藉由熱化學氣相沉積在矽奈米絲上成長奈米碳管及其場發射

Field Emission of Carbon Nanotubes Grown on Silicon Nanowires Using Thermal Chemical Vapor Deposition

本研究以熱化學氣相沉積法在矽奈米絲上成長奈米碳管。矽奈米絲的製備則是使用一種固相-液相-固相（solid-liquid-solid, SLS）機制，直接從矽基板藉由加熱來成長。甲烷與氬氣被用來正常氣壓、900°C 溫度下成長奈米碳管。本研究使用電子顯微鏡（scanning electron microscope, SEM）與穿透式電子顯微鏡（transmission electron microscopy, TEM）來觀察奈米碳管的表面形態，使用拉曼光譜（RAMAN）分析奈米碳管的結構性質。從SEM 及TEM 的研究結果清楚顯示，在矽奈米絲上成長的奈米碳管呈現多壁結構狀態，且奈米碳管管壁上存在有許多缺陷狀態及許多石墨奈米顆粒。從拉曼光譜數據可以發現，在矽奈米絲上所成長的奈米碳管，比在平面矽基板上成長的奈米碳管有較大的結晶缺陷與較多的非晶質碳存在。電性量測結果則呈現出在矽奈米絲上成長的奈米碳管會有較佳的場發射結果，且符合Fowler-Nordheim 場發射特徵。In this study, carbon nanotubes (CNTs) were synthesized on Si nanowires (SiNWs) using thermal chemical vapor deposition. SiNWs were directly synthesized onto Si substrates through a solid-liquid-solid (SLS) phase growth mechanism at elevated temperatures. The growth temperature for CNT was 900 °C at an ambient pressure. Methane and argon gases were used for CNT synthesis. In this study, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images were used to observe the surface morphology and sidewall structure, and Raman spectroscopy was employed to investigate the structure of CNTs. The carbon nanotubes grown on SiNWs demonstrated a multiwalled structure with defective graphite sheets in the wall. Raman spectra determined the SiNW carbon nanotubes had poor crystallinity, or more amorphous carbon, than those grown on plain Si substrate. Compared with CNTs grown on flat silicon substrates, CNTs grown on SiNWs exhibit superior field emission characteristics. The Fowler-Nordheim plot displayed a good linear fit, indicating the emission current of carbon nanotubes follows a Fowler-Nordheim behavior.