Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf The effect of deposition rate and thermal annealing on morphology and microstructural evolution of Nickel-Bismuth thin film Christopher Mtshali a, ⁎ , Charles Thethwayo b , Carlos Pineda-Vargas a , Muzi Ndwandwe b a iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, Cape Town, South Africa b Physics Department, University of Zululand, Private Bag 1001, KwaDlangezwa 3886, South Africa ARTICLE INFO Keywords: Nickel-Bismuth Islands Nanowires Electron beam evaporation Rutherford backscattering spectrometry X-ray diffraction Scanning electron microscope ABSTRACT Bismuth/Nickel thin films were deposited on borosilicate glass substrates using an electron beam evaporator equipped with thickness monitor. Thin film of Bi (10 nm) was deposited on top of pre-deposited Ni (10 nm) film at 0.6 and 1.8 Å/second deposition rates. The samples were then annealed at temperatures between 60 °C and 260 °C for 1 to 5 h under vacuum of ~1 × 10 −6 mbar. Scanning electron microscopy was used to investigate surface morphology. Scanning electron microscopy images depicted islands at all temperatures including the as- deposited sample. High resolution transmission electron microscopy reveals highly crystalline film and nano- wires with energy dispersive x-ray spectroscopy showing that the film and nanowires were formed by Bi and Ni elements with oxygen as impurity. Rutherford backscattering spectrometry revealed intermixing of layers at the interface. Furthermore, spontaneous formation of NiBi 3 and NiBi stoichiometry was observed attributed to re- action-diffusion mechanism during deposition. X-ray diffraction revealed structural transformation of the films from amorphous (as-deposited) to polycrystalline hexagonal β-NiBi crystal structure at 60 °C to 200 °C. X-ray diffraction pattern also revealed hexagonal crystal lattice with preferential growth orientation along the [1 0 1] plane with other supported planes [0 0 2], [1 0 2], [1 1 0] and [1 0 3]. The results pointed toward successful utilization of this approach to prepare templates for the synthesis of well controlled, vertically aligned and well distributed crystalline nanowires of Ni-Bi binary system more relevant to the industrial application. 1. Introduction Ni-Bi bimetallic alloys, NiBi and NiBi 3 , have received much interest from researchers in the past decade due to their display of interesting magnetic and superconducting properties [1–8]. NiBi 3 has been mostly investigated for its superconducting behavior [1–8] while NiBi has also been identified as potential candidate for lead free soldering material for electronics [9–11]. However, in microelectronics devices, the re- action of thin film metallization layer and solder materials at joints is critical and therefore proper care has to be considered when choosing materials to be used [9]. It has also been reported in the literature that low dimensional nanostructures of bi-metallic systems such as Ni-Bi are interesting and of fundamental importance for investigation of classical and quantum size effect that are becoming more interesting and re- levant for industrial application [12]. They can be used for single electron devices, optoelectronic devices, magnetic storage devices, and as nucleation sites for nanowires growth, and nanoscale interconnects [12]. In the context of quantum size effect, we chose to investigate the structural formation of Bi and Ni islands to be used as a template for nanowires growth for further magnetic and superconductivity studies. Various techniques have been employed to synthesize Bi and Ni-Bi bimetallic nanosystems but none of them have used electron beam evaporation. Ion beam mixing has been reported as one of the methods of mixing metallic and semiconductor materials [13–15]. Bin-Kun Wu et al., [16] used RF-sputtering technique to synthesize Bi nanowires while Siva et al., [17] investigated interdiffusion in Ni-Bi bilayers using ion beam mixing method. Chiu and Shih [18] fabricated Bi nanowires on Si substrate using an electron beam writing technique. Other reports suggested co-melted high purity Ni and Bi at high temperature of ~900 to 1100 °C to achieve NiBi 3 stoichiometry [19,20]. Other reports [21–25] suggested the use of chemical deposition as a better alternative method to physical deposition especially when it comes to creation of NiBi nanostructures with well controlled dimen- sions. The difficulty with chemical deposition is the alignment of structures such as nanowires. Some reports [18–20] suggest the use of template for nanowires formation but this method also poses a chal- lenge when it comes to preservation of nanowires during template etching process. Therefore physical deposition has been seen as a viable https://doi.org/10.1016/j.tsf.2017.10.064 Received 16 May 2017; Received in revised form 24 October 2017; Accepted 31 October 2017 ⁎ Corresponding author. E-mail address: mtshali@tlabs.ac.za (C. Mtshali). Thin Solid Films 645 (2018) 312–319 0040-6090/ © 2017 Elsevier B.V. All rights reserved. MARK