Modulation of PbSe QDs band gap by SnO addition in Germanosilicate Glasses

Abstract

Nano-sized semiconductors called quantum dots (QDs) have tunable optical and electrical properties when their sizes are smaller than Bohr exciton radius. Especially, lead chalcogenide (PbS, PbSe and PbTe) QDs have strong quantum confinement effect because of their large Bohr exciton radii (PbS 18nm, PbSe 46nm). Therefore, they are potential candidates as fiber-optic amplifiers, lasers, optical switches and solar cells operating at the infrared range of the light. Recently, transition metals such as Sn2+, Mn2+ and Co2+ doped lead selenide (PbSe) QDs have been reported because they can modulate band-gap without any remarkable changes in QDs size. Especially, Sn2+ doped PbSe bulk materials have band gap inversion tendency with Sn2+ concentration. Therefore, precipitation of Sn2+ doped PbSe QDs has possibilities that modulate band gap of QDs without changing their sizes. Furthermore, glasses composed of germania can precipitate large size of QDs due to their low viscosity. Therefore, using germania as host matrix of glasses is expected to modulate wavelength of QDs emission widely. In this study, PbSe QDs were precipitated in germanosilicate glasses containing SnO by heat treatment. The absorption bands blue-shifted and red-shifted with doping concentration of SnO into PbSe QDs. To analyze the effect of SnO on the formation of Pb1-XSnXSe QDs, the viscosities of silicate glasses and germanosilicate glasses were investigated. Furthermore, electron energy loss spectroscopy (EELS) element mapping and energy dispersive x-ray spectroscopy (EDS) analysis were performed to clearly investigate the incorporation amount of SnO in PbSe QDs.