Positron probing of quantum dots

CdSe quantum dots QDs.of different sizes were deposited as thin layers on glass slides and examined by positrons with the two detector coincident Doppler broadening technique coPAS.. Dots of 2.5 and 3.6 nm size were compared to the larger 4.4 nm size. It appears that the data on the smaller size 2.5 nm.display a shape consistent with positrons annihilating with electrons confined in the quantum dots. The next larger size is on the limit of QD behavior. The observed broadening in the annihilation line for the smallest size sample is consistent with annihilation with quantum-dot confined electrons. q1999 Elsevier Science B.V. All rights reserved