Reversible oxidation of ethylene on ferroelectric BaTiO(001): An X-ray photoelectron spectroscopy study.

Adsorption and desorption of ethylene on BaO-terminated (001) barium titanate are investigated by X-ray photoelectron spectroscopy. Carbon is found in an oxidized state, at a binding energy similar to that resulting from CO adsorption on BaTiO(001). The amount of carbon adsorbed on the surface is also similar to the case of CO/BaTiO(001).

Surface charge dynamics on air-exposed ferroelectric Pb(Zr,Ti)O(001) thin films.

Probing of the free surface ferroelectric properties of thin polar films can be achieved either by estimating the band bending variance under the top-most layer or by studying the extent of the extrinsic charge accumulated outside the surface. Photoemitted or incoming low-energy electrons can be used to characterize locally both properties in a spectromicroscopic approach. Thin ferroelectric lead zirco-titanate (PZT) is investigated by combining low energy/mirror electron microscopy (LEEM/MEM) with photoemission electron microscopy (PEEM) and high-resolution photoelectron spectroscopy (XPS).

Polarization landscape effects in soft X-ray-induced surface chemical decomposition of lead zirco-titanate, evidenced by photoelectron spectromicroscopy.

The stability of thin films of lead zirco-titanate (PZT) under intense soft X-ray beams is investigated by time-resolved photoelectron spectromicroscopy with a lateral resolution below 1 micrometer. Surface dissociation is observed when samples are irradiated with intense (5 × 10 photons per s per m) soft X-rays, with promotion of reduced lead on the surface. On areas exhibiting outwards polarization (P), the reduced lead is formed at the expense of P-PZT.

Iodine Migration and Degradation of Perovskite Solar Cells Enhanced by Metallic Electrodes.

We monitored the evolution in time of pinhole-free structures based on FTO/TiO/CHNHPbICl layers, with and without spiro-OMeTAD and counter electrodes (Ag, Mo/Ag, and Au), aged at 24 °C in a dark nitrogen atmosphere. In the absence of electrodes, no degradation occurs. While devices with Au show only a 10% drop in power conversion efficiency, remaining stable after a further overheating at 70 °C, >90% is lost when using Ag, with the process being slower for Mo/Ag.

Ferroelectric triggering of carbon monoxide adsorption on lead zirco-titanate (001) surfaces.

Atomically clean lead zirco-titanate PbZrTiO (001) layers exhibit a polarization oriented inwards P, visible by a band bending of all core levels towards lower binding energies, whereas as introduced layers exhibit P polarization under air or in ultrahigh vacuum. The magnitude of the inwards polarization decreases when the temperature is increased at 700 K. CO adsorption on P polarized surfaces saturates at about one quarter of a monolayer of carbon, and occurs in both molecular (oxidized) and dissociated (reduced) states of carbon, with a large majority of reduced state.

Polarization induced self-doping in epitaxial Pb(Zr0.20Ti0.80)O3 thin films.

The compensation of the depolarization field in ferroelectric layers requires the presence of a suitable amount of charges able to follow any variation of the ferroelectric polarization. These can be free carriers or charged defects located in the ferroelectric material or free carriers coming from the electrodes. Here we show that a self-doping phenomenon occurs in epitaxial, tetragonal ferroelectric films of Pb(Zr0.