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Effect of tantalum content on the structural properties and sensing performance of YbTaxOy electrolyte-insulator-semiconductor pH sensors
摘要： In this work, we developed YbTaxOy sensing membranes displaying super-Nernstian pH-sensitivity for use in electrolyte-insulator-semiconductor (EIS) pH sensors. We examined the effect of tantalum content on the structural properties and sensing characteristics of the YbTaxOy sensing membranes deposited through reactive co-sputtering onto Si substrates. X-ray diffraction, atomic force microscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy revealed the structural, morphological, depth, and chemical features, respectively, of these YbTaxOy films prepared under various Ta plasma power conditions (from 80 to 160 W). Among the tested systems, the YbTaxOy EIS device prepared at the 120 W condition exhibited the super-Nernstian sensitivity (70.24 mV/pH), the lowest hysteresis voltage (1.5 mV), and the lowest drift rate (0.26 mV/h). Presumably, this condition optimized the stoichiometry of YbTaO4 in the film and its surface roughness while reducing the crystal defect and suppressing silicate formation at the YbTaxOy-Si interface. The super-Nernstian pH-sensitivity may be attributed to the incorporation of Ta ions in the Yb2O3 forming a YbTaO4 stoichiometric film, enhancing a change in oxidation state of Yb from trivalent ion to bivalent ion and thus transferring one electron to two protons in the redox reaction.
关键词： Electrolyte-insulator-semiconductor (EIS),Sensing characteristics,Plasma power,pH sensitivity,YbTaxOy
更新于2025-09-23 15:22:29
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Room temperature synthesis of Au NR@Ag2S and Au NR@Ag2S/CdS core-shells using a facile photochemical approach
摘要： In this work, Au nanorods with tunable longitudinal plasmon resonance were synthesized using hydroquinone as complimentary surfactant. Ag2S quantum dots (QDs) were grown directly on Au nanorods using the replacement of cetyltrimethylammonium bromide (CTAB) with 3-Mercaptopropionic acid (MPA) via a novel photochemical approach. X-ray diffraction revealed the presence of Au cubic structure as well as Ag2S monoclinic phase. Fourier-transform infrared spectroscopy, electrochemical impedance spectroscopy and cyclic voltamettery confirmed the successful substitution of CTAB with MPA as an appropriate capping agent for the growth of Ag2S and CdS quantum dots. UV-Vis spectroscopy demonstrated a red shift of plasmon resonance peak from 750 nm up to 835 nm indicating the increase of dielectric constant of surrounded Au nanorods due to the formation of Ag2S QDs as shell. Photoluminescence spectroscopy revealed near Infrared (NIR) emission of Au@Ag2S core-shells as an indication of controllable size of Ag2S during the growth time. Transmission electron microscopy (TEM) images clearly showed the formation of Ag2S QDs as shell around Au nanorods. To indicate the flexibility of current growth method, CdS QDs were also grown on Au@Ag2S core-shells only by addition of Cd precursor to as prepared Au@Ag2S colloidal solution and continuation of UV illumination. The clear and intense visible light emission of the sample together with the NIR emission of Ag2S and gradual red shift of plasmon resonance of Au nanorods with elapsing photochemical treatment time were the indication of successful growth of Ag2S/CdS on Au nanorods. TEM images clearly showed Au@Ag2S/CdS almond shape core-shells. This method has the simplest chemistry and the procedure is very simple, rapid (less than 2 h), energy efficient and scalable for large production of such core-shells.
关键词： Au nanorods,Metal-semiconductor core-shells,Ag2S QDs,Photoluminescence,Electroimpedance spectroscopy
更新于2025-09-23 15:22:29
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Room temperature multi-phonon upconversion photoluminescence in monolayer semiconductor WS2
摘要： Photon upconversion is an anti-Stokes process in which an absorption of a photon leads to a reemission of a photon at an energy higher than the excitation energy. The upconversion photoemission has been already demonstrated in rare earth atoms in glasses, semiconductor quantum wells, nanobelts, carbon nanotubes and atomically thin semiconductors. Here, we demonstrate a room temperature upconversion photoluminescence process in a monolayer semiconductor WS2, with energy gain up to 150 meV. We attribute this process to transitions involving trions and many phonons and free exciton complexes. These results are very promising for energy harvesting, laser refrigeration and optoelectronics at the nanoscale.
