Cai-Wang Ge

Core–shell silicon nanowire array–Cu nanofilm Schottky junction for a sensitive self-powered near-infrared photodetector

A highly sensitive near infrared light (NIR) photodetector was fabricated by coating a thin layer of Cu film onto a vertical n-type SiNW array through a solution based reduction reaction. The as-fabricated core–shell SiNW array/Cu Schottky junction exhibits an obvious rectifying behavior in the dark with a turn-on voltage of ∼0.5 V and a rectification ratio of about 102 at ±1.5 V. In addition, it shows a pronounced photovoltaic performance when illuminated by NIR light with a wavelength of 980 nm. Such photovoltaic characteristics can allow the device to detect NIR illumination without exterior power supply. Further device analysis reveals that the self-powered NIR photodetector is capable of monitoring ultrafast optical signals with a frequency as high as 30 kHz. What is more, the present device also has obvious advantages of high responsivity, detectivity, on/off ratio, and response speed. Further theoretical simulation reveals that the good device performance is associated with excellent optical and electrical properties of core–shell heterojunction geometry.

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.

A sensitive red light nano-photodetector propelled by plasmonic copper nanoparticles

Plasmonic optoelectronic device based non-noble metal nanostructures (e.g. Al, In, etc.) have recently received increasing research interest due to their relatively low fabrication cost and tunable plasmon wavelength. In this study, we present a new plasmonic red light nano-photodetector by decorating a multi-layer graphene (MLG)–CdSe nanoribbon (CdSeNR) Schottky junction with a highly ordered plasmonic copper nanoparticle (CuNP) array, which exhibited obvious localized surface plasmon resonance in the range of 700–900 nm. Optoelectronic analysis reveals that the device metrics including the switch ratio, the responsivity and the detectivity considerably increased after functionalization with plasmonic CuNPs. Moreover, the response speed was fastened by nearly one order of magnitude. The observed optimization in device performance, according to theoretical simulations based on the finite element method (FEM) and experimental analysis, could be attributed to localized surface plasmon resonance (LSPR) induced hot electron injection. The above results signify that the present plasmonic CuNPs are equally important candidates for boosting the device performance of nano-optoelectronic devices.

High-efficiency refractive index sensor based on the metallic nanoslit arrays with gain-assisted materials

Abstract We have designed and investigated a three-band refractive index (RI) sensor in the range of 550–900 nm based on the metal nanoslit array with gain-assisted materials. The underlying mechanism of the three-band and enhanced characteristics of the metal nanoslit array with gain-assisted materials, have also been investigated theoretically and numerically. Three resonant peaks in transmission spectra are deemed to be in different plasmonic resonant modes in the metal nanoslit array, which leads to different responses for the plasmonic sensor. By embedding the structure into the CYTOP with proper gain-assisted materials, the sensing performances can be greatly enhanced due to a dramatic amplification of the extraordinary optical transmission (EOT) resonance by the gain medium. When the gain values reach their corresponding thresholds for the three plasmonic modes, the ultrahigh sensitivities in three bands can be obtained, and especially for the second resonant wavelength (λ2), the FOM=128.1 and FOM* = 39100 can be attained at the gain threshold of k =0.011. Due to these unique features, the designing scheme of the proposed gain-assisted nanoslit sensor could provide a powerful approach to optimize the performance of EOT-based sensors and offer an excellent platform for biological sensing.

Biosensors Based on Plasmonics

Because of the sensitivity to refractive index changes, plasmonics nanostructures have been investigated broadly for the bio-molecules detection through the excitations of the propagating surface plasmon resonance (PSPR) or localized surface plasmon resonance (LSPR). PSPR sensors can detect sub-monolayer quantities of bio-molecules at the gold film surface and provide real-time data through continuous optical measurements. LSPR sensors could be more sensitive to local refractive index changes and the factors of nanoparticle material, shape and size are all interrelated and contribute to the refractive index sensitivities.