Molecular beam epitaxy growth of high quality p-doped SnS van der Waals epitaxy on a graphene buffer layer

Journal Article · Tue May 01 00:00:00 EDT 2012 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4709732· OSTI ID:22036872

Wang, W; Leung, K K; Fong, W K; Wang, S F; Surya, C ^[1]; Hui, Y Y; Lau, S P ^[2]; Chen, Z; Shi, L J; Cao, C B ^[3]

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1. Department of Electronic and Information Engineering and Photonics Research Centre, Hong Kong Polytechnic University (Hong Kong)
2. Department of Applied Physics, Hong Kong Polytechnic University (Hong Kong)
3. Research Center of Materials Science, Beijing Institute of Technology, Beijing 100081 (China)

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 {mu}m is observed which is also significantly better than the existing results. Measurement of the absorption coefficient, {alpha}, is performed using a Hitachi U-4100 Spectrophotometer system which demonstrate large values of {alpha} of the order of 10{sup 4} cm{sup -1}. Sharp cutoff in the values of {alpha}, 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 10{sup 16} cm{sup -3} and 5 x 10{sup 17}cm{sup -3} by varying the temperature of the Cu K-cell. Hole mobility as high as 81 cm{sup 2}V{sup -1}s{sup -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.

• OSTI ID: 22036872
• Journal Information: Journal of Applied Physics, Vol. 111, Issue 9; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
C CODES
COPPER
DISLOCATIONS
DOPED MATERIALS
ENERGY DEPENDENCE
ENERGY GAP
GALLIUM ARSENIDES
GRAPHITE
HOLE MOBILITY
HOLES
INTERFACES
MOLECULAR BEAM EPITAXY
NANOSTRUCTURES
NEUTRON DIFFRACTION
SEMICONDUCTOR MATERIALS
SUBSTRATES
SURFACES
THIN FILMS
TIN SULFIDES
VAN DER WAALS FORCES