We report a direct determination of the specular scattering probability of acoustic phonons at a crystal boundary by observing the escape of incident coherent phonons from the coherent state during reflection. In the sub-THz frequency range where the phonon wavelength is much longer than the lattice constant, the acoustic phonon-interface interaction is found to agree well with the macroscopic theory on wave scattering from rough surfaces. This examination thus quantitatively verifies the dominant role of atomic-scale corrugations in the Kapitza anomaly observed at 1-10 K and further opens a new path to nondestructively estimate subnanoscale roughness of buried interfaces.

An application of ultra-high vacuum transmission electron microscopy (UHV TEM) is demonstrated for the fabrication of carbon nanotube (CNT) probes. In this study, all the fabrication processes -- such as CNT attachment, CNT orientation manipulation, and apex trimming -- are integrated into a single UHV TEM system. The in situ work under UHV conditions (<5 x 10(-10) mbar) allows us to clean the tip surface at the start of the fabrication process to ensure a good contact between the tip and CNT. Furthermore, the CNT size can be user-selected to meet the various needs for scanning probe microscopy (SPM). Most importantly, the in situ trimming enables a multi-walled CNT to have the sharpness of a single-walled CNT. The three advantages mentioned above are designed to improve conventional methods and will be shown in detail as the procedures of CNT probe fabrication by a series of high-resolution TEM images. Finally, we compare the scanned image via our CNT probes and conventional probes, where the typical artefacts coming from the conventional ones are addressed. We believe the technique we have developed here will further enhance the resolution of SPM measurements.

A two-dimensional (2D) dopant profiling technique is demonstrated in this work. We apply a unique cantilever probe in electrostatic force microscopy (EFM) modified by the attachment of a multiwalled carbon nanotube (MWNT). Furthermore, the tip apex of the MWNT was trimmed to the sharpness of a single-walled carbon nanotube (SWNT). This ultra-sharp MWNT tip helps us to resolve dopant features to within 10 nm in air, which approaches the resolution achieved by ultra-high vacuum scanning tunnelling microscopy (UHV STM). In this study, the CNT-probed EFM is used to profile 2D buried dopant distribution under a nano-scale device structure and shows the feasibility of device characterization for sub-45 nm complementary metal-oxide-semiconductor (CMOS) field-effect transistors.

The immature developments of p-type ZnO and ZnO-related ternary or quaternary compound and the small lattice mismatch between ZnO and GaN stimulate interest in the hybrid growth of ZnO and GaN. In this research, we compared the nanostructures and optical properties of two ZnO thin-film samples grown under the same conditions but on different underlying materials ͑sapphire and GaN͒. With the high growth temperature of 450 °C, both samples show domain structures. However, in contrast to the sample of ZnO on sapphire, the sample of ZnO on GaN starts with smaller domains ͑a few tens of nanometers in width͒ of almost vertical boundaries at the interface and evolves into larger domains ͑around 100 nm in width͒. The 30°twist of the basal plane in ZnO with respect to its underlying sapphire does not occur in the sample of ZnO on GaN. Within a domain of ZnO on sapphire, misfit and threading dislocations can be periodically observed along the interface with the separation of about 8 nm. The transition of the lattice structure across the interface between ZnO and GaN was quite smooth, indicating the high heterojunction quality in this sample. The x-ray diffraction results showed that the crystalline quality of ZnO on GaN is slightly better than that of ZnO on sapphire. However, based on the thermal quenching behavior of integrated photoluminescence intensity, we estimated that the optical quality of the two samples is about the same.

Non-degenerate fs pump-probe experiments in the UV-visible range for ultrafast carrier dynamics study of InGaN with adjustable pump and probe photon energies are implemented with simultaneously multiwavelength second-harmonic generation (SHG) of a 10 fs Ti:sapphire laser. The multi-wavelength SHG is realized with two beta-barium borate crystals of different cutting angles. The full-widths at half-maximum of the SHG pulses are around 150 fs, which are obtained from the cross-correlation measurement with a reverse-biased 280-nm light-emitting diode as the twophoton absorption photo-detector. Such pulses are used to perform nondegenerate pump-probe experiments on an InGaN thin film, in which indium-rich nano-clusters and compositional fluctuations have been identified. Relaxation of carriers from the pump level to the probe one through the scattering-induced local thermalization (<1 ps) and then the carrier-transport-dominating global thermalization (in several ps) processes is observed.