Tunneling Spectroscopy of Magnetic Impurities (=Mn,Fe,Co) in ZnO

The first observations have been made on the electronic density of states of Mn, Co and Fe-doped ZnO by tunneling spectroscopy. For Mn- and Co-doped ZnO, rising of DOS were observed around 2.8eV and 3.2eV below the bottom of the conduction band, respectively. In these cases, the Fermi level lay at the bottom of the conduction band. For Fe-doped ZnO, the DOS with about 1.2eV width was observed around the Fermi level in the mid-gap. The result reproduced the recent theoretical calculation.

FULLERENES ON METAL AND SEMICONDUCTOR SURFACES: SCANNING TUNNELING MICROSCOPY STUDIES

In this paper, we review our recent scanning tunnelling microscopy studies of fullerenes C 60 and C 70. We focus our work on adsorption and reaction of these fullerenes on Si(111)7×7 and Si (100)2×1 semiconductor surfaces, as well as on Cu (111)1×1 and Ag (111)1×1 noble metal surfaces. By using STM, the adsorption geometry and reconstructions of fullerenes are directly observed on these surfaces, and the intramolecular structures are revealed in high resolution STM images. It is found that fullerenes are strongly bonded to the Si(100) and Si(111) surfaces so that the free rotation of C 60 and C 70 in their bulk phases is stopped. Local orderings with c(3×4) and c(4×4) reconstructions are observed for the first layer of C60 on the Si(100) surface. Well-ordered crystalline multilayer films can be formed on the Si(100) surface. The intramolecular structures observed for C 60 on the Si(100) surface are interpreted based on the local charge distribution on the molecule, in good agreement with a recent theoretical calculation. The Cu (111)1×1 and Ag (111)1×1 surfaces are found to be good substrates for ordered C60 and C 70 film growth. While the interaction of fullerenes with Ag(111) surface is weaker than that on the Cu(111) surface, rotation of C 60 in bulk phase is stopped on both surfaces. Well-ordered commensurate reconstructions are observed for C 60 and C 70 on both surfaces. Bias-voltage-dependent intramolecular structures are observed for the first layer of both C60 and C 70, which reveal the local charge density distribution on these molecules. The results are in good agreement with a recent theoretical calculation. The interesting behavior of the C 60/ C 70 mixture on Cu(111) surface is also reported.

On the infrared spectrum of solid hydrogen deuteride

The spectrum of solid hydrogen deuteride has been studied in the far-infrared (80–200 cm−1) and mid-infrared (3600–4500 cm−1) regions using a Fourier transform spectrometer and a moderately high spectral resolution of 0.09 cm−1. Spectra of the liquid were also recorded for comparison purposes. The pure rotational R0(0) transition at 88 cm−1 was found to have an integrated intensity of 1.78 ± 0.10 cm−2, in good agreement with a recent theoretical prediction. The shape of R0(0) appears to be best represented as the sum of two near-Lorentzian components. These may be related to the presence or absence of nearest neighbor H2 or D2 impurities in the crystal. The fundamental band in the mid-infrared is more complicated, and its detailed shape is not completely understood at this time. The profile of the band in the 3710 cm−1 region of the R1(0) transition is compared with a recent theoretical calculation. The presence of numerous sharp lines due to Q1(1) transitions in impurity H2 molecules around 4150 cm−1 is also noted.