Measurement and modeling of Ar∕H2∕CH4 arc jet discharge chemical vapor deposition reactors II: Modeling of the spatial dependence of expanded plasma parameters and species number densities

Abstract

Articles you may be interested inStrange hardness characteristic of hydrogenated diamond-like carbon thin film by plasma enhanced chemical vapor deposition process Appl. Phys. Lett. 102, 011917 (2013); 10.1063/1.4775372Simulations of chemical vapor deposition diamond film growth using a kinetic Monte Carlo model and twodimensional models of microwave plasma and hot filament chemical vapor deposition reactors Synthesis of tin-incorporated nanocomposite diamond like carbon films by plasma enhanced chemical vapor deposition and their characterization Detailed methodology and results are presented for a two-dimensional ͑r , z͒ computer model applicable to dc arc jet reactors operating on argon/hydrogen/hydrocarbon gas mixtures and used for chemical vapor deposition of micro-and nanocrystalline diamond and diamondlike carbon films. The model incorporates gas activation, expansion into the low pressure reactor chamber, and the chemistry of the neutral and charged species. It predicts the spatial variation of temperature, flow velocities and number densities of 25 neutral and 14 charged species, and the dependence of these parameters on the operating conditions of the reactor such as flows of H 2 and CH 4 and input power. Selected outcomes of the model are compared with experimental data in the accompanying paper ͓C. J. Rennick et al., J. Appl. Phys. 102, 063309 ͑2007͔͒. Two-dimensional spatial maps of the number densities of key radical and molecular species in the reactor, derived from the model, provide a summary of the complicated chemical processing that occurs. In the vortex region beyond the plume, the key transformations are CH 4 → CH 3 ↔ C 2 H 2 ↔ large hydrocarbons; in the plume or the transition zone to the cooler regions, the chemical processing involves C Depending on the local gas temperature T g and the H / H 2 ratio, the equilibria of H-shifting reactions favor C, CH, and C 2 species ͑in the hot, H-rich axial region of the plume͒ or CH 2 , C 2 H, and C 2 H 2 species ͑at the outer boundary of the transition zone͒. Deductions are drawn about the most abundant C-containing radical species incident on the growing diamond surface ͑C atoms and CH radicals͒ within this reactor, and the importance of chemistry involving charged species is discussed. Modifications to the boundary conditions and model reactor geometry allow its application to a lower power arc jet reactor operated and extensively studied by Jeffries and co-workers at SRI International, and comparisons are drawn with the reported laser induced fluorescence data from these studies.

Combined experimental and modeling studies of microwave activated CH4/H2/Ar plasmas for microcrystalline, nanocrystalline, and ultrananocrystalline diamond deposition

“…We have extended our previous experimental/modeling studies of H 2 -rich C/H/Ar plasmas (e.g. 4.4%CH 4 /88.6%H 2 / 7%Ar, F total ¼ 565 sccm, p ¼ 150 Torr, P ¼ 1.5 kW) such as are used for growth of MCD films [22][23][24][25] to explore the consequences of major variations in the input H 2 /Ar ratio -from H 2 /Ar mole fraction ratios of > 10:1 as used for MCD growth, through ratios $1:6 (e.g., 0.5%CH 4 /14.7%H 2 / 84.8%Ar, F total ¼ 525 sccm, p ¼ 150 Torr, P ¼ 1.0 kW, the "base" conditions used in most of the present work) typical of those used for NCD growth, and extending to an H 2 /Ar ratio of $1:99 (e.g., 0.5%CH 4 /1%H 2 /98.5%Ar, F total ¼ 525 sccm, p ¼ 150 Torr, P ¼ 0.5 kW) as used for growth of UNCD material. As before, absolute column densities of C 2 (a) and CH(X) radicals and of H(n ¼ 2) atoms have been determined by CRDS, as functions of z and of process conditions [X 0 (H 2 ), X 0 (CH 4 ), X 0 (Ar), p, and P].…”

“…Such data can be obtained, however, by judicious intercomparison between experimental measurement and high level reactor modeling -as illustrated in our previous diagnoses of the gas phase environment in a dc arc jet reactor, 21,22 and in MW activated C/H, 23 B/H, 24 and B/C/H (Ref. 25) plasmas.…”

Understanding the chemical vapor deposition of diamond: recent progress

“…Modeling studies reported over the past two decades have provided progressively greater understanding and allowed optimization of diamond deposition processes in relatively simple hot filament CVD reactors [25,[80][81][82][83][84][85], in dc arc jet reactors [86] and in MPCVD reactors [53,65,[87][88][89][90][91][92][93][94][95][96][97]. The latter environment is considerably more challenging; many complex and interrelated phenomena require careful consideration in order to achieve an adequate simulation of the diamond deposition processes occurring in an MW PECVD reactor.…”

Determination of the number densities of CH(X2Π) and CH(A2Δ) radicals in a DC cascaded arc discharge plasma

“…Monitoring CH provides an insight into the reaction mechanism. CH radicals and C atoms contribute to the experimentally observed high and nonuniform diamond growth rates in the highpower Bristol reactor [7]. The level of CH concentration agreement between the model prediction and the experimental measurement can be used to test model predictions of hydrocarbon chemistry [8].…”