ZnSb Films on Flexible Substrates: Stability, Optical Bandgap, Electrical Properties, and Indium Doping

Abstract Undoped and In‐doped ZnSb thin films are deposited on rigid glass and flexible polyimide (Kapton) by physical vapor deposition. Detailed structural and chemical characterization is performed along with measurement of electrical and optical properties. These properties are very similar for films on glass and Kapton. Flexible ZnSb films show remarkable stability of electrical and optical properties, which are unchanged after 104 cycles of linear bending with surface strain 0.18%. Only severe flexing after this treatment (torsional bending with surface strain 1.7%) causes progressive degradation of conductivity over tens to hundreds of cycles. The ZnSb optical direct gap is determined to be 0.89 ± 0.05 eV. The optical direct gap of β Zn4Sb3 was 1.07 ± 0.05 eV. Other absorption features in the films, including smaller indirect gaps, are discussed.