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The polarity of AlN films grown epitaxially on the Si(0001) and C(000) faces of 6H?SiC substrates utilizing molecular beam epitaxy (MBE) were investigated. A number of small pits with sizes less than 10?20 nm were observed on the AlN surface. The pits in AlN film on the Si face combined with neighboring ones to form linear dents, while those on the C face were isolated from each other. X-ray photoelectron spectroscopy (XPS) measurement showed clear differences in the binding energy of Al2p and N1s core levels and in the intensity ratios of IN1s/IAl2p between the AlN films on the Si and C faces. The XPS spectra also showed that more oxygen was contained in the AlN film grown on the Si face than that on the C face. The results reveal that the {0001} surfaces of AlN films grown on the Si and C faces are terminated with aluminum and nitrogen, respectively.

We present the photonic band schemes of colloidal crystals with rhombohedral structures that are compressed along the [111] direction of a close-packed face-centered structure while maintaining the shapes of the colloidal particles. The compressed colloidal crystals transform from an A10 structure to an Ai structure through a simple cubic structure. The photonic band schemes reveal that, as the colloidal crystals are compressed, the stop-band frequencies increase for A10 structures and decrease for Ai structures upon becoming simple cubic structures. This transition can be explained by the change of the lattice plane responsible for Bragg diffraction.

In order to obtain a flat SiC surface, both the Si(0001) and the C(000) faces of 6H–SiC were annealed in vacuum at temperatures above 1700°C for 2 h. After removing graphite films grown on the Si face, scratches due to polishing vanished, and a smooth surface with atomically flat crystal terraces of width ranging from 200 to 400 nm and step height ranging from 0.8 to 2.2 nm appeared. On the other hand, a rough surface with many holes and particles was observed on the C face when using the same procedures as for the Si face. The etching technique for the Si face is useful for preparing SiC substrates for epitaxial growth, although there were some small pits on the surface due to the native defects in the crystal.

The reflection from colloidal crystals of core–shell particles is evaluated by the calculation of photonic band structures, and is compared with the prediction of the Bragg condition. Although the results of the calculation of the photonic band structures are consistent with those of the Bragg condition, generally, the photonic band structures predict another reflection which has no origin in the Bragg condition, when the shell of the particle is sufficiently thin and the difference in refractive index between the core and the shell is relatively large. Moreover, no reflection is expected in the case of moderate shell thickness and moderate refractive index difference.

We report here the temperature-dependent electronic structure of C60 molecules adsorbed on a Si(001)-(2×1) surface, measured by photoelectron spectroscopy. At room temperature, the valence spectra reveal that the interaction between a 1 monolayer (ML) C60 film and a Si(001)-(2×1) surface is mainly a physisorption. After annealing the 1 ML C60 film adsorbed on a Si(001)-(2×1) surface at 500 K, in the valence spectra the highest occupied molecular orbital (HOMO) of a C60 molecule splits into two peaks. The binding energies of the two peaks are 1.6 and 2.1 eV. We assign the 1.6-eV peak to the shifted HOMO and the 2.1-eV peak to the bonding state between C60 molecules and a Si(001)-(2×1) surface from the polarization-dependent measurement and the Si 2p core level spectrum. Moreover, the molecular orbitals and the C 1s core level of a C60 molecule shift to the lower binding energy side. These results indicate that the interaction between C60 molecules and the Si(001)-(2×1) surface changes from physisorption to chemisorption, which has both covalent and ionic characters, at 500 K.