Yu-Wei Su

Fabrication of high-performance, low-temperature solution processed amorphous indium oxide thin-film transistors using a volatile nitrate precursor

In this study, we fabricate amorphous indium oxide thin film transistors (TFTs) on a display glass substrate at various annealing temperatures from 200 °C to 300 °C. Using a volatile nitrate precursor, we were able to fabricate TFTs with excellent device performance within this annealing temperature range. Amorphous In2O3 films could be obtained by carefully controlling the film thickness and annealing temperature. TFTs based on amorphous In2O3 channel layers with an average mobility as high as 7.5 cm2 V−1 s−1, an Ion/Ioff ratio of 107, and Von = −5 V could be fabricated at 300 °C annealing temperature in air. The devices prepared at 200 °C still exhibit transistor characteristics with an average mobility of 0.04 cm2 V−1 s−1, an Ion/Ioff ratio of 105, and Von = 0 V. The temperature effects on the device performances are elucidated based on X-ray photoelectron spectroscopy and thermal gravimetric analysis characterization results of precursors and the resulting amorphous In2O3 thin films.

Investigate the Reacting Flux of Chemical Bath Deposition by a Continuous Flow Microreactor

Chemical bath deposition CBD is a commonly used and inexpensive technique to deposit a variety of semiconductor and oxide thin films for a variety of different applications. In this work, a continuous flow microreactor was used to better control the reacting flux present during the CBD reaction by offering a better temporal resolution. High quality CdS films at various thicknesses could be obtained by using a flux that avoided the formation of nanoparticles. The chemistry and growth kinetics of CdS CBD were elucidated using this microreactor. The results suggest that HS x7f ions formed during the thiourea hydrolysis

Effects of fluid flow on the growth and assembly of ZnO nanocrystals in a continuous flow microreactor

The assembly of nanocrystals is considered to be one of the most promising approaches to design nano-, microstructures and complex mesoscopic architectures. A variety of strategies to induce nanocrystal assembly have been reported, including directed assembly methods that apply external forces to fabricate assembled structures. In this study, ZnO nanocrystals were synthesized in an aqueous solution using a continuous flow microreactor. The growth mechanism and stability of the ZnO nanocrystals were studied by varying the pH and flow conditions of the aqueous solution. It was found that convective fluid flowing from Dean vortices in a winding microcapillary tube could be used for the assembly of ZnO nanocrystals. The ZnO nanocrystal assemblies formed three-dimensional mesoporous structures of different shapes, including a tactoid and a sphere. The assembly results from a competing interaction between the electrostatic forces caused by the surface charge of the nanocrystals and the collision of the nanocrystals associated with Dean vortices. The dispersion behaviours of the ZnO assembly in some solvents were also studied. MeOH, a strong precipitant, led to the precipitation of the ZnO assembly. This study shows that the external forces from convective fluid flow could be applied to fabricate an assembly of functional metal oxides with complex architectures using a continuous flow microreactor.

The effects of gallium on solution-derived indium oxide-based thin film transistors manufactured on display glass

Metal oxide semiconductor TFTs have been considerably investigated as a promising alternative to hydrogenated amorphous silicon and organic semiconductors. While many multicomponent oxide TFTs have been studied, there are only a few reports of TFTs using amorphous indium gallium oxide channel layers. In this study, the effects of gallium atomic ratio on the performance of solution-derived indium oxide-based TFTs on display glass were investigated for the first time. The morphological, optical, and electrical properties of IGO channel layers with different gallium atomic ratios were characterized. IGO TFTs with various chemical compositions were compared and interpreted based on the analysis of In3d, Ga2p, and O1s XPS data. It was found that gallium dopant suppresses the generation of oxygen vacancies, while promoting the formation of oxygen in the oxide lattice without oxygen vacancies by reducing the density of hydroxides. By adjusting the atomic ratio of gallium, we were able to fabricate IGO TFTs on display glass with an average field-effect mobility as high as 6.1 cm2 V−1 s−1, Von = −2 V, and on–off ratio of 107.

Cadmium Sulfide Nanoparticle Synthesis Using Oscillatory Flow Mixing

Microchannel mixers enable faster mixing times compared with batch stir mixing leading to the promise of higher throughput, better yields and less solvent usage for the solution-phase reactive precipitation of inorganic nanoparticles. However, reliance on diffusive transport for subsecond mixing requires channel dimensions in the tens of micrometers. These channel dimensions make diffusive micromixers vulnerable to clogging. In this paper, an oscillatory flow mixing strategy is explored to increase the contact area between reagents within larger microchannels. Forward and reverse oscillatory signals are designed to pump reactants through a 450 μm high serpentine microchannel to increase advection within the flow. Computational fluid dynamics simulations are performed to provide insight into flow behavior and nanoparticle morphology. Quantification of mixing performance is proposed using mixing quality and particle residence time metrics. Experimental validation is pursued through the reactive precipitation of CdS quantum dots using a reverse oscillatory mixing setup. Transmission electron microscopy provides insights into the particle size distribution and particle crystallinity.Copyright

Wetting Properties of Nanostructured Zn x Fe y O4 Thin Films Deposited by a Soft Solution Process

Zn x Fe y O 4 thin films were deposited by a light-enhanced soft-solution deposition process. A deposition rate of 0.13-0.15 μm/min was achieved. This deposition rate is sufficiently high for growing thick films that are needed for microwave applications. Scanning electron microscope and transmission electron microscopy images of deposited films show a platelike morphology with a fibrous texture. The contact angle measurements indicate that the wetting behavior of nanostructured Zn x Fe y O 4 thin films changes from hydrophobic to hydrophilic with increasing film thickness. This observation is attributed to the films surface roughness based on the surface profiling data.