Wafer-Scale 1T' MoTe2 for Fast Response Self-Powered Wide-Range Photodetectors.

The semimetal-based photodetector possesses the intrinsic advantage of high response speed, low power consumption, and wide-range photoresponse. Here, we report the synthesis and application of 1 inch wafer-scale polycrystalline few layer 1T'-MoTe2 on the SiO2/Si substrate by employing a modified chemical vapor deposition method of predeposition of precursors. A continuous film with seamlessly stitched micrometer scale grains has been realized, and the pure 1T' phase was confirmed by Raman spectroscopy. An asymmetric metal electrode photodetector device of Pd-MoTe2-Au was designed and fabricated by using shadow mask-assisted UHV deposition. By measuring the self-powered photocurrent under the illumination of Xe lamp, we show that the device is sensitive to a wide spectra range (λ = 320-1200 nm) while maintaining high performance of the ON/OFF ratio (∼103), responsivity (1.2 A/W), and specific detectivity (7.68 × 1012 Jones). Under 450, 648, and 850 nm pulsed laser illumination, the response time achieves tens of microsecond scale. The device shows polarized photoresponse as well. Our work may promote the potential application of a self-powered high-performance photodetector based on 1T'-MoTe2.

Nucleotide detection mechanism and comparison based on low-dimensional materials: A review.

The recent pandemic has led to the fabrication of new nucleic acid sensors that can detect infinitesimal limits immediately and effectively. Therefore, various techniques have been demonstrated using low-dimensional materials that exhibit ultrahigh detection and accuracy. Numerous detection approaches have been reported, and new methods for impulse sensing are being explored. All ongoing research converges at one unique point, that is, an impetus: the enhanced limit of detection of sensors. There are several reviews on the detection of viruses and other proteins related to disease control point of care; however, to the best of our knowledge, none summarizes the various nucleotide sensors and describes their limits of detection and mechanisms. To understand the far-reaching impact of this discipline, we briefly discussed conventional and nanomaterial-based sensors, and then proposed the feature prospects of these devices. Two types of sensing mechanisms were further divided into their sub-branches: polymerase chain reaction and photospectrometric-based sensors. The nanomaterial-based sensor was further subdivided into optical and electrical sensors. The optical sensors included fluorescence (FL), surface plasmon resonance (SPR), colorimetric, and surface-enhanced Raman scattering (SERS), while electrical sensors included electrochemical luminescence (ECL), microfluidic chip, and field-effect transistor (FET). A synopsis of sensing materials, mechanisms, detection limits, and ranges has been provided. The sensing mechanism and materials used were discussed for each category in terms of length, collectively forming a fusing platform to highlight the ultrahigh detection technique of nucleotide sensors. We discussed potential trends in improving the fabrication of nucleotide nanosensors based on low-dimensional materials. In this area, particular aspects, including sensitivity, detection mechanism, stability, and challenges, were addressed. The optimization of the sensing performance and selection of the best sensor were concluded. Recent trends in the atomic-scale simulation of the development of Deoxyribonucleic acid (DNA) sensors using 2D materials were highlighted. A critical overview of the challenges and opportunities of deoxyribonucleic acid sensors was explored, and progress made in deoxyribonucleic acid detection over the past decade with a family of deoxyribonucleic acid sensors was described. Areas in which further research is needed were included in the future scope.

Flexible infrared photodetector based on indium antimonide nanowire arrays.

