Teng-Fei Zhang

Graphene-β-Ga2 O3 Heterojunction for Highly Sensitive Deep UV Photodetector Application.

A deep UV light photodetector is assembled by coating multilayer graphene on beta-gallium oxide (β-Ga2 O3 ) wafer. Optoelectronic analysis reveals that the heterojunction device is virtually blind to light illumination with wavelength longer than 280 nm, but is highly sensitive to 254 nm light with very good stability and reproducibility.

A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

Abstract In this study, we present a simple ultraviolet (UV) light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

Tunable p-type doping of Si nanostructures for near infrared light photodetector application†

In this study, we present a simple oxide assisted p-type doping of Si nanostructures by evaporating a mixed powder composed of SiB6 and SiO. It was found that Si nanoribbons (Si NRs) which can be obtained at high SiB6 content, will give way to Si nanowires (Si NWs) when the content of SiB6 in the mixed powder was reduced. According to our transport measurement of field effect transistors (FETs) assembled on individual Si nanostructures, the as-prepared Si nanostructures with different boron doping levels all exhibit typical p-type conduction characteristics. Additionally, the electrical conductivity of the Si nanostructures can be tuned over 7 orders of magnitude from 8.98 × 102 S cm−1 for the highly doped sample to 3.36 × 10−5 S cm−1 for the lightly doped sample. We also assembled a nano-photodetector based on monolayer graphene and the as-prepared Si nanostructures, which exhibits ultra-sensitivity to 850 nm near infrared light (NIR) illumination with a nanosecond response speed (τrise/τfall: 181/233 ns). The generality of the above results suggest that the Si nanostructures are promising building blocks for future electronic and optoelectronic device applications.

Plasmonic hollow gold nanoparticles induced high-performance Bi2S3 nanoribbon photodetector

Abstract A high performance hollow gold nanoparticles (HGNs) decorated one-dimensional (1-D) Bi2S3 nanoribbon (NR) photodetector was fabricated for green light detection (560 nm). The single crystal 1-D Bi2S3 NRs with growth orientation along [001] were synthesized by a simple solvothermal approach. Optoelectronic analysis reveals that the performance of the plasmonic photodetector was greatly enhanced after decoration with HGNs. For example, the responsivity increases from 1.4 × 102 to 1.09 × 103 AW−1, the conductivity gain from 2.68 × 102 to 2.31 × 103, and the detectivity from 2.45 × 1012 to 2.78 × 1013, respectively. Such performance enhancement was attributed to the localized surface plasmon resonance (LSPR) effect caused by the HGNs according to both experiment and theoretical simulation. This study is believed to open up new opportunities for managing light and enhancing the device performance of other 1-D semiconductor nanostructures based optoelectronic devices and systems.

ZIF-67 derived porous Co3O4 hollow nanopolyhedron functionalized solution-gated graphene transistors for simultaneous detection of glucose and uric acid in tears

Biomarkers in tears have attracted much attention in daily healthcare sensing and monitoring. Here, highly sensitive sensors for simultaneous detection of glucose and uric acid are successfully constructed based on solution-gated graphene transistors (SGGTs) with two separate Au gate electrodes, modified with GOx-CHIT and BSA-CHIT respectively. The sensitivity of the SGGT is dramatically improved by co-modifying the Au gate with ZIF-67 derived porous Co3O4 hollow nanopolyhedrons. The sensing mechanism for glucose sensor is attributed to the reaction of H2O2 generated by the oxidation of glucose near the gate, while the sensing mechanism for uric acid is due to the direct electro-oxidation of uric acid molecules on the gate. The optimized glucose and uric acid sensors show the detection limits both down to 100nM, far beyond the sensitivity required for non-invasive detection of glucose and uric acid in tears. The glucose and uric acid in real tear samples was quantitatively detected at 323.2 ± 16.1μM and 98.5 ± 16.3μM by using the functionalized SGGT device. Due to the low-cost, high-biocompatibility and easy-fabrication features of the ZIF-67 derived porous Co3O4 hollow nanopolyhedron, they provide excellent electrocatalytic nanomaterials for enhancing sensitivity of SGGTs for a broad range of disease-related biomarkers.

Highly sensitive solution-gated graphene transistor based sensor for continuous and real-time detection of free chlorine

The concentration of free chlorine used for sterilizing drinking water, recreational water, and food processing water is critical for monitoring potential environmental and human health risks, and should be strictly controlled. Here, we report a highly efficient solution-gated graphene transistor (SGGT) device, for the detection of free chlorine in a real-time and convenient manner with excellent selectivity and high sensitivity. The detection mechanism of the SGGT with Au gate electrode is attributed to two combined effects: the reduction of the free chlorine on Au gate electrode; and the direct oxidization of graphene by the free chlorine in solution. The SGGT device shows a linear response range of free chlorine from 1 μM to 100 μM, with detection limit as low as 100 nM, far beyond the sensitivity required for practical applications. Finally, we also demonstrate the performance of the SGGT for determination of free chlorine in local tap water samples. The results presented herein have important implications in the development of portable and disposable devices based on SGGT sensing platform for the simple, real-time, and selective determination of free chlorine.