Cheng-Che Hsu

Atmospheric pressure plasma jet annealed ZnO films for MgZnO/ZnO heterojunctions

Rf-sputtered ZnO films, annealed by atmospheric pressure plasma jet (APPJ), are characterized and used for MgZnO/ZnO heterostructures. The highly reactive N2 plasma generated by APPJ allows much shorter treatment time compared with conventional thermal anneals. The APPJ treatment can increase the crystallinity of ZnO films and release the compressive residue stresses, verified by XRD and UV‐Vis transmission measurements. In our previous studies, we demonstrate that thermal anneal is the critical step for the formation of two-dimensional electron gases in defective rf-sputtered MgZnO/ZnO heterostructures. This paper reports the experimental results that APPJ treatments can be used for the same purpose with a much shorter processing time. A thirty-second APPJ anneal on ZnO can be used to replace 400 ◦ C×30min furnace-anneal to promote the formation of 2DEGs in MgZnO/ZnO heterostructure. The ultra-short processing time is attributed to the synergy of plasma reactivity and temperature of APPJ. (Some figures may appear in colour only in the online journal)

Modulation of cell attachment and collagen production of anterior cruciate ligament cells via submicron grooves/ridges structures with different cell affinity

This study aimed to investigate the effects of submicron‐grooved topography and surface cell affinity on the attachment, proliferation and collagen synthesis of anterior cruciate ligament (ACL) cells. Two grooved polystyrene (PS) surfaces (equal groove/ridge width of 800u2009nm) with a groove depth of 100 or 700u2009nm were fabricated and modified by oxygen plasma treatment, dopamine deposition and conjugation of RGD‐containing peptides to enhance cell affinity. The elongation and alignment of ACL cells was enhanced by grooved structures with increasing groove depths regardless of surface chemistry. On the other hand, cell spreading and proliferation mainly depended on surface chemistry, in accordance with surface cell affinity: O2 plasmau2009<u2009dopamine depositionu2009<u2009RGD conjugation. The synthesis of type I collagen was the highest by the ACL cells cultured on the 700u2009nm grooved surface conjugated with RGD peptides, indicating that both surface grooved topography and chemistry play a role in modulating collagen production of ACL cells. Furthermore, the type I collagen deposited on the 700u2009nm PS surface was aligned with grooves/ridges. Our results indicated that both ligand presentation and cell alignment are important in the physiological activities of ACL fibroblasts. Such information is critical for design of biomaterials for ACL tissue engineering. Biotechnol. Bioeng. 2013; 110: 327–337.

Vapor-based tri-functional coatings†

The tri-functional coating synthesized via CVD copolymerization is comprised of distinguished anchoring sites of acetylene, maleimide, and ketone that can synergically undergo specific conjugation reactions to render surfaces with distinct biological functions, simultaneously. In addition, these tri-functional coatings can be fabricated in a micro-structured fashion on non-conventional surfaces.

Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. I. Feature scale modeling

The authors developed a cellular based Monte Carlo (MC) feature scale model capable of direct coupling to the dominant plasma species ratios from a reactor scale model in order to simulate the profile evolution of shallow trench isolation etch in chlorine-based plasmas and its variation from the center to the edge of the wafer. Carefully planned experiments along with scanning electron microscopy (SEM) were used to calibrate the MC model, where one to two plasma parameters were systematically varied. Simulated feature profiles were found to agree well with experimental observations, capturing details such as microtrenching, faceting, tapering, and bowing. The particle counts used to achieve these fits agreed well with those estimated from SEM, corroborating the chemistry and physics used in the feature scale model. In addition, the feature scale model uses a novel surface representation that eliminates the artificial flux fluctuations originating from the discrete cells used in the simulation and enables ...

A Foldable Microplasma-Generation Device on a Paper Substrate

We report the fabrication of a plasma-generating device on a paper substrate. This device was fabricated using a screen print process. Plasmas were ignited between two parallel electrodes with a plasma gap of 237 to 710 μm using a dc power source. We demonstrated that a stable helium plasma can be sustained when the substrate is flat, rolled, and folded along various orientations. When the plasma was ignited with a 0.2-μL salt solution droplet with 1.4, 4.6, and 7.8 ng of Li, Na, and K respectively applied to the discharge gap, clear metallic emission lines emanated from the plasma. Our result demonstrates that this paper-based plasma device can be used in analytical applications.

A Flexible Paper-Based Microdischarge Array Device for Maskless Patterning on Nonflat Surfaces

This letter presents a simple and economical paper-based device that is able to generate an array of stable Ar microdischarges. This is a dielectric-barrier-discharge device that exhibits filamentary-type features. The device is sustained by an ac voltage with a 550-V amplitude and 10-kHz frequency. Optical emission spectra show that Ar lines dominate the emission, with a trace amount of CH and C2 emissions. Despite slight damage, the electrode lifetime exceeds 20 min. Results demonstrate that this device is flexible and is able to achieve maskless patterning of hydrophilic patterns on flat and curved glass surfaces.

