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Structural and temperature-dependent optical properties of thermally evaporated CdS thin films
摘要： In this work, structural and temperature dependent optical properties of thermally evaporated CdS thin films were investigated. X-ray diffraction, energy dispersive spectroscopy and Raman spectroscopy experiments were carried out to characterize the thin films and obtain information about the crystal structure, atomic composition, surface morphology and vibrational modes. Temperature-dependent transmission measurements were performed in between 10 and 300 K and in the spectral range of 400–1050 nm. The analyses of transmittance spectra were accomplished by two different methods called as the absorption coefficient and the derivative spectrophotometry analyses. All evaluated band gap energy values at each studied temperature were in good agreement with each other depending on the applied analyses techniques. Room temperature gap energy values were found around 2.39 eV and 2.40 eV from absorption coefficient and derivative spectrophotometry analyses, respectively. Band gap energy depending on the sample temperature was studied under the light of two different models to investigate average phonon energy, electron phonon coupling parameter and the rate of change of band gap energy with temperature.
关键词： Thin film,CdS,Optical properties
更新于2025-09-23 15:23:52
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CO Gas Sensor based on E-beam Evaporated ZnO, MgZnO and CdZnO Thin Films: A Comparative Study
摘要： This paper reports a comparative study of electron-beam evaporated ZnO, MgZnO and CdZnO thin film based gas sensor. At room temperature (RT), these semiconductive thin films were deposited on Si/SiO2 substrate and an interdigitated pattern of chromium electrode deposited on these films. Device properties such as structural, optical and electrical have been reported and analyzed. The sensors have been tested at different operating temperatures. At 250 ℃, the sensor shows the best response for CdZnO thin films. We have obtained sensor response 4.86 with response time 15 sec for 100 PPM carbon mono oxide (CO) gas concentration for CdZnO thin film. Based on experimental results, Cd-doped ZnO has been found most suitable among these semiconducting metal oxides, when used as a CO gas sensor. A correlation between structural, optical and electrical properties with these thin films has also been established.
关键词： Thin film,ZnO,MgZnO,CO Gas sensor,CdZnO,E-beam evaporation
更新于2025-09-23 15:23:52
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PVP-assisted thermal annealing of thin Au layer for creation of effective and reproducible SERS substrates
摘要： Creation of SERS substrate with the large active area and homogeneous distribution of hot spots is now one of the most important tasks in the field of SERS practical implementation. This problem has been solved by various techniques, but the most applicable of them are expensive due to highly technical nature. In this work, a simple alternative approach based on thermal annealing of sputtered Au layer has been proposed. Usually, the thermal annealing of the thin Au layer leads to the formation of gold clusters array with high plasmon efficiency but with too wide size distribution and highly disordered arrangement. To overcome this drawback the previous soaking of Au layer in the poly(vinylpyrrolidone) (PVP) solution was proposed, with the aim to affect clusters formation and achieve the more homogeneous distribution of created hot spots array. Annealed Au and Au-PVP thin layers were characterized by AFM, XRD, XPS, UV–Vis and Raman spectroscopy techniques. Present results indicate that the PVP treatment before thermal treatment significantly affect the growth of the clusters and provide the perspective way for increasing of SERS efficiency and reproducibility.
