Deposition of PbS Thin Films from Lead Hexadecyl and Octadecyl Xanthate Complexes Using the Spin Coating Method
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.106
DEPOSITION OF PbS THIN FILMS FROM LEAD HEXADECYL AND OCTADECYL XANTHATE COMPLEXES USING THE SPIN COATING METHOD Selina Ama Saah1*, Nathaniel Owusu Boadi2 and Christopher Wilkins3 1 Department of Chemical Sciences, University of Energy and Natural Resources, Sunyani-Ghana. Email:[email protected]
2
Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi-Ghana.
3
School of Materials, University of Manchester, Manchester-United Kingdom.
Abstract
Lead sulphide thin films have been successfully deposited by spin coating lead hexadecyl and octadecyl xanthate onto glass substrates and annealed at moderate temperatures. The thin films were characterized using powder x-ray diffractometer (p-XRD) and were found to be face centred cubic (FCC) with the (200) being the most preferred orientation. The optical band gaps obtained were 0.93 and 1.00 eV respectively for PbS from complexes (1) and (2) annealed at 350 °C. They were all blue shifted from the bulk value of 0.41 eV.
INTRODUCTION: Among the semiconductor nanocrystals, lead chalcogenides with diameters below their Bohr exciton radii have been a centre of interest [1, 2]. These functional materials are always at the forefront because of their unique properties which include quantum size effects, quantum confinement effects, surface effects and shape-dependent electronic structures [3, 4]. Lead sulphide (PbS), which is among the lead chalcogenides, is one of the most attractive metal sulphides for a wide variety of applications [5, 6]. PbS has been widely used in many fields including sensors, photography, detectors, optical switches and solar cells [7, 8].
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PbS is an important π-π semiconductor material with a narrow band gap energy (0.41 eV) and large exciton Bohr radius (18 nm) [9, 10]. The ability to easily manipulate its band gap makes PbS an ideal material for studying quantum size effects [11]. The two major factors that affect the quality of the nanomaterials formed are the technique employed for syntheses and the choice of starting materials [12]. These factors exert a significant influence over the purity, electronic behaviour and morphology of the nanomaterials [13, 14]. Several attempts have been made to synthesise these novel materials using various techniques which include hot injection [15], melt reactions [16], heat up [17], chemical vapour deposition [18], chemical bath deposition [19], successive ionic layer adsorption and reaction [20], liquid-liquid interface [21], spray pyrolysis [22], microwave [23] and spin coating [24]. With respect to the starting materials, the single source precursor (SSP) route has proven to be efficient and advantageous [13]. These SSPs have multiple advantages over
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