Electron sources in the form of one-dimensional nanotubes and nanowires are an essential tool for investigations in a variety of fields, such as X-ray computed tomography, flexible displays, chemical sensors and electron optics applications. However, field emission instability and the need to work under high-vacuum or high-temperature conditions have imposed stringent requirements that are currently limiting the range of application of electron sources. Here we report the fabrication of a LaB6 nanowire with only a few La atoms bonded on the tip that emits collimated electrons from a single point with high monochromaticity. The nanostructured tip has a low work function of 2.07 eV (lower than that of Cs) while remaining chemically inert, two properties usually regarded as mutually exclusive. Installed in a scanning electron microscope (SEM) field emission gun, our tip shows a current density gain that is about 1,000 times greater than that achievable with W(310) tips, and no emission decay for tens of hours of operation. Using this new SEM, we acquired very low-noise, high-resolution images together with rapid chemical compositional mapping using a tip operated at room temperature and at 10-times higher residual gas pressure than that required for W tips.

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The electronic structure and spin asymmetry of metal phthalocyanines (Pcs) (metal = Mn, Fe, Cu, and Mg) and metal-free Pc thin films of 1-monolayer (ML) thickness on an Fe(100) substrate were investigated using spin-polarized metastable deexcitation spectroscopy (SPMDS). The surface density-of-states (SDOS) of these Pcs observed in MDS was almost identical, and thus, insensitivity of the Pc electronic structure to the variation of the central metal atoms is indicated. On the other hand, the spin asymmetry in the SPMDS measurements exhibited noticeable differences among Pcs. These results are discussed from the viewpoint of the Pcs electronic structure calculated by a discrete variational X α method. The fact that differences are found in the spin asymmetry but not in SDOS among Pcs indicates an important role of the central metal atoms for spin polarization.

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From a structural analysis using low-energy ion scattering spectroscopy, it is shown that Cu-phthalocyanine (CuPc) molecules adsorb on the Fe(100) surface with their planes parallel to the surface when the film thickness is one monolayer, while the structure of the film becomes disordered with an increase in the thickness. This thickness dependence of the CuPc film structure agrees with that determined from the metastable deexcitation spectroscopy (MDS) spectra, and the origins of the CuPc peaks in the MDS spectra are determined. The spin polarization in the molecular orbitals of CuPc on Fe is detected by spin-polarized MDS (SPMDS). The polarity of the spin polarization in the CuPc molecular orbitals is the same as that of the Fe surface. The adsorption of oxygen on Fe prior to the CuPc deposition is found to induce a remarkable difference in the spin polarization of the CuPc orbitals.

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As the first step toward understanding the electrical properties of SiO2/GaN systems, the interface was characterized using high-resolution scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). An epitaxial crystalline intermediate layer with a thickness of ∼1.5 nm was observed at the SiO2/GaN interface. STEM-EDS analyses revealed that this intermediate layer contained gallium and oxygen and mostly comprised the ε-Ga2O3 phase. The ε-Ga2O3/GaN interface was atomically smooth and free from misfit dislocations despite lattice mismatch of ∼8.0%, suggesting that the initial oxidation of GaN surfaces is crucial to achieve good interfacial properties.