Growth of ZnO/sapphire heteroepitaxial thin films by radio-frequency sputtering with a raw powder target

• Published in: Thin solid films 2010-07, Vol.518 (18), p.5164-5168
• Main Authors: Seo, S.H., Kang, H.C.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition; Deposition by sputtering; Epitaxy; Exact sciences and technology; Heteroepitaxy; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nanostructure; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Photoluminescence; Physics; Powder target; Radio-frequency sputtering; Raw; Sintering; Spectroscopy; Sputtering; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; Thin films; X-ray diffraction; Zinc oxide
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.03.032

Epitaxial ZnO thin films were deposited by radio-frequency sputtering. In contrast to typical sputter growth, in which a ZnO sintered target was used, raw ZnO powder with a particle size smaller than 1 μm is used as the source material. In order to verify this approach, ZnO thin films were deposited on sapphire(0001) substrates and characterized by X-ray diffraction, atomic force microscopy, ultraviolet–visible–near-infrared (near-IR) transmission spectroscopy, and photoluminescence spectroscopy. The as-deposited ZnO thin films grew epitaxially on the sapphire(0001) substrate. A crossover in the growth mode from an initial 2-dimensional planar layer to later 3-dimensional islands was observed, which is consistent with the results obtained using a ZnO sintered target. The ZnO films showed band-edge emission with a bandgap energy of 3.27 eV and a high optical transmittance > 80% from visible to near-IR region. This shows that ZnO powder targets can be an alternative to relatively expensive sintered ones in the fabrication of ZnO nano-structures and doped ZnO.