High sensitive position-dependent photodetection observed in Cu-covered Si nanopyramids

Graphene-enhanced lateral photovoltaic effect observed in the Ag nanoparticle-covered graphene/n-type silicon

Graphene is a kind of two-dimensional material with a single-layer carbon structure and has been investigated in many high-performance photodetectors. The lateral photovoltaic effect (LPE) is widely used in the position-sensitive detectors (PSDs) owing to its linear response of photovoltage to the light position. In this Letter, a type of graphene-enhanced LPE is observed in the Ag nanoparticle-covered graphene/n-type Si. The LPE sensitivity can reach 97.3 mV/mm, much higher than the sensitivity of 1.3 mV/mm in the control sample of Ag/Si and 5.2 mV/mm of graphene/Si. Based on the photocarriers' diffusion mechanism, tailoring a photocarrier transfer at the interface of a heterojunction plays a key role for the enhancement. These findings exhibit great application potential of graphene in the field of PSDs and offer an effective method for the optimization of LPE devices.

Magnetic mesoporous Fe3O4@nSiO2@mSiO2 nanoparticles for high-throughput mass spectrometry detection of hydrolyzed products of organophosphorus nerve agents

Rapid and accurate detection of hydrolyzed products of organophosphorus nerve agents (OPNAs) is an important method to effectively confirm the use of these agents. OPNAs are rapidly hydrolyzed to the methyl phosphonates (MPs) in the environment, which can be used as environmental traceability marker for OPNAs. Herein, magnetic mesoporous materials combined with real-time in situ mass spectrometry (MS) were used to achieve high-throughput detection of MPs. Novel magnetic mesoporous nanoparticles Fe3O4@nSiO2@mSiO2 were synthesized via co-condensation of tetraethyl orthosilicate and cetyltrimethylammonium bromide (CTAB) on the surface of nonporous silica-coated Fe3O4 under alkaline conditions. CTAB templates were removed by the reflux of ethanol (0.0375 mM ammonium nitrate) to form mesoporous SiO2, which has a large specific surface area of 549 m2 g-1 and an excellent magnetization strength of 59.6 emu g-1. A quick, cost-effective, rugged, and safe magnetic preparation method, magnetic QuEChERS, was established with magnetic mesoporous nanoparticles (Fe3O4@nSiO2@mSiO2) as adsorption materials for direct analysis in real-time and tandem MS (DART-MS/MS) of MPs in environmental samples. The method exhibits good linearity (R2 > 0.992) in the range of 20.0-4.00 μg mL-1, the limits of detection were <5.00 ng mL-1, the limits of quantification were <20.0 ng mL-1, and the extraction recoveries were 70.2-98.1%, with relative standard deviations (RSDs) in the range of 1.97-10.6%. Additionally, using this method, analysis of 70 environmental samples could be completed within 20 min. Then, the M-QuEChERS-DART-MS/MS method was applied to the 52nd Organisation for the Prohibition of Chemical Weapons (OPCW) environmental spiked samples analysis, where the accuracy was 95.2-116%, and the RSD was 1.16-7.83%. The results demonstrated that Fe3O4@nSiO2@mSiO2 based on the QuEChERS method can quickly and efficiently remove the matrix of environmental samples and when coupled with the DART-MS/MS can achieve high-throughput determination of MPs in environmental samples.

Surface Engineering in SnO2/Si for High-Performance Broadband Photodetectors

Silicon-based photodetectors are important optoelectronic devices in many fields. Many investigations have been conducted to improve the performance of silicon-based photodetectors, such as spectral responsivity and sensitivity in the ultraviolet band. In this study, we combine the surface structure engineering of silicon with wide-bandgap semiconductor SnO₂ films to realize textured Si-based heterojunction photodetectors. The obtained SnO₂/T-Si photodetectors exhibit high responsivity ranging from ultraviolet to near-infrared light. Under a bias voltage of 1 V, SnO₂/T-Si photodetectors (PDs) with an inverted pyramid texture show the best performance, and the typical responsivities to ultraviolet, visible, and near-infrared light are 0.512, 0.538, 1.88 (800 nm, 67.7 μW/cm²) A/W@1 V, respectively. The photodetectors exhibit short rise and decay times of 18.07 and 29.16 ms, respectively. Our results demonstrate that SnO₂/T-Si can serve as a high-performance broadband photodetector.

Multifunctional high-performance position sensitive detector based on a Sb2Se3-nanorod/CdS core-shell heterojunction

Sb₂Se₃ exhibits fascinating optical and electrical properties owing to its unique one-dimensional crystal structure. In this study, a Sb₂Se₃-nanorod/CdS core-shell heterostructure was successfully constructed, and the lateral photovoltaic effect (LPE), as well as the lateral photocurrent and photoresistance effects, were first studied. The measurements indicate that this heterojunction exhibits excellent lateral photoelectric performance in a broad range of 405-1064 nm with the best position sensitivities (PSs) of 525.9 mV/mm, 79.1 µA/mm, and 25.6 kΩ/mm for the lateral photovoltage, photocurrent, and photoresistance, respectively, while the nonlinearity is maintained below 7%, demonstrating its great potential in a novel high-performance multifunctional position sensitive detector (PSD). Moreover, this PSD could work well at different frequencies with good stability and repeatability, and the rise and fall times were deduced to be 48 and 180 µs, respectively. Besides, large linear working distances are achieved in this heterojunction PSD, and the PS can still reach 75.5 mV/mm even at an ultra-large working distance of 9 mm. These outstanding performances can be attributed to the high-quality Sb₂Se₃ nanorod arrays and the fast charge-carrier separation and transport properties of this core-shell heterojunction. This study provides important ideas for developing high-performance, broadband, large working distances, and ultrafast multifunctional PSDs based on the new core-shell heterostructure.

