Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.     

Heating of powders in an r.f. inductively coupled plasma under dense loading conditions

A study was carried out of the heating of powders in an r.f. inductively coupled plasma under dense loading conditions. The results obtained using a mathematical model taking into account plasma-particle interaction effects reveal an important cooling of the plasma caused by the presence of the particles. This, in turn, gave rise to a corresponding drop of the efficiency of the melting of the particles in the plasma. The effect is shown to depend strongly on the thermodynamic properties of the material of the powder.     

Electrochromic nickel oxide films made by reactive r.f. sputtering from different targets

We describe the preparation and optical–electrical characterization of thin electrochromic layers based on nickel oxide (NiO_x). These layers were deposited by reactive radiofrequency (r.f.) sputtering from nickel or nickel oxide targets, maintaining the r.f. power and varying the oxygen flow in a gas mixture of Ar and O₂ from 5% up to 30%. The Ni/O ratio in the deposited thin films was determined by Rutherford backscattering spectroscopy (RBS) and the microstructure was investigated by x‐ray diffraction. The deposition rate was found to be strongly dependent on the type of target used. The electrochromic behaviour in aqueous alkaline electrolyte (0.1 N KOH solution) was investigated by electrochemical cyclization. Samples deposited by the NiO target exhibited the lowest N/O ratio (0.5) and the highest value of intercalated charge (～4.9 × 10^?2 mC cm^?2 nm^?1). Among the same samples the highest value of the intercalated charge was found for those deposited at low oxygen flow, but these samples exhibit the smallest reversible changes in optical absorption in the wavelength range 330–1200 nm. Samples deposited by the nickel target do not exhibit significant variations in the value of the exchanged charge; the measured Ni/O ratio indicates a stoichiometry closer to NiO. We also observed the switching behaviour by analysing the films in cyclic time mode at a fixed wavelength. The commutation response time is estimated by measurement under the application of a step waveform potential. Copyright © 2004 John Wiley & Sons, Ltd.     

Influence of target surface degradation on the properties of r.f. magnetron‐sputtered calcium phosphate coatings

This paper reports a detailed study of how repeated r.f. magnetron sputtering from a hydroxyapatite (HA) powder target affects the nature and reproducibility of a sequential series of thin‐film coatings deposited onto Ti6Al4V substrates. An evaluation of the effective lifespan of the HA sputter targets and the reproducibility of the calcium phosphate (CaP) coatings produced from them has been made from Fourier transform infrared spectroscopy, XPS and, as appropriate, atomic force microscopy and SEM/energy dispersive x‐ray analyses. The annulus region of the target surface, from which sputtering under r.f. magnetron conditions normally occurs, showed severe surface degradation after only one deposition run, as indicated by significant PO₄^3? and OH^? depletion. This deterioration continued after each subsequent deposition cycle but to a much lesser extent than that observed in the initial sputtering period. The layers produced from all of the sputter runs contained the expected Ca²⁺ and PO₄^3? species characteristic of a CaP system but were OH^? deficient in the as‐deposited state. However, the chemical and morphological properties of the coatings did not change significantly until after the third consecutive sputter cycle. Hence, these data indicate that, even though a significant level of degradation of the HA target occurs at the outset of the sputtering procedure, the general plasma conditions employed here have a dominant influence on the coating properties until a critical degradation condition is met. As such, the compacted HA powder targets of interest can have a life‐cycle greater than single usage without detriment to the chemistry and morphology of the coatings produced from them. Copyright © 2003 John Wiley & Sons, Ltd.     

