Optical Emission Diagnostics of an U-Shaped Argon Stabilized d.c. Arc

The radial distribution of parameters has been measured by using the optical emission spectroscopy of an U-shaped argon stabilized low current arc at atmospheric pressure. All the measurements reported here were performed from a side-on observation direction by applying the Abel inversion routine. Radial distributions of apparent temperatures (T_exc., T_e, T_i, T_g) and of electron number density (n_e) for the plasma were measured, with and without presence of KCl (spectrochemical buffer). The measured data of n_e are compared to the theoretically calculated values of the equilibrium plasma composition. On the basis of the measured data, the validity of LTE concept is considered. It was found that deviation from LTE increases to the plasma periphery.     

Nuclear probes in the materials science of solar cells

We present background material about solar cells and the copper-indium-sulphur system and then discuss three important processes for the production of CuInS₂ solar-cell material. These include: sulphurization of metallic copper-indium precursors, physical vapour deposition of the elements, and three-source molecular beam deposition. Using perturbed angular correlations with the¹¹¹In-¹¹¹Cd probe, we are able to identify the indium-containing phases of the system and thus to characterize the cited production processes. The prospects of nuclear probe methods in the development of solar-cell materials are discussed.     

The vapour phase Raman spectra,Raman band contour analyses,Coriolis coupling constants,and e-species force constants for the molecules HCF3, ClCF3, BrCF3, and ICF3

The vapour phase Raman spectra of the molecules HCF₃, ClCF₃, BrCF₃, and ICF₃ have been recorded at pressures of up to 1 atmosphere over the fundamental frequency regions. The Raman band contours of the e-species fundamentals have been analysed to yield first-order Coriolis coupling constants from which, together with the fundamental frequencies, e-species force constants of the general harmonic potential function have been evaluated. One force field was found for fluoroform, but two different ones were found for the molecules ClCF₃, BrCF₃ and ICF₃.     

"荧光-1"实验装置物理设计

本文主要介绍"荧光-1"实验装置物理参数设计, 并依据半经验公式预估在实验装置上可能达到的磁化等离子体状态参数. 理论设计结果表明: "荧光-1"实验装置最大放电电流1.5 MA, 四分之一周期3 μs, 最大反向磁场4 T; 以此为实验平台, 当θ箍缩线圈内充气压力50 mTorr(D₂气体)时, 形成的等离子体靶直径约为2 cm, 长度17 cm; 等离子体靶密度6.6×10¹⁶ cm^-3, 温度 (T_i+T_e) 约300 eV; 等离子体平均β值为0.95. 该状态参数接近磁化靶聚变所要求的等离子体靶初始状态参数. 关键词： 脉冲功率技术 反场构形 磁化等离子体 磁化靶聚变     

Investigation of the Plasma of a Magnetron Discharge during Titanium Deposition

In the present work the deposition of titanium layers using a planar-magnetron sputtering system is performed. To optimize the sputtering process and to improve the layer quality the plasma has been monitored in front of the target and near the substrate. The plasma was studied by means of Langmuir-probe diagnostics and optical emission spectroscopy (OES). The internal plasma parameters (n_e, k_B T_e) and the relative power dependence of the neutral densities (n_Ti) at the target as well as at the substrate have been determined as functions of discharge power and pressure. It was found that the plasma densities increase with power and pressure and reach a maximum at a certain gas pressure (0.8 Pa) connected with a maximum of the energy influx and a maximum of the mass density of the deposited films.     

Spatiotemporal spectroscopic diagnostics of a pulse-periodic strontium vapor laser

Results of spectroscopic investigations into plasma of a pulse-periodic strontium vapor laser operating in the superradiance mode on the infrared transition at λ = 6.45 μm are presented. The method of determining the electron temperature and concentration as well as the gas temperature – T _e , n _e , and T _g – based on measuring the absolute intensities of some SrI and SrII and buffer gas (helium or neon) spectral lines is used. Time dependences of the line intensities during a current pulse (τ = 150 ns) and near afterglow (up to 3 μs) are obtained under conditions of non-equilibrium plasma ionization and recombination. The optical system collects radiation from the entire length of the plasma column by means of separating radial volume zones, includingthe central zone and the zone closer to the walls, with the monochromator slit. The results obtained allow us not only to calculate T _e , n _e , and T _g values, but also to trace the spatiotemporal plasma evolution.     

