摻雜質之類鑽碳電性及光學性質研究

Abstract

本論文主要研究摻雜氮的類鑽碳(N:DLC)電性和光學方面的性質。先用霍爾效應儀量測樣品的電阻率、載子濃度和遷移率，由拉曼(Raman)、光致螢光激發(PL)和傅利葉轉換紅外光譜儀(FTIR)分析樣品結構和鍵結形式，再分別比較溫度、摻氮流量和退火對N:DLC的影響。 電性方面，電性傳輸機制主要是extended states的躍遷和hopping造成電阻率隨溫度上升而下降，雖然摻氮可降低DLC的電阻率、提高載子濃度，但也因摻雜氮之後成為有效施子的效率不高，使得載子濃度略有增加但不顯著，退火則可以大大降低電阻率和提升載子濃度。 經由拉曼光譜可知，摻氮會使N:DLC有石墨化的現象，且退火也會將鑽石結構轉為石墨；由PL實驗分析，發現DLC和N:DLC有相似的發光光譜，強度隨溫度上升而減弱，但退火後因晶格缺陷和失序的情形減少而使發光強度增加；藉由FTIR的透射光譜可知N:DLC中氮和碳的鍵結模式，有sp1的C N (nitrile)，sp2的＞C＝N (imine)，以及sp3 的C－N鍵結。

The electric and optical properties of the effects of nitrogen doing on diamond-like carbon films are studied in this thesis. The resistivity, carrier concentration, and mobility of the samples are measured by Hall effect. Raman, Photoluminescence (PL), and Fourier Transform Infrared (FTIR) spectroscopies were used to analyze the structure and bonding of our samples. We found that the electrical conduction of nitrogen doped diamond like carbon is due to the thermal activation of carriers into the extended states at high temperature and hopping conduction at low temperature. The resistivity and carrier concentration could be changed by doping with nitrogen but the doping efficiency is low and increasing flow rate of N2 during sample growth does not necessary yield higher electron concentration in the sample. The effect of annealing has a much better effect in decreasing the resistivity and in increasing the carrier concentration of the samples. Raman measurements show that the fraction of sp2 bonding in the diamond-like carbon increases with nitrogen doping. Annealing of the samples also increases the fraction the sp2 bonding in the diamond-like carbon. Both DLC and N:DLC have similar peaks in the PL spectra and the PL intensity increases after annealing. FTIR of nitrogen incorporated DLC films reveals the existence of numerous bands by tracing the intensity of the samples with different nitrogen doping concentration we could clearly identify the which of the absorption peaks are related to the bonding between carbon and nitrogen.