Photoluminescence dynamics of CdS nanocrystals fabricated by sequential ion implantation

We have studied photoluminescence (PL) dynamics of US nanocrystals fabricat ed by sequential Cd+ and S+ ion implantation into Al2O3 matrices. The PL sp ectrum and PL decay dynamics of US nanocrystals are sensitive to the measur ement temperature. This is because excitons trapped at shallow localized st ates are thermally excited to the high-energy state at high temperatures. T wo PL bands appear near the absorption edge at elevated temperatures near 1 00 K. From time-resolved PL spectra and the PL decay dynamics, it is conclu ded that the observed PL bands near the absorption edge are due to free exc itons and excitons trapped at shallow localized states. The PL mechanism in US nanocrystals is discussed.