Investigation of the Beam Plasma Discharge in Electronegative Gases Using the Second Derivative of Langmuir Probe Characteristics

The distribution of the charge carriers is measured and the influence of the attachment processes on the electron energy distribution function is demonstrated for beam plasma discharges in SF₆, CF₄ and O₂ with the aid of the second derivative of Langmuir probe characteristics. The structuration of the plasma into regions of predominating negative ions and regions of predominating electrons is determined by the the established radial T_e-profile. The dimension of the quasi electronfree plasma changes significantly as well at transition from the turbulent heating mechanism into the electron impact plasma generation as by occuring low-frequency instabilities. With increasing n_?/n_e a deficit of low energetic electrons appears in the electron energy distribution parallel to the formation of the negative ion peak. The saturation currents at n_e/n_?=0 yield the mass ratios between negative and positive ions.     

Axial distribution of plasma fluctuations,plasma parameters,deposition rate and grain size during copper deposition

Floating potential fluctuations, plasma parameters and deposition rate have been investigated as a function of axial distance during deposition of copper in direct current (DC) magnetron sputtering system. Fluctuations were analyzed using phase space, power spectra and amplitude bifurcation plots. It has been observed that the fluctuations are modified from chaotic to ordered state with increase in the axial distance from cathode. Plasma parameters such as electron density (n_e), electron temperature (T_e) and deposition rate (D_r) were measured and correlated with plasma fluctuations. It was found that more the deposition rate, greater the grain size, higher the electron density, higher the electron temperature and more chaotic the oscillations near the cathode. This observation could be helpful to the thin film technology industry to optimize the required film.     

Spectroscopic Measurement of Electron Temperature and Density in an Argon Plasma Jet Based on Collisional‐Radiative Model

The present paper describes a spectroscopic method or determining electron temperature T_e and density N_e in an argon plasma jet on the basis of a Collisional‐Radiative model of argon. Electron temperature and density in the argon plasma were measured by the method developed, and comparison of them was discussed with those obtained with a Langmuir probe. The results or T_e and N_e obtained by the spectroscopic method agreed roughly with those by the probe.     

Potential double layers in double plasma device

Results of the investigation on the formation of double layers in double plasma device are presented. By appropriate modifications in the biasing conditions, we have been able to obtain both weak (eΔφ<10KT _e ) and strong double layers (eΔφ>10kT _e ) in the device. Unlike previous experiments, we have not been limited to potential jumps equal to ionisation potential of the neutral gas. A detailed investigation has been carried out to find out why earlier experiments in similar devices were limited to only weak double layers. We have also investigated the phenomenon of the so-called psuedo-double layers and have shown that they are potential jumps over the thickness of the order of Debye length and precede plasma expanding with velocity many times the ion-acoustic velocity. They do not represent metastable states of the plasma as suggested by earlier investigators.     

Secondary-ion-mass spectrometry study on near-stoichiometric LiNbO3 strip waveguide fabricated by vapour transport equilibration and Ti co-diffusion

Secondary-ion-mass spectrometry was applied to study Ti-concentration profiles in the depth direction and on the surface of near-stoichiometric (NS) Ti:LiNbO₃ strip waveguides fabricated using vapour transport equilibration (VTE) and co-diffusion of Ti-metal strips. Results show that the profile of Ti concentration along the width direction on the waveguide surface can be well fitted by a sum of two error functions, while, in the depth direction, the Ti concentration follows either a complementary error function or a generalized Gaussian function. Surface Ti concentration, 1/e width and depth, mean diffusivities along the width and depth directions of the guide are, respectively, 1.04?×?10²¹?cm^–3, 8.5?µm, 6.3?µm, 0.18 and 0.1?µm²/h. Two-dimensional refractive index profile in the NS waveguides is indirectly constructed by assuming linearity between Ti-induced index change and Ti concentration. The surface refractive index increments at 1545?nm, Δn_o and Δn_e , are evaluated to be 3.132?×?10^–3 and 1.186?×?10^–2, respectively. All of the above-mentioned diffusion and optical parameters are compared with the corresponding data of the common congruent Ti:LiNbO₃ waveguide or NS waveguide fabricated starting from a NS substrate. The rationality of the assumed linear relationship between the index change and the Ti concentration is discussed. The results show that the assumed linearity remains controversial, and all expressions and data with regard to the refractive index are the approximate results and need to be verified by direct measurement on refractive index.     

