Thermoreflectance studies in CdNiTe nanocrystalline films

Abstract

CdNiTe ternary semiconductor thin films were deposited using the cathodic erosion by radiofrequency technique (r.f. sputtering), on 7059 Corning glass substrates. Cd1-xNixTe targets with different Ni compositions in the range 0 < x < 0. 15 were used. Structural analysis in these samples using SEM and X-ray diffraction have shown that films are polycrystalline with grain sizes between 26 and 35 nm

for higher Ni-content, films have smaller grain sizes. As-grown samples and thermal-annealed films in an inert atmosphere at temperatures of 300 and 400 T were studied using the thermoreflectance spectroscopy (TR) at room temperature. From these measurements the bandgap, energy variation as a function of the nanocrystallite size and the annealing temperatures was obtained. From the TR spectra a systematic shift to higher energies of the E-0-point as the grain size decreases has been measured, and we have interpreted this result as due to the CdTe-Ni alloying process added to a quantum-size effect in which the nanocrystallites act as quantum dots. We discuss the TR lineshapes and their evolution with thermal annealing. (C) 2003 Elsevier Science Ltd. All rights reserved.