OP-OPD-10 Synthesis and Characterization of Nanostructured SnO 2 /Graphene Composite Thin Film: Highly Sensitive UV-sensor Manish K Singh 1,2 , Pathik Kumbhakar 1 , Anchal Srivastava 2 , Shiju Abraham 2 , Himanshu Mishra 2 1 Dept.of Physics, National Institute of Technology Durgapur, W.B., India-713209 2 Dept.of Physics, Banaras Hindu University, Varanasi, U.P., India-221005 Author e-mail address: singhnitdgp@gmail.com Abstract: Different nanostructures and thin films of SnO 2 have extensively been studied and used as chemical sensors for environmental and industrial applications. Here, we report the unique method of fabrication of thin film which led to improvements in sensor response by reducing the size of the SnO 2 particles or thin films. Responsivity is enhanced when the particle grain size or film thickness approaches nanometer dimensions. Nanostructured SnO 2 /rGO film is deposited on the Si/SiO 2 and ITO substrates by using spray method. The structural property of SnO 2 has been characterized by XRD and SEM and optical properties are measured by optical micrograph and UV- Vis spectroscopy. Keywords: [SnO2 photodetector, photosensitivity, tin oxide film. Reduced Graphene Oxide “rGO”] 1. Introduction Wide band gap material such as, SnO 2 has attracted much attention, having potential applications in many practical devices, including as a transparent conducting electrode for organic light emitting diodes, visible-blind photodetectors and solar cells [1]. In addition, one- dimensional (1D) material have a high surface-to- volume ratio, the surface of nanorods can influence the conductivity remarkably. On the other hand, 1D nanostructure of semiconductors with a wide band-gap, such as GaN, ZnO, SnO 2 or other metal-oxide nanostructures, also show their potential for high- efficiency UV photodetection [2-4]. Photodetection in the ultraviolet (UV) region has drawn extensive attention owing to its various applications in industry, instrument, and our daily life. UV light is typically divided into four spectral regions: UV-A (320-400 nm), UV-B (280-320 nm), UV-C (200-280 nm), and far UV (10-200 nm). Although most of the UV light which comes from the Sun is absorbed by the atmospheric ozone layer but the solar radiation with wavelength longer than 280 nm penetrate the atmosphere and reach to the Earth surface. Therefore, UV detectors that have high sensitivity to UV-C and far UV radiation compared to radiation with wavelength longer than 280 nm can be called „solar-blind‟. Moreover, UV detectors find several applications, such as in UV dosimetry, solar UV measurements, flame sensors (fire alarm systems, missile plume detection, combustion engine control), biological and chemical sensors etc. [2]. Narrow bandgap semiconductors such as, Si and some III-V compounds (GaP, GaAsP) have first been used to design UV detection. However, in such applications the insertion of costly high pass optical filters and phosphors are necessary in order to tune the photodetecting system to the appropriate spectral range and for preventing the degradation of materials [5]. However, here we have used hydrothermal route to synthesize SnO 2 nanostructures as this method is very much practicable and cost effective for the production of different nanostructures as per requirement, just by varying its parameters, such as temperature and time of reaction [2]. In this work we have synthesized 1D nanostructures (nanowires) of SnO 2 and then thin film has been prepared with the mixture of rGO/SnO 2 solution, by spray coating on the Glass, ITO and Si/SiO 2 substrates. I-V characteristics of the prepared thin films have been measured for determining the applicability of the prepared thin film as UV-sensor. 2. Experimental work 2.1. Chemicals: Graphite flakes were purchased from Alfa Aesar (325 mesh), Sulfuric acid (H 2 SO 4 , 95–98%), phosphoric acid (H 3 PO 4 , 85%), potassium permanganate (KMnO 4 , 99.9%), and hydrogen peroxide (H 2 O 2 , 30%) has been purchased from Merck. Hydrogen chloride (HCl, 37%) was purchased from Sigma-Aldrich. Tin (IV) chloride pentahydrate (SnCl 4 5H 2 O, 98%) and absolute ethanol were purchased from Merck and Hi-Media Chemicals, respectively. Distilled water was used throughout the sample preparation. All chemicals were used as received without further purification. 2.2 Preparation of SnO 2 nanowires, rGO and SnO 2 - rGO thin-film: At first SnO 2 nanowires were synthesized via a hydrothermal method [6,7]. In a typical process, calculated amount of SnCl 4 .5H 2 O and NaOH were mixed with 40 ml de-ionized water under magnetic