AVS 49th International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Paper TF-MoA8
ZnO Thin Film Synthesis and Device Application

Monday, November 4, 2002, 4:20 pm, Room C-101

Session: Transparent Conductive Coatings
Presenter: R.S. McLean, DuPont Central Research and Development
Authors: R.S. McLean, DuPont Central Research and Development
M.H. Reilly, DuPont Central Research and Development
P.F. Carcia, DuPont Central Research and Development
Correspondent: Click to Email
ZnO is a wide bandgap, n-type semiconductor that can be doped degeneratively with Group III elements, making it useful as a transparent conducting electrode. Recently, there have been reports of successful p-type doping of ZnO, which would enable device applications ranging from uv lasers to transparent thin film transistors. ZnO is also attractive because polycrystalline films can be grown at low temperatures, compatible with temperature-sensitive plastic substrates, thus presenting the opportunity for fabricating good quality electronic devices on flexible substrates. In this paper we discuss synthesis and electronic properties of ZnO films on polyester substrates and device application. ZnO films were grown by rf magnetron, rf diode, and ion beam sputtering on substrates ostensibly at room temperature. Films grown at low oxygen partial pressure, p(O@sub2@), had the lowest resistivity, ~0.01 ohm-cm, with a dependence of resistivity on p(O@sub2@) that was exponential-like. Hall effect mobility measured in films with resistivity between 0.01 and 10 ohm-cm, was ~ 6-12 cm@super2@/V-s, independent of deposition technique. All film were polycrystalline with prominent c-axis orientation and small, uniform grain size, ~ 25 nm. Film stress increased with p(O@sub2@) and more energetic deposition conditions, suggesting that bombardment by negative oxygen ions likely caused high stress. Finally we fabricated a ZnO, transparent, thin-film transistor, and its properties will also be discussed.