• 한국재료학회지
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• 제34권6호
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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.

• 한국결정성장학회지
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• 제3권2호
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• pp.140-148
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• 1993

As-Se-Ge 3원계 칼코게나이드 유리의 비정질화와 결정화 및 박막화를 통하여 전기적, 광학적 특성을 평가코자 하였다. 조성의 범위는$As_{20~50}, Se_{40~70}, Ge_{10~40}$ at%였으며, Se을 40 at%로 고정시 As가 30 at%이상일 때 급격한 전기전도도의 증가를 가져왔으며,$As_{20}Se_{50}Ge_{30}$을 결정화시킨 경우, $476^{\circ}C$에서 3시간 결정을 성장시켰을 때의 전기전도도가 가장 양호하였으며, 주결정상으로 $GeSe_2와 As_2Se_3$의 흔정을 관찰할 수 있었다. 박막에서는1.8~2.4eV의 광에너지 영역에서 $2{times}10^3~7{times}10^4$의 광흡수계수를 나타냈고, 1.85eV의 광학적 에너지 갭을 나타냈다.

• 한국세라믹학회지
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• 제43권3호
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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.