近年來，硫屬化合物薄膜已證實可被應用於相變化光碟與相變化隨機存取記憶體用途，主要原因是這類材料的結構，可以快速地在結晶態與非晶態間轉變，且伴隨光學與電阻特性的大幅改變，這種材料行為過去被稱之為Ovonic現象，而具有這種現象的材料也被稱為相變化材料。實際應用上，硫屬化合物薄膜必須著重於提高相變化速度，以及增強其伴隨電阻或光學特性改變的差異。因此研究與控制相變化薄膜的光學與電阻特性改變，以及其結晶化的熱激活參數就成為重要的課題之ㄧ。
本研究使用射頻磁控濺鍍法，製作兩種成分之硫屬化合物薄膜，純SbTe合金薄膜(以下稱ST)與Ag/In複合添加SbTe薄膜(以下稱AIST)。第一部分的研究中，主要探討初鍍薄膜之微觀組織結構與薄膜電阻率，並釐清濺鍍參數對於膜厚及電阻率間之影響。結果顯示本研究設定之濺鍍條件範圍沉積之薄膜，藉由X-ray繞射與電子顯微鏡分析，確認AIST與ST初鍍薄膜皆具有非晶質結構。經測量該二種初鍍薄膜之電阻特性，除發現該初鍍薄膜具有極高之薄膜電阻值外，也發現該初鍍薄膜具有負電阻溫度係數。經比較不同膜厚試片的薄膜電阻率，發現非晶態的AIST薄膜，其電阻率與膜厚關係不遵循常見之尺寸效應。
第二部份的實驗中，主要係將相同條件之AIST與ST薄膜試片，於不同溫度下進行恆溫退火1小時後，以獲得完全與部分結晶化之試片。經調查該試片之薄膜電阻值，發現薄膜電阻值會隨結晶度增加而降低，且值得注意的結果是：非晶態薄膜與結晶化後薄膜間的電阻差異比例可達104。此外，比對X-ray繞射分析與電阻量測實驗結果，也發現兩者電阻發生轉變的臨界溫度分別為160 ℃與120 ℃，結晶化發生的臨界溫度也與電阻轉變相同，意味Ag/In的複合添加可以提高該薄膜的結晶溫度。配合穿透式電子顯微鏡觀察薄膜微觀組織特徵，顯示結晶化ST薄膜的主要結晶析出物為-Sb相，而經過複合添加Ag/In元素的AIST薄膜，除-Sb相外尚有AgSbTe2相生成。值得一提的觀察結果是經250 ℃退火1小時候的試片，可發現仍然有部分非晶相殘留，且無論是X-ray分析與電子顯微鏡觀察都未發現任何與In相關之化合物生成。
有關熱激活參數之研究，本研究利用DSC測量AIST與ST非晶薄膜之結晶活化能與結晶溫度，結果ST薄膜為0.82 eV，AIST薄膜為0.92 eV；結晶溫度 ST薄膜為172 ℃，AIST薄膜為202 ℃，顯示Ag/In複合添加可提高非晶薄膜之室溫穩定度。此外，本研究也利用試片電阻值隨結晶程度變化之現象，自行設計等溫即時電阻測量裝置，於較低退火溫度下進行恆溫退火，並即時記錄該薄膜電阻值隨加熱時間變化之圖形。獲得之實驗結果配合Johnson-Mehl- Avrami方程式，計算出非晶質AIST薄膜之結晶活化能約為0.815 eV；Avrami指數n約為1.1~1.4。根據實驗結果推論薄膜電阻值於過渡區間內發生急劇變化之現象，可來自於結晶化之電流通路模式的形成。

Chalcogenide films were able to be used as the recording layer of phase change recording media and in the application of phase change random access memory (PCRAM). The most attractive property of this material is its quick transformation between the amorphous and crystalline states, which phenomenon can accompany huge changes in the optical and electric properties. The reversible transformation between amorphous and crystalline phases was named as the Ovonic Memory phenomenon and materials with such kind of properties were also named as the phase change materials. In practical applications, major efforts have been focused on increasing the crystallization speed and improvement on the optical or electrical contrast between amorphous and crystalline state.
In this study, there are two chalcogenide films being deposited with RF-sputtering method, pure SbTe films (ST) and Ag/In added SbTe films (AIST). In the first part, the microstructure and sheet resistivity of AIST films deposited with different parameters were analyzed. The result shows that the as-deposited films possess amorphous structure no matter with what the sputtering parameter being adopted. The sheet resistivity measurement shows the amorphous films possess an extremely high resistivity and the temperature coefficient of resistivity (TCR) is negative. It is worthy noting that the relationship of amorphous AIST films between the sheet resistivity and film thickness was found to against the classic size effect.
In the second part, similar amorphous films were annealed isothermally at different temperatures to obtain their different crystallinity. The sheet resistance of the annealed specimens was measured at room temperature, where the sheet resistance of amorphous films can be 104 higher than that of the crystalline films. As comparing X-ray diffraction patterns of AIST films to that of ST films, the sheet resistance change of the specimens can be correlated to the crystallization of amorphous phases, which transition temperature of the change in the sheet is at about 160 ℃ for AIST and 120 ℃ for ST. Through transmission electron microscopy observations and X-ray diffraction, the major phase in the crystalline ST films is the delta-Sb phase and the mixture of delta-Sb and AgSbTe2 phases in the crystalline AIST films.
Concerning of the thermal activation measurements, the activation energy and crystallization temperature were measured with the differential scanning calorimeter (DSC). The activation energy of AIST films is about 0.92 eV and that of ST is about 0.82 eV, the crystallization temperature of AIST films is about 202 ℃ and that of ST films is about 172 ℃. The result reveals Ad/In added SbTe films possesses high room temperature stability. Because the sheet resistance has been proven to change with the crystallinity, an apparatus was developed to estimate the activation energy and the Avrami exponent of crystallization through Johnson-Mehl-Avrami formulism. The activation energy is estimated to be about 0.815 eV and the Avrami exponent n is about 1.1~1.4. The exponent indicates that the crystal can grow freely and the sheet resistance will decrease dramatically after the impingement occurring. A model is proposed to explain why the sheet resistance decreases within a very short period and the homogeneous nucleation and free growth during isothermal annealing in this study.

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