Ion and radical reactions in the silane glow discharge deposition of a-Si:H films

A mass spectrometric analysis of the positive ions and neutral products in a silane glow discharge has been performed. The active species, created by dissociation, disproportionation, and ion-molecule reactions are mainly SiH₂, SiH₃, and H. A calculation of the distribution of the SiH _n ⁺ ions shows that the silane concentration monitors the abundance of SiH ₃ ⁺ . The diffusional transport of radicals toward the discharge-tube walls can explain the observed deposition rates. The study of SiH₄-SiD₄ and SiH₄-D₂ plasmas emphasizes several reactions which modify the free-radical populations depending on the discharge conditions: disproportionation, termination, recombination, and abstraction. Heterogeneous reactions have also been observed: etching of the film by H atoms and direct incorporation of hydrogen in the growing film. A general scheme for the plasma deposition mechanism is proposed.     

Plasma deposition of silicon nitride-like thin films from organosilicon precursors

Plasmas containing hexamethyldisilazane or hexamethylcyclotrisilazane and nitrogen or ammonia were used to deposit silicon nitride-like films at low substrate temperature (T<60°C). Optical properties (refractive index and absorption coefficient), chemical composition of the deposit and film growth rate were examined with respect to the deposition parameters (rf power, pressure and feed composition). As deposited films from ammonia containing mixtures were silicon nitride-like, contained carbon, and were nearly oxygen free. Furthermore, only Si−N, Si−H, and N−H bonds were identified in as-deposited films. The reactive Si−H bonds progressively transformed into Si−O bonds as the films were exposed to air. Films deposited from highly ammonia-diluted mixtures, high RF power and low pressure showed the highest stability with refractive indices as high as 1.8.     

扫描速率对硅表面分子沉积膜纳米摩擦特性的影响

本研究小组曾简要报道过扫描速率对Au衬底表面分子沉积膜(MD)的纳米摩擦特性的影响[1],本文利用原子力显微镜(AFM)研究了硅表面、羟基化硅表面、氨丙基硅烷(aminopropylsilanized简称APS)化硅表面及硅衬底上磺化酞菁铜(CuT sPc)单层MD膜表面的摩擦力随针尖扫描速率变化的规律。1　实验方法1 1　仪器与试剂TMX2000型原子力显微镜(TopoMetrix公司)。甲苯、二甲苯、丙酮、无水乙醇、氯仿、浓硫酸、过氧化氢、浓盐酸(以上均为分析纯),3 氨丙基 三乙氧基硅烷(KH 550,ACROS产品),磺化酞菁铜(ALDRICH产品),去离子水(电阻率大于10…     

Kinetic study of the heterogeneous Si/H system under low-pressure plasma conditions by means of mass spectrometry

The kinetics of the silicon/hydrogen low-pressure discharge system have been measured using a flow technique and mass spectrometry. Results show that at long residence times the system operates under a partial chemical equilibrium even though it is not at thermodynamic equilibrium. The present work indicates that the decisive parameter controlling the structural properties of the deposit (i.e., the formation of either amorphous or microcrystalline silicon) is the departure of the system from the partial chemical equilibrium.     

An overall mechanism for the deposition of plasma polymers from methane in a low-pressure argon plasma jet

An overall mechanism for plasma polymer deposition from a methane-seeded argon plasma jet was established from experimental measurements and a simplified model of reaction kinetics within the plasma jet. Total mass deposition rates were obtained at various substrate positions and methane flow rates. Methane consumption was estimated from residual gas analysis. The influence of substrate coolant temperature on deposition rate was evaluated. The model was based on particle densities, jet temperature, and jet velocity data published previously, and reaction rate constants from the literature were used. No adjustable parameters were employed in this model. Experimental results for total deposition rate and methane consumption were in good agreement with model predictions. The overall deposition mechanism consists of three steps: Penning ionization of methane by excited argon neutrals, followed by dissociative recombination of CN _x ⁺ to yield CH, followed by incorporation of CH into the growing film upon impact. Contributions of species other than CH to the total deposition rate are minor, and adsorption is not a prerequisite for incorporation into the growing film.     

