Theoretical considerations in growing uniform epilayers

Abstract

Abstract. We briefly describe, theoretical considerations in the quest to grow crystalline films with perfection in uniformity of thickness. The endeavor of perfect crystallinity is best served by growing epitaxially. Thickness uniformity is facilitated by growing in a monolayer-by-monolayer mode-so called Frank-van der Merwe (FM) mode. The island (Volmer-Weber ---VW) mode is undesirable; it promotes roughening and the creation of crystalline imperfections. Equilibrium criteria, proposed by Bauer, on the basis of shape equilibrium, predict that FM growth is favored by strong substrate bonding. The dependence of shape equilibration on adatom migration barriers, substrate temperature, and deposition rate is discussed. Modification of the system to improve adverse conditions by intermixing, alloying, and the use of surfactants is outlined. VW growth may also commence after completion of one or a few monolayers (MLs) in FM mode. This form of island growth, also known as Stranski-Krastanov (SK) growth, is mainly due to electronic effects, but may also be triggered by epitaxial strain relief. The tailoring of growth into FM-like growth, when VW or SK conditions exist-by an appropriate increase of supersaturation usually effected by controlling the substrate temperature and deposition rate, is briefly discussed.

Effect of Surface Energy on Pentacene Growth and Characteristics of Organic Thin-Film Transistors

“…This kind of three-dimensional ͑3D͒ island growth mode is the well-known Volmer-Weber growth mode, and the layer-by-layer growth mode is the Frank-van der Merwe mode. 7,8 The growth modes are determined by the following relationship ␥ p + ␥ i Յ ␥ g ͑Frank-van der Merwe mode, layer-by-layer͒…”

Multilayer thin film growth on crystalline and quasicrystalline surfaces: A phase-field crystal study

“…That is, the film is assumed to grow in the so-called Frank-van der Merwe (or layer-by-layer) mode 40 , which is often observed in heteroepitaxial systems during early stages of growth. Furthermore, it is assumed that both the substrate and the previously deposited monolayers remain effectively "frozen" such that there is no intermixing between layers or elastic relaxation within the layers 21,[41][42][43] .…”

“…Furthermore, it is assumed that both the substrate and the previously deposited monolayers remain effectively "frozen" such that there is no intermixing between layers or elastic relaxation within the layers 21,[41][42][43] . Intermixing can be neglected when films are grown at sufficiently low temperatures where bulk diffusion does not play any significant role, and elastic relaxation processes associated with either misfit dislocation nucleation above a critical thickness 44 or a morphological transition from the layer-by-layer to 3D island growth mode 40,45 are not relevant for the systems of interest here. Under these assumptions, the dynamics governing the behavior of the local composition (c i ) and morphology (ρ i ) of the newly deposited partial or full monolayer can be described via the following dimensionless, non-linear, stochastic partial differential equations:…”

Low-Dimensional Group III-V Compound Semiconductor Structures

“…2 With the view more practical, a unified theory was developed to understand the physics of epitaxial thin films and applied to tailor epitaxial growth conditions to obtain perfect epitaxial thin films of uniform thickness. 3 The pursuit of superior epitaxial growth will continues to motivate scientists and engineers in a variety of technical fields for the years to come as the growing demand for high-quality single-crystal thin films needs to be met for a wide range of advanced solidstate devices. Apparently in epitaxial growth, one of the prerequisites that drive ordinary thin film deposition into epitaxial growth is the use of a single-crystal substrate.…”