Ferroelectric, dielectric and electrical behavior of two-dimensional lead sulphide nanosheets

Two-dimensional pure cubic phase lead sulphide (PbS) nanosheets were synthesized using solid state reaction method at ambient pressure and low temperature ∼190 °C. From 210 K–300 K, small polaron hopping conduction mechanism was found to be dominant in PbS nanosheets at frequencies 20 Hz–2 MHz. High values of dielectric constant (∼200) and electrical conductivity (of the order of 10⁻³ S m⁻¹ at 300 K) of PbS nanosheets were extracted suggesting that it is a proficient material for capacitive storage devices. A high value of density of states of the order of 10³² eV⁻¹ cm⁻³ was obtained for PbS nanosheets. The capacitance-voltage (CV) measurements of PbS nanosheets resulted in a stable butterfly loop due to switching of ferroelectric polarization at 300 K. The permittivity calculated at 0 V capacitance was ∼150 and the dielectric loss remained below ∼0.50. The polarization-voltage (QV) measurements showed a remnant polarization 23 µ C cm⁻² in PbS nanosheets. The leakage current density was below 0.5 mA cm⁻² in the range  ±5 V. (paper)