20 September 1999 Photoconductivity study at room temperature of the undoped photorefractive Bi12GeO20
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Reliable and reproducible results on Bi12GeO20 (BGO) crystals depend on the thermal and optical history of the samples. It is then necessary to find well defined state of the material for which the experimental observations are reproducible. The de-excited state is reached either by an annealing at 450 - 500 K, or by illumination with photons of energies less than 2.2 eV. The corresponding photoconductivity is called the background photoconductivity. The excited state is obtained when the crystal is illuminated with photons of energies higher than 2.4 eV until reaching an optical and electrical steady state. The corresponding photoconductivity is the photoinduced photoconductivity. Comparison between these two states show that for energies higher than 2.4 eV the background and the photoinduced photoconductivity are the same, but for energies lower than 2.2 eV they are very different and the ratio of their magnitudes can reach a factor 1000. This study allows to define the conditions of writing, reading and erasing information on the BGO crystals. These effects are explained in terms of charge transfers between deep and trap levels, induced by the appropriate illuminations.
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Mayer Tapiero, Mayer Tapiero, Jean-Claude Launay, Jean-Claude Launay, "Photoconductivity study at room temperature of the undoped photorefractive Bi12GeO20", Proc. SPIE 3801, Photorefractive Fiber and Crystal Devices: Materials, Optical Properties, and Applications V, (20 September 1999); doi: 10.1117/12.363942; https://doi.org/10.1117/12.363942

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