Modifications of structural, optical and electrical properties of nanocrystalline bismuth sulphide by using swift heavy ions R.R. Ahire a,b , Abhay A. Sagade a , S.D. Chavhan d , V. Huse a , Y.G. Gudage a , F. Singh c , D.K. Avasthi c , D.M. Phase e , Ramphal Sharma a, * a Thin Film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Begampura, Aurangabad 431 004, MS, India b S.G. Patil College, Department of Physics, Sakri 424304, MS, India c Inter-University Accelerator Center, Aruna Asaf Ali Marg, P.B. 10502, New Delhi 67, India d Department of Chemical Engineering, Chonbuk National Laboratory, Chonju, Jeonju, South Korea e UGC-DAE CSR, University Campus, Khandwa Road, Indore 452017, MP, India Received 8 January 2008; received in revised form 1 March 2008; accepted 14 March 2008 Available online 25 March 2008 Abstract Modified chemical bath deposited (MCBD) bismuth sulphide (Bi 2 S 3 ) thin films’ structural, optical and electrical properties are engi- neered separately by annealing in air for 1 h at 300 °C and irradiating with 100 MeV Au swift heavy ions (SHI) at 5  10 12 ions/cm 2 fluence. It is observed that the band gap of the films gets red shifted after annealing and irradiation from pristine (as deposited) films. In addition, there is an increase in the grain size of the films due to both annealing and irradiation, leading to the decrease in resistivity and increase in thermoemf of the films. These results were explained in the light of thermal spike model. Ó 2008 Elsevier B.V. All rights reserved. PACS: 73.61.J; 78.66; 61.80; 73.50.M Keywords: Annealing; Bismuth sulphide; Grain growth; SHI; Thermal spike; Thermoemf 1. Introduction Metal sulphides are fascinating the researchers continu- ously because of their interesting properties, which can be easily tailored by using different deposition techniques and/or by using different post-deposition treatments. Annealing at different temperatures and in various environ- ments is one of the well-known techniques. Nowadays, swift heavy ions (SHI) are also getting popular to engineer the materials’ properties. They have been extensively used for ion implantation, ion beam assisted self-assembled nanoparticles formation and template synthesis, etc. [1,2]. Since Bi 2 S 3 is an n-type semiconductor with remarkable applications in thermoelectric, optoelectronic and photo- electrochemical devices, ample efforts have been made to grow the material with required properties. Recently, many methods (including the single-source precursor method, microwave irradiation, sonochemical method, chemical bath deposition and spray pyrolysis) have been developed for the synthesis of low-dimensional Bi 2 S 3 nanostructures [3–6]. Ahire et al. have reported on the growth of bismuth sulphide thin films deposited by modified chemical bath (MCBD) [7]. As pointed out previously, post-deposition treatment is a very important task to be carried out to modify the mate- rials properties. Recently, we have shown that the effects of these two treatments were nearly equal on the cadmium sulphide [8]. But SHI is a more powerful way to tailor the structural, optical and electrical properties at nano- scale. And till date we did not find any report of this kind for bismuth sulphide. Here, we report on the SHI induced 1567-1739/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2008.03.005 * Corresponding author. E-mail address: ramphalsharma@yahoo.com (R. Sharma). www.elsevier.com/locate/cap www.kps.or.kr Available online at www.sciencedirect.com Current Applied Physics 9 (2009) 374–379