DC triode sputtering deposition and characterization of N-rich copper nitride thin films: Role of chemical composition N. Gordillo a,Ã , R. Gonzalez-Arrabal b , M.S. Martin-Gonzalez b , J. Olivares c , A. Rivera b , F. Briones b , F. Agullo ´ -Lo ´ pez a , D.O. Boerma a a Centro de Microana ´lisis de Materiales, Universidad Auto ´noma de Madrid, E-28049 Madrid, Spain b Instituto de Microelectro ´nica de Madrid CSIC C/ Isaac Newton, 8. Tres Cantos, E-28760 Madrid, Spain c Instituto de O ´ ptica ‘‘Daza de Valde´s’’, CSIC, C/Serrano 121, E-28006 Madrid, Spain article info Article history: Received 23 May 2008 Received in revised form 15 July 2008 Accepted 16 July 2008 Communicated by P. Rudolph Available online 20 July 2008 PACS: 68.55.a 78.20.Ci 78.40.Fy Keywords: A1. Optical properties A1. X-ray diffraction B1. Nitrides B2. Semiconducting materials abstract (N-rich) Cu 3 N polycrystalline films were deposited by DC triode sputtering from a copper target in a mixture of argon and nitrogen atmosphere. Their chemical composition, structure and electrical properties have been studied as a function of deposition parameters: nitrogen partial pressure (P N2 ) and DC bias. Depending on P N2 and DC bias, the atomic nitrogen incorporated into the layers ranges from 26 at% to a limit value of 33 at% as measured by ion beam analysis (IBA) techniques. X-ray diffraction (XRD) data show that most of the layers are single phase, polycrystalline and with preferential /100S orientation. Optical and electrical measurements indicate that all layers present intrinsic semiconductor behavior with a thermal gap around 0.21–0.25 eV and a direct optical gap between 1.5 and 1.7 eV. The physical properties observed for these films are discussed in relation to nitrogen contents and sputtering parameters. & 2008 Elsevier B.V. All rights reserved. 1. Introduction Metal nitrides (MN) have been extensively studied because of their potential for tribological, electrical and magnetic applica- tions. One of the major concerns in these studies is the tailoring of the physical properties of MN by changing their atomic nitrogen percentage [1–3]. Traditionally, most of the work done for MN has been focused on thermodynamically stable nitrides. However, in the last years metastable nitrides, such as copper nitrides, have attracted much attention because their decomposition above a certain temperature would be of use for the fabrication of microscopic metal lines with maskless laser or electron beam writing without involving any lithographic process [4–7]. To the best of our knowledge, two phases (without considering the very unstable copper azides) have been described in the literature for the Cu–N compound: the Cu 4 N and the Cu 3 N, which exhibit a metallic-like and a semiconducting-like behavior, respectively [8]. The Cu 3 N material presents an anti-ReO 3 -type crystal structure [9] where the face-centered cubic close-packed sites are vacant and can be filled by Pd [10]. Since the pioneer work by Terada et al. [11], most publications have dealt with RF sputter deposition and the characterization of the physical properties of the films as a function of deposition parameters: total pressure (P Ar +P N 2 ) in the chamber during the sputter deposition [12–14], partial pressure of nitrogen (P N 2 ) in the gas mixture [15,16] and substrate tempera- ture [17,18]. However, discrepancies in reported data are remark- able. For example, the reported optical gap varies from 1.2 to 1.9 eV (38% of variation) [5,17,19–23], and the measured electrical resistivity ranges from 2.6  10 5 to 1000 O cm, i.e. from a quasi- metallic to an intrinsic semiconductor behavior [5,17]. Part of the dispersion in the reported data for Cu 3 N might be associated with differences in the chemical composition [24,25]. However, unfortunately, reliable data in the Cu–N composition are not often shown. Indeed, the lack of an accurate chemical composition determination is doubtless the weakest point in almost all publications reported up to now. The purpose of this paper is to contribute to carry out a systematic study of the material chemical composition and its influence on structural and physical properties. To this end, we ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth 0022-0248/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2008.07.051 Ã Corresponding author. Tel.: +34914973621; fax: +34914973623. E-mail address: nuria.gordillo@uam.es (N. Gordillo). Journal of Crystal Growth 310 (2008) 4362–4367