Organic/inorganic interfaced field-effect transistor properties with a novel organic semiconducting material

A novel 1,3,4-oxadiazole-substituted benzo[b]triphenylene was synthesized by three-step synthetic procedure and OFET device design was successfully designed after theoretical calculations made using Gaussian software. For investigating the field-effect properties of designed organic electronic device, a SiO₂ (300 nm) was thermally grown on p-Si wafer at 1000 °C as a dielectric layer and gate, source and drain contacts have been deposited using Au metal with physical vapour deposition. 1,3,4-Oxadiazole-substituted benzo[b]triphenylene was spin coated on the source and drain electrodes of our device, forming organic/inorganic interfaced field-effect transistors. Surface morphology and thin film properties were investigated using AFM. All electrical measurements were done in air ambient. The device showed a typical p-type channel behaviour with increasing negative gate bias voltage values. Our results have surprisingly shown that the saturation regime of this device has high mobility (μ_FET), excellent on/off ratio (I_on/I_off), high transconductance (g_m) and a small threshold voltage (V_Th). The values of μ_FET, I_on/I_off, g_m and V_Th were found as 5.02 cm²/Vs, 0.7 × 10³, 5.64 μS/mm and 1.37 V, respectively. These values show that our novel organic material could be a potential candidate for organic electronic device applications in the future.     

MRCI+Q理论研究SiSe分子X1Σ+和A1Π电子态的光谱常数和分子常数

采用Davidson修正的内收缩多参考组态相互作用方法(MRCI+Q)及相关一致基aug-cc-pV5Z和aug-cc-pVQZ分别计算了SiSe分子X¹Σ⁺和A¹Π电子态的势能曲线. 为提高势能曲线的计算精度, 利用两点总能量外推公式, 将两个电子态的势能曲线外推至完全基组极限, 并对其进行了标量相对论修正, 相对论效应是在cc-pV5Z基组水平下使用三级Douglas-Kroll-Hess哈密顿算符计算的. 利用MRCI+Q/Q5+DK理论水平的势能曲线获得了这两个态的光谱常数(T_e, D_e, R_e, ω_e, ω_ex_e, ω_ey_e, B_e和α_e)和J=0时前30个振动态的B_υ和D_υ等分子常数. 其值与已有的实验结果非常一致. 本文得到的光谱常数和分子常数达到了很高精度, 能为进一步的光谱实验和理论研究提供可靠参考. 关键词： 势能曲线 基组外推和标量相对论修正 光谱常数 分子常数     

Emission Spectroscopic Investigation of the Decomposition of CCl4 in Plasma Etching Processes

The CCl₄ plasma decomposition and the etching of SiO₂ and Al by the CCl₄ plasma is investigated with the aid of emission intensity Iλ of such species as Cl₂, CCl, Cl and CO, which are influenced systematically by the etching process. A time independent electron density (n_e ≈ 2 · 10⁸ ?1 · 10¹⁰ cm^?3, dependent on plasma conditions) is measured by microwave diagnostics. The ratio Iλ/n_e and Iλ/I_reference' resp. (I_reference = I_Helium) is a relative measure of concentrations. The ratio I_cl2/I_ccl is very sensitive against CCl₄-decomposition and etching processes of SiO₂ and Al. Its changes during the etching process of SiO₂ and Al in a CCl₄ plasma are investigated.     

Kinetic electron reflection coefficient in a low-voltage Knudsen arc

The influence of the escape of fast plasma electrons on the electron distribution function (EDF) in a low-voltage cesium Knudsen arc is discussed. It is shown that even with a large Knudsen parameter l _e /h∼5–10 (where h is the gap and l _e is the mean free path of electrons with energy of the order of the anode barrier) the electron flux from the plasma to the anode is virtually identical to that calculated with a Maxwellian EDF. Zh. Tekh. Fiz. 68, 61–64 (May 1998)     

Nonequilibrium Ionization by Vibrationally Excited Molecules in Supersonic Flows

The results of experimental investigations on thermal nonequilibrium ionization in CO₂: N₂: He mixtures are presented. Measurements of electron density, n_e, in vibrationally excited nitrogen were made in a supersonic flow with different CO₂ contents as well as in a CO₂: N₂: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N₂ and CO₂ + He was used in some experiments. The measured values of n_e in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser-active medium are discussed.     

