Owing to their sensitive chemical-to-electrical transducer capabilities and compatibility with deviee miniaturization and low operation temperature, single-walled carbon nanotube field-effect transistor (SWCNT-FET) represents an attractive platform to provide solutions in the gas sensing field. In this work, SWCNT-FETs were fabricated and their performances for detecting low NO2 concentrations were evaluated. Outstanding deviees response was obtained, which was shown to follow a 2 power law dependence between the response and the NOz concentration in the range of 100 ppb up to 10 ppm. Such ultra-high response is attributed to an enhancement of the Schottky barrier modulation triggered by the specifie deviee configuration. The deviee configuration is based on individual semiconducting SWCNTs directly connecting the interdigitated Source-Drain electrodes. To the best of our knowledge, the results reported here correspond to the most sensitive deviee among the deviees based on non-functionalized carbon materials and operational at low temperatures. Furthermore, the obtained results are supported by a deep SWCNT characterization, and the changes in Schottky barrier's height induced by the,presence of gas molecules are estimated and discussed. Overall, the present reported results provide useful information for establishing a robust process for the fabrication of the next generation of CNT based gas-sensing devices.
Catalyst engineering is a key point for selective growth of single-walled carbon nanotubes (SWCNT) with chemical vapor deposition (CVD). Here, we develop a new general synthesis method able to produce a wide range of homogenous bimetallic catalyst nanoparticles with controlled stoichiometry and sizes. The basics of this catalyst synthesis is to use preformed stoichiometric bimetallic Prussian blue analog (PBA) nanoparticles. Catalyst nanoparticles are then prepared in-situ in a hot filament CVD reactor with subsequent high temperature treatment in reducing atmosphere prior to SWCNT growth. The capabilities of the synthesis route are demonstrated by testing five PBA systems involving various transition metals. Transmission electron microscopy (TEM), scanning TEM and energy dispersive X-ray spectroscopy (STEM-EDX), and in-situ X-ray photoelectron spectroscopy (XPS) measurements are used to finely follow the size and composition of the catalyst at each step of the process. Each system yields small size catalysts with a narrow distribution, which act as efficient catalysts for SWCNT growth with a good yield and small diameter distribution. The versatility of the PBA family paves a new way for a fine tuning of the catalyst properties monitored by the metal involved in the PBA, and for opening routes to more selective SWCNT synthesis.
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