Use of Focused Ion Beam Milling for Patterned Growth of Carbon Nanotubes
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1089-Y03-09
Use of Focused Ion Beam Milling for Patterned Growth of Carbon Nanotubes Jun Yu, Ying Chen, Hua Chen, and James S Williams Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, The Australian National University, Mills Road, Canberra, ACT 0200, Australia
ABSTRACT Focused ion beam milling was used to create trenches on Si wafer surface as the template and carbon nanotubes (CNTs) only nucleated and grew inside the trenches under a controlled pyrolysis process of iron phthalocyanine at 1000 oC. Using this new template technique, CNTs in various patterns were formed on Si surface without pre-deposition of metal catalysts. The selective growth in the trenches is due to special morphology, surface crystalline structure and capillarity effect. Keywords: carbon nanotube, template, patterned growth, focused ion beam milling
Introduction Patterned growth of CNTs on silica (SiO2) substrates using chemical vapor deposition (CVD) method have been investigated extensively[1-3]. Relatively, it is difficult to grow CNTs on pure Si surfaces using the same approach without a pre-deposition of metal catalysts because metal catalysts (i.e. Fe) readily reacts with Si with the formation of non-catalytic Fe-Si alloys [4]. A few years ago, we found that nanotubes can be formed only on scratched areas of Si wafer surface, which can be achieved simply by mechanically scratching using a diamond pen the smooth Si wafer before the CVD process [5]. The process is simple and efficient, but it is difficult to control the size and shape of the scratches at nanoscale and the mechanical scratching causes severe surface damage affecting future applications. Focused ion beam milling (FIB) can be used to replace the diamond pen for creating nanoscale surface structures served as the template for nanotube selective growth so that the disadvantage of mechanical scratching can be avoided. The patterns created by FIB are easily control in micro or nano scale and the FIB trenches have less damage on silicon wafer, which is important for batch production of nanoscaled devices. In this paper, we report influences of growth conditions on the selective growth of CNTs on the trenches created by using FIB. Although FIB has been used to help catalyst deposition for CNT selective growth[6, 7], FIB has not been used to create a template for nanotube growth previously. FIB is a simple and effective tool to create template on Si wafer to allow selectively grow carbon nanotubes in a patterned manner. The role of Si trenches on the nanotube nucleation is discussed.
Experimental A dual focused ion beam (FIB) system (Orsay Physics-Jeol Camion 6460LVSEM) using Ga ions at ion beam energy of 30keV and a current of 1.5 μA was used for creating patterns on Si substrates. The trench width can be varied from a few nanometers to several hundreds nanometers by adjusting the beam size. The trench depth is normally in the range from 10 to 100 nm depending on the scan speed. Iron phthalocyanine (FePc) was used as the pre
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