Kuei-Yi Lee

Synthesis of Aligned Carbon Nanofibers at 200°C

Aligned carbon nanofibers (CNFs) were synthesized at a growth temperature as low as 200°C by inductively coupled plasma chemical vapor deposition with hydrogen and methane gas mixtures. The synthesized CNFs were aligned perpendicular to the substrate and capped with a single-crystal Ni nanoparticle. The results indicate that the hydrogen species play a significant role in both the reduction of carbonaceous particles deposits and the formation of catalyst particles by effecting a moderate etching during the inductively coupled chemical vapor deposition.

Synthesis of Vertically Aligned Carbon Nanofiber Films by RF Magnetron Sputtering

Abstract : The aligned carbon nanofibers were synthesized on Si substrates using RF magnetron sputtering with a hot filament. The hot filament was made of tungsten wire and its temperature was up to 2000 degrees C during the deposition. Nitrogen was used as the sputter gas at a relatively low pressure of 2xlO(exp-2) Torr. The sputtering deposition was carried out at a substrate temperature of 700 degrees C. The nanofibers were grown vertically on the substrates. The diameters and the density of the fibers were about 30-45 nm and 10(exp 9) cm(exp-2), respectively.

Local Etching of Insulator-Coated Carbon Nanotubes towards Passivated Nanoprobes

We present a method for local etching of the tip region of insulator-coated carbon nanotubes (CNTs) towards passivated nanoprobes. By reactive ion etching (RIE), a 20-nm-thick SiO2 layer, which was uniformly wrapped around vertically oriented CNTs, was selectively removed from the tip, maintaining the crystallinity of inner CNT. It was found that the length of exposed CNT is controlled via etching time at an etching rate of 16 nm/min. This local etching was achieved by RIE using CF4 as an etchant, and photoresist as a passivation mask.

Development of New Apparatus for Field Emission Measurement.

A field emission measurement profiler, which not only can measure the field emission of the entire film as well as its local points but also can present a two-dimensional map of the current density distribution, is developed. This apparatus is operated under an ultrahigh vacuum condition to measure the field emission distribution of amorphous carbon (a-C) films deposited by a RF magnetron sputtering system. The results show that the film surface consists of strong and weak emission sites. We also obtain the field emission maps of micrometer order from strong and weak emission sites; these can help us understand the mechanism of field emission for improving the procedure for growing films.

Formation of carbon nanofiber films by RF magnetron sputtering method

The carbon nanofiber thin films have been successfully grown by using the unique method of RF magnetron sputtering with hot filament which enables us to control the alignment, diameter, and density of the nanofiber.

Study on Properties Change of a-C Thin Film by N 2 Plasma Treatment

Amorphous carbon (a-C) films have been deposited on Si(100) substrate using RF magnetron system in order to investigate the electron field emission properties. The a-C films were treated by gas plasma at room temperature. Surface morphologices and structural properties of the a-C films before and after plasma treatment were observed by scanning electron microscopy and Raman spectroscope, respectively. Structural properties and surface morphology of the a-C films were changed by plasma treatment. The emission properties can be improved by the plasma treatment according to the contents of nitrogen on the a-C films which is varied by plasma treatment time. Before the plasma treatment, the a-C films are found to have a threshold field of 14 V/m, but the a-C film treated by plasma for 30 min exhibit threshold field as low as 6.5 V/m.