Highly conductive, undoped ZnO thin films deposited by electron-cyclotron-resonance plasma sputtering on silica glass substrate

• Published in: Thin solid films Vol. 518; no. 1; pp. 22 - 26
• Main Author: Akazawa, Housei
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02.11.2009; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Electrical properties of specific thin films; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Exact sciences and technology; Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects); 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; Optical properties of specific thin films; Physics; Sputtering; Transparent conductive oxide; Zinc oxide; Transparent conductive oxide; Zinc oxide; Sputtering; Electrical conductivity; Vacancies; Electrical properties; Hall mobility; Electron cyclotron-resonance; XRD; Thin films; Ambient temperature; Optical properties; Rocking curve; Absorption spectra; Carrier density; Crystal structure
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2009.06.008

The electrical and optical properties of undoped ZnO films deposited by electron cyclotron resonance (ECR) plasma sputtering at room temperature were characterized. The lowest resistivity we achieved was 2.6 × 10 − 3  Ωcm with optical transmittance at visible wavelengths higher than 85%. The X-ray diffraction (002) peak was weak and the rocking curve was asymmetrical, indicating that oxygen vacancies prevented large crystalline domains from forming. At low argon-sputtering-gas pressure, carrier concentration and Hall mobility increased with increasing argon pressure. When the optimum pressure (40 mPa) was exceeded, however, Hall mobility and optical transmittance were severely reduced, which indicated that excess Zn atoms were populated at the interstitials of the network. Admitting only 0.67 mPa of O 2 gas during deposition deteriorated resistivity over 1 MΩcm due to high excitation efficiency in the ECR plasma. Deposition under a higher magnetic field produced lower resistivities.