Growth and decay of persistent spectral holes in CuBr semiconductor quantum dots

Persistent changes of absorption and photoluminescence (PL) induced by lase r excitation of CuBr nanocrystals in a glass matrix are studied. Sharp reso nant holes in the absorption spectrum are produced by selective excitation within the Z(1,2) absorption band but not by the excitation above this band . Wide wavy changes of absorption are induced by both resonant and non-reso nant excitation. Observed PL changes are broad and quite independent of the wavelength of the exciting laser. Trapped excitons and biexcitons seem to play a key role in the photoinduced reaction. The photoproduct is a single- or multiple-charged nanocrystal, in which the local electric held affects the electronic energy levels through the DC Stark effect. The evolution of the hole depth during burning and its relaxation after burning are describe d as first-order dispersive reactions, which proceed through the phonon-ass isted tunneling between different excited states (forward reaction) and gro und states (backward reaction) of the NC/matrix system. (C) 2000 Elsevier S cience B.V. All rights reserved.