关键词： Thin gold film,SERS,Annealing,Reproducibility
更新于2025-09-23 15:23:52
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Highly conductive, transparent and metal-free electrodes with a PEDOT:PSS/SWNT bilayer for high-performance organic thin film transistors
摘要： Conductive organic materials including polymers, small molecules, and carbon nanotubes (CNTs) are a promising alternative to inorganic materials in electronic devices. Conventionally, organic electrodes employing CNTs are designed using functionalization of their surfaces or formation of nanocomposites with a conductive polymer. However, phase separation limits the concentration of CNTs in a polymer matrix, hindering the formation of highly dense CNT networks and leading to poor electrical conductivity. In this paper, we introduce bilayer electrodes comprising poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and single-walled CNTs (SWNTs) chemically modified by HNO3 treatment. Impressive conductivities of 2432 and 2438 S cm?1 are found for the SWNT/PEDOT:PSS (S/P) and PEDOT:PSS/SWNT (P/S) electrodes, respectively. Further, an increase in the work function of the electrodes after HNO3 treatment lowers the hole injection barrier, which facilitates hole injection from pentacene. The smooth surface of PEDOT:PSS also contributes to growth of large pentacene grains; consequently, the field-effect mobility of pentacene-based thin film transistors is 1.88 cm2 V?1 s?1 when the P/S electrode is employed. The metal-free electrodes also exhibit a high optical transparency of 88.7%, which suggests that they have great potential for applications in optoelectronics.
关键词： Electrode,PEDOT:PSS,Carbon nanotube,Pentacene,Thin film transistor
更新于2025-09-23 15:23:52
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RF Characterization of NiO and TiO <sub/>2</sub> Based Metal-Insulator-Metal (MIM) Diodes on Flexible Substrates
摘要： This paper presents the fabrication and characterization of metal-insulator-metal (MIM) diodes on flexible substrates for RF and microwave circuit applications. Diodes using two types of insulators, titanium dioxide (TiO2) and nickel oxide (NiO), are investigated. These insulators are obtained using different oxidation techniques, i.e., in-situ oxidation for TiO2 and plasma oxidation for NiO. Asymmetric metal contacts (Ti-TiO2-Pd and Ni-NiO-Mo) are utilized to achieve nonlinear I–V characteristics. The fabricated diodes show strong non-linearity, high current densities, and low turn-ON voltage. The diodes show RF to dc rectification with near-ideal behavior and rectification sensitivity of 22 V/W (18 GHz) and 46 V/W (18 GHz) for TiO2 and NiO, respectively. NiO-based diodes barrier shows higher current density and higher cutoff frequency in comparison with TiO2 as expected diodes due to thinner oxide and lower dielectric constant. The diodes also work well as frequency doublers over a wide frequency range of 1–4 GHz for TiO2 and 2–10 GHz for NiO-based diodes. Good dc and RF performance of diodes indicate that good quality oxide can be achieved on plastic substrates and MIM devices can provide a perfect solution for RF and microwave circuits on a flexible substrate.
关键词： MIM diodes,rectification,Flexible electronics,harmonic generation,thin film devices,microwave circuits
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Elimination of the Hump Current of P-Channel Polycrystalline Silicon Thin-Film Transistor After Positive Bias Stress
摘要： The stability of p-channel low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) under positive bias stress (PBS) is investigated in this paper. Interestingly, it is observed that the transfer curves show different degradation phenomena from the previous reports, i.e., the threshold voltage (Vth) shifts to the negative gate bias direction, and the hump current in the subthreshold region clearly shrinks with the increase of the stress time, and finally disappears under the PBS, which is explained by the creation and accumulation of positive charges in the gate oxide. It is also observed that the hump current in p-channel TFTs is eliminated at a higher temperature and one possible mechanism for the appearance of hump current is proposed.
关键词： thin-film transistors,positive bias stress (PBS),hump current,p-channel
更新于2025-09-23 15:23:52
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Fracture strength of silicon torsional mirror resonators fully coated with submicrometer-thick PECVD DLC film
摘要： In this work, we attempted to enhance the torsional fracture strength of single crystal silicon (SCS) resonators for micro mirrors application by introducing a 300 nm-thick diamond-like carbon (DLC) coating. The SCS torsional beams of the resonators were 20 μm wide and 9 μm thick, and fully coated with DLC films using plasma enhanced chemical vapor deposition (PECVD) at three different deposition bias voltages. The resonators were driven by a piezoelectric actuator and their angular amplitude was measured by a custom-made torsional test system. Average nominal torsional fracture strength of DLC coated resonators was 11.1–30.0% higher than that of bare SCS, reaching a value of 2.93 GPa. The torsional fracture strength of resonators exhibited a good agreement with the tensile fracture strength. Deviations in torsional strength were reduced with increasing deposition bias voltage due to the compressive residual stress of DLC films.
