ABSTRACT
Carbon nanotubes (CNTs) offer tremendous promise as emerging materials for sensing applications. However, we still lack a systematic approach for realization of functional nanodevices based on carbon nanotubes. An approach that produces carbon nanotubes with a conventional complementary metal oxide semiconductor (CMOS) technology will address such challenges. A simple methodology for integrating single-walled carbon nanotubes (SWNTs) onto CMOS integrated circuits is presented. The SWNTs are incorporated onto a CMOS chip between electrodes made with available metal layers from the CMOS process. For proof of concept, assembly of SWNTs serving as feedback resistors of a two-stage Miller compensated operational amplifier utilizing dielectrophoretic (DEP) assembly is demonstrated. The measured electrical properties from the integrated SWNTs yield ohmic behavior with a two-terminal resistance of ~37.5 KΩ. The measured small signal ac gain (about −2) from the inverting amplifier confirmed successful integration of CNTs onto the CMOS circuitry. Furthermore, the temperature response of the SWNTs integrated onto CMOS circuitry exhibited a temperature coefficient of resistance (TCR) of −0.4%/°C. Bare SWNTs were reported sensitive to various chemicals, and functionalization of SWNTs with biomolecular complexes further enhances their specificity and sensitivity. After decorating ss-DNA on SWNTs, the sensing response of the gas sensor is enhanced (up to ~300 and ~250% for methanol vapor and isopropanol alcohol vapor, respectively) compared with bare SWNTs. This methodology for integrating SWNTs onto CMOS technology is versatile, high yield, and paves the way to the realization of novel miniature CNT-based sensor systems.
