Homoepitaxy of germanium by hyperthermal ion irradiation

• Ge (001) surfaces are irradiated by hyperthermal Ar+ ions at different temperatures.
• A checkerboard pattern is developed above the Ge recrystallization temperature.
• The instability is caused by biased diffusion together with the slope selection.

A dense array of faceted nanostructures evolves on the Ge (001) surfaces for normal incidence hyperthermal ion bombardment at elevated temperatures. There is a narrow window of temperatures, just above the crystal annealing temperature, in which the grown pattern resembles to the checkerboard pattern of alternating mounds and pits as often observed under the conditions of molecular beam epitaxial growth process. The measured roughness exponent characterizing the interface morphology is found to be extremely sensitive to substrate temperature and follows the dynamics of diffusion-bias-generated growth processes.