Decomposition of SiCl4 and deposition of Si in inductively coupled plasmas of H2+SiCl4

The mechanism of homogeneous reactions in plasmas of H₂+5%SiCl₄ was studied by mass spectrometry and was compared to the mechanism observed in plasmas of Ar+H₂+SiCl₄. Contrary to the behavior with Ar, the results indicate that without argon the SiCl₄ molecule undergoes only fragmentation and the deposition proceeds through SiCl₂. No polymerization was observed. The deposition rates of c-Si were lower and the amounts of chlorine incorporated in the films were higher in the plasma of SiCl₄+H₂ than in the argon-containing plasma.     

Spectroscopic study of a D.C. discharge in an argon-silane-nitrogen gas mixture under silicon nitride thin film deposition conditions

A detailed experimental investigation of a D.C. discharge in an argon-silanenitrogen gas mixture is undertaken using mainly spatially resolved spectroscopy. Discharge parameters are studied as functions of the gas mixture composition, and the influence of nitrogen concentration on the dissociation phenomena of SiH₄ and on dehydrogenation mechanisms of the growing film surface is particularly discussed.     

A study of the deposition of polymeric material onto surfaces from fluorocarbon RF plasmas

A series of fluorocarbon gases, viz., CF₄, C₂F₆, C₃F₈, and CHF₃, have been compared for their relative tendencies to deposit polymeric material onto various surfaces, including Si and SiO₂, under RF plasma conditions. The plasmas were examined by optical emission spectroscopy. C₃F₈ and CHF₃ were found to produce the highest yields of polymers, although these exhibited significant differences in structure (as shown by XPS and IR) and differences in thermal stability, both of which could be minimized by replacing the C₃F₈ gas with a C₃F₈/H₂ mixture. The polymers produced from CHF₃ under the conditions of the present study were found to accumulate preferentially onto Si rather than SiO₂, as verified by the technique of Rutherford backscattering spectrometry.     

Modeling of the elementary gas-phase reaction during chemical vapor deposition of silicon carbide from CH3SiCl3/H2

We established a gas-phase, elementary reaction model for chemical vapor deposition of silicon carbide from methyltrichlorosilane (MTS) and H₂, based on the model developed at Iowa State University (ISU). The ISU model did not reproduce our experimental results, decomposition behavior of MTS in the gas phase in an environment with H₂. Therefore, we made several modifications to the ISU model. Of the reactions included in existing models, 236 were lacking in the ISU model, and thus were added to the model. In addition, we modified the rate constants of the unimolecular reactions and the recombination reactions, which were treated as a high-pressure limit in the ISU model, into pressure-dependent rate expressions based on the previous reports (to yield the ISU+ model), for example, H₂(+M) → H + H(+M), but decomposition behavior remained poorly reproducible. To incorporate the pressure dependencies of unimolecular decomposition rate constants, and to increase the accuracies of these constants, we recalculated the rate constants of five unimolecular decomposition reactions of MTS using the Rice-Ramsperger-Kassel-Marcus method at the CBS-QB3 level. These chemistries were added to the ISU+ model to yield the UT2014 model. The UT2014 model reproduced overall MTS decomposition. From the results of our model, we confirmed that MTS mainly decomposes into CH₃ and SiCl₃ at the temperature around 1000°C as reported in the several studies.     

Mathematical simulation of gas-phase deposition of epitaxial silicon films in the Si-C-H and Si-H systems

The effect of experimental conditions on the magnitude and uniformity of the deposition rate of epitaxial silicon obtained by chemical deposition from the gas phase in the SiCl₄-H₂, SiHCl₃-H₂, and SiH₄-H₂ systems (in the temperature ranges from 1300 to 1520 K for the chloride and 1270 to 1370 K for the silane systems) has been examined. Chloride and silane processes are compared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1217–1222, July, 1995.     

