Microstructural and optical properties of nanocrystalline MgS thin film as wide band gap barrier material B. A. Taleatu • E. Omotoso • E. A. A. Arbab • R. A. Lasisi • W. O. Makinde • G. T. Mola Received: 9 May 2014 / Accepted: 27 August 2014 / Published online: 14 September 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Magnesium sulphide (MgS) thin films have been successfully grown by electrochemical deposition process at room temperature. X-ray diffraction studies revealed that the films have distinct features of crystallin- ity. Prominent characteristic peaks corresponding to cubic structure were identified along (200) and (222) reflections. Surface morphology indicated that the grain sizes of the films ranging between 15 and 17 nm were uniformly dis- tributed across the substrate. Post-deposition annealing enhanced the shape and particle size of the films. Growth height and surface roughness were obtained from atomic force microscope topographic images. Analysis of the optical data gave the values of energy band gaps of the three MgS thin films under study. Energy gaps of the annealed samples were estimated as 3.54 and 3.73 eV while that of as-deposited was given as 4.10 eV. 1 Introduction Magnesium sulphide (MgS) is an alkaline earth sulphide with face-centred cubic (F.C.C) structure, and when embedded and activated with phosphors, it has been found useful in radiation dosimetry [1]. The zinc blend (ZB)- phase MgS (b-MgS) is a wide band gap semiconductor material with emerging useful physical characteristics; it can be used as barrier material with some II–VI semicon- ductors to produce outstanding quantum confinement [2– 4]. In epitaxial lift-off technology, MgS thin film can be used as sacrificial layer due to its high reactivity with dilute acids resulting in higher etching rate compared to other II– VI compounds such as ZnSe [3, 4]. In optoelectronic application, metastable b-MgS in epitaxial structures is mainly essential; hence, control of growth criteria and knowledge of materials properties are prerequisites for its use in the development of electronic device [5]. Growing fairly thick metastable ZB phase of MgS film has been very difficult, and attempts with some growth techniques such as molecular beam epitaxy (MBE) have led to the conversion of the ZB phase to the more stable rock salt (RS) structure probably as a result of chemical interaction with substrate [4, 6]. Several authors have successfully produced ternary and quaternary MgS-rich alloys by MBE, but few works on pure MgS have been published. Moug et al. [3], Davidson et al. [7] and others had reported molecular beam epitaxial growth of ZnMgSSe alloy on GaAs substrate having ZnSe as buffer layer. In this study, we are reporting some growth conditions under which RS structure of MgS thin film could be obtained from wet chemistry (electrochemical deposition) without any buffer layer. The electrolytic solution was made of combination of MgSO 4 and NaS 2 O 3 salts only. This growth technique is very cheap and offers several advantages such as tailoring of nanostructure B. A. Taleatu (&)  E. Omotoso Department of Physics, Obafemi Awolowo University, Ile-Ife, Nigeria e-mail: bdntaleatu@gmail.com B. A. Taleatu  E. A. A. Arbab  G. T. Mola School of Chemistry and Physics, University of KwaZulu Natal, P Bag X01, Scottsville, Pietermaritzburg 3209, South Africa R. A. Lasisi Federal College of Education, Kotangora, Niger State, Nigeria W. O. Makinde Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria 123 Appl. Phys. A (2015) 118:539–545 DOI 10.1007/s00339-014-8753-0