Silicon and silicon-germanium nanoparticles obtained by Pulsed Laser Deposition

Abstract

Semiconductor nanoparticles are of great interest in the area of microelectronics and can also be used in many optoelectrical devices as for example optical converters for photovoltaic applications.Silicon (Si) and silicon-germanium (SiGe) quantum dots can be used as high-energy photon converters, known as “red-shift” photoluminescence (PL) in solar cells in order to improve their efficiency. We report on the possibility to produce SiGe nanoparticles by Pulsed Laser Deposition (PLD) on silicon dioxide substrates. We keep the focus on the control of morphological properties of nanoparticles considering various deposition parameters like temperature, fluence and the amount of deposited material. Si0.5Ge0.5 controlled ratio is obtained by optimizing the amount of matter ablated successively from Si and Ge pure targets. Rutherford Backscattering Spectroscopy (RBS) is used to confirm the stoichiometry of the deposited structures. Morphological characterization is performed by Atomic Force Microscopy (AFM), determining average diameter, height and density of the nanoparticles. In order to confirm the crystalline character of the deposited particles, Raman analyses have been performed, helping in determining the optimal deposition temperature. PLD allows to condense a very small and controlled amount of material during the deposition process, permitting this way the growth of nanostructures in a 10 nm range. With these dimensions, SiGe quantum dots are subject to have a photoluminescent (PL) behaviour. However, no photoluminescence is observed on the deposited nanoparticles.