Dexin Wu

Controllable preparation of patterns of aligned carbon nanotubes on metals and metal-coated silicon substrates

Patterns and alignment of carbon nanotubes (CNTs) are particularly important for fabricating functional devices such as field emitters, scanning probes, sensors, and nanoelectronics. In this paper, the effects of various metal substrates on CNT growth are studied. Depending on the different growth mechanisms associated with the various substrate surfaces, two- or three-dimensional micropatterns of aligned carbon nanotubes have been prepared via pyrolysis of iron(II) phthalocyanine. Patterns created on silicon substrates were obtained by photolithographic techniques. The prepared CNT patterns have resolutions down to the micrometer scale. Possible growth mechanisms of aligned carbon nanotubes on different metal surfaces are also discussed.

Study of AlN dielectric film on graphene by Raman microscopy

Dielectric film on graphene severely affects the performance of graphene field-effect transistors (GFETs). The authors investigated AlN dielectric film on graphene by Raman microscopy. AlN deposition led to the appearance of disorder-related peaks and to a wider Raman-active peak. The intensities of the disorder-related modes decreased exponentially with an increase in the layer number of graphene, indicating that AlN dielectric film mainly affected the surface of graphene. According to the experimental results, the authors suggested that few-layer graphene might be a better choice than single-layer graphene for the application of GFET.

Noncoplanar organic field-effect transistor based on copper phthalocyanine

We present a method of fabricating noncoplanar channel organic field-effect transistors (OFETs) by a conventional photolithographic technique. Using this method, OFETs with micrometer critical features in slanting configurations and submicrometer critical features in vertical configurations were fabricated. The critical channel length over 1μm was controlled by the patterning technique, while the one of 0.5μm was defined by the thickness of an insulating layer between the drain and source electrodes. Also, we demonstrate that the OFETs containing two different metals as source and drain electrodes, respectively, are easily realized. All the OFETs based on copper phthalocyanine exhibit a high performance.

Orientational self-assembled field-effect transistors based on a single-walled carbon nanotube

We fabricate single-walled carbon nanotube field-effect transistors (SWNT FETs) with a simple, low-cost, high-efficiency, and solution-based orientational self-assembly method. The SWNT was first functionalized with thiol groups, then suspended in an N,N-dimethylformamide solution, and finally self-assembled on predefined gold contact pads by an orientational N2 blow. A relatively high mobility of 9.2×102cm2∕Vs and an on∕off ratio greater than 105 at a bias voltage of −1V have been achieved as a result of directly covalent interaction between end-thiolated SWNT and gold contacts, which favors the fabrication of SWNT FETs as compared to the SWNT FETs bearing the similar geometry but relies on random deposition. Therefore, this orientational self-assembly approach should be a valuable tool in the mass fabrication of high-performance SWNT FETs and SWNT-based molecular-scale electronic devices.