層狀材料TiSe2之電荷密度波研究

Study of charge-density waves in the layered material TiSe2

鄭智謙(Chih-Chien Cheng)

指導教授 ： 杜昭宏

淡江大學/理學院/物理學系碩士班/碩士(2014年)

https://doi.org/10.6846/TKU.2014.00398

摘要

電荷密度波(CDW)常出現於低維度材料，即具有異向性一維的線性鏈或二維的平面的材料，如K0.3MoO3、NbSe3、TaS2、 K2Pt(CN)4Br0.3?32H2O等皆屬於這類的材料；在眾多電荷密度波材料中，二維層狀結構的TiSe2已受到長時間的關注，據文獻記載其電荷密度波會出現於(H±0.5 K±0.5 L±0.5)的位置並為對掌形電荷有序。
在經過退火過後， TiSe2受溫度影響Se元素會有些許消散使晶格排列改變，如此一來可能會造成相變溫度的轉變，本論文利用電子微探分析(Electron Probe Microanalyzer)確定Se含量，並藉由電性和磁性量測來估計其相變溫度，並藉由X-ray的散射來確認實際TiSe2的電荷密度波相變溫度，如此能了解不同的退火溫度樣品的品質會出現差異，且探討Se含量和退火溫度對相變溫度造成的影響 。

關鍵字

硬X光 ； 電荷密度波 ； 層狀材料

並列摘要

The modulated structure due to the formation of charge density wave (CDW) usually exists in low-dimensional materals, such as K0.3MoO3, NbSe3, TaS2, K2Pt(CN)4Br0.3?32H2O　and so on. The study of the charge modulations are mostly relied on the use of electron beams, x-rays, and neutrons. Among them, x-rays have the merits of high-spatial resolution and sensitive to charges over other two probes. In this study, we use the high-resolution x-rays to investigate the CDW modulation in a layered compound TiSe2 under different annealing temperatures.
Measurements on a series of crystals of TiSe2 being annealed at different temperatures show the different conductivity behavior, which were observed to relate to the Se contents by the use of Electron Probe X-Ray Microanalyzer.Using high-resolution x-ray scattering, many satellite reflections caused by the CDW were located at positions (H± 0.5 K± 0.5 L± 0.5) at low temperatures, and the transition temperature of CDW was also observed to depend on annealing temperatures.

並列關鍵字

Hard X-ray ； Charge-Density Wave ； Layered Material

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