Trapped charge-induced pyroelectric-like transient response in single high-resistivity Sb₂Se₃ nanowires

Dynamic scanning photocurrent microscopy was applied to Sb₂Se₃ crystalline single nanowires (NWs) to analyze their transient photocurrent responses. These NWs exhibited switching behavior with rapid rise and decay times upon illumination by laser pulses. The estimated spectral responsivity and external quantum efficiency for a freshly-prepared NW at a bias voltage of 0.3 V and excitation wavelength of 488 nm were ∼16.9 mA/W and ∼42.9%, respectively. A pyroelectric-like current transient was observed with reduced spectral responsivity when nonpolar Sb₂Se₃ single-crystalline NWs were excited by laser pulses. Because Sb₂Se₃ NWs were nonpyroelectric or ferroelectric, the pyroelectric-like current could possibly be attributed to temperature dependent nonlinear space-charge distributions. Defects produced by the external electrical bias generated and re-distributed space charges in the NWs. As a result, the temperature dependent inhomogeneous electric field led to nonlinear expansions or contractions of the lattice (electrostriction) that can produce pyroelectric current. We obtained a lower bound of equivalent pyroelectric coefficient α ≥ 60.09 μC/m² K from these materials by fitting the electrical transients.