Sensitive Silicon Nanowire Ultraviolet B Photodetector Induced by Leakage Mode Resonances

Ultraviolet photodetectors (UVPDs) have played an important role both in civil and military applications. While various studies have shown that traditional UVPDs based on wide-band-gap semiconductors (WBSs) have excellent device performances, it is, however, undeniable that the practical application of WBS-based UVPDs is largely limited by the relatively high fabrication cost. In this work, we propose a new silicon nanowire (Si NW) UVPD that is very sensitive to UVB light illumination. The Si NWs with a diameter of about 36 nm are fabricated by a metal-assisted chemical etching method. Performance analysis revealed that the Si NW device was only sensitive to UVB light and almost blind to illumination in the visible and near-infrared regions. Such abnormal spectral selectivity was associated with the leakage mode resonances (LMRs) of the small diameter, according to our theoretical simulation. Under 300 nm illumination, the responsivity, external quantum efficiency, and specific detectivity were estimated to be 10.2 AW^-1, 4.22 × 10³%, and 2.14 × 10¹⁰ Jones, respectively, which were comparable to or even higher than those of some WBS-based UVPDs. These results illustrate that the small dimension Si NWs are potential building blocks for low-cost and high-performance UVPDs in the future.

High-Sensitivity Infrared Photoelectric Detection Based on WS2 /Si Structure Tuned by Ferroelectrics

As one of the typical transition-metal dichalcogenides with distinct optical and electrical properties, WS₂ exhibits tremendous potential for optoelectronic devices. However, its inherent band gap range limits the application in the infrared region. To overcome this draw-back and improve the sensitivity, P(VDF-CTFE) is used as a ferroelectric gate to control the states of WS₂ /Si junctions and achieve an enhanced infrared photodetection. The polarization electric field not only broadens the range of absorption wavelength (405-1550 nm) but also greatly promotes the sensitivity of lateral photovoltaic effect (LPE) (from 198.6 to 503.2 mV mm^-1 ). This phenomenon is attributed to the reduction of WS₂ band gap and the change of potential barrier at the interface of the junction. Meanwhile, the response speed is improved significantly due to the increase of carrier initial kinetic energy. This new scheme for ferroelectric tuned LPE opens up a way to realize high-sensitivity, ultrafast, and stable infrared photodetection.

Heterojunction interface-induced enhancement of position-sensitive photodetection in the nano-film of Ti/SrTiO3 based on the p-type silicon

Complex oxide perovskites exhibit a range of novel, to the best of our knowledge, physical phenomena and have gained popularity as a material system in the past decades. Strontium titanate (SrTiO₃) is an iconic material among oxide perovskite due to its unusual electronic transport behavior and has been investigated in many electronic devices. In this Letter, a type of SrTiO₃ nano-film-induced enhancement of lateral photovoltaic effect (LPE) is observed in the heterojunction of Ti/SrTiO₃/p-type Si. Optimizing the thickness of SrTiO₃, the LPE sensitivity can reach 123.2 mV/mm, which is much higher than the sensitivity in the control samples of Ti/Si (55.3 mV/mm) and SrTiO₃/Si (∼0mV/mm). These findings offer an effective way to improve the sensitivity and will be helpful in the development of oxide-based photodetection devices.

On-chip programmable optical switch based on CdS multibranched nanowire arrays

Micro/nano optoelectronic devices are widely studied as basic building blocks for on-chip integrated microsystem and multichannel logic units with excellent optoelectronic properties that are especially important part for interconnection route construction. Here, based on anisotropic waveguides, an optical switch with an on/off ratio of 2.14 is built up in a 2D CdS branched nanowire array. Because the branches are obliquely distributed at the same side of the trunk in a highly ordered form, the guided photoluminescence (PL) intensity from the trunk into the branch tightly relates to its angle. Based on the different intensity of the guided PL emitted from the end of each branch, the position of the incident spot in the backbone area can be identified accurately, making a feasible construction of an on-chip position-sensitive detector to realize an all-optical information process.

Ultrahigh position sensitivity and fast optical relaxation time of lateral photovoltaic effect in Sb2Se3/p-Si junctions

A large lateral photovoltaic (LPV) effect with good linearity and fast response time is necessary for developing high-performance position-sensitive detectors (PSD). In this paper, we investigated the influence of the resistance of Sb₂Se₃ film and the Si on the LPV properties of the Sb₂Se₃/p-Si junctions. The LPV exhibits a linear dependence on the laser spot position, with a maximum position sensitivity as high as 448 mV/mm. The optical relaxation time of the LPV was about 4.98 μs, which was due to the formation of the inversion layer at the Sb₂Se₃/p-Si interface. Our results revealed that the high resistivity of Sb₂Se₃ film facilitate the LPV and confirmed the resistivity of Si substrate play a key role in the LPV properties. The giant position sensitivity and fast relaxation times of the LPV suggest that the Sb₂Se₃/p-Si junction is a promising candidate for a wide range of optoelectronic device applications.