Interactions of SiH radicals with silicon surfaces: An atomic-scale simulation study

Abstract

A comprehensive study is presented of the interactions of SiH radicals originating in silane containing plasmas with crystalline and amorphous silicon surfaces based on a detailed atomic-scale analysis. The hydrogen concentration on the surface is established to be the main factor that controls both the surface reaction mechanism and the reaction probability; other important factors include the location of impingement of the radical on the surface, as well as the molecular orientation of the radical with respect to the surface. On the ordered crystalline surfaces, the radical reacts in such a way as to maximize the number of Si–Si bonds it can form even if such bond formation requires dissociation of the radical and introduction of defects in the crystal structure. The radical is established to be fully reactive with the pristine Si(001)-(2×1) surface. This chemical reactivity is reduced significantly for the corresponding H-terminated surface with a hydrogen coverage of one monolayer. SiH is found to be highly reactive with surfaces of hydrogenated amorphous silicon films, independent of radical orientation and the location of impingement. Our simulations predict an average reaction probability of 95% for SiH with a-Si:H film surfaces, which is in excellent agreement with experimental data.

Internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles

“…11 This interatomic potential for silicon was originally developed by Stillinger and Weber 46 and extended by Kohen et al 39 to include Si-H and H-H interactions. Similar sets of potential energy functions have also been developed by Murty and Atwater, 47 Ohira and co-workers 33,34,36 and Ramalingam et al 37 where a Tersoff-type potential 48 -51 was extended to describe interatomic interactions in the Si:H system. This extended version of the Tersoff potential has been tested successfully for its accuracy in describing the Si:H system in several earlier studies; however, the simulation of liquid silicon has not been well described by the potential.…”

“…Although hydrogenated amorphous silicon has found a variety of technological applications, and has been studied extensively, 19 these previous studies focused on the electronic and optical properties, [20][21][22][23][24][25][26] thin film growth, 27,28 and the deposition of clusters on hydrogenated surface. [29][30][31][32][33][34][35][36][37][38] To our best knowledge, surface tension and diffusion coefficient of hydrogenated Si nanoparticles have not been reported on.…”

Time-resolved cavity ringdown study of the Si and SiH3 surface reaction probability during plasma deposition of a-Si:H at different substrate temperatures

“…Moreover, direct measurements of ␤ for the silane radicals have been carried out by means of the various diagnostics mentioned in Sec. I, revealing ␤ values of ϳ0.2-0.3, 6,8,[10][11][12][13]20,25 [40][41][42][43][44] and molecular dynamics simulations, 41,[45][46][47][48] which address the surface reactions at the atomistic scale. For SiH 3 , only indirect information is available about the dependence of ␤ on the substrate temperature from the early study of Matsuda et al 6 This study, though, suffers from the uncertainty that the measured ␤ values are averaged overall plasma species.…”

“…This trend is in agreement with the observations from molecular dynamics (MD) simulations. [45][46][47][48] To get an indication of the relative importance of the different radicals to a-Si: H film growth, the Si growth flux due to a specific radical, ⌫ Si (i.e., the number of Si atoms deposited per second by the specific radical) can be estimated from the value of ␤ and the density n in the plasma: 54 …”

Some fundamental aspects of elementary gas-surface interactions

“…The in¯uence of the surface coverage and of the adsorption site on the recombination dynamics were also investigated in this work [28]. Surface processes relevant to plasma-etching and plasma CVD have been simulated in many classical MD calculations with the use of semiempirical and ab initio based semiempirical potentials for the Si±H and Si±F interactions [17,19,30]. The sticking coef®cient for F atom abstraction in F 2 ±Si(100) interactions has been recently calculated in a wide range of collisional energies [31].…”