IDENTIFICATION OF THE ELECTRONIC STATES OF SE-2(-) MOLECULES EMBEDDEDIN BOROSILICATE GLASSES AND IN SE-BASED NANOMETER-SIZED CRYSTALS

Electron spin resonance (ESR), Raman, and photoluminescence spectra we re measured to identify the electronic states of Se; molecules embedde d in potassium borosilicate glasses. The ESR spectra of all samples sh ow a lineshape that is attributed to orthorhombic symmetry around the molecule. Photoluminescence spectra show a broad luminescence band bet ween 500 and 900 nm that is identified as the pi(u) --> pi(g) transiti on between the electronic levels of the Se-2(-) molecule. An electron- lattice interaction gives rise to overtones of the fundamental vibrati on (322 cm(-1)) of the Se; molecule and they are identified by Raman s cattering measurements. The role of Se, molecules as surface traps in Se-based semiconductor quantum dots is examined. (C) 1998 Published by Elsevier Science B.V. All rights reserved.