Charge Transfer to LaAlO3/SrTiO3 Interfaces Controlled by Surface Water Adsorption and Proton Hopping

Electronic properties of low dimensional systems are particularly sensitive to surface adsorbates. Clear understanding of such phenomena can lead to highly effective and nondestructive material engineering techniques. In this work, water adsorption at the surface of LaAlO₃/SrTiO₃ heterostructures is systematically studied. The saturation of surface dangling bonds by spontaneous water chemisorptions is found to be a main enabler of the formation of the interface 2D electron gas. In particular, when imbalanced distributions of water based ions, namely protons and hydroxyls, are generated, interface electron doping or depletion becomes surface adsorbates dominant and independent of the LaAlO₃ layer thickness. The investigations also reveal the importance of hydrogen bonding through molecular water layers, which provides an energetically feasible pathway for manipulating the surface‐bond protons and thus the interface electrical characteristics.     

Effect of coupling crater structure and Ag nanoparticles on SERS enhancement

Journal of Materials Science - This study was aimed at enhancing surface plasmon resonance through a combination of Ag nanoparticles (NPs) and an asymmetric crater structure capable of...     

An Efficient Viewport-Dependent 360 VR System Based on Adaptive Tiled Streaming

Recent advances in 360 video streaming technologies have enhanced the immersive experience of video streaming services. Particularly, there is immense potential for the application of 360 video encoding formats to achieve highly immersive virtual reality (VR) systems. However, 360 video streaming requires considerable bandwidth, and its performance depends on several factors. Consequently, the optimization of 360 video bitstreams according to viewport texture is crucial. Therefore, we propose an adaptive solution for VR systems using viewport-dependent tiled 360 video streaming. To increase the degrees of freedom of users, the moving picture experts group (MPEG) recently defined three degrees plus of freedom (3DoF+) and six degrees of freedom (6DoF) to support free user movement within camera-captured scenes. The proposed method supports 6DoF to allow users to move their heads freely. Herein, we propose viewport-dependent tiled 360 video streaming based on users’ head movements. The proposed system generates an adaptive bitstream using tile sets that are selected according to a parameter set of user’s viewport area. This extracted bitstream is then transmitted to the user’s computer. After decoding, the user’s viewport is generated and rendered on VR head-mounted display (HMD). Furthermore, we introduce certain approaches to reduce the motion-to-photon latency. The experimental results demonstrated that, in contrast with non-tiled streaming, the proposed method achieved high-performance 360 video streaming for VR systems, with a 25.89% BD-rate saving for Y-PSNR and 61.16% for decoding time.     

Anion conductive tetra-sulfonium hydroxides poly(fluorenylene ether sulfone) membrane for fuel cell application

A series of anion exchange membranes of poly (fluorenylene ether sulfone) containing tertiary sulfonium hydroxide-functionalized fluorenyl groups were synthesized by sequential polycondensation, chloromethylation, substitution with dimethyl sulfide and ion exchange. They showed excellent solubility in polar aprotic solvents. Consequently, flexible and tough alkaline membranes with varying ionic contents were obtained by an anion exchange of tertiary sulfonium chloride polymers with 1.0 M KOH at room temperature. Different levels of substitution were performed to achieve high ionic conductivity as well as upholding the membranes’ mechanical stability. The tertiary sulfonium membranes demonstrated lower water uptake compared to quaternary ammonium membrane. High hydroxide ion conductivity was achieved up to 18.3 mS cm^?1 at 80 °C with the membrane of the highest ion exchange capacity (IEC, 1.51 mmol g^?1). The resulting alkaline polymers were characterized by ¹H NMR, FT-IR, thermogravimetric analysis (TGA), water uptake, IEC, atomic force microscopic (AFM) images.