Chung-Min Tsai

Indium-doped molybdenum oxide as a new p-type transparent conductive oxide

New p-type transparent conductive oxide materials, MoO3:In single crystal nanowires and amorphous films, are synthesized in this work. Both nanowires and amorphous films exhibit high optical transmittance, 80–88% for 80 nm thick films at 400–800 nm wavelength, and low resistivity (down to 5.98 × 10−4 Ω cm) suitable for photovoltaic device applications. The amorphous films are also deposited on flexible polyimide substrates and exhibit excellent electrical properties even after bending. Besides, p-MoO3:In/i-ZnO/n-AZO devices are fabricated to demonstrate the potential for all-transparent flexible electronic applications.

Solution-processed all-oxide nanostructures for heterojunction solar cells

A low-cost, non-toxic, environmentally friendly, and solution-processed new oxide-based semiconducting material (Sn1−xCoxO2) was developed as an absorption material for all oxide solar cell fabrication in this work. The newly developed n-type cobalt-doped tin oxide (n-Sn1−xCoxO2) nanoparticles and p-type copper oxide (p-Cu2O) nanostructures were successfully synthesized via a low-temperature solution process. Combined with the use of non-vacuum spray and hot-press processes, the n-Sn1−xCoxO2/p-Cu2O heterojunction solar cells exhibit low-cost and large-scale fabrication advantages. The highest power conversion efficiency (PCE) of 1.2% can be obtained from the solar cells with n-Sn0.86Co0.14O2/p-Cu2O, under AM 1.5 illumination, a noteworthy improvement in solution-processed all-oxide-based nanostructures heterojunction solar cells.

Tungsten nanocrystal memory devices improved by supercritical fluid treatment

A supercritical CO2 (SCCO2) fluid technique is proposed to improve electrical characteristics for W nanocrystal nonvolatile memory devices, since the thickness and quality of tunnel oxide are critical issues for the fabrication of nonvolatile memory devices. After SCCO2 treatments, C-V curves are restored to normal, as well as the leakage current of W nanocrystal memory devices are reduced significantly. It reveals that W nanocrystal memory devices could be formed with shorter oxidation time, moreover, dangling bonds and trapping states initially created within an incomplete oxidized film will be efficiently repaired after SCCO2 treatment.

Activation of Carbon Nanotube Emitters by Using Supercritical Carbon Dioxide Fluids with Propyl Alcohol

Carbon nanotubes CNTs as electric field emitters have especially received great attention, due to their high mechanical strength and chemical stability coupled with very high aspect ratios, leading to extremely strong local fields. 1-3 These attractive properties of CNTs make them extraordinary materials for field emission display FED applications. 4 For most electrical applications, the nanotubes need to be produced free of impurities, contamination, and minimized moisture adsorption. The two major sources of contamination in the growth of CNTs, including amorphous carbon and extraneous metal catalyst, can be eliminated by the cautious use of etching gases and by optimizing the catalyst formula, respectively. 5,6 However, few studies have been reported for the efficient drying methods to minimize residual moisture in the nanostructure CNTs. In general, a trace of residual moisture in electronic devices tends to degrade electrical performance and cause electrical instability. As for the field emission characteristics of CNTs, experimental work really focused on the study of the moisture adsoption effect also has been lacking so far. Therefore, in this work the influence of residual moisture on the field emission of CNTs is investigated first. In addition, the application of supercritical carbon dioxide SCCO2 fluids is proposed to activate CNT emitters, minimizing residual moisture uptake with no possible damage to the CNTs. The CO2-based processing is attractive because of its environmental compatibility, as it is nontoxic, nonflammable, and unreactive under most conditions. 7 SCCO2 is similar to liquid CO2 since it also dissolves methanol. Additionally, it possesses gas-like properties of diffusivity and viscosity that allow it to remove solvents from the narrow spaces between micro- and nanotructure surfaces. 8 Also, the extremely low surface tension of SCCO2 can account for its negligible effect i.e., extremely low damage on the morphology and microstructures. 9-11

Low Temperature Electroless Ni–P Catalyst Deposition Enhanced by UV Exposure for Carbon Nanofiber and Nanotube Growth

Electroless Ni-P nanoparticles deposition enhanced by UV exposure was investigated to catalyze the synthesis of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) by thermal chemical vapor deposition at 400°C for interconnect formation that can reduce process complexity. The Ni-P nanoparticles with a size of 6-15 nm were deposited by using a UV-assisted electroless plating on the SiO 2 trench wall at ~28°C for CNF wiring formation. Besides, the Ni-P nanoparticles were selectively deposited at the bottom of the via-hole with a size of 100 nm by using electroless plating at 70°C for CNT-via formation.

Carbon nanotube formation by laser direct writing

This letter presents carbon nanotube (CNT) formation by laser direct writing using 248nm KrF excimer pulsed laser in air at room temperature, which was applied to irradiate amorphous carbon (a-C) assisted by Ni catalysts underneath for the transformation of carbon species into CNTs. The CNTs were synthesized under appropriate combination of laser energy density and a-C thickness. The growth mechanism and key parameters to determine the success of CNT formation were also discussed. The demonstration of the CNT growth by laser direct writing in air at room temperature opens an opportunity of in-position CNT formation at low temperatures.

Ni–Cr alloy to enhance single- and double-walled carbon nanotube synthesis for field-effect transistor fabrication

Single- and double-walled carbon nanotubes were synthesized between predefined Ti∕Ni∕Cr∕Ti multilayer stacks for field-effect transistor fabrication by thermal chemical vapor deposition at 900°C. The Ni nanoprecipitates were induced from Cr matrix because of phase segregation during high temperature process of carbon nanotube growth. The Ni–Cr catalyst was shown to significantly enhance the synthesis of single- and double-walled carbon nanotubes compared to those using pure Ni catalyst, which was demonstrated by both physical and electrical characteristics of the carbon nanotube field-effect transistor fabricated.