Un-Jeong Kim

Single-walled carbon nanotube growth on glass

We report the growth of single-walled carbon nanotubes (SWNTs) on glass substrate using water-assisted plasma CVD. Highly pure SWNTs are successfully grown on glass at 550 °C, below the strain point of the glass. The growth behaviour of SWNTs on glass is not only influenced by the growth temperature, but is also highly dependent on the buffer layer. Two different buffer layers are studied: Al2O3 and SiO2. Detailed effects on the grown nanotubes are discussed through Raman spectroscopy. This work suggests that the application area of SWNTs may extend to thin film transistors (TFTs) in micro-electronics for opto-electronics with a flexible choice of substrates.

Strain on field effect transistors with single–walled–carbon nanotube network on flexible substrate

We have systematically analyzed the effect of strain on the electrical properties of flexible field effect transistors with a single-walled carbon nanotube (SWCNT) network on a polyethersulfone substrate. The strain was applied and estimated at the microscopic scale (<1 μm) by using scanning electron microscope (SEM) equipped with indigenously designed special bending jig. Interestingly, the strain estimated at the microscopic scale was found to be significantly different from the strain calculated at the macroscopic scale (centimeter-scale), by a factor of up to 4. Further in-depth analysis using SEM indicated that the significant difference in strain, obtained from two different measurement scales (microscale and macroscale), could be attributed to the formation of cracks and tears in the SWCNT network, or at the junction of SWCNT network and electrode during the strain process. Due to this irreversible morphological change, the electrical properties, such as on current level and field effect mobility, lowered by 14.3% and 4.6%, respectively.