Stable a-MnS thin film deposited by two-electrode cell: synthesis, structural characterization and photoemission spectroscopic studies Bidini A. Taleatu 1,2 • Elhadi A. A. Arbab 2 • Genene T. Mola 2 Received: 15 March 2015 / Accepted: 26 May 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract Stable MnS thin film was deposited from cat- alyst-free inorganic solution by electrochemical cell. The film was characterized by some surface profiling tech- niques. Morphology revealed that film’s particles were fairly distributed across substrate’s surface. Crystallinity and surface growth height/roughness were observed before and after post-deposition annealing. Optical studies further showed that annealing has improved film transmittance across visible wavelength region. Reflections from planes associated with only rock salt structure of MnS were prominently identified by diffraction studies. An estimated average crystal size of 17.40 nm suggested that the deposited film is mainly composed of nanocrystalline particles. Film durability was appraised by core-level profiling of Mn and S binding energy (BE) positions during X-ray photoemission spectroscopy (XPS). The results indicated that before and after vacuum annealing, chemical states of Mn and S remained the same suggesting that the film did not undergo any form of transformation after long exposure to ambient environment. This study demonstrated sustainability of MnS electrode in extreme environmental condition. 1 Introduction Submicroscopic and nanocrystalline materials are very attractive because of remarkable difference in their prop- erties compared to bulk form. Variable morphologies and crystal structures of these materials enable them useful as building units for designing and assembling nanodevices. These unique properties are achieved due to ample possi- bilities for fine tuning and flexibility in preparation of various group II–VI semiconductor compounds [1]. Man- ganese chalcogenides (S, Se, Te, etc.) are one of such compounds. MnS is a p-type semiconductor. It has fairly wide band gap (E g C 3.1 eV) suitable for short-wavelength optoelectronic applications such as solar cell, optical win- dows, buffer layer, photoconductive devices and lumines- cent materials [1, 2]. If II–VI compounds are doped with manganese, dilute magnetic semiconductor (DMS) with good magneto-optical properties can be produced. MnS has been found in three different phases. The green coloured stable a-MnS (rock salt) structure and two pink metastable modifications: b-MnS (sphalerite) and c-MnS (wurtzite). The two metastable phases are tetrahedrally coordinated and exist at low-temperature range. If subjected to tem- perature between 100 and 400 °C and or high pressure, they can be transformed irreversibly to octahedrally stable a-MnS [1–3]. These phases and various morphologies can be synthesized by altering process parameters such as concentration of reacting solution, solvents, surfactant, reaction temperature and time, film growth conditions as well as post-deposition heat treatment [1]. Reports have indicated syntheses of various MnS structures by some complex systems involving hydrothermal, vapour deposi- tion, sputtering, etc. [4–6]. Fabrication under mild condi- tions remains a challenge. In this study, we investigated how a thin film of MnS could be synthesized from common & Bidini A. Taleatu bdntaleatu@gmail.com 1 Department of Physics and Engineering Physics, Obafemi Awolowo University, Ile-Ife, Nigeria 2 School of Chemistry and Physics, University of KwaZulu-Natal, P Bag X01 Scottsville, Pietermaritzburg 3209, South Africa 123 Appl. Phys. A DOI 10.1007/s00339-015-9262-5