Abstract
Due to the unique optical properties as well as the potential in developing silicon-based optoelectronic device applications, enormous studies have been conducted investigating on the synthesis of group IV and VI nanoscale semiconductor materials in amorphous dielectric materials. However, the possible origin of the luminescence induced by these nanoscale semiconductor materials are indefinite and still in debate because of the complex mechanisms and inconsistent results reported by various research teams. In this study, ion implantation and following annealing process were employed to synthesize Ge nanoparticles in SiO2 thin film in order to achieve a strong room-temperature luminescence originating from nanostructure material. By changing the implantation dose, annealing temperature, and annealing ambient gas, we can clarify the correlations between photoluminescence properties and experimental parameters. Furthermore, transmission electron microscopy and Fourier transform infrared spectroscopy, Raman spectroscopy was employed to examin the microstructure and specific chemical bonding configurations of Ge nanoparticles. The results revealed that the luminescent characteristics originate from the oxygen deficient defects at the interface between Ge nanoparticles and SiO2 matrix. Moreover, according to the independence of peak position on nanoparticle size distribution, we can exclude the possibility of quantum confinement effect which dominates this luminescence band in Ge-implanted SiO2 film. Also, the oxygen gas existing in high-temperature annealing ambient would cause the oxidation of germanium. The formation of nonstoichiometry germanium oxide (GeOx) nanoparticles leads to an improvement in low temperature PL intensity, and decreases available germanium content. Based on the oxidation degree as well as the number of Ge nanoparticles, PL spectra showed an inconsistent trend in different gas atmospheres. In addition, a large number of defects were produced by the collision of incident ions during the ion implantation process. Non-radiative recombination defects significantly reduce the emission intensity of material. Due to the fact that the luminescence centers are dependent on the interface between nanopariticles and SiO2 matrix, smaller and unoxidized Ge nanoparticles have a much better photoluminescence efficiency than GeOx particles do. In conclusion, particle size, density, and oxidation degree of Ge nanoparticles should play a crucial role in determining the effective intensity of the luminescence. Therefore, by optimizing the implantation dose, annealing temperature, and annealing ambient gas, we can suppress the oxidation and coalescence of Ge nanoparticles, so as to enhance photoluminescence intensity in the case of well separated small Ge nanoparticles. These results can be a useful guidance in light emission in UV-blue region from Ge-implanted SiO2.