Po-Chuan Yang

Risk of betel chewing for oesophageal cancer in Taiwan

Among 104 cases of squamous-cell oesophageal carcinoma patients and 277 controls in Taiwan, after adjusting for cigarette smoking, alcohol consumption, and other confounders, we found that subjects who chewed from 1 to 495 betel-year and more than 495 betel-years (about 20 betel quid per day for 20 years) had 3.6-fold (95% Cl = 1.3–10.1) and 9.2-fold risk (95% Cl = 1.8–46.7), respectively, of developing oesophageal cancer, compared to those who did not chew betel.

Energy-recycling pixel for active-matrix organic light-emitting diode display

The authors report a pixel structure for active-matrix organic light-emitting diode (OLED) displays that has a hydrogenated amorphous silicon solar cell inserted between the driving polycrystalline Si thin-film transistor and the pixel OLED. Such an active-matrix OLED pixel structure not only exhibits a reduced reflection (and thus improved contrast) compared to conventional OLEDs but also is capable of recycling both incident photon energies and internally generated OLED radiation. Such a feature of energy recycling may be of use for portable/mobile electronics, which are particularly power aware.

Plasmonic multilayer nanoparticles enhanced photocurrent in thin film hydrogenated amorphous silicon solar cells

A plasmonic-structure incorporated double layer of Au nanoparticles embedded in the transparent conducting oxide at the back-reflector of the hydrogenated amorphous silicon (a-Si:H) solar cells is demonstrated. These devices exhibit an increase of energy conversion efficiency of 18.4% and short-circuit current density of 9.8% while improving fill-factor and without sacrificing open-circuit voltage. The increase in photocurrent is correlated with the enhanced optical absorption in the cell, with improved optical-path-length by a factor of 7 at the wavelength of 800 nm, due to enhanced diffuse scattering of light through resonant plasmon excitations within Au nanoparticles. In addition to enhanced scattering, applying high-work-function Au nanoparticles can improve the work function match at TCO/a-Si:H interface.

Cytosolic PKM2 stabilizes mutant EGFR protein expression through regulating HSP90-EGFR association.

Secondary mutation of epidermal growth factor receptor (EGFR) resulting in drug resistance is one of the most critical issues in lung cancer therapy. Several drugs are being developed to overcome EGFR tyrosine kinase inhibitor (TKI) resistance. Here, we report that pyruvate kinase M2 (PKM2) stabilized mutant EGFR protein by direct interaction and sustained cell survival signaling in lung cancer cells. PKM2 silencing resulted in markedly reduced mutant EGFR expression in TKI-sensitive or -resistant human lung cancer cells, and in inhibition of tumor growth in their xenografts, concomitant with downregulation of EGFR-related signaling. Mechanistically, PKM2 directly interacted with mutant EGFR and heat-shock protein 90 (HSP90), and thus stabilized EGFR by maintaining its binding with HSP90 and co-chaperones. Stabilization of EGFR relied on dimeric PKM2, and the protein half-life of mutant EGFR decreased when PKM2 was forced into its tetramer form. Clinical levels of PKM2 positively correlated with mutant EGFR expression and with patient outcome. These results reveal a previously undescribed non-glycolysis function of PKM2 in the cytoplasm, which contribute to EGFR-dependent tumorigenesis and provide a novel strategy to overcome drug resistance to EGFR TKIs.

Influence of the absorber layer thickness and rod length on the performance of three-dimensional nanorods thin film hydrogenated amorphous silicon solar cells

Performance of substrate-configured hydrogenated amorphous silicon solar cells based on ZnO nanorod arrays prepared by hydrothermal method has been investigated. The light harvest ability of three-dimensional nanorods solar cells is a compromise between the absorber layer thickness and the nanorods geometry. By optimizing the intrinsic a-Si:H absorber layer thickness from 75 to 250 nm and varying the length of the nanorods from 600 to 1800 nm, the highest energy conversion efficiency of 6.07% is obtained for the nanorods solar cell having thin absorber layer thickness of 200 nm with the rod length of 600 nm. This represents up to 28% enhanced efficiency compared to the conventional flat reference cell with similar absorber layer thickness.

