Abstract

Three-dimensional (3D) carrier confinement in semiconductor nanocrystals (NC's) results in size-dependent photoluminescence and absorption spectra and significantly modifies the nonlinear optical properties and carrier dynamics with respect to those in bulk materials. So far, most experimental and theoretical studies have concentrated on NC's formed by direct-gap II-VI semiconductors such as CdS and CdSe. Recently, we reported the preparation, linear and picosecond nonlinear transmission of NC's of a new type: NC's formed by different copper sulfide phases [1]. Depending on the copper deficiency, the energy band gap in copper sulfide varies from 1.2 (x = 2) to 1.5 eV (x = 1.8) with an accompanying transformation of the semiconductor from indirect-gap to direct-gap one. These interesting properties as well as a small electron mass provide the broad phase/size controlled tuning range and give the opportunity to compare the effects of 3D confinement on nonlinear optical proterties in direct and indirect-gap semiconductors.

© 1996 Optical Society of America