Thin-film growth dynamics with shadowing and re-emission effects

Abstract

Growth dynamics of thin-films involves both shadowing and re-emission effects. Shadowing can originate from obliquely incident atoms being preferentially deposited on hills of the surface, which leads to a long range geometrical effect, as well as from an atomic shadowing process that can occur even during normal angle deposition. Re-emission effect is a result of nonsticking atoms, which can bounce off from hills and deposit on valleys of the surface. In the case of an energetic incident flux, re-emission can also originate from a resputtering process that includes a surface atom being knocked off by an incident ion/atom followed by redeposition to another surface point. Due to their long-range nonlocal nature, both the shadowing effect (which tries to roughen the surface) and re-emission effect (which has a smoothening effect) have been shown to be more dominant over local effects such as surface diffusion, and have been proven to be critical processes in accurately determining the dynamic evolution of surface roughness. Recent Monte Carlo simulation methods that involve shadowing, re-emission, surface diffusion, and noise effects successfully predicted many experimentally relevant surface roughness evolution results reported in the literature. For example, root-mean-square surface roughness (ω) of Monte Carlo simulated thin-films have evolved with time t according to a power law behavior ω ∼ t β , with β values ranging from about 0 to 1 for a growth with strong re-emission effects (i.e., low sticking coefficients) and a growth with dominant shadowing effects (i.e., with high sticking coefficients), respectively. Potential future thin-film growth modeling studies are also discussed. These include advanced simulation approaches that can incorporate atomistic details of physical and chemical processes and a recently developed network growth model that can potentially capture some universal aspects of thin-film growth dynamics independent of the details of growth process. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Morphological and electrical evolution of ZnO: Al thin filmsdeposited by RF magnetron sputtering onto glass substrates

“…The surface morphology of a thin film may indicate its dynamic growth [13][14][15] . Typically, growth of a thin film is a non-equilibrium process, which can lead to the formation of a roughened surface with granular or pyramidal structures 4,13,15 .…”

“…Typically, growth of a thin film is a non-equilibrium process, which can lead to the formation of a roughened surface with granular or pyramidal structures 4,13,15 . Moreover, the properties of the surface of a thin film, especially the surface roughness, may strongly influence their applications 4,13,16 .…”

“…Typically, growth of a thin film is a non-equilibrium process, which can lead to the formation of a roughened surface with granular or pyramidal structures 4,13,15 . Moreover, the properties of the surface of a thin film, especially the surface roughness, may strongly influence their applications 4,13,16 . There are also intrinsic relations between the surface morphology and other factors, such as crystalline structure and film thickness, which have been found to play important roles in determining physical and chemical film properties 15,17 .…”

Microstructure of mixed oxide thin films prepared by magnetron sputtering at oblique angles

“…Monte Carlo calculations have also been considered to simulate the columnar microstructure of OAD film growth. This approach allows developing systematic correlations between tilt angles of the developed microstructure, source-sample distance, process pressure, and material deposited [11,[26][27][28]. In general these calculations predict that the stronger the thermalization of the flux of material, the lower the tilt angle of the deposited microstructure.…”

Coating of Tungsten Wire with Ni/Al Multilayers for Self-Healing Applications

“…The irregular waviness can result from the atomic shadowing effect, which should be more pronounced and always present for wire substrates. In fact, in sputtered films, the atomic shadowing could be responsible for the formation of columns, because during rotation, and for certain positions, there are atoms arriving at the substrate with low angles of incidence [14]. For the curved surface of wire substrates there are always atoms impinging the substrate at low angles of incidence, which should influence the nucleation process giving rise to an atypical morphology.…”