We investigated electrical and structural properties of Ta-doped SnO2 (TTO) films on anatase TiO2 seed layers with various growth parameters of pulsed laser deposition. We found that anatase TiO2 seed layers induced pseudo-epitaxial (100) growth of TTO films with enhanced mobility (μ) in a wide range of growth parameters. The highest μ of 83 cm2V-1s-1 [resistivity (ρ) of 2.8 × 10-4 Ωcm] and the lowest ρ of 1.8 × 10-4 Ωcm (μ of 60 cm2V-1s-1) were obtained at a substrate temperature of 600 °C. Amorphization and (101)-preferred growth competed with (100) growth on the TiO2 seed layer at low temperatures. Introducing sufficient process oxygen suppressed such unwanted film growth, resulting in improved transport properties.

We investigated electrical conduction of anatase Ti0.94Nb0.06O2 (TNO) epitaxial thin films in relation to oxygen defects generated by post-annealing. Annealing of TNO in oxygen was found to cause dramatic decreases in ne. Resonant photoemission spectroscopy measurements revealed that a deep acceptor state just above the top of valence band evolves, synchronized with the decrease of ne. We proposed that the acceptor state originates from interstitial oxygen atoms combined with Nb dopants and compensates electron carriers.

We prepared quasi single crystalline pentacene monolayer films on Bi-terminated Si(111) by using bunched steps on vicinally-cut surfaces as an orientation template. Band dispersion in the conduction plane of pentacene was clearly observed by angle-resolved photoelectron spectroscopy.

We developed a variable-temperature scanning microwave microscope (VT-SμM) that can perform high-throughput materials characterization in the temperature range between 4K and room temperature. As a sensor probe we used a high-Q coaxial cavity resonator, which was mounted on the low-temperature stage to allow variable-temperature measurements. We carried out systematic studies on the thermal degradation of the conducting polymers using the combinatorial libraries of polyaniline and polythiophene thin films, which showed rapid decrease of conductivity above 300C and 250C, respectively. The low-temperature performance of the VT-SμM was demonstrated by the measurement of composition-spread Nd1-xSrxMnO3 thin film, for which we succeeded in detecting the clear metal-insulator transition at 100K. We also propose a simple and easy method for the quantitative analysis of conductive thin films, by using the standard composition-spread thin films of Ti1-xNbxO2.

We have discovered new transparent conducting oxides (TCOs), anatase Ti1-xMxO2 (M=Nb,Ta), in thin film form. Both films with 0.03 ≤ × ≤ 0.06 showed resistivity of 2−3 × 10−4 Ωcm and internal transmittance of ∼95% in the visible light region (40 nm in thickness), at room temperature. These values are comparable to those of typical TCOs, such as In2−xSnxO3 (ITO).

We developed a scanning microwave microscope (SμM) designed for characterizing local electric properties at low temperatures. A high-Q λ/4coaxial cavity was used as a sensor probe, which can detect the change of quality factor due to the tip-sample interaction with enough accuracy. From the measurements of combinatorial samples, it was demonstrated that this SμM system has enough performance for high-throughput characterization of sample conductance under variable temperature conditions.

A scanning microwave microscope (Sm M) for high-throughput characterization of combinatorial dielectric materials has been developed using a lumped constant resonator probe. The probe consists of a microwave oscillator module equipped with a thin conducting needle and an outer conductor ring, which detects the dielectric constant of the sample just beneath the needle as a frequency shift of the resonator. The quantitative analysis of the dielectric constant for the bulk and the thin-film samples was carried out based on the measurement of gap-length dependence of the frequency shift. The analysis method was successfully applied to the characterization of composition-spread BaxSr1-xTiO3 thin film sample. The evaluation of far-field contribution to the frequency shift was found to be crucial for the accurate determination of dielectric constant especially in the characterization of combinatorial thin films.