Strong ultraviolet emission and rectifying behavior of nanocrystalline ZnO films

• Published in: Optical materials Vol. 28; no. 10; pp. 1192 - 1196
• Main Authors: Zhang, Yang, Lin, Bixia, Fu, Zhuxi, Liu, Cihui, Han, Wei
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2006; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Ii-vi semiconductors; Optical materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Optics; Other nonlinear optical materials; photorefractive and semiconductor materials; Photoluminescence; Physics; Rectification; Sol–gel; ZnO films; 78.55.Et; 78.66.Hf; Rectification; 73.40.Ei; Photoluminescence; ZnO films; Sol–gel; Raman spectra; Voltage measurement; Ultraviolet spectra; Polycrystals; Binary compounds; XRD; Nanostructures; 78.55.Et; 78.66.Hf; 73.40.Ei; Thin films; Zinc oxides; Monocrystals; Excitons; II-VI semiconductors; Emission spectra; Ambient temperature; Optical materials; ZnO films; Sol-gel; Photoluminescence; Rectification; Nanostructured materials; Sol-gel process; Nanocrystal
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2005.08.016

Nanocrystalline ZnO thin films on p-type Si(1 0 0) substrates have been prepared by a sol-gel method. X-ray diffraction results showed polycrystalline wurtzite with a preferential (0 0 2) orientation. Morphology studies revealed that the films consisted of uniform grains in size of ∼33 nm. A strong ultraviolet emission with no distinct visible emissions was observed in room temperature photoluminescence spectrum. The ultraviolet emission results from the recombination of free exciton with stronger longitudinal optical (LO) phonon replica. Stronger LO phonon replica may be ascribed to the strong interaction between the exciton and LO phonon in nanostructure. Nanostructure of films is also responsible for the blueshift of free exciton emission compared with single-crystal ZnO. The absence of E 1 (LO) mode in Raman spectrum further confirmed low defect density in as-grown nanocrystalline ZnO films. The electrical junction properties characterized by current–voltage measurement showed a rectifying behavior.