以奈米碳點異質結構於高效率有機染劑光降解之應用

摘要半導體異質奈米結構在光電、能源、生醫與環保等領域皆展現極為優異的材料特性，本研究所採用震盪與鍛燒兩步驟製程以製備功能性奈米碳點，具備製程快速、簡單、光敏感度高、耐光、耐酸鹼等優點外，其產率更是高達48.6%，遠超越傳統鍛燒製程之產率[9-11]。奈米碳點是由碳氧雙鍵、碳氧鍵、羥基等官能基修飾表面的石墨晶體結構，其平均粒徑約5.68 nm、能隙約3.45 eV且其螢光特性優越並具備高光敏感性，藉由滴塗法製程奈米碳點/矽奈米線展現出超親水 (接觸角<4o)，並證明材料與染劑之間的接觸面積非常大，利於提升光觸媒材料的光降解效率，並由其特殊的能帶結構使奈米碳點/矽奈米線於可見光 (580 nm)與紫外光 (420 nm)在沒有添加其他化學藥劑的情況下具備優越寬頻的光觸媒效果：在580 nm光源照射下120分鐘降解率52.4%，420 nm光源照射下120分鐘降解率46.9%。奈米碳點薄膜/矽基板光偵測器亦是由滴塗法將奈米碳點均勻沉積於矽基板上後進行鍛燒處理製程，可精準控制薄膜厚度於30~95 nm之間，其穿透率高達95%，並於XRD分析中驗證其(100)石墨晶體結構的特徵峰，顯示奈米碳點薄膜是由官能基表面修飾的奈米石墨晶體堆積而成，同時具備厚度可控制與高光穿透性的薄膜。本研究並針對薄膜與不同摻雜的矽基板異質接面造成的電性與載子濃度變化進行探討，設計出奈米碳點薄膜/矽基板異質結構的異質接面。以不同厚度奈米碳薄膜光偵測結果確認光偵測器的最佳條件為40 nm的奈米碳點薄膜並且同時確認奈米碳點薄膜具備主動層的可能性，其最佳條件於580 nm的光源下其光電流增益可高達2.86 mA。證實奈米碳點應用於奈米碳點/ 矽材料的複合結構的可靠性。

關鍵字

半導體；異質結構；奈米碳點；矽奈米線；光觸媒；光偵測器

並列摘要

Abstract The semiconductor heterostructures exhibited extremely excellent properties such as photovoltaics, energy materials, biomedicine, and environmental protection etc. In this study, a fast and simple two-step process of sonication and post-thermal was used to prepare functional carbon-nanodots. With the advantages of high photo-sensitivity, photo-resistance, and high yield 48.6 %, it was far exceeding the traditional thermal process [9-11]. Carbon-nanodot were composed of graphitic crystal structures which was modified with functional groups such as Carbonyl group, Hydroxy group, etc. The average particle size of Carbon-nanodot was about 5.68 nm, and the energy gap was about 3.45 eV ,and it possessed superior fluorescent characteristics and sensitivity. Heterostructure of carbon-nanodot/silicon nanowire which was prepared by drop-coating method provided super hydrophilic property (with contact angle < 4o), and demonstrated that contact area between dye solution and photocatalyst were large, it was beneficial to enhance the photodegradation efficiency of photocatalyst. Due the its special energy band structure carbon-nanodot/silicon nanowires provided excellent broadband photocatalyst effect in visible light (580 nm) and ultraviolet light (420 nm) without adding other chemical agents : The photodegradation rate was 52.4% in 120 minutes at 580 nm light source and 46.9 % in 120 minutes at 420 nm light source. Carbon-nanodot film /silicon wafer heterostructure photodetector also fabricated by drop-coating method and post-thermal method. Which could accurately control the thickness of the carbon-nanodot thin film between 30 to 95 nm. It also showed that high transmittance (95%) on glass substate. The crystal structure of graphite (100) was also discussed with XRD analysis, it demonstrated that carbon-nanodot possessed high-crystalline carbon structures and function groups. In addition, the electrical properties and differences of carrier concetration caused by the heterostructure between carbon-nanodot and different doped silicon wafer was discussed in this research. The carbon-nanodot heterostructure photodetector was designed by its band structure. The photodetection test showed the optimal condition of carbon-nanodot film was 40 nm, and also confirmed that carbon-nanodot film had the possibility of active layer. The optimal condition caused that the photocurrent gain can be 2.86 mA under the 580 nm light source. The reliability of the heterostructure of carbon-nanodot /silicon materials was confirmed.