Electron transport in lead selenide nanocrystal arrays

Abstract

I have investigated electrical properties of arrays of lead selenide (PbSe) nanocrystals (NC's) of approximately 6nm diameter. The films become substantially more conducting when annealed at 400K, although no chemical changes of the capping layer occur at this low temperature. There is no evidence based on TEM images of annealed and unannealed films that the interparticle spacing changes at 400K. The dependence of the conductance on the voltage applied to a gate separated from the sample by 350nm of SiO2 was also measured. At 77K and 150K, a U-shaped curve is observed with a minimum in conductance near zero gate voltage, indicating that both electrons and holes are injected. At 294K, the conductance falls monotonically with increasing gate voltage, indicating injection of holes only. I calculate the electron and hole mobilities, [mu]e and [mu]h at 77K and 150K and find effective mobilities 10 orders of magnitude smaller than those of bulk PbSe at 77K.