SILICON NANODOTS GROWN ON SAPPHIRE SUBSTRATE BY A SELF ASSEMBLY GROWTH METHOD

Abstract

Silicon quantum dots have been grown on sapphire substrate using a self-assembly method of physical vapour deposition. The samples were fabricated at low sputtering rate and varying experimental conditions. Apparently, the onset of nucleation took place during the first 5 minutes of deposition, followed by a further growth of stable islands so-called nanodots, with the measured radii comparable to the predicted values. Other measurement results confirmed the existence of these dots, including the bandgap energy ∼ 1.80 eV from PL and a 5% at. silicon from EDX. The nucleation parameters were predicted as follows: Free energy change per unit volume ΔGv ∼ -2.4x105 Jmol^-1; Surface energies per unit area, γLN = 1.48 Jm^-2, γNS = 21.6 - 88.3 Jcm^-2 and γLS = 0.82 x 10^-2 Jm^-2; Critical energies ΔG* = 6.83x10^-16 - 3.68x10^-14 J; Critical radii r* = 20- 72 nm. This experimental evidence strongly support the early stage growth model of silicon quantum dot deposited on corning glass substrate.