No abstract

We have fabricated n-layer graphene field effect transistors on epitaxial ferroelectric Pb(Zr 0.2 Ti 0.8 )O 3 (PZT) thin films. At low gate voltages, PZT behaves as a high- dielectric with  up to 100. An unusual resistance hysteresis occurs in gate sweeps at high voltages, with its direction opposite to that expected from the polarization switching of PZT. The relaxation of the metastable state is thermally activated, with an activation barrier of 50-110 meV and a time constant of 6 hours at 300 K. We attribute its origin to the slow dissociation/recombination dynamics of water molecules adsorbed at the graphene-PZT interface. This robust hysteresis can potentially be used to construct graphene-ferroelectric hybrid memory devices.

Lead halide perovskites have recently shown great potential as X-ray scintillators; however, the toxicity of the lead element seriously restricts their applications. Herein we report a new lead-free and self-absorption-free scintillator based on Rb 2 CuCl 3 metal halide. The Rb 2 CuCl 3 exhibits a near-unity photoluminescence quantum yield (99.4%) as well as a long photoluminescence lifetime (11.3 μs). Furthermore, Rb 2 CuCl 3 demonstrates an appreciable light yield of 16 600 photons per megaelectronvolt and a large scintillation response with a linear range from 48.6 nGy air s −1 to 15.7 μGy air s −1 . Notably, the detection limit is as low as 88.5 nGy air s −1 , enabling a reduced radiation dose to the human body when a medical and security check is conducted. In addition, Rb 2 CuCl 3 exhibits good stability against the atmosphere, continuous ultraviolet light, as well as X-ray irradiation. The combination of the decent scintillation performance, low toxicity and good stability suggests the Rb 2 CuCl 3 could be a possible promising X-ray scintillator.