| 摘要: | 本研究是以熱蒸鍍的方式，將鍺不同厚度(0.5-10nm)的材料蒸鍍在不同大小（10、20、50 和100nm）的奈米玻璃球上(silica nanospheres)，觀察半導體材料在奈米尺寸，所產生的常溫磁性或是低溫磁性研究。在奈米玻璃球上鍍鍺薄膜後再升溫退火，觀察溫度對表面形貌且相對於磁性的影響。
鍺薄膜在奈米玻璃球表面大範圍的均勻覆蓋，在薄膜厚度小於3nm時，所有的奈米玻璃球頂端均會蓋上奈米尺寸的薄膜，在20nm 玻璃球上鍍鍺薄膜2nm 厚，出現最佳的飽和磁化率約為1553 emu/立方公分。飽和磁化最佳的樣品進行退火，退火後樣品的飽和磁化隨之遞減，在退火溫度達到450℃時鍺材料的常溫磁性完全消逝。
綜觀以上研究資料得知，半導體材料（鍺）在奈米尺寸所產生的磁性不僅只於跟尺寸大小有關，也與其內部的原子排列有著密切的關係，而且不同的退火溫度或不同的成長溫度影響著奈米尺寸半導體內的原子排列狀況。
In this study, the ferromagnetism of Ge layers with various thickness (1-10nm) deposited on top of the self-organized silica nanospheres (10, 20, 50 and 100nm in diameter) were investigated. Ferromagnetism was dependent on the thickness of the Ge layers, the size of the silica nanospheres and growth temperatures. At saturate, a maximum magnetization (1553 emu/cm^3) appeared in Ge samples with 2 nm thick on nanospheres of 20nm diameter. And diamagnetism was observed in thick (≧ 5nm) layers deposited on large(≧ 50nm) nanospheres or at high temperatures(≧600K).
We postulate that heat treatments changed the size and the atomic arrangements of quantum dots (QDs) and hence varied their magnetic properties. Magnetic moment in each Ge QDs were attributed to both the size effect and the atomic arrangement in the QD. |
