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 HfO/sub 2/ for nano-sensor applications.
Proceedings of the 39th European Solid-State Device Research Conference. ESSDERC 2009, .
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A carbon nanotube (CNT) growth process on HfO/sub 2/ 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 mu m length/ mu m/sup 2/ 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 (S/D) contacts and a H/sub 2/ anneal at 400 degrees C. The transistors exhibit p-FET behavior with an I/sub on//I/sub off/ ratio of 10/sup 5/ and a steep sub-threshold slope of 130 mV/dec. These results are rather surprising, as earlier research in the literature on CNTFETs with Al S/D electrodes showed n-FET behavior. The p-FET behavior is shown to be due to the H/sub 2/ 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 H/sub 2/ anneal, which tends to confirm this explanation.
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