Growth of high-density Si nanoparticles on Si3N4 and SiO2 thin films by hot-wire chemical vapor deposition

Abstract

High-density (>1×1012 cm−2) Si nanoparticles have been successfully grown on Si3N4 and SiO2 thin films by hot-wire chemical vapor deposition (HW-CVD) using disilane, in which Si atoms are generated on a heated tungsten filament and, after desorbing, impinge on the substrate. The highest density, 1.1×1012 cm−2 as measured by scanning electron microscopy (SEM) and 2.1×1012 cm−2 by scanning tunneling microscopy, is achieved by depositing 1.8 monolayer Si on Si3N4 at 600 °C and a disilane pressure of 1.2×10−6 Torr. The corresponding Si nanoparticles have an average size of about 5 nm. Different densities are reported because scanning tunneling microscopy imaged Si nanoparticles of ∼4 nm, beyond the resolution of SEM. At temperatures above 600 °C, parallel thermal chemical vapor deposition (CVD) during HW-CVD becomes important. Parallel thermal CVD broadens the size distribution of Si nanoparticles and causes coalescence of neighboring nanoparticles, leading to a decrease of nanoparticle density. High densities can be realized above 600 °C if a two-step procedure is used to reduce parallel thermal CVD by starting the growth at a lower temperature.