Hua-Chiang Wen

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An ultrafast terahertz ͑THz͒ source has been employed to study the nonlinear response of semiconductors to near-half-cycle femtosecond pulses in the THz regime. We report nonlinear absorption and self-phase modulation of the THz pulses associated with ultrafast impact ionization processes and the development of an electron cascade on femtosecond time scales(More)
Diffusion-weighted MRI studies generally lose signal intensity to physiological motion, which can adversely affect quantification/diagnosis. Averaging over multiple repetitions, often used to improve image quality, does not eliminate the signal loss. In this article, PCATMIP, a combined principal component analysis and temporal maximum intensity projection(More)
The effects of H 2 flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs) by using the microwave plasma chemical vapor deposition are investigated in this study. A H 2 and CH 4 gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/ Si(100) substrates. The structure and(More)
ZnO is a defect-governed oxide and emits light at both visible and UV regimes. This work employs atomic layer deposition to produce oxide particles on oxygenated carbon nanotubes, and the composites only show emission profiles at short wavelengths. The quenching of defect-related emissions at long wavelengths is verified, owing to carboxyl diffusion into(More)
We investigated in this study structural and nanomechanical properties of zinc oxide (ZnO) thin films deposited onto Langasite sub-strates at 200 °C through radio frequency magnetron sputtering with an radio frequency power at 200 W in an O 2 /Ar gas mixture for different deposition time at 1, 2, and 3 h. Surface morphologies and crystalline structural(More)
In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN) epilayers on c-and a-axis sapphire substrates and then used the nanoscratch technique and atomic force microscopy (AFM) to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies(More)