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The two-dimensional electron system (2DES) formed at the interface of LaAlO3 (LAO) and SrTiO3 (STO), both band insulators in bulk, exhibits properties not easily attainable in conventional electronic materials. The extreme shallowness of the 2DES, only a few nanometers below the surface, opens up unique possibilities such as tunneling spectroscopy, local electronic sensing, and in situ patterning by manipulating the surface properties. It is particularly tempting to manipulate the charge carriers with surface acoustic wave (SAW) phonons, which are confined to the surface. However, the absence of intrinsic piezoelectricity in both LAO and STO complicates the electric generation of SAWs, as well as the induction of an acoustoelectric current. Here, we present robust acoustoelectric coupling between SAWs and the LAO/STO 2DES by using electrostriction in STO, induced by a dc electric field. Electromechanical coupling to the carriers is provided by phonon-induced modulation of the 2DES potential well, leading to SAW-induced carrier transport. The ability to control charge carriers with SAWs brings the versatile LAO/STO 2DES into reach of quantum acoustics, opening possibilities to study the interplay of nanoscale mechanical waves and the rich physics exhibited by nonpiezoelectric complex oxides, including superconductivity, magnetism, and correlated insulator states.

We present the effect of introducing a TiO2 buffer layer at the SrTiO3/Co:TiO2 interface on the magnetic and structural properties of anatase Co:TiO2 (1.4 at. % Co). Inserting the buffer layer leads to suppression of the room-temperature anomalous Hall effect, accompanied by a reduced density of Co clusters, and a different depth distribution of such clusters. Co clusters in Co:TiO2 with a buffer layer are mostly formed at the surface, such that they are situated outside the current path and cannot contribute to the transverse anomalous Hall resistivity. These results indicate extrinsic origins of magnetism in anatase Co:TiO2.

The optical emission properties of mass-transport regions of GaN grown by hydride vapor phase epitaxy are studied by cathodoluminescence imaging and spectroscopy. A strong donor–acceptor pair emission is observed from the mass-transport regions. Spatially resolved cathodoluminescence reveals a strong intensity contrast between the exciton and donor–acceptor bands from mass-transport and nontransport regions. Focused Auger electron and x-ray photoelectron spectroscopies were employed to investigate the impurity incorporation in the different regions. A preferential moderate increase of residual impurity incorporation or redistribution in mass-transport regions is suggested to be responsible for the observed change of the dominant radiative mechanism.

A cause for degradation of polymer light-emitting diodes is the oxidation of the polymer by oxygen diffusing out of the indium-tin-oxide (ITO) anode. This problem can be solved by the introduction of an organic hole-injecting film, poly-(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS), between the ITO and the emissive polymer. Indeed, a dramatic improvement of the lifetime and also the luminous efficiency has been observed. However, our Rutherford backscattering (RBS) studies show that the ITO/PEDOT:PSS interface is not stable. In as prepared glass/ITO/PEDOT:PSS samples 0.02 at. % indium was found in the PEDOT:PSS film. Annealing in a nitrogen atmosphere at 100 °C during 2500 h increased the indium concentration to 0.2 at. %. Upon exposure to air much faster degradation of the ITO/PEDOT:PSS interface was observed; after several days in air the amount of indium reached a saturation concentration of 1.2 at. %. The degradation of the interface can be explained by etching of the ITO due to the strong acidic nature of PEDOT:PSS. ©2000 American Institute of Physics.

We have studied the electronic and magnetic properties of the interface between C(60) molecules and a Fe(001) surface. X-ray absorption spectroscopy and x-ray magnetic circular dichroism studies of C(60) monolayers on Fe(001) surfaces show that hybridization between the frontier orbitals of C(60) and continuum states of Fe leads to a significant magnetic polarization of C(60) pi*-derived orbitals. The magnitude and also the sign of this polarization were found to depend markedly on the excitation energy. These observations underline the importance of tailoring the interfacial spin polarization at the Fermi level of ferromagnet/organic semiconductor interfaces for applications in organic spintronics. Original Publication: T. L. A. Tran, P. K. J. Wong, M. P. de Jong, W. G. van der Wiel, Yiqiang Zhan and Mats Fahlman, Hybridization-induced oscillatory magnetic polarization of C(60) orbitals at the C(60)/Fe(001) interface, 2011, Applied Physics Letters, (98), 22, 222505. http://dx.doi.org/10.1063/1.3595269 Copyright: American Institute of Physics http://www.aip.org/

Photoelectron spectroscopy was employed to examine the energetics, and therefore charge injection barriers, at top and bottom contact configurations of gold and conjugated polymers, i.e., polymer spin coated on gold and vapor-deposited gold on polymer interfaces. Very similar results are obtained for both ex situ (contaminated) and in situ (clean) prepared interfaces: a 0.7–0.8eV decrease in the vacuum energy levels is consistently observed as compared to bare polycrystalline gold. These observations are explained by changes of the metal work function upon contacting either polymers or contaminants, associated with the reduction of the electron density tail that extends outside the metal surface.