Jia-Yaw Chang

Oriented assembly of Au nanorods using biorecognition system

The design and formation of a linear assembly of gold nanorods using a biomolecular recognition system are described. Anti-mouse IgG was immobilized on the {111} end faces of gold nanorods through a thioctic acid containing a terminal carboxyl group. The biofunctionalized nanorods can be assembled with the desired length using mouse IgG for biorecognition and binding. The gold nanorods can be assembled to extended nanorod chains, which can be as long as 3 microm. These assembled nanostructures may be used as the precursors for future nanodevices.

Nanometer-scale conversion of Si3N4 to SiOx

It has been found that atomic force microscope (AFM) induced local oxidation is an effective way for converting thin (<5 nm) Si3N4 films to SiOx. The threshold voltage for the 4.2 nm film is as low as 5 V and the initial growth rate is on the order of 103 nm/s at 10 V. Micro-Auger analysis of the selectively oxidized region revealed the formation of SiOx. Due to the large chemical selectivity in various etchants and great thermal oxidation rate difference between Si3N4, SiO2, and Si, AFM patterning of Si3N4 films can be a promising method for fabricating nanoscale structures.

Opening and thinning of multiwall carbon nanotubes in supercritical water

Supercritical water (SCW) in the presence and absence of oxygen is used for the first time for the opening and thinning of multiwall carbon nanotubes (MWNTs). The influence of variation of pressure, temperature, and time on the opening and thinning of MWNTs is examined. In SCW, opening and thinning of MWNTs is observed both in the presence and absence of oxygen. In addition, the presence of oxygen (∼2 mmol) shows improved thinning of MWNTs with the collapsed outer graphene layers tending towards the inner layers. The morphology of MWNTs are critically analyzed using transmission electron micrographs (TEM) and Raman spectra.

Morphological variation of multiwall carbon nanotubesin supercritical water oxidation

Multiwall carbon nanotubes (MWNTs) with different morphology were prepared using supercritical water (SCW) oxidation and investigated by transmission electron microscope (TEM) and electron energy-loss spectroscopy (EELS). TEM results indicate that the peeling and sharpening of MWNTs are influenced by the etching process in SCW oxidation, of which oxidation time and amount of oxygen used is crucial. A simplified etching model is proposed, which indicates that the difference of mean etching rate between two adjoining blocks causes the morphological variation of MWNTs. The EELS results show change in characteristic energy-loss peaks as a function of total shell numbers along longitudinal axis of individual peeled tube.

Supercritical carbon dioxide-assisted oxidative degradation and removal of polymer residue after reactive ion etching of photoresist

A green cleaning method involving oxidative degradation in supercritical carbon dioxide (scCO2) to remove the polymer residue from chlorine reactive ion etching (RIE) and ashing of photoresist was developed. Benzoyl peroxide dissolved in pentane-2,4-dione was used as an oxidizing reagent to degrade the polymer residue. Random chain scission products from oxidative degradation were removed by scCO2. Surface characterization and microscopic examination were conducted to investigate the polymer residue. The results indicate that oxidative degradation by benzoyl peroxide in scCO2 provides an effective alternative route to remove post-RIE polymer residue in semiconductor devices.

Transportation of silver nanopaticles in nanochannels of carbon nanotubes with supercritical water

Supercritical water (SCW) as a highly destructive environment has been utilized to open multiwall carbon nanotubes (MWNTs) and to break silver aggregates into nanoparticles (diameter 2-20 nm). Water was drawn into open-ended MWNTs by capillary suction, pulling Ag nanoparticles into the MWNTs. The Ag nanoparticles (solid), presumably transported in the nanochannels of MWNTs by the fluidity of SCW, stacked, and fused to form nanorods, suggesting SCW associated with MWNTs (hollow interior) might be exploited as a nanoreactor.