Question

Describe the three different growth modes and the properties of the three modes that distinguish them conceptually and use Young’s equation to distinguish experimentally

Answer 1

Answer :-

The three growth modes are as follows :-

1. Volmer–Weber (VW) Growth :- In this growth, adatom–adatom interactions are stronger than those of the adatom with the surface, leading to the formation of three-dimensional adatom clusters or islands. Growth of these clusters, along with coarsening, will cause rough multi-layer films to grow on the substrate surface.

2. Frank–van der Merwe (FM) Growth :- During this growth adatoms attach preferentially to surface sites resulting in atomically smooth, fully formed layers. This layer-by-layer growth is two-dimensional, indicating that complete films form prior to growth of subsequent layers.

3. Stranski–Krastanov (SK) Growth :- It is an intermediary process characterized by both 2D layer and 3D island growth. Transition from the layer-by-layer to island-based growth occurs at a critical layer thickness which is highly dependent on the chemical and physical properties, such as surface energies and lattice parameters, of the substrate and film.

Cross-section views of the three primary modes of thin-film growth including (a) Volmer–Weber (VW: island formation), (b) Frank–van der Merwe (FM: layer-by-layer), and (c) Stranski–Krastanov (SK: layer-plus-island) are given below :- (Each mode is shown for several different amounts of surface coverage, Θ.)