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Electron emission from thin ferroelectric Pb(Zr0.4 Ti0.6)O3 films is demonstrated reaching emission current densities of up to 3×10-8 A cm-2 for pulsed excitation voltages of 60 V. Nevertheless, the emission process sets in at voltages as low as 10 V. Thin lead zirconate titanate (PZT) films were prepared with a structured top electrode, which exhibits nanometer-sized regularly arranged apertures. The emission current was measured under UHV conditions by both a single electron detector for small emission currents and an amperemeter for larger currents. The voltage dependent polarization state within the emission apertures was imaged using piezoresponse force microscopy and revealed that an increased fraction of the free surface area is switched by an increased applied voltage. This shows that the emission process is strongly correlated to the switching of ferroelectric polarization. Moreover, with the help of a metal grid in front of the detector, the maximum kinetic energy of emitted electrons was investigated and found to be limited by the excitation voltage, only. [ABSTRACT FROM AUTHOR]

SrTiO3 (STO) is the most frequently used substrate material for complex oxide films. In this work, STO is explored as a buffer layer on piezoelectric pseudocubic Pb(Mg1/3Nb2/3)0.72Ti0.28O3(001) (PMN-PT) substrates, which serve to reversibly strain thin films. The STO buffer layer reduces the in-plane lattice parameter and allows for a better lattice matching to a broader range of thin film materials. STO films (30 nm) have been grown with epitaxial orientation on PMN-PT with an in-plane lattice parameter close to that of bulk STO. The substrate’s rhombohedral domain structure has been imaged by atomic force microscopy. The related ferroelectric domain structure has been investigated by piezoresponse force microscopy. Within a domain, STO grows with a rather low roughness (rms<0.2 nm). The transfer of the piezoelectric substrate strain to the STO film and its variation with an applied electric field are studied using x-ray diffraction. The strain dependence of the electrical resistance is measured for a ferromagnetic manganite film grown on top of the STO. Both experiments confirm qualitatively that the STO buffer transfers the substrate strain into a functional film deposited on top. [ABSTRACT FROM AUTHOR]

SrTi[O.sub.3] (STO) film is analyzed as a buffer layer on piezoelectric pseudocubic Pb[([Mg.sub.1/3][Nb.sub.2/3]).sub.0.72][Ti.sub.0.28][O.sub.3](001) (PMN-PT) substrates, which has served to reversibly strain thin films. The STO films have displayed in-plane lattice parameter close to that of bulk STO and are used as a buffer material that reduces the lattice mismatch for a number of materials such as many complex oxides.

Electron emission from [Pb(Mg1/3Nb2/3)O3]0.72 [PbTiO3]0.28 (PMN-PT) thin ferroelectric single crystals is reported at ultralow voltages down to 20V per 400μm thickness, and for up to 109 switching cycles. The PMN-PT samples were prepared with split gold top electrodes exhibiting a 25μm wide gap region. Applying a sinusoidal voltage between the two top electrodes and the bottom electrode initiated electron emission from the gap region. The emitted electrons were collected under UHV conditions using two single electron counters arranged under an angle of 90°. Two emission regimes have been identified. Both are attributable to weak electron emission, however, clearly separated by the onset of complete ferroelectric polarization switching. This is also confirmed by recording nanoscale ferroelectric hysteresis loops by means of piezoresponse force microscopy. The emitted electrons are found to have a broad energy distribution with the maximum kinetic energies reaching 110 and 50 eV for applied switching voltages of 140 and 110 V, respectively. Our results confirm that polarization reversal is the governing mechanism behind the electron-emission process in the thin PMN-PT samples. Also, the applied electric field strengths needed to trigger electron emission from the PMN-PT crystals are about 10 times lower compared to most other (ferroelectric) materials reported in the literature. [ABSTRACT FROM AUTHOR]

The investigation of the local polarization switching including direct domain writing, local hysteresis measurements, and domain stability testing was carried out in single-crystalline stoichiometric lithium tantalate using the Scanning Probe Microscope. Piezoresponse Force Microscopy was utilized for domain visualization and recording of local switching characteristics. Two variants of domain patterning were shown: ‘direct writing’ and ‘self-assembled formation.’ The polarization reversal in direction opposite to applied field (‘anti-parallel switching’) was studied in details and attributed to screening of external field. [ABSTRACT FROM AUTHOR]