Thermally induced morphology evolution of pit-patterned Si substrate and its effect on nucleation properties of Ge dots

Abstract

We demonstrate the effect of the pre-growth heat treatment process on the nucleation properties of Ge dots grown on pit-patterned Si(001) substrates. The prefabricated 200 nm diameter pits inherently evolve into truncated inverted pyramids (TIPs) with < 110 > base edges and a 7 degrees-9 degrees sidewall slope during heat treatment; this morphology transformation is robust against variations in shape and orientation of the pit patterns. Uniform Ge dots with an areal density of 4 x 10(9) cm(-2) were obtained on the Si substrates having TIPs. Each TIP contains four aligned Ge dots locating symmetrically with respect to < 110 >. These dots exhibit an elliptical dome shape with major axis oriented along < 100 >. The nucleation position, shape and spatial orientation of these Ge dots coincide with the calculated surface chemical potential distribution of the TIP.