Uchino, T., Ayre, G.N., Smith, D.C., Hutchison, J.L., de Groot, C.H. and Ashburn, P.
Fe/Ge catalyzed carbon nanotube growth on HfO2 for nanosensor applications.
At IEEE Solid State Devices & Materials (SSDM) Conference, Miyagi, Japan,
07 - 09 Oct 2009.
A carbon nanotube (CNT) growth process on Hf02 is reported for the first time for application in nano-sensors, The process uses a combination of Ge nanoparticles and ferric nitrate dispersion and achieves an increase in CNT density from 0.15 to 6.2 Um length/um2 compared with the use of ferric nitrate dispersion alone. The growth process is validated by the fabrication of back-gate CNT field-effect transistors (CNTFETs) using Al source/drain (SID) contacts and a H2 anneal at 400°C. The transistors exhibit p-FET behavior with an Ion/off ratio of 1E5 and a steep sub-threshold slope of 130 mY/dec. These results are rather surprising, as earlier research in the literature on CNTFETs with AI S/D electrodes showed n-FET behavior. The p-FET behavior is shown to be due to the H2 anneal, which we ascribe to the smaller electron affinity of hydrogenised CNTs. Measurements of the temperature dependence of the drain current show low Schottky barrier height Al S/D contacts after a H2 anneal, which tends to confirm this explanation.
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