The influence of annealing temperature on the synthesis of silicon quantum dots embedded in hydrogenated amorphous Si-rich silicon carbide matrix

Abstract

Hydrogenated amorphous silicon carbide thin films (a-SiC:H) were prepared by plasma-enhanced chemical vapor deposition (PECVD) and thermal annealed at temperatures of 900, 1050, and 1200°C, respectively. The influence of annealing temperature on the silicon quantum dot (QD) synthesis was investigated by Raman scattering spectroscopy, X-ray diffraction spectroscopy, and high-resolution transmission electron microscopy. The influence of annealing temperature on the chemical bonding configurations was revealed by Fourier transform infrared absorption microscopy. The element ratios of the as-deposited sample were deduced by X-ray photoelectron spectroscopy. Results reveal that the samples are in silicon-rich nature. Silicon in the as-deposited sample and the 900°C annealed sample are amorphous. When the annealing temperature is increased to 1050°C, crystal silicon QDs have come into being. The calculated number density is about 2.15±0.03×1012cm−2 and more than 80±3% of the silicon QDs fall within a narrow size range of 2–3nm. When the annealing temperature is increased to 1200°C, the average size of crystal silicon QDs is tuned from 2.6 to 3.2nm, while the crystallinity is enhanced from 56.7±2.5 to 67.1±1.5%. We attribute the influence of annealing temperature on the synthesis of silicon QDs to be dependent on the evolution of chemical bonding configurations and the agglomeration of silicon atoms from the host matrix.