This paper presents a complementary metal oxide semiconductor compatible method for the chemical vapor deposition of singlewalled carbon nanotubes ͑SWNTs͒. The method uses Ge implantation into a SiO 2 layer to create Ge nanocrystals, which are then used to produce SWNTs. The results of atomic force microscopy and scanning electron microscopy analyses indicate that Ge implantation provides good control of particle size and delivers a well-controlled SWNT growth process. The SWNT area density of 4.1 Ϯ 1.2 m in length/m 2 obtained from the Ge nanocrystals is comparable to that obtained from metal-catalyst-based methods used to fabricate SWNT field-effect transistors. A carbon implantation after Ge nanocrystal formation significantly enhances the process operating window for the growth of the SWNTs and increases the area density.
This work examines the recent developments in non-traditional catalyst-assisted chemical vapour deposition of carbon nanotubes (CNTs) with a view to determining the essential role of the catalyst in nanotube growth. A brief overview of the techniques reliant on the structural reorganization of carbon to form CNTs is provided. Additionally, CNT synthesis methods based upon ceramic, noble metal, and semiconducting nanoparticle catalysts are presented. Experimental evidence is provided for CNT growth using noble metal and semiconducting nanoparticle catalysts. A model for CNT growth consistent with the experimental results is proposed, in which the structural reorganization of carbon to form CNTs is paramount.
Carbon nanotube (CNT) growth on HfO 2 is reported for the first time. The process uses a combination of Ge and Fe nanoparticles and achieves an increase in CNT density from 0.15 to 6.2 mm length/mm 2 compared with Fe nanoparticles alone. The synthesized CNTs are assessed by the fabrication of back-gate CNT field-effect transistors with Al source/drain contacts for nano-sensor applications. The devices exhibit excellent p-type behavior with an I on =I off ratio of 10 5 and a steep sub-threshold slope of 130 mV/dec. #
A technique to synthesize high-quality single walled carbon nanotubes (SWNTs) using chemical vapour deposition (CVD) on Ge Stranski-Krastanow dots has been developed. From transmission electron microscopy and Raman measurements, the grown carbon nanotubes (CNTs) are identified as SWNTs with diameters ranging from 1.6 to 2.1 nm. Extensive scanning electron microscopy and atomic force characterisation of the effect of each stage in the growth process is presented. Our hypothesis is that pre-treatment stages lead to the formation of Ge nanoparticles, which act as seeds for CNT growth. This technique demonstrates the ability to synthesize high-quality SWNTs without the need for a metal catalyst, using processes and equipment standard to a silicon foundry.
A detailed study of the electrical transport properties of Pd contacted carbon nanotube (CNT)/Si heterojunctions is presented. The CNT with a diameter ranging from 1.2 to 2.0 nm on n-type Si substrates showed rectifying behavior with the ideality factor of 1.1-2.2 and turn on voltage of 0.05-0.34 V. The current-voltage characteristics of the CNT/n + -Si diodes were investigated in the temperature range from 50 to 300 K. The transition from thermionic emission to tunneling process was seen in the forward current around 150 K and the Schottky barrier height at Pd/CNT interface is estimated to be 0.3-0.5 eV.
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