Experiments towards size and dopant control of germanium quantum dots for solar applications

oleh: Brittany L. Oliva-Chatelain, Andrew R. Barron

Format: Article
Diterbitkan: AIMS Press 2015-12-01

Deskripsi

While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post-synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO<sub>2</sub> coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl<sub>4</sub> with LiAlH<sub>4</sub> results in Ge QDs with a low level of chlorine atoms on the surface; however, during the H<sub>2</sub>PtCl<sub>6</sub> catalyzed alkylation of the surface with allylamine, to enable water solubility of the Ge QDs, chlorine functionalization of the surface occurs resulting in p-type doping of the QD. A similar location of the dopant is proposed for phosphorus when incorporated by the addition of PCl<sub>3</sub> during QD synthesis; however, the electronic doping effect is greater. The detected dopants are all present on the surface of the QD (<em>s</em>-type), suggesting a self-purification process is operative. Attempts to incorporate boron or gallium during synthesis were unsuccessful.