Sensors & Transducers, Vol. 220, Issue 2, February 2018, pp. 37-44 37 Sensors & Transducers Published by IFSA Publishing, S. L., 2018 http://www.sensorsportal.com Characterization of Cuprous Oxide Thin Films Prepared by Reactive Direct Current Magnetron Sputtering 1, * Ørnulf NORDSETH, 2 Irinela CHILIBON, 3 Raj KUMAR, 3 Kristin BERGUM, 2 Cristina VASILIU, 2 Raluca IORDANESCU, 2 Laurentiu BASCHIR, 2 Dan SAVASTRU, 2 Adrian KISS, 2 Anca PARAU, 4 Laurentiu FARA, 5 Roxana TRUSCA, 3 Edouard MONAKHOV, 1 Sean Erik FOSS and 3 Bengt Gunnar SVENSSON 1 Institute for Energy Technology (IFE), Instituttveien 18, NO-2007 Kjeller, Norway 2 National Institute of R&D for Optoelectronics (INOE-2000), P.O. Box MG-5, RO-077125 Bucharest-Magurele, Romania 3 Department of Physics/Center for Materials Science and Nanotechnology (SMN), University of Oslo, P.O. Box 1048, Blindern, NO-0316 Oslo, Norway 4 University Politehnica of Bucharest, 313 Spl. Independentei, RO-060042 Bucharest, Romania 5 METAV-CD, 31 C. A. Rossetti, RO-020011 Bucharest, Romania * Tel.: +47 6380 6000, fax: +47 6921 2201 * E-mail: ornulf.nordseth@ife.no Received: 10 November 2017 /Accepted: 5 February 2018 /Published: 28 February 2018 Abstract: In this work, cuprous oxide (Cu 2 O) thin films were prepared on silicon and quartz substrates by reactive direct current magnetron sputtering. The morphological and structural properties of the sputter- deposited Cu 2 O thin films were investigated by scanning electron microscopy, atomic force microscope, and X-ray diffraction, whereas the optical properties were determined by spectroscopic ellipsometry and ultraviolet– visible spectrophotometer measurements. Thin film characterization showed that the average grain size for 500 nm thick Cu 2 O film increases from about 70 nm for the as-grown film to about 600 nm after annealing the film at 900 °C in vacuum. Moreover, the surface roughness increased after annealing, whereas the optical absorption was reduced after annealing, presumably as a result of increased grain size and less strained films. The optical band gap increased from E g = 2.06 eV for the as-grown Cu 2 O film to E g = 2.19 eV after annealing. X-ray diffraction scans showed diffraction peaks of (111), (200), and (220) planes of Cu 2 O for both the as- grown and annealed film. The film resistivity and hole mobility were respectively 200 Ohm⋅cm and 50 cm 2 /V⋅s for the annealed Cu 2 O film, derived from Hall effect measurements. Keywords: Cuprous oxide, Thin films, Magnetron sputtering, Morphology, Optical properties. 1. Introduction The p-type semiconductor cuprous oxide (Cu 2 O) has been intensively studied due to its high optical absorption coefficient and favorable carrier transport properties. These characteristics combined with its non-toxic nature and abundant availability make Cu 2 O attractive for various thin film technologies, such as photoelectrochemical systems [1], solar cells [2-3], photodetectors [4], and transistors [5]. Often, http://www.sensorsportal.com/HTML/DIGEST/P_2977.htm