ISSN 1063-7842, Technical Physics, 2008, Vol. 53, No. 8, pp. 1065–1069. © Pleiades Publishing, Ltd., 2008. Original Russian Text © V.A. Krivchenko, D.V. Lopaev, P.V. Pashchenko, V.G. Pirogov, A.T. Rakhimov, N.V. Suetin, A.S. Trifonov, 2008, published in Zhurnal Tekhnicheskoœ Fiziki, 2008, Vol. 78, No. 8, pp. 107–111. 1065 INTRODUCTION Zinc oxide (ZnO) is a wide-band semiconductor with a bandgap roughly equal to 3.3 eV [1]. This fact, combined with a high binding energy of excitons at room temperature, renders this material promising for UV light-emitting diodes [2–4]. As applied to solar- blinded (UV) photodetectors [5–7] and gas sensors [8], the main advantages of ZnO over other materials are its transparency in the visible range, high thermal stability, and high chemical inertness [9]. A number of efficient UV detectors based on single- crystalline ZnO [6], polycrystalline ZnO films [5], and nanocrystalline ZnO films [7] have been described in the literature to date. It was reported, for example, that application of high-purity single-crystalline ZnO allows designers to raise the efficiency of UV detectors to 61%; however, such a technology is expensive, related devices are limited in size, and tailor-made sub- strates are required. In the case of nanocrystalline ZnO films, the maximal efficiency of the detectors, 18%, was reached in a multilayer p(20-nm-thick NiO)–i(200- nm-thick ZnO)–n(50-nm-thick ITO) structure grown on a glass substrate [7]. The disadvantage of such struc- tures is that they, as a rule, are prone to degradation because of chemical reactions at the interfaces. Photo- detectors based on polycrystalline ZnO also show a high quantum efficiency (44.9%) [5]. However, their fabrication requires sapphire substrates, multistage ZnO evaporation, and heat treatment of the substrate. This all may considerably complicate the fabrication technology of the detectors. In this work, we study a simpler and more stable design of UV detectors based on nanocrystalline ZnO films. The films were deposited by magnetron sputter- ing in an rf discharge. Our goal was to see how the type of sputtered target and ZnO film deposition conditions influence the photoelectric performance of the UV detectors. In addition, we studied the efficiency of the detector versus its surface topology, which was exam- ined with an atomic force microscope (AFM). EXPERIMENTAL ZnO films were deposited on glass plates with pre- applied contacts. The contacts were applied by magne- tron sputtering of Ti (50 nm) and Au (50 nm) layers and patterned by photolithography. We used an interdigi- tated structure of electrodes (contacts) with spacings of 10 and 20 μm (Figs. 1a, 1b). Then, the contacts were covered by 2-μm-thick ZnO films applied by magne- UV Detectors Based on Nanocrystalline ZnO Films V. A. Krivchenko, D. V. Lopaev, P. V. Pashchenko, V. G. Pirogov, A. T. Rakhimov, N. V. Suetin, and A. S. Trifonov Research Institute of Nuclear Physics, Moscow State University, Moscow, 119992 Russia e-mail: victi81@mail.ru Received August 20, 2007 Abstract—Nanocrystalline films of zinc oxide deposited by rf magnetron sputtering are used as a working material of UV detectors. The photoelectric performance of UV detectors versus ZnO deposition conditions is studied. The influence of the surface topology of the UV detectors on their efficiency is examined with an atomic force microscope. PACS numbers: 72.80.Ey, 73.40.Sx, 73.50.Pz, 73.63.Bd DOI: 10.1134/S1063784208080148 OPTICS, QUANTUM ELECTRONICS (a) (b) (c) (d) 300–600 nm 0–30 V 10 20 ZnO film Gold contacts ZnO film Au contacts Glass substrate A Fig. 1. (a, b) Optical microscopic images of the substrates used in the experiment, (c) circuit used in measuring the photoelectric properties of the UV detectors, and (d) cross- sectional view of the UV detector (not to scale). Amplifier