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.

Excitation relaxation in copper selenide nanowires

“…This estimation gives that about 9500 e-h pairs were created in a single nw under 23 mJ/cm 2 intensity excitation with 1.55 eV energy pulses, while at the lowest used intensity of 0.63 mJ/cm 2 about 260 e-h pairs were created. In earlier studies of the copper selenide nanostructures it was concluded that a nonradiative Auger recombination is a dominant mechanism at the early stages of the nonequilibrium carrier relaxation [15]. However, our results are in contradiction to this conclusion since the obtained initial decay rates are getting slower with the increase in the excitation intensity.…”

Effect of hydrogen doping on the loading of titania nanotube films with copper selenide species via alternating current deposition

“…It is reasonable to mention that similar solution has been suggested by us earlier for porous alumina coloring [11][12][13][14]. As seen, in this solution under the constant AC peak-to-peak voltage (U p-to-p ) mode, densely packed crystallites in size of from 60 to 160 nm appear to be deposited mainly at the TiNT film surface.…”

“…No reports, however, have been dedicated to the application of p-type selenide species that can be organized in both stoichiometric (CuSe, Cu 2 Se, CuSe 2 , Cu 2 Se 3 ) or non-stoichiometric (Cu 2-x Se) composition. As reported previously, copper selenide nanowired arrays encased in alumina matrices and glasses behave as a direct band gap of 2.2 to 2.4 eV and an indirect band gap of 1.1-1.7 eV light absorbers [11][12][13][14][15]. Therefore, in this study, we attempted to couple copper selenide species with TiO 2 by alternating current (AC) deposition from appropriate aqueous solution comprising Cu 2?…”

Optical investigation and application of copper selenide nanowires

“…tion peak in near-IR, which leads to optical nonlinearity effects [10]. The observed absorption range appears to be consistent with the first harmonic of YAG type solid state laser (wavelength within 1-1.5 µm).…”

“…Under ambient conditions the material exists as a series of stable and metastable phases, with the stoichiometry coefficients x and y varying from 1 to 3. Variation in stoichiometry results in change of crystalline structure, absorption spectra, and both direct and indirect band gap E g,dir , E g,indir values [10]. Moreover, the crystalline structure and phase composition of copper selenide leads to different optical and other properties obtainable by annealing of specimens.…”