鑲埋矽基量子點之鑽石(111)同質磊晶成長

Abstract

本論文製備矽基量子點於鑲埋(111)面同質磊晶鑽石膜，並分析與探討相關之性質。第一部份以磁控濺鍍製備(Magnetron Sputtering)的SiOx薄膜於(111)單晶鑽石基板，並分析薄膜組成及其經過電漿處理後的形貌、性質變化。第二部份為濺鍍的SiOx薄膜在鑽石膜成長時，經由電漿蝕刻並被鑽石覆蓋而變成矽基量子點。除了探討CVD鑽石膜性質，也探討矽基量子點之光致發光(PL)發光性質。 SiOx薄膜是以Ar電漿濺鍍Si靶材而形成，利用X光能量散射光譜(EDS)、拉曼光譜(Raman)與X光繞射(XRD)分析SiOx薄膜的性質與成分。(111)單晶鑽石基板上的SiOx薄膜經過進行不同時間之氫電漿處理後，由掃描式電子顯微鏡(SEM)的影像觀察顯示SiOx薄膜會被蝕刻成顆粒狀，且隨蝕刻時間越長顆粒尺寸越小；在拉曼光譜上，隨著氫電漿處理時間越長，非晶矽480cm-1波峰強度越弱。 在SiOx薄膜上以化學氣相沉積(CVD)鑽石膜之後，以穿透式電子顯微鏡(TEM)及掃描穿透式電子顯微鏡(STEM)得知SiOx埋在鑽石膜底下，尺寸約4 nm大小，形成非晶量子點，而鑽石膜以側向接合成長，形成同質磊晶。鑲埋矽基量子點使CVD鑽石膜品質略微下降，對鑽石膜的應力調整具有效果，但不顯著。針對量子點的成分比例，以~ 1 Å電子束進行STEM-EDS分析出成分為SiO0.6。PL測量鑲埋於鑽石膜中之SiOx量子點的發光性質，發現在510-536 nm波長出現發光峰；量子點尺寸較大，則PL發光波長較長，這種尺寸對PL發光波長的變化符合量子侷限效應(Quantum Confinement Effect)。

This thesis focuses on growth of (111) homoepitaxial diamond films with embedded silicon-based quantum dots (QDs) and analyses of related properties. The first part of this thesis deals with SiOx film deposited by magnetron sputtering, and the evolution of SiOx after treatment of hydrogen plasma. The second part emphasizes on Si-based QDs, which are transformed from SiOx after diamond film growth. Properties of CVD diamond film and silicon-based QDs are analyzed and discussed as well. First of all, sputtered SiOx films were obtained after sputtering a Si target with Ar plasma in high vacuum. The films were characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, photoluminescence (PL), and X-ray diffraction analysis (XRD) for crystallinity and chemical compositions. The SiOx films deposited on the surface of single crystalline diamond (111) substrate exhibited particle-like morphology after hydrogen plasma treatment. The particle size decrease with increasing the duration of hydrogen plasma treatment. After growth of CVD diamond films, the amorphous SiOx quantum dots (QDs) around 4nm in size were formed and embedded in diamond as shown by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). Also, TEM and XRD results show that the deposited diamond films in homoepitaxy are grown through epitaxial lateral overgrowth (ELO) on SiOx QDs. The quality of diamond films was slightly decreased by embedded QDs; however, the QDs have a small but significant effect on relaxation of film stress which may result in formation of cracks in diamond film in thicker films than those grown on substrate without SiOx coating. Sub-angstrom probe STEM-EDS analyses reveal that the embedded QDs have a composition of SiO0.6. PL measurements show that the emission peak from the QDs exhibit blue shift in the wavelength range of 510-536 nm, with the decrease of the QD size due to the quantum confinement effect.