High transmittance–low resistivity cadmium oxide films grown by reactive pulsed laser deposition Raid A. Ismail Æ Bassam G. Rasheed Æ Evan T. Salm Æ Mukram Al-Hadethy Received: 2 November 2006 / Accepted: 29 January 2007 / Published online: 22 February 2007 Ó Springer Science+Business Media, LLC 2007 Abstract High transmittance, low resistivity, and highly oriented cadmium oxide thin films were prepared by pulsed Nd:YAG laser ablation of Cd target in the pres- ence of oxygen as reactive atmosphere. The structural, optical, and electrical properties of CdO films were dependent on the background oxygen pressure PO 2 . The XRD data show that the grown CdO film at 350 Torr oxygen pressure exhibited preferential orientation along (111) crystal plane. The average transmittance of the CdO films in the visible region was found to be in the range of 65–85% and the corresponding optical energy gap found to be in the range of 2.5–2.8 eV depending on oxygen pressure. The lowest electrical resistivity was found to be 7.56 · 10 –3 Wcm for CdO film prepared at 350 Torr of oxygen ambient without using post-deposi- tion heat treatment. 1 Introduction In recent years, the transparent conductive oxide (TCO) films have been found to be used for extensive applications in optoelectronic devices such as, solar cells, flat panel display, and photodetectors [1–4]. CdO is n-type semiconductor with rock-salt crystal structure (FCC) having a direct optical band gap of 2.2 eV [5]. CdO has attracted attention as TCO because of its high electrical conductivity even without doping and high transparency in the visible region with moderate refractive index [6]. Many deposition techniques are used to grow cadmium oxide thin films such as sol–gel [7], spray pyrolysis [2], chemical bath deposition (CBD) [5], sputtering [8], activated reactive evapora- tion [9] and metal organic chemical vapor deposition (MOCVD) [10]. Almost all published data were showed that the grown CdO films were polycrystalline with relative poor crystalline qualities, which are not compatible for use in optoelectronic devices applica- tions. Dewei et al. have recently prepared highly (200)- oriented CdO films using DC reactive magnetron sputtering method [11]. M. Yan et al. [12] prepared low resistivity pure and doped CdO films by PLD using excimer laser to ablate sintered CdO target in ultrahigh vacuum. In comparison with other techniques, pulsed laser deposition of TCO has many advantages such as (i) accurate stoichiometery (ii) good film-to-film reproducibility (iii) smoothness of the deposited film (iv) good adhesion of film with substrate (v) highly oriented films (vi) good film quality deposited at rela- tivity low temperature. In the present work, we have investigated the possibility of growing good quality CdO films by using pulsed laser deposition technique. The second objective of this work is to determine the growth conditions that can produce highly oriented, lower resistivity and highly transparent films for opto- electronic devices applications. 2 Experiment Undoped CdO thin films were deposited on cleaned glass substrates by using pulsed Nd:YAG laser R. A. Ismail  B. G. Rasheed  E. T. Salm  M. Al-Hadethy University of Technology, Baghdad, Iraq Present Address: R. A. Ismail (&) Faculty of Education, Haduramout University, Al-Jabri, 00967 Seiyun, Yemen e-mail: raidismail@yahoo.com 123 J Mater Sci: Mater Electron (2007) 18:1027–1030 DOI 10.1007/s10854-007-9129-4