Characterization of structural defects in SnSe2 thin films grown by molecular beam epitaxy on GaAs (111)B substrates

• High quality SnSe2 thin films can be grown by molecular beam epitaxy using high Se:Sn flux ratios.
• Highly defective SnSe results from using low Se:Sn flux ratios during MBE growth.
• Structure and lattice parameters of tin monoselenide and tin diselenide thin films is consistent with bulk materials.

Tin selenide thin films have been grown by molecular beam epitaxy on GaAs (111)B substrates at a growth temperature of 150 °C, and a microstructural study has been carried out, primarily using the technique of transmission electron microscopy. The Se:Sn flux ratio during growth was systematically varied and found to have a strong impact on the resultant crystal structure and quality. Low flux ratios (Se:Sn=3:1) led to defective films consisting primarily of SnSe, whereas high flux ratios (Se:Sn>10:1) gave higher quality, single-phase SnSe2. The structure of the monoselenide films was found to be consistent with the Space Group Pnma with the epitaxial growth relationship of [011]SnSe//[11¯0]GaAs, while the diselenide films were consistent with the Space Group P3¯m1, and had the epitaxial growth relationship [21¯1¯0]SnSe2//[11¯0]GaAs.