Byeong-Joo Lee

Fabrication and electrical properties of single wall carbon nanotube channel and graphene electrode based transistors arrays

A transistor structure composed of an individual single-walled carbon nanotube (SWNT) channel with a graphene electrode was demonstrated. The integrated arrays of transistor devices were prepared by transferring patterned graphene electrode patterns on top of the aligned SWNT along one direction. Both single and multi layer graphene were used for the electrode materials; typical p-type transistor and Schottky diode behavior were observed, respectively. Based on our fabrication method and device performances, several issues are suggested and discussed to improve the device reliability and finally to realize all carbon based future electronic systems.

Direct Growth Of Vertically Aligned Carbon Nanotubes On Cu Foils For Applications In Lithium Ion Batteries

We report direct growth of vertically aligned carbon nanotubes (VCNTs) on Cu foils using thermal chemical vapor deposition and present the feasibility of possible applications as anode materials in lithium ion batteries. The VCNTs were vertically standing on the Cu foils which were covered with catalytic iron and alumina buffer layers. The growth temperature was 725°C and acetylene under atmospheric pressure was used as a hydrocarbon source. The VCNT grown had mean diameter of 5.8 nm and showed electrical ohmic contact to Cu foils. Electrochemical properties of Li ion battery cell using VCNT anode were examined and high capacitance was observed.

Graphene Doping by Ammonia Plasma Surface Treatment

Graphene has attracted much attention due to its remarkable physical properties and potential applications in many fields. In special, the electronic properties of graphene are influenced by the number of layer, stacking sequence, edge state, and doping of foreign elements. Recently, many efforts have been dedicated to alter the electronic properties by doping of various species, such as hydrogen, oxygen, nitrogen, ammonia and etc. Here, we report our recent results of plasma doping on graphene. We prepared mechanically exfoliated graphene, and performed the plasma treatment using ammonia gas for nitrogen doping. The direct-current plasma system was used for plasma ignition. The doping level was estimated from the number of peak shift of G-band in Raman spectra. The upshift of G-band was observed after ammonia plasma treatment, which implies electron doping to graphene.