Please cite this article in press as: J. Sultana, et al., Chemical bath deposited (CBD) CuO thin ﬁlms on n-silicon substrate for electronic and optical applications: Impact of growth time, Appl. Surf. Sci. (2016), http://dx.doi.org/10.1016/j.apsusc.2016.12.139 ARTICLE IN PRESS G Model APSUSC-34686; No. of Pages 8 Applied Surface Science xxx (2016) xxx–xxx Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Full Length Article Chemical bath deposited (CBD) CuO thin ﬁlms on n-silicon substrate for electronic and optical applications: Impact of growth time Jenifar Sultana a , Somdatta Paul a , Anupam Karmakar b , Ren Yi c , Goutam Kumar Dalapati c , Sanatan Chattopadhyay b,∗ a Centre for Research in Nanoscience and Nanotechnology (CRNN), Kolkata, 700098, India b Department of Electronic Science, University of Calcutta, Kolkata, 700009, India c Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, Innovis, #08-03, 138634, Singapore a r t i c l e i n f o Article history: Received 9 September 2016 Received in revised form 16 December 2016 Accepted 17 December 2016 Available online xxx Keywords: CuO thin ﬁlm Time dependent growth Thickness optimization p-CuO/n-Si heterojunctions Electronic and optical properties a b s t r a c t Thin ﬁlm of p-type cupric oxide (p-CuO) is grown on silicon (n-Si) substrate by using chemical bath deposition (CBD) technique and a precise control of thickness from 60 nm to 178 nm has been achieved. The structural properties and stoichiometric composition of the grown ﬁlms are observed to depend signiﬁcantly on the growth time. The chemical composition, optical properties, and structural quality are investigated in detail by employing XRD, ellipsometric measurements and SEM images. Also, the elemental composition and the oxidation states of Cu and O in the grown samples have been studied in detail by XPS measurements. Thin ﬁlm of 110 nm thicknesses exhibited the best performance in terms of crystal quality, refractive index, dielectric constant, band-gap, and optical properties. The study suggests synthesis route for developing high quality CuO thin ﬁlm using CBD method for electronic and optical applications. © 2016 Published by Elsevier B.V. 1. Introduction Copper oxides are semiconducting in nature and currently have drawn signiﬁcant research interests due to its fundamental advan- tages of reasonably good electrical and optical properties, natural abundance of source materials, inexpensive and simple growth technology and non-toxic behavior [1]. Copper monoxide (CuO) has a monoclinic structure with lattice parameters: a = 4.684 Å, b = 3.425 Å, c = 5.129 Å and  = 99.28 ◦ [2]. It exhibits p-type con- ductivity due to the presence of holes in the valence band (VB) arising from doping/annealing [3] and also, has huge potential for its selective high solar absorbance and low thermal emittance [4]. Copper oxide thin ﬁlms have wide range of applications including energy harvesting and storage as solar cells [1,5], photo- electro-chemical cells [6], photo-catalysts [7], and lithium ion batteries [8]. These also ﬁnd applications in the domain of cata- lysts [9], ﬁeld-emission devices [10], gas sensors [11], photovoltaic ∗ Corresponding author. E-mail addresses: sultanajenifar@gmail.com (J. Sultana), paul.somdatta@gmail.com (S. Paul), akelc@caluniv.ac.in (A. Karmakar), reny@imre.a-star.edu (R. Yi), dalapatig@imre.a-star.edu.sg (G.K. Dalapati), scelc@caluniv.ac.in (S. Chattopadhyay). devices [12], and superconductors [13]. Thus, developing a good quality CuO thin ﬁlm is highly important to fabricate electronic and photovoltaic devices with superior performance by utilizing such ﬁlms. In this context, several techniques have already been employed to grow CuO ﬁlms with superior quality [14–23]. Fur- ther, the chemical as well as physical properties of CuO depend signiﬁcantly on thickness and morphology of the ﬁlm [24], and therefore, the precise control and thickness optimization along with its morphology is immensely crucial for utilizing such ﬁlms in nano-electronics, optoelectronics and bio-sensing applications [25]. Chemical bath deposition (CBD) is a growth process that has drawn signiﬁcant attention of the global research community due to its simplicity, cost-effectiveness, reproducibility and capa- bility of large area scaling for commercial production [26]. The deposition rate and hence thickness of the deposited ﬁlm can be precisely controlled by varying pH, reaction time, temperature and concentration of the solution. The solubility product of the solution determines homogeneity and stoichiometry of the ﬁlm [27–31]. The thickness and morphology of the grown ﬁlm have been observed to modify the electrical and photovoltaic behavior of the junction. However, no systematic reports are available on the thickness dependent performance of p-CuO/n-Si heterojunc- http://dx.doi.org/10.1016/j.apsusc.2016.12.139 0169-4332/© 2016 Published by Elsevier B.V.