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| Title: | Molecular beam epitaxy growth of high quality p-doped SnS van der Waals epitaxy on a graphene buffer layer | Authors: | Wang, W Leung, KK Fong, WKP Wang, SF Hui, YY Lau, SP Chen, Z Shi, LJ Cao, CB Surya, C |
Issue Date: | 1-May-2012 | Source: | Journal of applied physics, 1 May 2012, v. 111, no. 9, 093520, p. 1-8 | Abstract: | We report on the systematic investigation of optoelectronic properties of tin (IV) sulfide (SnS) van der Waals epitaxies (vdWEs) grown by molecular beam epitaxy (MBE) technique. Energy band simulation using commercial CASTEP code indicates that SnS has an indirect bandgap of size 0.982 eV. Furthermore, our simulation shows that elemental Cu can be used as a p-type dopant for the material. Growth of high quality SnS thin films is accomplished by MBE technique using graphene as the buffer layer. We observed significant reduction in the rocking curve FWHM over the existing published values. Crystallite size in the range of 2–3 μm is observed which is also significantly better than the existing results. Measurement of the absorption coefficient, α, is performed using a Hitachi U-4100 Spectrophotometer system which demonstrate large values of α of the order of 10⁴cm⁻¹. Sharp cutoff in the values of α, as a function of energy, is observed for the films grown using a graphene buffer layer indicating low concentration of localized states in the bandgap. Cu-doping is achieved by co-evaporation technique. It is demonstrated that the hole concentration of the films can be controlled between 10¹⁶ cm⁻³ and 5 × 10¹⁷cm⁻³ by varying the temperature of the Cu K-cell. Hole mobility as high as 81 cm²2V⁻¹s⁻¹ is observed for SnS films on graphene/GaAs(100) substrates. The improvements in the physical properties of the films are attributed to the unique layered structure and chemically saturated bonds at the surface for both SnS and the graphene buffer layer. Consequently, the interaction between the SnS thin films and the graphene buffer layer is dominated by van der Waals force and structural defects at the interface, such as dangling bonds or dislocations, are substantially reduced. | Keywords: | Band structure Copper Dangling bounds Dislocations Energy gap Hole mobility IV-VI semiconductors Localised states Molecular beam epitaxial growth Semiconductor epitaxial layers Semiconductor growth Semiconductor thin films Tin compounds Ultraviolet spectra Vacuum deposition Van der Waals forces Visible spectra |
Publisher: | American Institute of Physics | Journal: | Journal of applied physics | ISSN: | 0021-8979 | EISSN: | 1089-7550 | DOI: | 10.1063/1.4709732 | Rights: | © 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in W. Wang et al., J. Appl. Phys. 111, 093520 (2012) and may be found at http://link.aip.org/link/?jap/111/093520. |
| Appears in Collections: | Journal/Magazine Article |
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| Wang_Epitaxy_SnS_Waals.pdf | 3.15 MB | Adobe PDF | View/Open |
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