Characterizations of contact and sheet resistances of vertically aligned carbon nanotubeforests with intrinsic bottom contacts

Abstract

Comprehensive studies on the sheet and contact resistances of vertically alignedcarbon nanotube (CNT) forests with as-grown bottom contacts to the metallayer have been conducted. Using microfabrication and four distinct methods:(1) the transfer length method (TLM), (2) the contact chain method, (3) theKelvin method, and (4) the four point probe method, we have designed multipletesting devices to characterize the resistances of CNT-forest-based devices.Experimental results show that devices based on stripe-shaped CNT forests100 µm in heightand 100 µm in width have a sheet resistance of approximately . The corresponding specific contact resistance to the molybdenum layer is roughly5 × 104 Ω µm2. Consistency of the results from the four different methods validates the study. After twomonths of storage of the CNT forest samples in open air, less than 0.9% deviations in theresistance values were observed. We further demonstrated one application of CNT forests as anNH3 gas sensor and measured 0.5 ppm of sensing resolution with a detection response time of1 min.