Ge nanoparticles produced by Pulsed Laser Deposition: morphological, structural and optical properties

Abstract

Semiconductor nanometer-sized particles (nanoparticles, NPs) have been widely investigated due to their unique size dependent properties. The interest in Ge NPs is recently increasing because of their interesting physical properties such as large carrier mobility, large Bohr exciton radius and near-direct band gap that are suitable for the development of advanced optoelectronic devices and solar cells. Pulsed laser deposition (PLD) is a versatile technique that allows one to produce NPs in a one-step process when a gas atmosphere is introduced in the deposition chamber at low substrate temperatures [1]. In this work, we have produced Ge NPs by PLD using a KrF excimer laser (wavelength = 248 nm, pulse time = 10ns) under Ar pressure at room temperature (RT). Uncapped Ge NPs on Si (100)substrates were deposited for AFM and SEM morphological characterization. Ge NPs films between amorphous alumina layers were deposited on Si (100) and fused silica substrates for structural and optical characterization, respectively. In order to avoid the direct deposition of micronsized liquid droplets typically obtained in the ablation process, the deposition process was performed by combining a shadow mask and an off-axis setup configuration. The influence of Ar gas pressure, time deposition, laser energy fluence and setup configuration on the morphological NPs properties is presented. Ge NPs structural characterization is performed by Raman spectroscopy on as-deposited and annealed samples by rapid thermal annealing (RTA).