Copper selenide nanowires and nanocrystallites in alumina: Carrier relaxation, recombination, and trapping

Abstract

Nonequilibrium carrier dynamics in copper selenide (Cu2−δSe δ=0.15, Cu3Se2) nanowires (diameter ≈18 nm, height ≈2 μm) and nanocrystallites (diameter≈18 nm) in femto- and picosecond time domains by the means of a transient dynamic grating technique were investigated. Bulk and quantum confinement approaches were used to fit the experimental results using nonequilibrium carrier fast relaxation, recombination, and trapping mechanisms. A nonradiative Auger recombination was concluded to be the main mechanism of nonequilibrium carrier recombination. The Auger coefficient for copper selenide was estimated of the order of 10−30−10−29 cm6 s−1. Hole trapping at shallow impurity centers in nanowires was interpreted. From calculating the experimental results the trapping parameters and high concentration of centers >1020 cm−3 were evaluated. Finally, direct measurement of carrier lifetime in copper selenide nanostructures showed values of the order of ≈10−10 s. Samples were characterized by the means of transmission electron microscopy, scanning electron microscopy, x-ray diffraction, and optical spectroscopy.