Metalorganic chemical vapor deposition of Bi₂Se₃thin films for topological insulator applications

Abstract

The growth of thin Bi 2 Se 3 films on (0001) sapphire substrates by metalorganic chemical vapor deposition (MOCVD) was investigated. A two-heater configuration was employed to pre-crack the metalorganic sources upstream of the substrate while maintaining a low substrate temperature (<250 o C). Epitaxial Bi 2 Se 3 films with (006) x-ray rocking curve full-width-at-half-maximum values on the order of 160 arcsecs were obtained at growth rates of ~6 nm/min or lower while higher growth rates resulted in polycrystalline films. The background electron concentration of the films was found to depend strongly on the substrate temperature and Se/Bi inlet ratio. Bi 2 Se 3 films with a room temperature electron concentration of 6.7x10 19 cm -3 and mobility of 155 cm 2 /Vs were obtained at 200 o C with a Se/Bi ratio of 80. Higher substrate temperature and lower Se/Bi ratios resulted in an increase in electron concentration and corresponding reduction in mobility. The results demonstrate the potential of MOCVD for the growth of Bi 2 Se 3 and related materials for topological insulator studies.