• Korean Journal of Materials Research
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• v.34 no.6
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• pp.267-274
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• 2024

In this study, four different samples of Se₆₀Ge_40-xBi_x chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10^-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E₁ and E₂). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(E_ext) and localized states N(E_loc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 10¹⁴ to 4.2 × 10¹² (ev^-1 cm^-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 10²¹ to 5.86 × 10²¹ (ev^-1 cm^-3), indicating a reduction in the mullet's randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.140-148
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• 1993

In this study, the electrical and optical properties of amorphous, crystallization and thin film of As-Ge-Se Chalcogenide System was investigated. Typical composition of this material has $As_{20~50}Se_{40~70} and Ge_{10~40}$ at%. Materials having Se was fixed to 40 at% and As was above 30 at% much more increased the electrical conductivity. After crystallization at the temperature of $476^{\circ}C$ for 3 hour was showed the best electrical conductivity of 1.74E-13$(\Omega cm)^{-l}$. And the main crystalline phase of this sample can be investigated using the mixed crystalline, i.e, $GeSe_2 and As_2Se_3$ phases. The thin film shows the optical absorption coefficient in the range $2{times}10^3 to 7{times}10^4$ and the optical energy gap of 1.85eV.

• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.177-184
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• 2006

Dy $L_3$-edge XANES and EXAFS spectra of chalcogenide Ge-As-S glass doped with ca. 0.2 wt% dysprosium have been investigated along with some reference Dy-containing crystals. Amplitude of the white-line peak in XANES spectrum of the glass sample turns out to be stronger than that of other reference crystals, i.e., $DY_2S_3,\;Dy_2O_3\;and\;DyBr_3$. It has been verified from the Dy $L_3$-edge EXAFS spectra that a central Dy atom is surrounded by $6.7{\pm}0.5$ sulfur atoms in its first coordination shell in the Ge-As-S glass, which is relatively smaller than 7.5 of the $Dy_2S_3$ crystal. Averaged Dy-S inter-atomic-distance of the glass ($2.78{\pm}0.01{\AA}$) also turns out to be somewhat shorter than that of the $Dy_2S_3$ crystal ($2.82{\pm}0.01{\AA}$). Such nanostructural changes occurring at Dy atoms imply there being stronger covalency of Dy-S chemical bonds in the Ge-As-S glass than in the crystal counterpart. The enhanced covalency in the nanostructural environment of $Dy^{3+}$ ions inside the glass would then be responsible for optical characteristics of the $4f{\leftrightarrow}4f$ transitions of the dopants, i.e., increase of oscillator strengths and spontaneous radiative transition probabilities.