Low Temperature Polycrystalline Silicon TFTs on Polyimide and Glass Substrates

This paper presents results on low temperature poly-silicon thin film transistors (TFTs) prepared by KrF excimer laser annealing of hydrogenated amorphous silicon (a-Si:H) on polyimide and glass substrate. Two step laser annealing is used in dehydrogenation and crystallization of the a-Si:H into poly-Si on polyimide substrate. From the Raman spectrum, it is found that the crystallinity of the poly-Si on the polyimide substrate is better than that on the glass. The fabricated poly-Si TFT on polyimide shows a very good performance with field effect mobility of 370 cm2/V-sec and on/off current ratio > 106.

Improvement of heterojunction silicon solar cell efficiency by Au nanoparticles

The application of metallic nanoparticles on heterjunction (HJ) silicon solar cell was investigated in recent years. In this paper, the gold (Au) nanoparticles (NPs) colloidal solution diluted with different concentration was coated on the surface of crystalline silicon (c-Si) and embedded in p-type amorphous silicon (a-Si) emitter layer and indium tin oxide (ITO) in order to enhance the light trapping of the HJ silicon solar cell. The density of Au NPs is very important to improve the performances of the HJ silicon solar cell. At the optimum process parameters, HJ silicon solar cell improved the power conversion efficiency and the short-circuit current (Jsc) by Au NPs coated on c-Si surface.

Uniform Square Polycrystalline Silicon Fabricated by Employing Periodic Metallic Pads and SiON Absorption Layer for Thin Film Transistors

The poly crystalline silicon with regular square grains is fabricated by employing metallic (Cr/Al) periodic pads as the heat sinks and with underlying silicon oxynitride (SiON) as the heat absorption layer. The maximum lateral growth length of the poly-Si is 1.78 mum by this method. If the metal pads are periodically arranged, the poly-Si can grow to regular square grains following the high power excimer laser annealing. After removing the metallic pads, the low power laser shot transfers the a-Si:H under the original metallic pads to poly-Si without destroying the square grains. The TFTs fabricated by this method achieve a field effect mobility of 450 cm2/Vmiddots and an on/off current ratio exceeding 107. It is found that the TFT with smaller channel width and length results in a better subthreshold swing because it contains fewer grain boundaries and defects.

Poly-Si Thin Fim Transistor with Multiple Nanowire Channels Prepared by Excimer Laser Annealing

Low temperature ( 10) , better subthreshold swing and suppressed kink effect. Figure 1 shows the schematic diagram of this process . First, 50 nm thick intrinsic amorphous Si and 20 nm thick n-type doped amorphous Si layer were deposited by plasma enhanced chemical vapor deposition (PECVD) on oxidized Si substrate. During deposition, the substrate temperature, RF power density and chamber pressure were fixed at 250C, 0.11 W/cm and 0.45 torr. Second, the channel region was defined and samples were sent to furnace to expel hydrogen in the film for 10 minutes at 500 C under nitrogen environment. After annealing by the excimer laser ( KrF, duration time 28ns, 330mJ/cm), multiple nanowires were patterned by electron beam lithography(EBL) and transferred by reactive ion etching (RIE). Then, 100nm thick SiOx was deposited by PECVD at 250 C as a gate insulator. The contact windows for source and drain were opened. The samples were treated by NH3 plasma at 250 C to passivate the grain boundary for 3 hours. Finally, a 150 nm thick aluminum was evaporated on the device to form ohmic contact and gate/source/drain electrodes. Devices are divided into three groups based on their channel number and width as listed in Table I. Figure 2 shows the scanning electron microscope (SEM) picture of the active pattern of E3 device. As the inset shows, each nanowire channel is 40 nm wide, and the distance between neighboring channel is 1 μm. In order to examine the effect of multi-channel, the transfer curves of multiple and single channel devices are compared in Figure 3.It is clear that the multichannel devices exhibit higher ON/OFF current ratio and better subthreshold swing. Fig. 4 displays the output characteristics of E1, E2 and E3 devices. E3 shows a better result. Basically, it is because that more channel areas were exposed in the NH3 plasma and grain boundary defects were passivated. Table II lists the device performance of three groups of poly-Si TFTs. Table I. Device dimension of E1,E2 and E3 poly-Si TFT. Fig. 1. The schematic diagram of poly-Si TFT. Fig. 2.SEM pic the 40 n