以即時電性量測法探討AgInSbTe及其奈米複合薄膜之相變化動力學研究

Abstract

本研究以自組之即時電性量測系統（In-situ Electrical Property Measurement）探討AgInSbTe（AIST）與AIST-SiO2奈米複合薄膜之相變化動力學。X光繞射分析（X-ray Diffraction，XRD）顯示初鍍之非晶態AIST經加熱至約200□C後轉變為結晶態之Sb2Te相。在等升溫實驗中，相變化溫度（Tc）隨膜厚與升溫速度之增加而降低，由Kissinger分析知相變化活化能（Activation Energy，Ea）隨著膜厚的減少而增加，顯示試片維度會抑制晶粒成長；在相同膜厚下，在AIST-SiO2奈米複合薄膜中掺入SiO2會增加其活化能，意味著SiO2抑制了AIST再結晶時的晶粒成長，故使Ea值上升。在恆溫實驗中，以Johnson-Mehl-Avami-Kolmogorov（JMAK）理論探討薄膜之成長模式發現AIST之晶粒成長模式介於二維與三維；當SiO2摻雜量為15 wt.%且膜厚為50 nm以上時，其成長轉為三維模式；推測其原因應為SiO2顆粒在薄膜內部提供了許多異質成核（Heterogeneous Nucleation）位置，均勻分佈的SiO2顆粒使相變化過程趨向於三維模式。適當活化能（Appropriate Activation Energy，□H）之量測顯示ΔΗ值隨著膜厚的增加而增加，與JMAK分析所得之三維成長趨勢結果一致。 本研究亦研究加入Ti及GeN潤濕層對含AIST奈米複合記錄層光碟之短T訊號品質之影響，但目前之實驗結果尚無法獲得理想的品質改善。

In this study, a self-assembly in-situ electrical property measurement system was adopted to study the phase-change kinetics of AgInSbTe (AIST) and AIST-SiO2 nanocomposite thin films. X-Ray diffraction (XRD) showed that the as-deposited amorphous AIST transforms to crystalline Sb2Te phase when heated to a temperature above 200□C. In the constant-heating-rate experiment, the phase transition temperatures were found to increase with the increase of film thickness and heat rate. The calculation of activation energy (Ea) using Kissinger’s analysis indicated that the Ea values of AIST and its nanocomposite layers increase with the decrease of film thickness. This indicated that the sample dimension affects the progress of phase transition. However, in the same thickness condition, the Ea’s increases with the addition of SiO2 in nanocomposite layers, denoting the embedment of SiO2 restrains the grain growth of AIST during recrystallization. Isothermal experiment in conjunction with Johnson-Mehl-Avrami-Kolomogrov (JMAK) analysis revealed that the phase transition of AIST occurs in a mode in between two-dimensional to three-dimensional manner. As to the AIST-SiO2 nanocomposite layers, the phase change mode becomes three-dimensional when the SiO2 content exceeds 15 wt.% and the film thickness is greater than 50 nm. This is ascribed to the numerous heterogeneous nucleation sites provided by the embedment of SiO2 so that the grain growth mode of AIST becomes three-dimensional. This is in good agreement with the measurement of appropriate activation energy (□H) which shows that the values of □H increase with the increasing film thickness. This work also reports the improvement of short T signals of optical disk containing AIST-SiO2 nanocomposite recording layer by addition the Ti and GeN wetting layers. Unfortunately, no substantial improvement on the quality of short T signals was found.