Syunichi Hishita

Study of Optical Property in ZnO Thin Film Implanted with Eu by Combinatorial Ion Implantation Techniques

Combinatorial ion implantation techniques with mask and digital scanning systems were applied to optimize conditions of the optimal Eu dose for the orange luminescence originating from Eu phosphor in ZnO thin films. Eu ions accelerated to 150 keV were implanted continuously in the range of 1×1016 to 2×1017 ions/cm2. The sample was annealed at 600°C for 10 min in air, in order to observe the orange luminescence at 618 nm. Optimal Eu dose was determined to be about 1×1017 ions/cm2. The luminescence intensity related to Eu3+ was decreased by the annealing at 800°C. The intensity of orange luminescence is related to the degree of recovery from radiation damage.

Oxygen diffusion in ion-implanted layer of Nb-doped SrTiO3

Abstract Oxygen diffusion phenomena were investigated on Nb-doped SrTiO3 crystals after Ar or F ion implantation. SIMS measurements indicated that oxygen diffusion profiles consisted of high and low diffusivity regions; the profiles were analyzed by a two-layer model and diffusion coefficients were evaluated. According to TEM observation, there existed three layers in the implanted region whose boundaries were in good agreement with the positions analyzed. A large number of dislocations were produced by the ion implantation, which disappeared upon thermal annealing. The distribution of oxygen vacancies was determined from the diffusion coefficients, and compared with the results of TRIM simulations.

Combinatorial Ion Implantation Techniques Application to Optical Characteristics of ZnO

We report on the application of combinatorial ion implantation techniques such as the moving mask system and the digital scanning system. The combinatorial library formed by ion implantation was used to optimize the green light emission from ZnO thin films.

Dephasing of coherent THz phonons in bismuth studied by femtosecond pump-probe technique

Abstract We have studied the effect of point defects on coherent optical phonons and photo-generated carriers in ion-implanted bismuth polycrystalline films and single crystals by means of pump–probe reflectivity technique. The dephasing time of the A1g phonon decreases monotonically with increasing ion dose, which is explained by phonon–defect scattering. The relaxation time of photo-excited carriers decreases as the ion dose increases, being attributed to trapping of carriers by defect-induced deep levels. The behavior of the carrier and phonon dynamics for the polycrystalline film is compared with those for the single crystal.

Optimization of Annealing Time and Cu Concentration for Study of Luminescence Properties of Cu-Implanted ZnO Thin Films

New ion implantation techniques were applied to optimize conditions such as annealing time, Cu dose, and Cu concentration for the green emission originating from Cu phosphor in ZnO thin films. Copper ions accelerated to 150 keV were implanted at room temperature. In the ZnO thin films implanted with Cu, the suitable annealing time was 90 min at 800°C. The optimal Cu dose was determined to be 4.5 ×1014 ions/cm2. The ZnO thin films optimized for effective green emission had a Cu concentration of 9 ×1018 ions/cm3.

Oxygen Tracer Diffusion in BaTiO3 Ceramics - Effect of Zr Impurity from Planetary Ball Milling

We investigated the effect of Zr impurities on the oxygen diffusion pathway in BaTiO3 ceramics by using an ion-imaging technique. Zr impurities were introduced into BaTiO3 ceramics by a planetary ball milling process. The oxygen tracer diffused quickly from the surface up to the grain boundary and then appeared as discontinuous steps at the grain boundary. The results indicate that the grain boundary acted as a blocking layer against oxygen diffusion. The blocking for oxygen diffusion at the grain boundary is thought to originate during the formation and distribution of complex defects between the charged oxygen vacancies and the Ba vacancies near the grain boundary.

Electric property of ZnO based transparent conductor films in GHz range

Newly developed transparent transmission line structures using ZnO film and fine metal wiring that is not visible by eye have been designed. In this paper, some electromagnetic field simulations suggest that the structure improves transmission characteristics while keeping high transparency. It was revealed that the reflection characteristic of a new transparent coplanar waveguide (CPW) could be improved and the characteristic impedance was controlled well by the width of signal line of ZnO film.

Redistributing Unintentional Defects Induced by Heavy Ion Implantation in ZnO Ceramics

The relationship between the defect structure and luminescence property of ZnO ceramics implanted with Ar of 2×1015 – 60×1015 ions/cm2 was studied. After annealing, the heavy dose-implanted sample (Ar ≥ 30×1015 ions/cm2) was characterized by a luminescence peak at the 730-nm wavelength. Defects in the implanted region formed voids during post-annealing. Oxygen tracer experiments indicated that grain boundary diffusion in the implanted region was enhanced significantly.