Fabrication of nanostructured materials by anodic aluminum oxide templation and study of their electron field emission characteristics

• Main Authors: Te-Ming Chen, 陳德銘
• Other Authors: Fu-Ming Pan
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/36963145762599685401

博士 === 國立交通大學 === 材料科學與工程系所 === 97 === Fabrication of highly ordered nanostructures and investigation on the corresponding field emission characteristics were engaged with nanoporous anodic aluminum oxides (AAO) as templates to regulate the formation arrangement of TiOx nanodot arrays, which were consequently employed as nanomasks to etch TiN layers and the underlying layers to manufacture nanostructures of highly ordered arrangements. Nanostructures developed by AAO templates included TiN nanopillars, Si nanotips, amorphous carbon coated silicon nanotips and IrO2 electrodeposited on Si nanotips for field emitter applications. Sequential deposition of TiN and Al on Si substrates and the successive electrochemical anodization of film stacks fabricated TiOx nanodot arrays to be used as masks to reactive-ion-etch (RIE) the underlying TiN layers. TiN nanopillars arranged in a compliant pattern with AAO had a ridge-shaped edge on the top after the removal of TiOx nanomasks. TiN nanorods with a high aspect ratio and the protruding top edge, of which the field enhancement effect was evaluated by the ellipsoidal cylinder model, showed a low turn-on voltage of 1.6 V/um. An underestimation by around 26% was found for comparison with the enhancement factor derived from the Fowler-Nordheim (F-N) plot. Similar processes were performed for Si nanotips. During the preparation of well-ordered AAO pore channel arrays, underlying TiN layers were anodically oxidized as well in the late stage of the AAO anodization to form titanium oxide nanomasks for Si nanotip fabrication. Well-ordered Si nanotip arrays were produced as a result of the arrangement pattern transfer of AAO pore channel arrays to Si substrates with titanium oxide nanomasks by the plasma etch in the MPCVD system. a-C layers about 5 nm thick and rich in nanocrystalline graphitic carbons according to Raman and Auger electron spectroscopies were in-situ deposited on Si nanotips during the MPCVD process. Nanocrystalline graphitic carbons in the coating and the sharp tip shape improved Si nanotips as excellent field emitters with a large field enhancement factor. In order to obtain thermally stable field emitters with high field-emission efficiency, well dispersed IrO2 nanoparticles with a uniform size distribution below 5 nm were deposited on ordered Si nanotips by bipolar pulse electrodeposition. Small curvature and lower work function assured IrO2/Si nanotips to be superior to bare Si nanotips in field emission performance in terms of the turn-on field and the field enhancement factor.