Hung-Cheng Lin

Highly Sensitive Ammonia Sensor with Organic Vertical Nanojunctions for Noninvasive Detection of Hepatic Injury

We successfully demonstrate the first solid-state sensor to have reliable responses to breath ammonia of rat. For thioacetamide (TAA)-induced hepatopathy rats, we observe that the proposed sensor can detect liver that undergoes acute-moderate hepatopathy with a p-value less than 0.05. The proposed sensor is an organic diode with vertical nanojunctions produced by using low-cost colloidal lithography. Its simple structure and low production cost facilitates the development of point-of-care technology. We also anticipate that the study is a starting point for investigating sophisticated breath-ammonia-related disease models.

Deep ultraviolet laser direct write for patterning sol-gel InGaZnO semiconducting micro/nanowires and improving field-effect mobility

Deep-UV (DUV) laser was used to directly write indium-gallium-zinc-oxide (IGZO) precursor solution and form micro and nanoscale patterns. The directional DUV laser beam avoids the substrate heating and suppresses the diffraction effect. A IGZO precursor solution was also developed to fulfill the requirements for direct photopatterning and for achieving semi-conducting properties with thermal annealing at moderate temperature. The DUV-induced crosslinking of the starting material allows direct write of semi-conducting channels in thin-film transistors but also it improves the field-effect mobility and surface roughness. Material analysis has been carried out by XPS, FTIR, spectroscopic ellipsometry and AFM and the effect of DUV on the final material structure is discussed. The DUV irradiation step results in photolysis and a partial condensation of the inorganic network that freezes the sol-gel layer in a homogeneous distribution, lowering possibilities of thermally induced reorganization at the atomic scale. Laser irradiation allows high-resolution photopatterning and high-enough field-effect mobility, which enables the easy fabrication of oxide nanowires for applications in solar cell, display, flexible electronics, and biomedical sensors.

Porous Organic TFTs for the Applications on Real-Time and Sensitive Gas Sensors

A pentacene-based organic thin-film transistor (OTFT) with a porous active layer is demonstrated for the first time. The porous OTFT exhibits a fast, sensitive, and reversible response to ammonia gas with a detection limit as 500 ppb, whereas the OTFT without porous structure has a slow response and a poor recovery behavior. The sensing mechanism dominated by the dissociation of hydroxyl groups of the polymer dielectric layer is raised and discussed. The proposed device is the first OTFT-based ammonia sensor with reversible response and high sensitivity in low parts-per-million range. It is promising for the development of a diagnostic breath analysis system.

Spontaneous formation of Al rich and Ga rich AlxGa1−xAs/AlyGa1−yAs superlattice and strong enhancement of optical properties

Long range composition ordering and spontaneous formation of Al rich and Ga rich AlxGa1−xAs/AlyGa1−yAs superlattice were demonstrated. This was observed by cross‐sectional transmission electron microscopy (TEM) in a 280 A Al0.4GaAs quantum well laser diode heterostructure with Al0.7GaAs barriers grown on (111)B GaAs substrates. On the contrary, none of above superstructure was observed by TEM on a side‐by‐side grown (100) oriented substrate. More evidence is shown in the (111)B Al0.7GaAs barriers which were disordered due to a high growth temperature and did not show any superstructure. 10 K photoluminescence was shown with 32 meV redshift and a 12‐times peak intensity enhancement in (111)B orientation.

Review of a solution-processed vertical organic transistor as a solid-state vacuum tube

In this paper, we investigate the key issues in raising the on/off current ratio and increasing the output current. A 1 V operated inverter composed of an enhancement-mode space–charge-limited transistor (SCLT) and a depletion-mode SCLT is demonstrated using the self-assembled monolayer modulation process. With a bulk-conduction mechanism, good bias-stress reliability, and good bending durability are obtained. Finally, key scaling-up processes, including nanoimprinting and blade-coated nanospheres, are demonstrated.

Submicron organic thin-film transistors fabricated by film profile engineering method

In this work, we explore and demonstrate the feasibility of a film profile engineering (FPE) concept in fabricating pentacene-based organic thin-film transistors (OTFTs) with submicron channel length. The FPE scheme utilizes a suspended bridge built on the wafer and the specific deposition conditions to form thin films with desirable profiles. In order to form a continuous pentacene channel under the bridge, the background pressure of thermal evaporator is adjusted by pumping down the filling N2 to a specific level. The results show that, by setting the deposition pressure at 3 mtorr, functional operations of OTFTs with channel length ranging from 0.4 to 0.6 μm are obtained.

Blade-coated sol-gel indium-gallium-zinc-oxide for inverted polymer solar cell

The inverted organic solar cell was fabricated by using sol-gel indium-gallium-zinc-oxide (IGZO) as the electron-transport layer. The IGZO precursor solution was deposited by blade coating with simultaneous substrate heating at 120 °C from the bottom and hot wind from above. Uniform IGZO film of around 30 nm was formed after annealing at 400 °C. Using the blend of low band-gap polymer poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b’)dithiophene)-2,6-diyl-alt- (4-(2-ethylhexanoyl)-thieno [3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-C-T) and [6,6]-Phenyl C71 butyric acid methyl ester ([70]PCBM) as the active layer for the inverted organic solar cell, an efficiency of 6.2% was achieved with a blade speed of 180 mm/s for the IGZO. The efficiency of the inverted organic solar cells was found to depend on the coating speed of the IGZO films, which was attributed to the change in the concentration of surface OH groups. Compared to organic solar cells of conventional structure using PBDTTT-C-T: [70]PCBM as active laye...

Vertical organic transistors withstanding high voltage bias

Vertical organic transistors withstanding high voltage bias were realized with an insulating silicon monoxide layer obliquely deposited on both the surface of the base electrode and sidewalls of the vertically oriented cylindrical nanopores. No noticeable insulating layer can be observed on the emitter electrode at the bottom of the cylindrical nanopores. The leakage current between the electrodes was suppressed and an operating voltage as high as 15 V was obtained. An on/off current ratio of 103–104 and an output current density of 5–10 mA/cm2 were achieved.

Effect of Ge incorporation on the performance of p-channel polycrystalline Si1−xGex thin-film transistors

In this study, p-channel polycrystalline silicon-germanium thin-film transistors (poly-Si1−xGex TFTs) with different Ge contents in the channel layer were fabricated and characterized. A novel device process was developed to fabricate the test samples. The device structure utilized the in situ boron-doped poly-Si0.79Ge0.21 with an extremely low resistivity (below 2 mΩ cm) as the source/drain and the undoped poly-Si (or Si1−xGex) as the channel layer. It is observed that the addition of Ge atoms in the channel would significantly increase the amount of trap density at grain boundaries thus degrading the device performance. Based on these results, we recommend the use of poly-Si1−xGex source/drain to reduce the contact resistance but do not recommend that it is appropriate to replace poly-Si as the channel material of TFTs.