Direct growth of graphene on hyper-doped silicon to enhance carrier transport for infrared photodetection.

The importance of infrared photodetectors cannot be overstated, especially in fields such as security, communication, and military. While silicon-based infrared photodetectors are widely used due to the maturity of the semiconductor industry, their band gap of 1.12 eV limits their infrared light absorption above 1100 nm, making them less effective. To overcome this limitation, we report a novel infrared photodetector prepared by growing graphene on the surface of zinc hyper-doped silicon. This technique utilizes hyper-doping to introduce deep level assisted infrared light absorption benefit from the enhanced carrier collection capacity of graphene. Without introducing new energy consumption, the hyper-doped substrate annealing treatment is completed during the growth of graphene. By the improvement of transport and collection of charge carriers, the graphene growth adjusts the band structure to upgrade electrode contact, resulting in a response of 1.6 mA W-1under laser irradiation with a wavelength of 1550 nm and a power of 2 mW. In comparison, the response of the photodetector without graphene was only 0.51 mA W-1, indicating a three-fold performance improvement. Additionally, the device has lower dark current and lower noise current, resulting in a noise equivalent power of 7.6 × 10-8W Hz-0.5. Thus, the combination of transition metal hyper-doping and graphene growth technology has enormous potential for developing the next generation of infrared photodetectors.

High detectivity graphene/si heterostructure photodetector with a single hydrogenated graphene atomic interlayer for passivation and carrier tunneling.

Hydrogenated graphene is easy to prepare and chemically stable. Besides, hydrogenation of graphene can open the band gap, which is vital for electronic and optoelectronic applications. Graphene/Si photodetector (PD) has been widely studied in imaging, telecommunications, and other fields. The direct contact between graphene and Si can form a Schottky junction. However, it suffers from poor interface state, where the carrier recombination at the interface causes serious leakage current, which in turn leads to a decrease in the detectivity. Hence, in this study, hydrogenated graphene is used as an interfacial layer, which passivates the interface of graphene/Si (Gr/Si) heterostructure. Besides, the single atomic layer thickness of hydrogenated graphene is also crucial for the tunneling transport of charge carriers and its suitable energy band position reduces the recombination of carrier. The fabricated graphene/hydrogenated-graphene/Si (Gr/H-Gr/Si) heterostructure PD showed an extremely low dark current about 10-7A. As a result, it had low noise current and exhibited a high specific detectivity of âˆ¼2.3 × 1011Jones at 0 V bias with 532 nm laser illumination. Moreover, the responsivity of the fabricated PD was found to be 0.245 A W-1at 532 nm illumination with 10µW power. These promising results show a great potential of hydrogenated graphene to be used as an interface passivation and carrier tunneling layer for the fabrication of high-performance Gr/Si heterostructure PDs.

Two-Dimensional Co@N-Carbon Nanocomposites Facilely Derived from Metal-Organic Framework Nanosheets for Efficient Bifunctional Electrocatalysis.

Metal-organic frameworks (MOFs) and MOF-derived nanomaterials have recently attracted great interest as highly efficient, non-noble-metal catalysts. In particular, two-dimensional MOF nanosheet materials possess the advantages of both 2D layered nanomaterials and MOFs and are considered to be promising nanomaterials. Herein, we report a facile and scalable in situ hydrothermal synthesis of Co-hypoxanthine (HPA) MOF nanosheets, which were then directly carbonized to prepare uniform Co@N-Carbon nanosheets for efficient bifunctional electrocatalytic hydrogen-evolution reactions (HERs) and oxygen-evolution reactions (OERs). The Co embedded in N-doped carbon shows excellent and stable catalytic performance for bifunctional electrocatalytic OERs and HERs. For OERs, the overpotential of Co@N-Carbon at 10 mA cm-2 was 400 mV (vs. reversible hydrogen electrode, RHE). The current density of Co@N-Carbon reached 100 mA cm-2 at an overpotential of 560 mV, which showed much better performance than RuO2 ; the largest current density of RuO2 that could be reached was only 44 mA cm-2 . The Tafel slope of Co@N-Carbon was 61 mV dec-1 , which is comparable to that of commercial RuO2 (58 mV dec-1 ). The excellent electrocatalytic properties can be attributed to the nanosheet structure and well-dispersed carbon-encapsulated Co, CoN nanoparticles, and N-dopant sites, which provided high conductivity and a large number of accessible active sites. The results highlight the great potential of utilizing MOF nanosheet materials as promising templates for the preparation of 2D Co@N-Carbon materials for electrocatalysis and will pave the way to the development of more efficient 2D nanomaterials for various catalytic applications.