Structural, electronic, and optical properties of nanocrystalline As-doped ZnO films on quartz substrates determined by Raman scattering and infrared to ultraviolet spectra

• Published in: Thin solid films 2011-09, Vol.519 (22), p.8166-8172
• Main Authors: Li, W.W., Yu, W.L., Wu, J.D., Gan, J., Zhu, M., Hu, Z.G., Chu, J.H.
• Format: Article
• Language: English
• Subjects: Arsenic doped Zinc Oxide; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Doping; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Laser deposition; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nanocrystalline Films; Nanocrystals; Nanoscale materials and structures: fabrication and characterization; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Optical Spectroscopy; Other topics in nanoscale materials and structures; Physics; Pulsed Laser Deposition; Quartz; Raman scattering; Raman Spectroscopy; Reflectance; Surface and interface electron states; X-ray Diffraction; Zinc oxide
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2011.05.049

Nanocrystalline As-doped ZnO films with different laser power energy (40 mJ and 55 mJ) and As doping concentrations (C As from 1% to 3%) have been grown on quartz substrates by pulsed laser deposition. The average grain size of the films was calculated from the (002) peak of x-ray diffraction patterns and is estimated to vary from 9 to 13 nm. Electronic transitions and optical properties of the films have been investigated by Raman scattering, far-infrared reflectance, and infrared-ultraviolet spectral transmittance technique. With increasing doping concentration, the A 1 longitudinal optical phonon mode shifts towards the lower energy side and can be described by (564-75C As) cm -1 owing to the increment of free carrier concentration. The E 1 transverse optical phonon frequency is located at about 415 cm -1 and does not show an obvious decreasing trend with the C As. The optical constants in the photon energy range of 0.5–6.5 eV have been extracted by fitting the experimental data with the Adachi's model. The refractive index dispersion in the transparent region can be well expressed by a Sellmeier's single oscillator function. Due to different doping concentration and hexagonal crystalline structure, the optical band gap of the films grown at 40 mJ linearly decreases with increasing As concentration. The phenomena agree well with the results from the theoretical calculations.