关键词： Single crystal silicon,Micro mirror resonator,Diamond-like carbon film,Strength deviation,Torsional fracture strength
更新于2025-09-23 15:23:52
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Reusable surface plasmon resonance sensor for rapid detection of Cu2+ based on modified-chitosan thin film as an active layer
摘要： In this article, a reusable surface plasmon resonance (SPR) sensor for rapid detection of copper ions (Cu2+), based on optimized silver/gold (Ag/Au) composite film modified by modified-chitosan (MCS) thin film as an active layer, was achieved. We employed a four-layer Kretchmann semi-cylindrical prism configuration and induced a reference beam into the experimental system to improve the sensitivity and stability, and investigated the cross-linking technique of CS solution, the spin coating process of MCS film, the stability of active layer, the rebirth power of SPR sensor, and the detection for trace Cu2+. The rate of swelling or dissolution of MCS film after flushing sensor chip for four times is less than 9×10?4/min, and the decline of signal value is less than 1.5% after MCS film adsorbing Cu2+ and multiple flushing. The elution and capacity rates are above 96% after five times of elution for the sensor by EDTA solution with 0.5mmol/L. Within 1-5ppm, the SPR sensor was found to possess sensitivity of 0.7271ppm?1. The LOD is 18ppb for the trace Cu2+. The present SPR sensor not only could be used in trace monitoring of Cu2+ but also could be extended to other potential applications.
关键词： Copper ions,Reutilization,Composite film,Modified-chitosan,Surface plasmon resonance
更新于2025-09-23 15:23:52
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A highly sensitive photocatalytic plastic optic-fiber sensor for selective detection of phenol in aqueous solutions
摘要： We present a highly sensitive photocatalytic plastic optic-fiber (POF) sensor for the selective detection of phenol in aqueous solutions. To obtain high sensitivity and low limit of detection (LOD) of the sensor, part of the POF cladding was removed and replaced by a Canada balsam doped with GeO2 (CBG); a UV-visible-light-driven photocatalytic material, that is a CdS-sensitized Er3+YAlO3/SiO2/TiO2 (EYST) composite, was coated on the CBG film. To realize highly selective detection of phenol in water, a high phenol permselectivity and pH independence polymer membrane was fixed on the CdS-sensitized EYST-CBG-coated POF. Furthermore, a model was developed to show that the phenol concentration can be determined by measuring the change in transmitted light intensity of the POF sensor and the sensitivity of the sensors can be improved by employing the CdS-sensitized EYST film. The results showed that the proposed photocatalytic POF sensor has a high sensitivity of -0.39 (mg·mL-1)-1 and low LOD of 15 μg·L-1 for the selective detection of phenol in aqueous solutions with pH ranging from 2.0 to 14.0.
关键词： Cds sensitization,Phenol concentration,High sensitivity and selectivity,Upconversion luminescence agent,Plastic optical fiber,TiO2 composite film
更新于2025-09-23 15:23:52
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Turning electrical switching behaviors in WO <sub/><i>x</i> </sub> thin films by thickness
摘要： The tunability of electrical switching behaviors in WOx thin films were investigated in this paper. Electrical responses of the WOx films were observed to be highly sensitive to the film thickness. As the film thickness increases from 50 to 100 nm, the switching behavior changes from complementary resistive switching (CRS) to threshold switching (TS). A defect-related dynamic evolution of filament is responsible for the switching behavior. Such a controllable electrical switching can well broaden the application of the WOx thin film.
关键词： threshold switching,WOx thin film,Electrical switching behavior,turning,complementary resistive switching
更新于2025-09-23 15:23:52