LAUSR

Single-walled carbon nanotubes (SWNTs) are incorporated in different device configurations such as chemiresistors and field-effect transistors (FETs) as a sensing element for the fabrication of highly sensitive and specific biochemical sensors. For this purpose, sorting and aligning of semiconducting SWNTs between the electrodes is advantageous. In this work, silicon shadow mask, fabricated using conventional semiconductor processes and silicon bulk micromachining were used to make metal contacts over SWNTs with a minimum feature of 1 µm gap between the electrodes. The developed silicon shadow mask-based metal contacts patterning process is cost-effective, free from photoresist (PR) chemical coatings and thermal processing. After the detailed investigation, sodium dodecyl sulphate (SDS) an anionic surfactant along with ultrasonication process was found effective for the removal of unclamped and metallic SWNTs, resulting in aligned and clamped semiconducting SWNTs between the electrodes. The presence of aligned semiconducting SWNTs was confirmed using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and Raman spectroscopy techniques. The fabricated devices were tested for nitrogen dioxide (NO2) gas sensing as a test case. The sensitivity enhancement of ~21% to 76% in the 20-80 ppm NO2 concentration range has been observed in the case of aligned semiconducting SWNTs devices as compared to the random network SWNT-based sensors.