Atoms landing on a substrate diffuse before sticking. Whether they spread into smooth layers (Frank–van der Merwe), pile into 3D islands (Volmer–Weber), or do a bit of both (Stranski–Krastanov) depends on the balance of surface energies and how far atoms can hop before a new layer buries them.
Diffusion length ∝ exp(−E_diff / k_BT) (hotter substrate ⇒ atoms travel further ⇒ smoother film)
Wetting: layer growth favoured when γ_substrate ≥ γ_film + γ_interface
Thin-film colour: constructive interference when 2·n·d = (m+½)·λ
- Deposition rate — faster arrival gives atoms less time to find a low-energy site before being buried, roughening the film.
- Substrate temperature — more thermal energy lets atoms diffuse further, favouring smooth layer-by-layer growth.
- Wetting — how much the film "wants" to spread over the substrate versus ball up into islands.
Real-world relevance: this exact competition between diffusion and burial rate is what semiconductor fabs control precisely (via temperature and deposition rate) to grow atomically flat layers for computer chips — get it wrong and the film grows rough and unusable.