Electrophoretic deposition of multiwalled carbon nanotubes onto porous silicon with enhanced NO2-sensing characteristics

Abstract The multiwalled carbon nanotubes were successfully electrophoresis deposited onto porous silicon to form a multiwalled carbon nanotubes/porous silicon composite and were then fabricated into chemiresistive gas sensors. The morphology, microstructure and NO2-sensing characteristics of the composite were investigated by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and gas-sensing test. The results indicated that all the carbon nanotubes/porous silicon sensors showed typical p-type semiconductor behavior at room temperature (∼25°C) of the optimal working temperature. The carbon nanotubes/porous silicon sensor under the electrophoresis time of 5 min yielded the best NO2-sensing characteristics, including a high sensor response (∼8.5), fast response-recovery time (∼37 s and ∼34 s), good repeatability and selectivity toward 1 ppm NO2. The heterostructure effect as well as the high specific surface area and the unblocked porous structure was considered essential for the gas-sensing performance.