition of about 2 nm min^?1 (0.12 μm h^?1) was found, and the spectra indicated that Si₃N₄ was obtained for a fraction of nitrogen higher than 0.50. However, the AES spectra also indicated that the sputtered silicon nitride films were contaminated with oxygen and carbon and contained significant amounts of iron, nickel, and chromium, most probably sputtered from the holder of the substrate and target.     

Use of the ring gap plasmatron for high rate sputtering

The application of ring gas plasmatron discharges for high rate sputtering using a model PPS-5 planar plasmatron sputter source is discussed. Characteristic sputter rates of the order of 0.1 g min^-1 kW^-1, i.e. rates similar to those of electron beam evaporators with water-cooled crucibles, are obtained. The working pressure giving the highest sputter rates is 0.5 Pa but discharge pressure levels down to about 0.07 Pa are possible. Any damage to the substrates is prevented by the underlying discharge mechanism, especially by the low energy charge carriers in the plasma and the concentration of the latter on the target. In addition, carrier impingement on the substrates can be avoided without difficulty.When using the plasmatron for sputtering, the specific energy expended is about three times lower than that expended with conventional sputtering techniques, e.g. with diode sputtering. With bias sputtering, the PPS-5 planar plasmatron sputter source (at a discharge power of 5 kW) gives a bias current of approximately 1 A even at a substrate bias voltage of only a few volts.Typical performance parameters of the high rate sputter source are a discharge voltage of 500 V, a discharge current of 10 A, a sputter rate for copper in argon of 0.7 g min^-1 and, at a distance of 50 mm, a condensation rate of 25 000 Å min^-1.