Step-flow growth

In spite of its simplicity this approximation retains the necessary information and is justified because the vast majority of MOMs are layered and thus structurally anisotropic. Arrows in Fig. 5.2 aim to succinctly describe the basic atomistic mechanisms of step-flow growth, based on the BCF model (Burton et al., 1951). 

Under conditions of step flow, the ability to grow good crystalline material is related to the mobility of the adatoms on the surface. These must be able to diffuse freely and find the proper crystal lattice sites for growth, wherever these are available. In this section, we discuss our calculations of the diffusion barriers on the Si (100) surface and the single-height steps. We shall restrict our discussion to the motion of adatoms even though there is considerable evidence that mass transport via dimer diffusion plays a role at high temperatures as well. ... 

Ultrahigh-vacuum (UHV) surface spectroscopy has been used with molecular beams of SiH4 and mass spectroscopy to elucidate the Si growth mechanism (67, 143). Joyce et al. (67) found that Si growth is preceded by an induction period when surface oxide was removed as SiO. The subsequent film growth proceeds by growth and coalescence of adjacent nuclei with no apparent formation of defects. Henderson and Helm (144) proposed a step-flow model in which adatoms from SiH4 surface reactions difluse to kink sites. 

Dunphy JC, Klyachko D, Xu H, Chen DM (1997) A Novel Bi-directional Step-flow Growth Mode C60 on Ge(100)and GaAs(llO) Surf Sci 383 760-765... 

A further elaboration of the two-step process was done by depositing a B-doped layer on an undoped (100) HOD film [265]. The source gas was a mixture of CH4 and trimethyl borane [B(CH4)3], whose concentrations were 0.5% and 10 ppm, respectively. As a result, a significant lateral growth of B-doped diamond film occurred, which (i) reduced the density of microtwins and (ii) enhanced a step-flow growth. The former result (i) is consistent with those of Refs. [4, 294]. 

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