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Graphene/GaAs heterojunction for highly sensitive, self-powered Visible/NIR photodetectors
摘要： Graphene/GaAs heterojunction has been demonstrated by transferring monolayer graphene on the surface of n-GaAs substrate, and the carrier transfer at the interface has been investigated by monitoring Raman shift of graphene on different substrates. The photovoltaic behavior and rectifying characteristic of the graphene/GaAs heterojunctions enable us to fabricate high-performance self-powered photodetector at zero bias. The device has been demonstrated to be sensitive to visible/near-infrared light (405–850 nm) at room temperature, giving rise to maximum responsivity of 122 mA W?1 and detectivity of 4.3 × 1012 Jones with quick response and recover time (0.5 ms and 0.35 ms), respectively. Such high photoelectric response is attributed to the efficient photo-generated carrier separation and transfer at the interface, which is caused by the strong built-in electric field between grapheme and GaAs because of a large barrier (0.87 eV). Our results confirm that the graphene/GaAs heterojunction has a great potential for high performance self-powered broadband photodetectors.
关键词： Photodetectors,Raman shift,Heterojunction,Graphene,Charge transfer
更新于2025-09-23 15:19:57
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Raman spectroscopy of poly (methyl methacrylate) under laser shock and static compression
摘要： Time-resolved Raman spectroscopy for visualizing molecular fingerprint snapshots at nanosecond time scale is a useful tool for detailed understanding of in situ shock behaviour of materials. This technique was applied to study the changes in molecular vibrations of poly (methyl methacrylate) (PMMA) under laser driven shock compression up to ~1.9 GPa in a confinement geometry. A layered target configuration is used to enhance the shock pressure. The vibrational modes are measured as a function of dynamic shock and static compression. The Grüneisen parameters and bond anharmonicities in PMMA are determined using compression behaviour of Raman modes. The deduced shock velocity (~3.5 ± 0.4 km/s) in PMMA based on the time evolution of shocked Raman mode at 1.9 GPa is in agreement with the one calculated (~3.7 km/s) from 1-D radiation hydrodynamic simulations. A comparative study on shock experiment and static high pressure Raman spectroscopic measurements is done. Static pressure measurement up to ~16 GPa show rapid blue shifting of C–H stretching modes.
关键词： Raman spectroscopy,PMMA,confinement geometry,Raman shift,laser shock,diamond anvil cell (DAC),static experiment
更新于2025-09-16 10:30:52