Effects of N$_{2}$ dilution on fabrication of Ge nanoparticles by rf sputtering

Multiple exciton generation (MEG) in QDs is expected to enhance significantly the energy conversion efficiency of solar cells. Although there are several reports on MEG characteristics from various QD materials such as PbS, CdSe, CdS ZnS, and Ag$_{2}$S, such materials have disadvantages of their toxicity and limited resources. Here we have developed quantum-dots (QDs) solar cells using Ge nanoparticles fabricated by rf sputtering method under high pressure. We fabricated Ge nanoparticles by rf sputtering at a pressure of 1.5 Torr. Since the mean free path of Ge atoms is an order of micrometer, and Ge nanoparticles are formed in gas phase. We fabricated Ge nanoparticles using Ar and N$_{2}$ to terminate surface defects by N. Ge and Ar emission intensities decrease significantly with increasing N$_{2}$ partial pressure. The electron density was measured with a plasma absorption probe. The electron density decreases with increasing N$_{2}$ partial pressure.