| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The purpose of this study is to elucidate luminescence excitation mechanisms in erbiumdoped porous silicon, excitated with a high-speed light pulse, through observing the temporal relations between visible and infrared luminescence from the porous silicon and the erbium doped therein, respectively, as well as modelling the energy transfer between them.
The porous silicons formed on p-type silicon wafers with a resistivity of 1O-2OOMEGAcm by anodization were doped with the erbium using a method of immersion, and were made optically active by therml treatments. Time-resolved photo- luminescence measurements employing the pulse laser excitation was performed for the prepared samples. Differences between temporal responses of visible and infrared region suggested that it is necessary to postulate the existence of luminescence centers originating from the Coulomb interactions between optically generated electron-hole pairs and erbium ions in the host.
In relation to the elucidation of lumines
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cence mechanisms, the local structure within the samples was investigated by the X-ray absorption fine structure spectroscopy, to find the atomic coordination of the optically active center is such that an erbium atom is bonded with six oxygen atoms asymmetrically. Through experiments applying an electric-field to the sample to gain a knowledge regarding a possible quenching of luminescence, it was found that the photo- luminescence decreases rapidly for fields exceeding a critical value, probably due to the dissociation of electron-hole pairs. In addition, for erbium-doped nano-crystalline silicon samples prepared by the laser ablation, their characteristics under a high-speed pulse excitation are found to be very similar to those of erbium-doped porous silicon.
As to the observed results, the solutions of rate equations assuming the mechanism of energy transfer via luminescence centers ( vertual levels ) were in a good agreement with the experimental results. Hence, a conclusion was reached that the infrared luminescence from doped- erbium at the wavelength of 1.54 mum comes from the energy transfer to doped erbium atoms from electron-hole pairs generated within the porous silicon host. Less
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