Effects of Annealing Temperature on Structural, Optical and Electrical Properties of Ge Nanocrystals Embedded in GeO x Matrix Mahendra Singh Rathore, Arun Vinod, and N. Srinivasa Rao* In this paper, the effects of annealing temperature on the growth of Ge nanocrystals embedded in GeO x matrix have been investigated. GeO x 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 Semi- conductor 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 GeO 2 . However, a further increase in temperature reflects only GeO 2 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 GeO 2 . 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 GeO x matrix has been reported in detail. 1. Introduction In recent years, elemental semiconductor nanocrystals (NCs) or quantum dots such as Silicon (Si) and Germanium (Ge) have been studied extensively due to their potential applications in optoelectronics, nanophotonics and microelectronics devices. [1,2] Although Si is one of the promising materials, Ge is rather much fascinating material as compared to Si because of its effective mass and smaller energy band gap, that it should be easier to tune the electronic structure around the band gap. The exciton Bohr radius of Ge is much larger than Si, which implies that quantum confinement effects are more prominent in Ge nanostructures even for relatively larger sizes of the nanocrystals, [3] which leads to strong enhancement of the radiative transition yield for nanocrystals. [4] On the other hand, the sub-oxide group of Ge such as GeO 2 subdues their Si counterparts because of higher refractive index and higher linear coefficient of thermal expansion than silicon oxide. [5] Moreover, semiconductor nanocrystals embedded in dielectric oxide matrix have attracted much attention because of their technological applications for future high speed and low power consuming memory devices. [6,7] In recent years, there are reports available on the synthesis of Ge nanocrystals embedded in GeO x films using different methods, such as ion beam irradiation, [8,9] thermal anneal- ing of Ge implanted films, [10] and thermal annealing of GeO x films up to 600  C. [11,12] However, there are no systematic reports available on the impact of annealing temperature above 600  C, on structural, optical and electrical properties of GeO x thin films, and on the growth of Ge nanocrystals from phase separation of GeO x films in detail. In this study, GeO x films prepared by electron beam evaporation were subjected to thermal anneal- ing at 650, 750 and 850  C in nitrogen ambience. Various properties of pristine and annealed films have been investigated by XRD, Raman, AFM, UV–Visible spectroscopy and SDA. Ge nanocrystals embedded in GeO x matrix were synthesized and coexistence of crystalline Ge and GeO 2 has been observed upon annealing up to 750  C. Annealing at 850  C resulted in GeO 2 phase only. The effects of annealing temperature in tuning the structural, optical and electrical properties of Ge nanocrystals embedded in GeO x matrix have been reported. 2. Experimental Section Germanium oxide (GeO x ) thin films were deposited onto p-type Si (100) and quartz substrates by the evaporation of GeO 2 target in high vacuum using electron beam evaporation method. GeO 2 powder of purity 99.998% (Sigma–Aldrich) in a pellet form was used as source material for deposition of GeO 2 thin films. Prior to deposition, the substrates were thoroughly cleaned using M. S. Rathore, A. Vinod, N.S. Rao Department of Physics, Malaviya National Institute of Technology Jaipur J.L.N. Marg, Jaipur-302017, India E-mail: srnelamarri.phy@mnit.ac.in DOI: 10.1002/masy.201700024 Macromolecular Symposia Raman Pectroscopy www.ms-journal.de ARTICLE Macromol. Symp. 2017, 376, 1700024 © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1700024 (1 of 5)