Fabrication method of high-quality Ge nanocrystals on patterned Si substrates by local melting point control

藉由具圖案矽基板可控制鍺薄膜局部熔點分佈，熱退火時，因矽基板與鍺薄膜熱膨脹係數差異，鍺薄膜於奈米洞陣列中所承受之壓力隨位置改變而不同，導致鍺薄膜中，熔點為一空間分佈而非定值；利用此特性，控制氧原子於鍺薄膜中分佈，產生氧化蝕刻效應，降低矽基板與鍺奈米粒子接觸面積，減少鍺奈米粒子與矽基板間應力，進而提升其結晶度。 利用電子束熱蒸鍍機台將鍺薄膜沉積於具圖案矽基板上，經適當熱處理，鍺奈米粒子可由鍺薄膜聚集而成，藉由穿透式電子顯微鏡及拉曼頻譜驗證，所製作鍺奈米粒子尺寸超過20奈米，且於特定樣品中，具有遠紅外光發光特性，其發光波長為1157奈米。 非破壞性掃描式近場光學顯微鏡技術亦應用於檢驗樣品特性，此光學顯微鏡具有1.55微米波長的雷射光源，此雷射光波長可穿透樣品中矽及二氧化矽層，但為鍺奈米粒子吸收，故從穿透圖案中，可得知鍺奈米粒子於樣品中之分佈，且其中鍺奈米粒子直徑超過一個微米，遠大於從穿透式電子顯微鏡中觀察得到之奈米粒子尺寸。The local melting point of a Ge thin film can be controlled by a hole-array pattern on the host Si substrate due to the variations in the stress distribution and the surface morphology induced by the pattern. A simple annealing process is developed from this effect to produce Ge NCs with a single-domain-crystal size over 20 nm, confirmed by transmission electron microscopy and Raman spectroscopy, from an electron-gun evaporated Ge thin film on the patterned Si substrate. The effect of dimensions of the hole array is also investigated. Photoluminescence observed around 1157 nm from some of the samples shows the possibility of improving the infrared emission capability by this proposed method. A non-destructive testing method based on near field scanning optical microscopy with a 1.55