Narrow bandgap semiconductors like indium antimonide (InSb) are very suitable for high-performance room temperature infrared photodetectors, but the fragile nature of the wafer materials hinders their application as flexible/wearable devices. Here, we present a method to fabricate a photodetector device of assembled crystalline InSb nanowire (NW) arrays on a flexible substrate that balances high performance and flexibility, facilitating its application in wearable devices. The InSb NWs were synthesized by means of a vapor-liquid-solid technique, with gold nanoclusters as seeding particles. The morphological and crystal properties were investigated using scanning electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy, which revealed the unique spike shape and high crystallinity with (111) and (220) planes of InSb NWs. The flexible infrared photodetector devices were fabricated by transferring the NWs onto transparent and stretchable polydimethylsiloxane substrate with pre-deposited gold electrodes. Current versus time measurement of the photodetector devices under light showed photoresponsivity and sensitivity to mid-infrared at bias as low as 0.1 V while attached to curved surfaces (suitable for skin implants). A high-performance NW device yielded efficient rise and decay times down to 1 s and short time lag for infrared detection. Based on dark current, calculated specific detectivity of the flexible photodetector was 1.4 × 1012Jones. The performance and durability render such devices promising for use as wearable infrared photodetectors.

Twofold Porosity and Surface Functionalization Effect on Pt-Porous GaN for High-Performance H2-Gas Sensors at Room Temperature.

The achievement of H2 detection, up to 25 ppm, at room temperature using sulfur-treated, platinum (Pt)-decorated porous GaN is reported in this study. This achievement is attributed to the large lateral pore size, Pt catalyst, and surface treatment using organic sulfide. The performance of H2-gas sensors is studied as a function of the operating temperature by providing an adsorption activation energy of 22 meV at 30 ppm H2, confirming the higher sensitivity of the sulfide-treated Pt-porous GaN sensor. Furthermore, the sensing response of the sulfide-treated Pt-porous GaN gas sensor increases with the increase in porosity (surface-to-volume ratio) and pore radii. Using the Knudsen diffusion-surface reaction equation, the H2 gas concentration profile is simulated and fitted within the porous GaN layer, revealing that H2 diffusion is limited by small pore radii because of its low diffusion rate. The simulated gas sensor responses to H2 versus the pore diameter show the same trend as observed for the experimental data. The sulfide-treated Pt-porous GaN sensor achieves ultrasensitive H2 detection at room temperature for 125 nm pore radii.

Indium Antimonide Nanowires: Synthesis and Properties.

This article summarizes some of the critical features of pure indium antimonide nanowires (InSb NWs) growth and their potential applications in the industry. In the first section, historical studies on the growth of InSb NWs have been presented, while in the second part, a comprehensive overview of the various synthesis techniques is demonstrated briefly. The major emphasis of current review is vapor phase deposition of NWs by manifold techniques. In addition, author review various protocols and methodologies employed to generate NWs from diverse material systems via self-organized fabrication procedures comprising chemical vapor deposition, annealing in reactive atmosphere, evaporation of InSb, molecular/ chemical beam epitaxy, solution-based techniques, and top-down fabrication method. The benefits and ill effects of the gold and self-catalyzed materials for the growth of NWs are explained at length. Afterward, in the next part, four thermodynamic characteristics of NW growth criterion concerning the expansion of NWs, growth velocity, Gibbs-Thomson effect, and growth model were expounded and discussed concisely. Recent progress in device fabrications is explained in the third part, in which the electrical and optical properties of InSb NWs were reviewed by considering the effects of conductivity which are diameter dependent and the applications of NWs in the fabrications of field-effect transistors, quantum devices, thermoelectrics, and detectors.

High responsivity photoconductors based on iron pyrite nanowires using sulfurization of anodized iron oxide nanotubes.

Iron pyrite (FeS2) nanostructures are of considerable interest for photovoltaic applications due to improved material quality compared to their bulk counterpart. As an abundant and nontoxic semiconductor, FeS2 nanomaterials offer great opportunities for low-cost and green photovoltaic technology. This paper describes the fabrication of FeS2 nanowire arrays via sulfurization of iron oxide nanotubes at relatively low temperatures. A facile synthesis of ordered iron oxide nanotubes was achieved through anodization of iron foils. Characterization of the iron sulfide nanowires indicates that pyrite structures were formed. A prototype FeS2 nanowire photoconductor demonstrates very high responsivity (>3.0 A/W). The presented method can be further explored to fabricate various FeS2 nanostructures, such as nanoparticles, nanoflowers, and nanoplates.