Tomonori Yamaoka

Crystallization of amorphous Si on a glass substrate through nucleation by Si+ ion implantation

Crystallization of amorphous Si films on a glass substrate by Si+ implantation (acceleration energy: 180 keV, beam current density: 10 μA/cm, ion dose: 1×1017 ions/cm2) was performed without external heating of the substrate. Transmission electron microscopy images of the crystallized specimens lead to the following conclusions: (1) crystallization was achieved through bulk nucleation by Si+ implantation, which is a low temperature and rapid process compared with the ordinary thermal process, (2) the crystallization is strongly related to the ion‐solid interaction, not due to ‘‘pure’’ thermal annealing by ion beam heating.

The Dependence of Field Effect Mobilities on Substrate Temperature for Amorphous Silicon Deposition for Amorphous Silicon Thin Film Transistors

We evaluated the field effect mobility ( µFE) for a-Si TFTs at different temperatures for a-Si deposition (Tsub). The µFE showed a maximum in the temperature range of 200~250°C. We estimated the tail localized state distribution of the a-Si films for each Tsub value from theoretical curves modified by the measurement temperature dependence of µFE. The result of the fittings showed that the a-Si tail localized state was suppressed in the Tsub range 200~250°C.

Ion implantation for large-area optoelectronics on glass substrates

Abstract The authors have investigated the possibility of large-area optoelectronics on glass substrates fabricated by ion implantation, particularly AM-LCD (active-matrix liquid crystal display) and highly intelligent functional devices. Basic knowledge and technologies have been obtained for the formation of SiON- and PSG-layer underneath the glass surfaces by ion implantation. These layers can prevent sodium diffusion into the optoelectronic devices fabricated on glass substrates. Planarization of glass surfaces by ion implantation and the crystallization of amorphous Si by ion implantation without external heating are also discussed.

Grain‐size distribution in ion‐irradiated amorphous Si films on glass substrates

Amorphous Si films containing crystal seeds can be converted to a polycrystal by an ion beam with heating at 350 °C on silica glass substrates, and the density of the crystal grain is almost the same as that of the initial seed. However, the size and density of the crystal seed decrease when the ion irradiation is performed without external heating. The average grain size in the completely crystallized film can be controlled by decreasing the crystal seed density before crystallization. The growth process of crystal grains (average grain diameter R and standard deviation σR) is reported and the gradient ΔσR/ΔR is estimated to be about 0.15. A model calculation is performed to estimate the gradient on the assumption that the growth rate is governed by the plane (111) crystallization and the calculated value is 0.05.