Electrically induced ferromagnetism at room temperature in cobalt-doped titanium dioxide.

The electric field effect in ferromagnetic semiconductors enables switching of the magnetization, which is a key technology for spintronic applications. We demonstrated electric field-induced ferromagnetism at room temperature in a magnetic oxide semiconductor, (Ti,Co)O(2), by means of electric double-layer gating with high-density electron accumulation (>10(14) per square centimeter). By applying a gate voltage of a few volts, a low-carrier paramagnetic state was transformed into a high-carrier ferromagnetic state, thereby revealing the considerable role of electron carriers in high-temperature ferromagnetism and demonstrating a route to room-temperature semiconductor spintronics.

Advances in EELS spectroscopy by using new detector and new specimen preparation technologies.

First results obtained with a Gatan UHV Enfina system, which was attached to a VG HB 501 UX dedicated STEM, are reported. The Enfina system is based on a CCD detector and offers, compared to the previously used photodiode array, a narrower point-spread function, higher sensitivity, and faster read-out capabilities. These improvements are demonstrated with electron energy-loss measurements on various oxides, such as Al2O3, TiO2 and SrTiO3. It is shown that a better energy resolution is achieved and that acquisition of high-energy absorption edges with a reasonable signal-to-noise ratio becomes possible. Furthermore, we report on the influence of the TEM specimen quality on the energy-loss spectra. Thin amorphous layers at the specimen surfaces, which are induced by ion-milling processes, can modify specific electron energy-loss near-edge structure features. We found that for the investigated ceramics the use of low-energy ion-milling systems is highly recommended, since the loss of energy-loss near-edge structure details by the presence of the amorphous layers is considerably reduced. This is especially true for very thin specimens.

Dynamic chemical mapping near a Si/SiO2 interface at elevated temperatures using plasmon-loss images.

Plasmon-loss imaging was applied to chemical mapping during an in-situ heating experiment. The technique was applied to observation of vibration of a Si/SiO2 interface which took place during reduction of SiO2 at high temperature. The chemical maps of Si and SiO2 were recorded dynamically using a conventional TV-VTR system at a time resolution of 1/30 s.

In situ high resolution electron microscopy/electron energy loss spectroscopy observation of wetting of a Si surface by molten Al.

Electron energy loss spectroscopy was used to observe the segregation of Al on a Si surface above the melting point of Al. A mixture of Al and Si particles was heated above the melting point of Al in a vacuum of 1 x 10(-5) Pa. The Si surface, which initially had been covered with an amorphous oxide layer before heating, became clean and atomically facetted when the Al melted. It was shown that the Si surface was segregated with Al.

Direct Observation of the Atomic Structure in a Solid-Liquid Interface.

An experimental high-resolution image of a solid-liquid interface of solid Si and liquid Al-Si alloy has been compared with theoretical images obtained by computer simulation. It has been concluded that the solid-liquid interface has a transition layer, the structure of which is compatible with the 1 x 1 Si-{111} surface.

In Situ Transmission Electron Microscope Observation of Melting of Aluminum Particles.

; The processes of melting and freezing of aluminum (Al) particles have been observed directly in a transmission electron microscope. The liquid phase nucleated preferentially at the surface of an Al particle, surrounding the crystalline solid at the onset of melting. The liquid phase then propagated inside the Al particle at the expense of the solid.