A carbon nanotube (CNT) growth process on HfO2 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 μm length/μm2 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 AI source/drain (S/D) contacts and a H2 anneal at 400°C. The transistors exhibit p-FET behavior with an Ion/Ioff ratio of 105 and a steep sub-threshold slope of 130 mV/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 AI S/D contacts after a H2 anneal, which tends to confirm this explanation.