奈米鑽石輔助高效能紫外光感測器之設計及性能

Design and Performance of Highly Efficient Ultraviolet NCD-assisted Detectors

劉定彥(Ting-Yen Liu)

指導教授 ： 林啟瑞

國立臺北科技大學/機電學院/機電整合研究所/碩士(2013年)

摘要

奈米晶鑽石(Nanocrystalline diamond, NCD)薄膜擁有許多獨特的物理與化學複合特性，其中平滑的表面形貌更使其在許多元件應用之可行性上甚至超越微米晶鑽石(Microcrystalline diamond, MCD)薄膜。本研究將利用微波電漿束化學氣相沈積(Microwave Plasma Jet Chemical Vapor Deposition, MPJCVD)系統合成NCD薄膜並探討改變工作壓力、甲烷濃度及微波功率的影響，研究中由掃描試電子顯微鏡(Scanning electron microscopy, SEM)、原子力顯微鏡(Atomic force microscopy, AFM)、拉曼光譜儀(Raman spectroscopy)、OES及薄膜表面水滴濕潤角分析發現當降低工作壓力以及提升甲烷濃度將使得MCD薄膜轉變成NCD薄膜，且MPJCVD系統具有激發高密度電漿與產生高活性物種，在低微波功率下保持優異的解離率，合成出低表面粗糙度以及晶粒大小為奈米級之鑽石薄膜。
利用NCD薄膜製出紫外光感測器於光電導之探討，搭配金膜指狀電極製出紫外光感測器後，以500℃退火處理可獲得線性的電流-電壓曲線達到良好的歐姆接觸。另外也探討鑽石薄膜晶粒大小、表面粗糙度、穿透率、量測溫度以及紫外光強度對鑽石薄膜紫外光感測器的影響，發現當晶粒小且平滑之NCD薄膜得到明顯的電流值變化(10-102 times)，並且具備有良好的時間響應以及穩定的再現性，其上升時間與下降時間分別為0.3秒以及0.5秒，已達到紫外光感測器的應用標準，且具有偵測紫外光光源強度之能力。

關鍵字

奈米晶鑽石薄膜 ； 微波電漿束化學氣相沈積系統 ； 紫外光感測器

並列摘要

Nanocrystalline diamond (NCD) films are promising material for wide-spreading applications due to their outstanding chemical, physical characteristics, and highly smooth surface in comparison with microcrystalline diamond (MCD) films. In this study, NCD thin films have been synthesized using Microwave Plasma Jet Chemical vapor Deposition (MPJCVD) system with CH4/H2 as precursor gases. Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Optical electron spectroscopy (OES), Raman spectroscopy, and contact angle measurement techniques were employed to investigate the effects of the deposition pressure, CH4 concentration, and microwave power on the characteristics of the as-deposited diamond films. The analysis showed that low deposition pressure and high CH4 concentration ensure the alteration of the diamond films from MCD to NCD structure. In addition, high density and activity plasma species were obtained under low deposition pressure as a result of the excitation of the focused plasma jet.
The as-deposited NCD thin films were then employed to fabricate diamond-based Ultraviolet (UV) detector. In order to investigate the photoconductivity properties of the fabricated UV detectors, interdigital finger (IDF) Au electrodes were coated onto the NCD films followed by rapid thermal annealing (RTA) procedures. Moreover, the effects of grain size, surface roughness, optical transparence, and measurement temperature on the characterization of the UV detector were investigated. It was found that the Ohmic contact between NCD and Au films were obtained under 500 oC of the annealing temperature. Also, the I-V curve measurements under a rage of UV irradiances (10-4-10-2 W/cm-2) exhibit the significant deference of the dark current and photo current (10-102 times) of the diamond based UV detector could be obtained with smaller grain size and low surface roughness of the NCD films. The time-dependent measurements of photoresponse were applied to study the rise and decay time (0.2 and 0.3 s, respectively) upon switch UV light on and off. All the aforementioned outstanding results indeed open up an avenue for applications of NCD films in UV detector devices.

並列關鍵字

Nanocrystalline diamond ； Microwave Plasma Jet Chemical Vapor Deposition system ； diamond-based Ultraviolet (UV) detector

參考文獻

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