15 research outputs found
Charge writing at the LaAlO3/SrTiO3 surface
Biased conducting-tip atomic force microscopy (AFM) has been shown to write
and erase nanoscale metallic lines at the LaAlO3/SrTiO3 interface. Using
various AFM modes, we show the mechanism of conductivity switching is the
writing of surface charge. These charges are stably deposited on a wide range
of LaAlO3 thicknesses, including bulk crystals. A strong asymmetry with writing
polarity was found for 1 and 2 unit cells of LaAlO3, providing experimental
evidence for a theoretically predicted built-in potential.Comment: 12 pages, 4 figures, plus supplementary information, submitted to
Nano Letter
Termination Control of the Interface Dipole in LaSrMnO/Nb:SrTiO (001) Schottky Junctions
In order to investigate the interface termination dependence of perovskite
band alignments, we have studied the Schottky barrier height at
LaSrMnO/Nb:SrTiO (001) heterointerfaces. As the
Nb:SrTiO semiconductor was varied from TiO termination to SrO
termination by variable insertion of a SrMnO layer, a large systematic
increase in the Schottky barrier height was observed. This can be ascribed to
the evolution of the interface dipole induced to screen the polar discontinuity
at the interface, which gives a large internal degree of freedom for tuning
band diagrams in oxides.Comment: 10 pages, 5 figure
A heteroepitaxial perovskite metal-base transistor
'More than Moore' captures a concept for overcoming limitations in silicon electronics by incorporating new functionalities in the constituent materials. Perovskite oxides are candidates because of their vast array of physical properties in a common structure. They also enable new electronic devices based on strongly-correlated electrons. The field effect transistor and its derivatives have been the principal oxide devices investigated thus far, but another option is available in a different geometry: if the current is perpendicular to the interface, the strong internal electric fields generated at back-to-back heterojunctions can be used for oxide electronics, analogous to bipolar transistors. Here we demonstrate a perovskite heteroepitaxial metal-base transistor operating at room temperature, enabled by interface dipole engineering. Analysis of many devices quantifies the evolution from hot-electron to permeable-base behaviour. This device provides a platform for incorporating the exotic ground states of perovskite oxides, as well as novel electronic phases at their interfaces
Experimental evidence of zone-center optical phonon softening by accumulating holes in thin Ge
We discuss the impact of free carriers on the zone-center optical phonon frequency in germanium (Ge). By taking advantage of the Ge-on-insulator structure, we measured the Raman spectroscopy by applying back-gate bias. Phonon softening by accumulating holes in Ge film was clearly observed. This fact strongly suggests that the phonon softening in heavily-doped Ge is mainly attributed to the free carrier effect rather than the dopant atom counterpart. Furthermore, we propose that the free carrier effect on phonon softening is simply understandable from the viewpoint of covalent bonding modification by free carriers