Selective growth of nanometer-scale Ga dots on Si(111) surface windows formed in an ultrathin SiO2 film

摘要

Selective growth of nanometer-scale Ga dots on patterned ultrathin SiO2 films was studied by using scanning-reflection electron microscopy and energy-dispersive x-ray spectroscopy (EDX). Nanometer-scale Si(111) surface windows were fabricated by electron-beam-induced thermal decomposition of the film. Ga was deposited on the patterned surfaces at room temperature to 550 degrees C. Under certain deposition and annealing conditions, Ga dots were present only on the Si(111) surface windows, and the smallest size of the dots was about 20 nm. To understand the selective growth of Ga dots, we measured the desorption rate and the surface-diffusion length of Ga atoms until all atoms desorbed from the SiO2 surface and nucleated forming random dots. The EDX measurement showed that the desorption rate from Ga dots on SiO2 films was 2 to 2.5 times larger than that on Si(111) surfaces, and that the activation energy of desorption rate from SiO2 films was 1.33 eV. The Ga surface-diffusion length was estimated by measuring the temperature dependence of the Ga depleted zone width near the linear Si surface windows. The surface-diffusion length of Ga atoms on ultrathin SiO2 films increased when the substrate temperature was increased. Thus, we were able to selectively grow Ga dots on only the Si(111) surface windows. [S0163-1829(99)02716-2]. [References: 20]