Effects of Annealing Temperature on Structural, Optical and Electrical Properties of Ge Nanocrystals Embedded in GeO_x Matrix

Abstract

In this paper, the effects of annealing temperature on the growth of Ge nanocrystals embedded in GeOx matrix have been investigated. GeOx thin films deposited on Si and quartz substrates using electron beam evaporation were annealed under nitrogen ambience at 650, 750 and 850 °C. The pristine and annealed samples have been characterized using X‐ray diffraction, Raman spectroscopy, Atomic force microscopy, UV‐Visible spectroscopy and Semiconductor Device Analyzer (SDA). It is evident from XRD that the as‐deposited films are amorphous in nature, whereas the annealed films upto 750°C reveal the coexistence of crystalline Ge and GeO2. However, a further increase in temperature reflects only GeO2 phase and disappearance of Ge peak. The sharp and intense peak at 299 cm−1 for the films annealed up to 750 °C in the Raman spectra indicates the formation of Ge nanocrystals and the peak around 436 cm−1 is attributed to crystalline GeO2. The optical band gap of pristine and annealed films was calculated using UV–Vis spectroscopy. The I–V measurements of annealed films show the ohmic behavior. The results reveal that the annealing temperature significantly affects the crystallinity, size of nanocrystals and optical band gap of films. The impact of annealing temperature on the structural, optical and electrical properties of nc‐Ge embedded in GeOx matrix has been reported in detail.