We report a photovoltaic effect in ferroelectric BiFeO3 thin films. The all-oxide heterostructures with SrRuO3 bottom and tin doped indium oxide top electrodes are characterized by open-circuit voltages ∼0.8–0.9 V and external quantum efficiencies up to ∼10% when illuminated with the appropriate light. Efficiencies are at least an order of magnitude larger than the maximum efficiency under sunlight (AM 1.5) thus far reported for ferroelectric-based devices. The dependence of the measured open-circuit voltage on film thickness suggests contributions to the large open-circuit voltage from both the ferroelectric polarization and band offsets at the BiFeO3/tin doped indium oxide interface.
We used mechanical trapping of molecular interactions to demonstrate a highly parallel approach to measure the kinetics of biomolecular interactions. This approach consumes 25 fmol of material per measurement and permits 320 measurements in a single experiment. We measured association and dissociation curves for the interactions of 6-His and T7 epitope tags with their antibodies, from which we determined the off rates, on rates, and dissociation constants.
Atomic-force and Kelvin-probe microscopies were employed in ultrahigh vacuum to image the surface topography and contact potential of the hydrogen-terminated and unterminated surfaces of diamond. A variation of about 25 meV in the contact potential was measured on a length scale of 20 nm and ascribed to differently orientated surface domains resulting from hydrogen-plasma processing of the sample. Shifts in the work function arising from sample heating in vacuum and the adsorption of C₆₀ were measured. The Fermi level was found to be 0.7 and 1.1 eV below the valence band maximum for C₆₀ coverages of 1 and 4 monolayer, respectively.3 page(s
We propose and demonstrate a remote sensor scheme by applying the quantummechanical concept of fidelity loss to classical waves. The sensor makesexplicit use of time-reversal invariance and spatial reciprocity in a wavechaotic system to sensitively and remotely measure the presence of smallperturbations. The loss of fidelity is measured through a classical wave-analogof the Loschmidt echo by employing a single-channel time-reversal mirror torebroadcast a probe signal into the perturbed system. We also introduce the useof exponential amplification of the probe signal to partially overcome theeffects of propagation losses and to vary the sensitivity.