Electrical and thermal characterization techniques for carbon nanotube transistors and networks

Carbon Nanotube (CNT);Graphene;Electrical Thermometry;Hysteresis;Semiconductor;Mobility;Metrology

Estrada, David ; Pop ; Eric

关键词: Carbon Nanotube (CNT);    Graphene;    Electrical Thermometry;    Hysteresis;    Semiconductor;    Mobility;    Metrology;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/17417/David_Estrada_MS_Thesis_Aug2009_Final.pdf?sequence=2&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In this study, pulsed measurement techniques to suppress hysteresis in carbon nanotube (CNT) field-effect transistor (CNTFET) transfer characteristics are demonstrated. As hysteresis is reduced, both forward and backward gate voltage sweeps move toward a common, unique central transfer characteristic that reveals the “true” device mobility. Time constants associated with environmental charge trapping, atvarious ambient temperatures from 80 to 453 K are extracted. Hysteresis dependence ofpulsed measurements is compared under air, high-temperature, and vacuum conditions.Using such measurements we investigate the error on carrier mobility associated withmobility extractions from forward and backward DC gate voltage sweeps. A pulsedelectrical breakdown technique to increase the ION/IOFF ratio of carbon nanotube randomnetwork transistors is also demonstrated. The ratio is increased by three orders ofmagnitude, with minimal reduction in ION (< 50%). It is shown that adsorbed water ratherthan oxygen promotes nanotube breakdown. Finally, the design of an electricalthermometry platform for measuring the thermal properties of nanoscale films ispresented, with possible application to single-walled CNT random networks and perfectly aligned arrays. The platform is freely suspended to confine heat flow to one dimension, leading to challenging stress patterns in the constituent SiO2 membrane. Using sputtered SiO2 reduces stress by a factor of 20 and results in a “flatter,” more robust membrane for thermal measurements. Methods of incorporating CNT networks in the device fabrication process are discussed. As a calibration step, the thermal conductivity for a 320 nm freestanding thin film of RF sputtered SiO2 is found to be 0.45 Wm^-1K^-1 at 300 K, inagreement with previous measurements of thin SiO2 films on bulk Si.