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Reusable surface-enhanced Raman substrates using microwave annealing
摘要： In this work, we report the fabrication of large-scale homogeneous surface-enhanced Raman scattering (SERS) substrates using a microwave annealing (MWA) process on Ag thin films on silicon, using a typical low-cost domestic microwave oven, avoiding the use of chemicals and stabilizing agents, or time-consuming and expensive approaches. We provide evidence that in 5–15 s, uniform and reproducible SERS substrates of several centimeter squares can be grown, providing a Raman signal enhancement of five orders of magnitude, for an incident Raman laser with an intensity as low as ~ 0.035 mW, against the characterization of Rhodamine 6G, which is a standard test molecule for SERS. Moreover, we tested the reusability of the fabricated MWA SERS substrates under conditions as tough as ultrasonic sonication in isopropyl alcohol and acetone for 15 min, respectively, and we demonstrate that our SERS substrates can be efficiently reused for more than six times after sonication, which is quite critical since it minimizes the cost of the procedure to minimum.
关键词： Surface-enhanced Raman scattering (SERS),Ag thin films,Rhodamine 6G (R6G),Reusable substrates,Microwave annealing (MWA)
更新于2025-09-10 09:29:36
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A Low-Cost Stable SERS Substrate Based on Modified Silicon Nanowires
摘要： In this paper, we report fabrication of a simple, stable, low-cost, and easy-to-fabricate substrate for surface enhanced Raman spectroscopy (SERS) applications. Silicon nanowires are one of the widely used nanostructures in different fields of nanotechnology. Through creating and varying the gap between nanowires and reducing their filling ratio and tapering, silicon nanowires are converted to applicable SERS substrates. Furthermore, the effects of annealing and post-KOH etching on these silver-coated silicon nanowire substrates are examined. It is shown that the applied processes remarkably enhance the captured Raman signal. For samples etched with KOH method, an optimized etching time at which the Raman signal reaches its maximum value is obtained as well. Finally, an ultra-high enhancement in the Raman signal is obtained.
关键词： Silicon nanowire,Surface-enhanced Raman spectroscopy,SERS substrates
更新于2025-09-10 09:29:36
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Growth and properties of CdZnTe films on different substrates
摘要： High quality CdZnTe films were deposited on polished CdZnTe film, Si wafer and fluorine doped tin oxide (FTO) glass by close spaced sublimation (CSS) method. The influences of different substrates on the growth rate, composition, structural and electrical properties of CdZnTe films were investigated. The results showed that the CdZnTe film prepared on the polished CdZnTe film substrate had a higher growth rate and a better crystalline quality. The film prepared on the polished CdZnTe film substrate also exhibited lower leakage current, which is promising for high energy particle detection.
关键词： Close spaced sublimation method,Substrates,CdZnTe films
更新于2025-09-10 09:29:36
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Dislocations behavior in highly mismatched III-Sb growth and their impact on the fabrication of <i>top-down</i> n?+?InAs/p?+?GaSb nanowire tunneling devices
摘要： We study in this work the growth and fabrication of top-down highly doped n + InAs(Si)/p + GaSb(Si) Esaki tunneling diodes on (001) GaAs substrates. A careful investigation on the highly mismatched GaSb/GaAs growth is first conducted by means of Reflection High-Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and X-Ray Diffraction (XRD) analyses. These results are expected to pave the way to methods for III-Sb buffer layer’s integration with low threading dislocation (TD) densities. A comparison between AFM, XRD, defect revealing by chemical etching and transmission electron microscopy (TEM) is then presented to calculate the precise TD density and its influence on the device structure. In the last part, we report on first operating sub-30 nm III-V vertical NW tunneling devices on (001) commercial GaAs substrates.
关键词： III-Sb growth,AFM,dislocations,TEM,nanowire tunneling devices,XRD,RHEED,GaAs substrates
更新于2025-09-10 09:29:36
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Investigation of the performance of strain-engineered silicon nanowire field effect transistors (?-Si-NWFET) on IOS substrates
摘要： In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green’s function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ～104 μS/μm, sub-threshold swing of ～100 mV/dec, and drain-induced-barrier-lowering of ～100 mV/V.
关键词： IOS substrates,high-k gate insulators,strain-engineered,silicon nanowire,non-equilibrium Green’s function,quantum-electrostatic framework,field-effect transistors
更新于2025-09-10 09:29:36
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Recent Developments Accelerating SiC Adoption
摘要： The benefits of SiC devices for use in power electronics has been long understood, and over 25 years of sustained development in materials and devices has brought adoption to a tipping point [1,15]. It takes the confluence of many separate developments to build the necessary momentum for accelerated adoption, and we will examine these factors.
