Nb-doped TiO2 (TNO) films, Ga-doped ZnO (GZO) films and TNO/GZO layered films were fabricated on glass substrates and electrical properties of TNO/GZO layered films were investigated in terms of interaction between TNO and GZO layers. By a thermal annealing in vacuum, the observed resistivity of the TNO/GZO layered films was lower than that of the single layered films fabricated and annealed at the same conditions. The resistivity reduction observed in the layered structure is not explained by the parallel connection of the TNO and GZO layers, indicating that there exists an interaction between these two layers. The TNO/GZO films with low resistivity have still been transparent.

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.

This paper reports a novel means of integrating a high-performance dual-modal ZnO piezoelectric transducer with a flexible stainless steel substrate (SUS304) to construct dual-modal vibration-power transducers. To fabricate vibration-power transducers, the off-axis RF magnetron sputtering method for the growth of ZnO piezoelectric thin films is adopted. The stainless steel substrate has a higher Young’s modulus than those of the other substrates, and behaves the long-term stability under vibration. The transducer includes a ZnO piezoelectric thin film deposited on the stainless steel substrate combined with Pt/Ti layers at room temperature, which is fabricated by an RF magnetron two-step sputtering system. In this report, the ZnO piezoelectric thin films deposited with the tilting angle of 34° are set by controlling the deposition parameters. Scanning electron microscopy and X-ray diffraction of ZnO piezoelectric thin films reveal a rigid surface structure and a high dual-modal orientation. To investigate the generating characteristics of the dual-modal transducer, two basic experiments of longitudinal and shear modes are carried out. Based on cantilever vibration theory, the cantilever length of 1 cm and a vibration area of 1 cm2 are used to fabricate a transducer with a low resonant-frequency of 65 Hz for the natural vibration. A mass loading at the front-end of the cantilever is critical to increase the amplitude of vibration and the power generated by the piezoelectric transducer. The maximum open circuit voltage of the power transducer is 19.4 V.