氫氣電漿前處理對於合成奈米碳管之影響

Abstract

本實驗使用6吋矽晶圓 (100) 型，使用標準RCA 製程清洗，除去晶圓上之塵粒和化學污染。鎳(Ni) 觸媒厚度 (1､5､7 nm)，以800 watt微波功率沉積緩衝層氮化鈦(TiN)､氮化鉭(TaN)，並以微波電漿化學氣相沉積 (MP-CVD) 系統進行前處理。 合成奈米碳管時，鎳觸媒使用500､600℃ 及不同的氫氣量 (100､200､300sccm) 作前處理 (10 min)。嘗試在不同溫度､不同氣體流量，以及不同觸媒層厚度､不同緩衝層的參數下，藉由此全面性比較，以尋求前處理後，觸媒顆粒性質對奈米碳管成長的影響。 前處理後，利用掃描式電子顯微鏡 (SEM) 觀測前處理後觸媒層表面形貌，使用原子力顯微鏡 (AFM) 進行觸媒粗糙度分析，高解析穿透式電子顯微鏡 (HRTEM ) 進行晶格結構分析。 實驗結果顯示，在無緩衝層的狀態下，即使改變觸媒層厚度，也不易成長出理想的奈米碳管。氮化鉭緩衝層不僅能增加觸媒活性，而且能防止鎳與矽基材產生矽化鎳，適當的氫電漿前處理能夠提升鎳觸媒在氮化鉭 (TaN) 緩衝層上的顆粒化；。鎳觸媒層經氫電漿前處理十分鐘後，能有效提升鎳觸媒顆粒化與合成 CNTs；結果顯示，密集的觸媒顆粒有助於合成 CNTs 的陣列。

The substrates used in the experiments were 6-inch p-type (100) orientated silicon wafers and cleaned using standard RCA cleaning procedures in order to remove chemical impurities and particles.

The Nickel-coated (10,50,70Å), TiN and TaN buffer layers were deposited with a power of 800 Watt at a sputtering pressure of 6.4m Torr. The uniform nanosized catalytic seeds were formed by A 915 MHz micro-wave plasma chemical vapor deposition (MP-CVD) system.

During the deposition of CNTs, the substrates were heated using a graphite heater. The nickel-coated substrates were first pretreated with hydrogen plasma at 550, 600°C for 10 minutes with various hydrogen flow ratio (100,200,300 sccm). The nickel-nanoparticles were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM).

The suitable hydrogen plasma treatment can enhance the nucleation of Ni catalytic seeds on the TaN buffer layer. This result reveal the role of TaN layer not only induce the activity but also prevent Ni atom which were diffused to the silicon substrate.

The catalyst films were pretreated in H2 plasma for 10 min to promote the formation of catalyst particles and growth of CNTs . They showed densely and enhanced the growth of the carbon nanotubes (CNTs) arrays.