Investigation of the dependency of JET midplane separatrix density as a function of engineering parameters

Midplane separatrix density is a crucial parameter in tokamaks since it strongly impacts divertor conditions. Scaling midplane separatrix density, n_{e, SEP} , and pedestal density, n_{e, PED} , as function of engineering parameters such as auxiliary heating P_injected, toroidal magnetic field B_T, and plasma poloidal current I_p are relevant to observe the effect of tuning these parameters on, for example, quality of confinement and divertor regime governed by n_{e, PED} and n_{e, SEP} , respectively. Thus, a dataset of JET H-mode pulses performed with Iter like wall (ILW) has been analysed. Midplane density data are collected from an HRTS (high-resolution Thomson scattering) diagnostic and n_{e, SEP} is determined using the power balance method. Parallel heat flux model is chosen using transport code SOLEDGE2D (S2D) applying power balance method over a simulated n_{e, SEP} and T_{e, SEP} profiles to obtain separatrix positions. The parameters are averaged over time windows with order of (85–185 ms ) and the magnetic configuration has been fixed to avoid divertor geometrical effect on n_{e, SEP} determination, configuration chosen is corner–corner. A ratio between separatrix density and pedestal density at outer midplane ranges between 0.3 and 0.7 on the data set. A scaling law of n_{e, SEP}/n_{e, PED} is obtained as function of P_injected, B_T, and I_P.     

Interaction of germanium with silicon dioxide

The interaction of germanium (Ge) adatoms with SiO₂ (silica) plays an important role in selective, heteroepitaxial growth of Ge(100) through windows created in silica on Si(100) and in the selective growth of Ge nanoparticles on hafnia, located at the bottom of pores etched through silica. Both processes rely on the inability of Ge to accumulate on silica. In hot wire chemical vapor deposition of Ge nanoparticles from GeH₄, etching of the silica has been invoked as one path to prevent accumulation of Ge on silica; whereas dense silica is not etched when Ge atoms are incident on the surface in molecular beam processes. Surface studies were conducted to determine the nature of oxidized Ge on SiO₂, to reconcile the etching claim with GeH₄, and to look for the additional etching product that must accompany GeO, namely SiO. Etching of silica is not found with GeH₄ or GeH_x fragments. A more complete examination of the Ge isotopes reveals instead the m/e 90 signal, previously attributed to GeO, originates from interactions between iron oxide impurities in the molybdenum holder, and hydrogen and GeH_x fragments. Coating the Mo with gold eliminates m/e 90 from Ge TPD spectra. The high temperature m/e 74 and m/e 2 peaks observed from 800 to 900 K are attributed to GeH_x decomposition to Ge and H followed by their desorption, while the appearance of GeO_x is attributed to possible reactions between GeH_x species with hydroxyl groups and/or oxidation of Ge clusters by background oxidants.     

Coherent backscattering of electromagnetic waves in a magnetised plasma

Summary A microwave coherent backscattering experiment has been carried out on Mirabelle, a weakly ionised plasma device, with the objective of measuring the electron density fluctuation level. The experiment is a preliminary step in order to prepare the detection system for a microwave stimulated backscattering experiment. The incident electromagnetic wave is focused in front of a plane grid which excites ion acoustic or electron Bernstein waves inducing fluctuations in the plasma. The backscattering signal is collected by the launching circuit and detected by homodyne mixing. The typical ratio of the scattered power to the incident power is about 10⁻¹² and the relative density fluctuations are of the order of δn _e/n _e=10⁻³ against a background electron density ofn _e=1–5·10⁹ cm⁻³. The backscattering measurement is compared with Langmuir probe measurements. The spectral width of the backscattered signal has also been studied, by taking into account effects due to the incident wave focusing and plasma wave damping. The authors of this paper have agreed to not receive the proofs for correction