明日のエレクトロニクス材料・ダイヤモンド

早稲田大学創立125周年記念シンポジウム 半導体・ナノエレクトロニクス―技術立国日本のこれから― 2007年10月23日 早稲田大学国際会議場井深大記念ホー

Smart Power Devices and ICs Using GaAs and Wide and Extreme Bandgap Semiconductors

We evaluate and compare the performance and potential of GaAs and of wide and extreme bandgap semiconductors (SiC, GaN, Ga2O3, diamond), relative to silicon, for power electronics applications. We examine their device structures and associated materials/process technologies and selectively review the recent experimental demonstrations of high voltage power devices and IC structures of these semiconductors. We discuss the technical obstacles that still need to be addressed and overcome before large-scale commercialization commences

Holes in the valence band of superconducting boron-doped diamond film studied by soft X-ray absorption and emission spectroscopy

Carbon- and boron-2$p$ states of superconducting and non-superconducting boron-doped diamond samples are measured using soft X-ray emission and absorption spectroscopy. For the superconducting sample, a large density of hole states is observed in the valence band in addition to the states in the impurity band. The hole states in the valence band is located at about 1.3 eV below the valence band maximum regardless of the doping level, which cannot be interpreted within a simple rigid band model. Present experimental results, combined with the first principles calculations, suggest that superconductivity is to be attributed to the holes in the valence band.Comment: 4 pages, 4 figure

Fabrication of photo-electrochemical biosensors for ultrasensitive screening of mono-bioactive molecules: the effect of geometrical structures and crystal surfaces

The controlled design of biosensors based on the photo-electrochemical technique with high selectivity, sensitivity, and rapid response for monitoring of mono-bioactive molecules, particularly dopamine (DA) levels in neuronal cells is highly necessary for clinical diagnosis. Hierarchical carbon-, nitrogen-doped (CN) nickel oxide spear thistle (ST) flowers associated in single-heads (S), and symmetric and asymmetric-double heads (D and A, respectively) that are tightly connected through a micrometric dipole-like rod or trunk were fabricated by using a simple synthetic protocol. The CN-ST flower heads were decorated with dense nano-tubular like hedgehog needle skins in vertical alignments. These designated architectures are key features for creating biosensor surface electrodes for photo-electrochemical, ultrasensitive screening of mono-bioactive molecules. The exceptional electrode designs produced numerous catalytically active sites, large surface area, and high electron-transfer mobility. The active coating of carbon–nitrogen nanospheres significantly enhanced the photo-electrocatalytic activity of the prepared biosensor electrodes and prevented leakage of photocatalytic activity under long-term exposure to irradiation. Among all photo-electrochemical assays, the biosensors showed significant sensitivity and selectivity for DA in the presence of interfering molecules such as ascorbic acid (AA), uric acid (UA), adrenaline (A), and noradrenaline (NA). The photo-electrochemical property of the CN-SST-{110} crystal surface electrode showed significant sensing performance for DA in terms of unimpeded diffusion pathways, a wide concentration-detection range, and a low detection limit, even in the presence of potentially interfering molecules compared with other electrode-modified CN-DST-{111} and CN-AST-{101} crystal surfaces. Furthermore, the CN-SST photo-biosensor electrode shows potential in the selective and sensitive determination of DA in real samples, such as human serum and secreted DA from living cells. This finding indicates that the hierarchical ST biosensor may enable analytical discrimination and monitoring of DA and can be employed for clinical diagnosis application

A comparative modelling study of new robust packaging technology 1mm2 VCSEL packages and their mechanical stress properties

Face recognition is one of the most sophisticated disciplines of biometric systems. The use of VCSEL in automotive applications is one of the most recent advances. The existing VCSEL package with a diffuser on top of a lens intended for automotive applications could not satisfy the criteria of the automotive TS16949: 2009 specification because the package was harmed and developed a lens fracture during 100 thermal cycle tests. In order to complete a cycle, the temperature rises from −40 °C to 150 °C and then rises again from 150 °C to 260 °C. The package then needs to be tested 500 times to ensure it fits the requirements without failing in terms of appearance or functionality. To this extent, the goal of this research is to develop packaging for 1 mm2 VCSEL chips with a diffuser on top that prevents fractures or damage to the package during heat cycle testing with multiple materials. The package was created using the applications SolidWorks 2017 and AutoCAD Mechanical 2017. The ANSYS Mechanical Structural FEA Analysis program simulated all packages for mechanical stress to guarantee that all packages generated were resilient to high temperature conditions. All packages exhibit no abnormalities and are robust for various temperatures ranging from low to high. Therefore, these packaged 1 mm2 VCSEL chips with a diffuser on top provide an effective approach for the application of VCSEL suitable in high temperature conditions