关键词： SiC MOSFET,SiC reliability,SiC Schottky Diode,SiC gate oxide,SiC Cascode,Supercascode,Silicon Carbide,SiC,SiC packaging,SiC applications,SiC epitaxy,SiC substrates
更新于2025-09-09 09:28:46
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Top-gated graphene field-effect transistors by low-temperature synthesized SiN <i> <sub/>x</sub></i> insulator on SiC substrates
摘要： Top-gated devices made from an epitaxial graphene film on a 4H-SiC substrate were fabricated. Atomic force microscopy and Raman spectroscopy results showed that a large-scale highly uniform monolayer graphene film was synthesized on the SiC substrate. A SiNx passivation film was deposited on a SiC graphene device as a top gate insulator by catalytic chemical-vapor deposition (Cat-CVD) below 65 °C. After the top gate electrode was formed on the SiNx film, no leakage current flowed between the gate and source electrodes. The transport characteristics showed clear ambipolar characteristics from 8 to 280 K, and the temperature dependences of the conductance and field-effect mobility of the devices implied that monolayer graphene devices can be successfully fabricated. Moreover, the position of the charge neutrality point after SiNx deposition was around 0 V, indicating p-doping characteristics. These results indicate that SiNx films synthesized by Cat-CVD can be used as gate insulators and that the carrier type may be controlled by adjusting the deposition conditions.
关键词： SiNx,Cat-CVD,field-effect transistors,graphene,SiC substrates
更新于2025-09-09 09:28:46
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Degradation of GaN-on-GaN vertical diodes submitted to high current stress
摘要： GaN-on-GaN vertical devices are expected to ?nd wide application in power electronics, thanks to the high current densities, the low on-resistance and the high breakdown voltage. So far, only few papers on the reliability of GaN-on-GaN vertical devices have been published in the literature. This paper investigates the degradation of GaN-on-GaN pn diodes submitted to stress at high current density. The study was carried out by means of electrical characterization and electroluminescence (EL) measurements. We demonstrate that: (i) when submitted to stress at high current density, the devices show signi?cant changes in the electrical characteristics: an increase in on-resistance/turn-on voltage, an increase in the generation/recombination components, the creation of shunt-paths. (ii) the increase in on-resistance is strongly correlated to the decrease in the EL signal emitted by the diodes. (iii) the degradation kinetics have a square-root dependence on time, indicative of a di?usion process. The results are interpreted by considering that stress induces a di?usion of hydrogen from the highly-p-type doped surface towards the pn junction. This results in a decrease in hole concentration, due to the creation of MgeH bonds, and in a lower hole injection. As a consequence, on-resistance increases while EL signal shows a correlated decrease.
关键词： Wide band gap semiconductors,Bulk GaN substrates,Vertical diodes,pn junction,Di?usion,Gallium nitride,Hydrogen,Degradation
更新于2025-09-09 09:28:46
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A simple strategy to improve the sensitivity of probe molecules on SERS substrates
摘要： In this work, we report a simple strategy to improve the detection sensitivity as well as the spectral quality of probe molecules on surface-enhanced Raman scattering (SERS) substrates. On normal SERS substrates, due to the decreased absorption capacity and changes in the molecule orientations, SERS signals disappear when the analyte molecule concentrations reach a limit value. To solve this problem, the molecular template reagent (MTR) technique, a simple strategy based on SERS surface selection rules, is considered. By choosing the best MTR according to different samples, the effect of adjusting the molecular orientations of samples can be studied. In this process, 1-butanethiol, 1-hexanethiol, 1-octanethiol, 1-decanethiol, and 1-dodecanethiol, which are MTRs, are used to adjust the orientations of probe molecules under optimized conditions. The use of the MTR technique indicated that the limit of detection (LOD) of the probe molecules of p-aminobenzenethiol and 4-mercaptobenzoic acid on noble metal substrates showed an increase of one order of magnitude over the LOD of the pure probing molecule systems. Hence, the proposed method introduces a way to detect the molecules with an improved sensitivity at extremely low concentrations. The study corresponds to a proof-of-concept study of MTR-assisted SERS for SERS-based applications in ultrasensitive analyses.
关键词： Surface-enhanced Raman scattering (SERS),Molecular template reagent (MTR),Ultrasensitive analyses,SERS substrates
更新于2025-09-09 09:28:46
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Growth of tr6-CaSi <sub/>2</sub> thin films on Si(111) substrates
摘要： Uniform and high-quality tr6-CaSi2 films were successfully grown via the co-deposition of Ca and Si on a Si(111) substrate. Using reactive Ca deposition, the films tended to form mixed phases of orthorhombic CaSi and two trigonal CaSi2 (three-layer repeat: tr3-CaSi2; six-layer repeat: tr6-CaSi2) structures at low substrate temperatures below 580 °C. A tr6-CaSi2 film was formed when the substrate temperature and thickness of the deposited Ca were controlled. By supplying an external source of Si along with Ca deposition, the formation of CaSi and tr3-CaSi2 was suppressed, and single-phase tr6-CaSi2 was obtained.
关键词： co-deposition,thin films,molecular beam epitaxy,Si(111) substrates,tr6-CaSi2
更新于2025-09-09 09:28:46