Temperature Effects on Film Morphological Development

Thick-Film Development

Substrate temperature not only determines the initial development of a film, but its subsequent thickening as well. A model for film morphology was given by Grovenor et al. (1984) derived from experiments on films grown in high vacuum. The gross microstructure changes as a function of the homologous temperature, T_h=T/T_m, where T is the temperature of the substrate. All temperatures are in degrees of Kelvin. Based on there model, small grains of 5-20 nm in diameter are observed at T_h<0.2.

When T_h is within the range from 0.2 to 0.3, it is suggested that grain boundaries of a single orientation are mobile so that favorably oriented boundaries grow and surface diffusion may contribute to a more dense morphology.

When T_h is within the range from 0.3 to 0.5, all grain boudaries become mobile and the formation of columnar grains requires surface recrystallization and diffusion.

When T_h is larger than 0.5, bulk diffusion, surface, and bulk recrystallization all occur leaving a larger grain structure.

In general, the 'best' value of the substrate temperature for high-quality thin film growth is from 0.3 to 0.5. In this regime, there is sufficient surface diffusion to allow surface atoms to minimize their surface energy.

For inital stages of film growth, please refer to this link