Characterization and Raman investigations on high-quality ZnO thin films fabricated by reactive electron beam evaporation technique

• Published in: Journal of crystal growth Vol. 279; no. 3; pp. 394 - 402
• Main Authors: Al Asmar, R., Atanas, J.P., Ajaka, M., Zaatar, Y., Ferblantier, G., Sauvajol, J.L., Jabbour, J., Juillaget, S., Foucaran, A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2005; Elsevier
• Subjects: A1. Annealing treatment; A1. Growth temperature; A1. Optical transmittance; A1. Raman studies; A3. Electron beam evaporation; B1. Zinc oxide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronics; Engineering Sciences; Exact sciences and technology; Iii-v and ii-vi semiconductors; Infrared and raman spectra and scattering; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Vapor phase epitaxy; growth from vapor phase; A1. Growth temperature; A3. Electron beam evaporation; A1. Raman studies; A1. Optical transmittance; B1. Zinc oxide; A1. Annealing treatment; A1. OpticA1 transmittance; Raman spectra; Inorganic compounds; Crystal orientation; Photoluminescence; Controlled atmospheres; XRD; Thin films; Grain size; Annealing; Vacancies; Transition element compounds; Crystallization; Binary compounds; Residual stresses; Experimental study; Transmittance; A1. AnneA1ing treatment; Hexagonal lattices; Zinc oxides; II-VI semiconductors; Wurtzite structure; Electron beam evaporation
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2005.02.035

High-quality zinc oxide thin films have been evaporated by reactive e-beam in an oxygen environment. Photoluminescence (PL) on ZnO evaporated at 300 °C reveals an enhancement of the ultraviolet near band edge emission at 3.28 eV and shows the smallest full-width at half-maximum of the NBE peak about 150 meV, proving that the optimum growth temperature is 300 °C. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented and that the linewidth of the (0 0 2) peak is sensitive to the variation of substrate temperature. The best crystallinity occurred at 300 °C, correlating with the PL measurements. The optical transmittance is the highest at 300 °C and has been increased after annealing in air, showing an improvement of the optical quality. Raman spectroscopy has been found to be an efficient tool to evaluate the residual stress in the as-grown ZnO films from the position of the E 2 (high) mode. On the other hand, the vanishing of the 574 cm −1 Raman feature after annealing has been explained as due to an increase of grain size and the reduction of O vacancy and Zn interstitial. A model has been developed in this work to determinate the normal mode frequencies from Fourier analysis by considering the five force constants starting from the five elastic constants of the material. The vibrational modes at about 100, 435 and 1123 cm −1 have been found from the model for a ZnO thickness of 0.3 μm.