Electric Field Induced Carbon Nanostructures for Electronics and High Surface Areaapplications
- PDF / 3,419,825 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 26 Downloads / 213 Views
Q11.11.1
ELECTRIC FIELD INDUCED CARBON NANOSTRUCTURES FOR ELECTRONICS AND HIGH SURFACE AREA APPLICATIONS Chao Hsun Lin1,2, Shu Hsing Lee1,2, Chih Ming Hsu2, Ming Her Tsai1 and Cheng Tzu Kuo1 1 Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan 2 Photoetching Lab., Materials Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan ABSTRACT Strong influence of the applied or self-induced (i.e. self-biasing) electric field on the alignment, orientation and structures was found in the carbon nano-structure deposition process. This study applied microwave-plasma electron-cyclotron-resonance CVD (ECR-CVD) technique for carbon nano-structure deposition. The deposited structures and properties were characterized with SEM and field emission I-V measurements. The result shows that a negative dc bias applied on the substrate is a necessary condition. In this condition, all carbon nanostructures were well aligned and perpendicular to the substrate surfaces and independent to the plasma/gas flowing directions. Interestingly, when applied an additional electric field near the substrate surface by a guiding metal plate, the CNT growth direction could be manipulated from perpendicular to nearly parallel to the substrate surface. Moreover, a rattan-like CNT would form when prolonging the deposition time or increasing the plasma carbon concentration. These novel nanostructures are expected to have high potential in energy storage, field emission display, nanoelectronics and gas sensing applications accordingly. INTRODUCTION Since the discovery of carbon nanotube in 1991 by Iijima [1], carbon nanostructures have attracted intensive researches due to their unique properties and applications, such as nanoelectronics [2], field emitters [3], hydrogen storage [4], scanning probe [5] and sensors [6,7]. There are several techniques for synthesizing carbon nanostructures, e.g. arc discharge [1], laser ablation [8], thermal CVD [9], microwave plasma CVD (MPCVD) [10], microwave plasma electron cyclotron resonance CVD (ECR-CVD) [11], and a few deposition mechanisms for forming nanostructures have been proposed [12-16]. However, the role of electric field on the nanostructures formation has not been emphasized. The purposes of this work were to synthesize various carbon nanostructures under different electrical field conditions and to study their morphologies, properties and formation mechanisms. EXPERIMENTAL DETAILS The seaweed-like carbon nanosheets were synthesized on Si wafers without catalyst assistance by ECR-CVD method with CH4 (20 sccm) as the source gases and 20 min deposition time. The Co (10 nm thickness) and Ni (10 nm thickness too) catalyst for CNTs growth was applied on Si wafer by physical vapor deposition (PVD) method, and followed by hydrogen plasma pretreatment for 15 min to become well-distributed nano-sized catalysts. For CNT growth rate and morphology studies, the pretreated catalysts/substrates were deposited with CH4/CO2 (20/2 sccm) plasma gas b
Data Loading...