The bubble to jetting transition mechanism of plasmas in NaNO3 solutions sustained by pulsed power

Plasmas in NaNO3 solutions sustained by pulsed power with Tonxa0=xa010–500xa0µs are studied. With an applied voltage equal to or lower than 100xa0V, the bubble mode is observed. In this mode, bubbles, a few hundred μm in diameter, are formed and detached continuously at the electrode surface because of the buoyant force. An increase in the applied voltage to 125xa0V results in a bubble to jetting transition. When this transition occurs, bubbles with diameters smaller than 100xa0µm are formed and are rapidly jetted away continuously. The examination of various conditions shows that the transition occurs when the power and energy input simultaneously exceed critical values 4.4xa0×xa010−3xa0±xa06xa0×xa010−4xa0J and 45xa0±xa05xa0W, respectively, within Ton. Given the electrode surface area, this critical power is equivalent to a heat flux of 229xa0±xa025xa0MWxa0m−2, which is close to the heat flux required, 223xa0MWxa0m−2, for the occurrence of explosive vaporization reported in the literature. Such an observation strongly supports the hypothesis that the bubble to jetting transition is induced by the electrothermal effect.

Ultra-low-cost and flexible paper-based microplasma generation devices for maskless patterning of poly(ethylene oxide)-like films.

This work presents the use of an ultra-low-cost and flexible paper-based microplasma array to perform maskless patterning of poly(ethylene oxide)-like (PEO-like) thin films with a feature size down to submillimeter scale. In this process, the liquid precursor was directly applied to the paper substrate, gradually vaporized, and dissociated in the microplasma cavity, which leads to plasma polymerization. The FTIR and XPS spectra of the deposited film confirm the PEO-like structures. The protein adsorption test using the absorption of fluorescence-labeled fibrinogen conjugates on the treated surface shows the deposited films possessed the antifouling property with decent pattern transfer fidelity defined by the geometry of the microplasma array.

Numerical Simulation of Downstream Kinetics of an Atmospheric-Pressure Nitrogen Plasma Jet

We report the results of the numerical simulation of an atmospheric-pressure nitrogen plasma jet with the focus on the downstream kinetics. The goal is to assess the effect of ambient air on the spatial profile of reactive species densities of the plasma jet. The modeling results show that oxygen readily enters the jet downstream, and the excited-state nitrogen densities decrease drastically with the interaction of oxygen and the jet. A direct comparison of the spatial profile of the excited-state nitrogen density (N2B3Πg) and the visual appearance of the plasma jet obtained experimentally shows that the model qualitatively captures the change of the jet size when the jet is in contact with ambient air.

Feature profile evolution during shallow trench isolation etch in chlorine-based plasmas. II. Coupling reactor and feature scale models

A two-dimensional numerical fluid model was developed to investigate the effects of reactor design on the radial profiles of plasma species, namely, etch products and positive ions, during shallow trench isolation etching in Cl2∕O2∕Ar inductively coupled plasmas. Specifically, the dual-coil and dual gas-feed designs of the reactor were examined. The former parameter was determined to be effective in tailoring the radial ion flux profile at pressures higher than 20mT, while the latter parameter was shown to alter the etch product transport in the convection-dominant flow regime. Coupling of the reactor scale model to a feature scale model allowed investigation of minor center to edge variations in the etched feature profile. This hybrid model suggests that the general radial decrease in the etch depth seen from a set of design of experiments is caused by an inherent decrease in the spatial distribution of chlorine radicals. In addition, the increase in the silicon sidewall angle from center to edge can be qualitatively explained by the radial profile of the etch products.A two-dimensional numerical fluid model was developed to investigate the effects of reactor design on the radial profiles of plasma species, namely, etch products and positive ions, during shallow trench isolation etching in Cl2∕O2∕Ar inductively coupled plasmas. Specifically, the dual-coil and dual gas-feed designs of the reactor were examined. The former parameter was determined to be effective in tailoring the radial ion flux profile at pressures higher than 20mT, while the latter parameter was shown to alter the etch product transport in the convection-dominant flow regime. Coupling of the reactor scale model to a feature scale model allowed investigation of minor center to edge variations in the etched feature profile. This hybrid model suggests that the general radial decrease in the etch depth seen from a set of design of experiments is caused by an inherent decrease in the spatial distribution of chlorine radicals. In addition, the increase in the silicon sidewall angle from center to edge can be ...