Glow discharge deposition of silicon dioxide and aluminum oxide films: A kinetic model of the surface processes

Silicon oxide films have been deposited in a RF discharge plasma using hexamethyl-disiloxane (HMDSO) and Ar/O₂ or N₂O. Also, aluminum oxide layers have been deposited using trimethylaluminum (TMA) and N₂O or CO₂. The influence of the nature and the proportion q( the oxidizing gases and file suhstrate temperature effect have been studied. As far as the films obtained with HMDSO and TMA tire concerned, the most important experimental finding is the decrease of the deposition rate with increasing substrate temperature. FTIR, ESCA, and refractive index measurements show that the decrease of the deposition rate correlates with a nearly stoichiometric film. Low negative apparent activation energies are deduced from Arrhenius plots and are representative of deposition rates controlled hr fire adsorption of radical and surface di fusivities. A kinetic rnodel shows that the rate-limiting step is the adsorption of HMDSO or TMA radicals at low temperatures while for temperatures above 250°C the oxidation reactions control the deposition rate.     

The influence of flow rate and pressure on the excitation conditions in low-pressure microwave induced plasmas

Using a double probe technique, electron temperatures and electron concentrations together with spectral line intensities have been measured in low-pressure microwave induced plasmas at various pressures and flow rates of monoatomic and polyatomic support gases. For two distinct pressures viz. 0.2 and 1.0 torr (0.267–1.333 mbar) the flow rate has been independently varied.

Measurements of spectral-line intensities in the absence and presence of the probes demonstrate that the probes exert little or no influence upon the plasma conditions. The results show that when low-pressure microwave induced plasmas in flow systems are applied for quantitative analytical purposes exact specification of both flow rate and pressure of the carrier gas is required.     

两种葱属植物提取物对香蕉枯萎病菌有抑制作用组分的气相色谱-质谱分析

以葱、韭菜根的石油醚和乙酸乙酯提取物对香蕉枯萎病菌进行了抑菌实验,结果表明:葱茎的石油醚提取液对香蕉枯萎病菌的抑制效果最明显,采用气相色谱-质谱法对葱茎的石油醚提取液进行分析,发现其中含有42.07％的二硫化物和16.29％的噻烷类化合物,推断这2种化学成分可能是抑菌的主要成分.进一步对葱的根、茎、叶和韭菜根的石油醚提...     

西非灰毛豆中鱼藤素的分析

改进了植物中鱼藤素的HPLC检测方法;比较UV吸收光谱发现,检测波长设为260nm可以有选择地检测鱼藤素,减少鱼藤酮的干扰;CHCl3-MeOH(体积比91)溶剂适于提取植物中鱼藤素,经C-18柱层析,用MeOH-H2O(体积比2080)洗脱能有效去除大部分杂质,而用MeOH-H2O(体积比8515～1000)洗脱可收集鱼藤素;对西非灰毛豆植株中鱼藤素的含量分析试验结果表明,该植物中的鱼藤素主要存在于叶中,平均含量为200×10-3(w),其中又以上部叶和新叶含量最多,分别为25.2×10-3和22.0×10-3(w);根和枝条中含量很低,尤其是枝条仅含0.65×10-3(w),基本上没有实用价值;鱼藤素的杀虫活性不如鱼藤酮,但由于其含量高,在制作杀虫剂时也不能忽视其作用.     

Open questions regarding the mechanism of plasma-induced deposition of silicon

Recently published values of the rate constant for the insertion of silylene into silane have been used to reevaluate our earlier estimates of the critical coil cell ration of silane, [SiH₄]_crit above which the formation of disilane dominates the plasma-induced deposition of silicon. Because the recently published values of the rate constant are significantly higher than those available at the time of writing of our earlier paper, the new values on [SiH₄]_crit are significantly lower than the earlier ones. It is shown that there is no unambiguous experimental evidence for SiH₃ to be the dominant species for the deposition of crystalline .silicon. Disilane formation and insertion of silylene into the surface o the growing filin mar explain the data as well. Several open questions are addressed.