Effect of annealing on optical, dielectric and ac conduction properties of Bi₂Se₃ thin films

Abstract

Bi₂Se₃ thin films, prepared by thermal evaporation onto well-cleaned glass and freshly cleaved KBr substrates, have been annealed for 30 min under a vacuum pressure of 2.7x10^-3 Pa at different temperatures (373-473 K). The variation in optical constants with annealing temperature for these films has been studied in detail. Large changes in transmittance <i>(</i>Δ<i>T= </i>13% at 633 nm), reflectance (ΔR

=8% at 633 nm) and high absorption coefficient (α>10⁴cm^-1) are noticed for these annealed films. Thin film capacitors (Al –Bi₂Se₃-Al) have also been fabricated and studies on capacitance and dielectric constant as a function of temperature and frequency carried out. Loss minimum (tanδ_min) has been observed and found to shift towards high frequency side as the temperature increases. The frequency and temperature dependence of their ac conductivity reveal that the conduction in these films proceeds via electron hopping.