关键词： photoluminescence,monolayer semiconductor,phonons,energy gain,room temperature,WS2,excitons,trions,upconversion
更新于2025-09-23 15:22:29
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Heteroepitaxial growth of thick <i>α</i> -Ga <sub/>2</sub> O <sub/>3</sub> film on sapphire (0001) by MIST-CVD technique
摘要： The 8 μm thick single-crystalline α-Ga2O3 epilayers have been heteroepitaxially grown on sapphire (0001) substrates via mist chemical vapor deposition technique. High resolution X-ray diffraction measurements show that the full-widths-at-half-maximum (FWHM) of rocking curves for the (0006) and (10-14) planes are 0.024° and 0.24°, and the corresponding densities of screw and edge dislocations are 2.24 × 106 and 1.63 × 109 cm?2, respectively, indicative of high single crystallinity. The out-of-plane and in-plane epitaxial relationships are [0001] α-Ga2O3//[0001] α-Al2O3 and [11-20] α-Ga2O3//[11-20] α-Al2O3, respectively. The lateral domain size is in micron scale and the indirect bandgap is determined as 5.03 eV by transmittance spectra. Raman measurement indicates that the lattice-mismatch induced compressive residual strain cannot be ruled out despite the large thickness of the α-Ga2O3 epilayer. The achieved high quality α-Ga2O3 may provide an alternative material platform for developing high performance power devices and solar-blind photodetectors.
关键词： chemical vapor deposition,ultra-wide bandgap semiconductor,gallium oxide,epitaxy
更新于2025-09-23 15:22:29
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An In-Depth Study on Electrical and Hydrogen Sensing Characteristics of ZnO Thin Film with Radio Frequency Sputtered Gold Schottky Contacts
摘要： Electrical and hydrogen sensing characteristics of radio frequency sputtered Au/ZnO thin film Schottky diodes on n-silicon substrate have been investigated over a wide temperature range. Current-voltage characterizations of the device in the temperature range of 25°C to 200°C confirm its excellent rectifying property with forward to reverse current ratio of 1610 at an external bias of 5 V. Ideality factor in the range of 4.12 to 2.98 is obtained for Au/ZnO Schottky diode in the aforementioned temperature range, at atmospheric conditions. On exposing diode to hydrogen, a reduction in ideality factor is observed which makes thermionic emission more prominent. The proposed device has proven to be hydrogen sensitive, on account of the lateral shift observed in I ? V characteristics at different hydrogen concentrations (50 ppm-1000 ppm). Maximum barrier height variation of 99 meV and sensitivity of 144% have been observed at 1000 ppm hydrogen at 200°C. A Detailed perusal of the steady-state reaction kinetics of the sensor using I ? V characteristics affirmed that the atomistic hydrogen adsorption at Au/ZnO interface is accountable for the barrier height modulation. The studied sensor depicts remarkable performance for high-temperature detection.
关键词： Hydrogen sensing,Zinc oxide (ZnO) thin film,Electrical characteristics,Schottky diode,Metal-semiconductor interface,Palladium catalyst
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - High Frequency Optical Probe for BAW/SAW Devices
摘要： Optical properties of semiconductor devices for LED and OLED devices. We present a novel optical tool based on heterodyne interferometry that is capable of detecting surface and subsurface defects in semiconductor materials with high precision. The tool operates at frequencies up to 25 GHz and can achieve a detection limit of less than 1 nm. This method is particularly useful for quality control in the optoelectronics industry, as it allows for non-destructive testing of devices such as LEDs and OLEDs. Our results demonstrate that this tool can effectively identify defects that are not detectable with conventional optical microscopy.
关键词： non-destructive testing,defect detection,optoelectronics,semiconductor devices,LED,OLED,heterodyne interferometry
更新于2025-09-23 15:22:29
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Characterization of CMP Slurries Using Densitometry and Refractive Index Measurements
摘要： We investigated the possibility of employing refractive index (RI) measurements for inline incoming slurry control at the point of use (POU), as an alternative to the widespread densitometry method. As such, it became necessary to determine if RI could detect smaller changes in slurry composition and, therefore, provide a tighter control. Three industrially-relevant silica-based slurries, namely, Fujimi PL-7106, Klebosol 1501-50, and CMC W7801, were characterized using both densitometry and RI measurements. Initial solutions of the three slurries were prepared and increasingly small amounts of ultrapurified water (UPW) were added to study the change in slurry properties. Results showed that both density and RI decreased linearly with the addition of water for all three slurries, with the 1501-50 being the most sensitive to water addition. A linear correlation between the two properties was found, with R2 values that exceeded 0.95 in all cases. Furthermore, the approximate limit of detection of both metrology tools was estimated based on the slope of the fitting line and resolution. When compared to densitometry, RI was found to be the far superior method for detecting smaller changes in water concentration.
关键词： semiconductor technology,slurry characterization,in-line monitoring and control,chemical mechanical planarization
更新于2025-09-23 15:22:29
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Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa
摘要： ZnO has the built-in characteristics of both ionic and covalent compound semiconductors, which makes the metal–ZnO carrier transport mechanism quite intricate. The growth mechanism-centric change in ZnO defect density and carrier concentration also makes the contact formation and behavior unpredictable. This study investigates the uncertainty in Au–ZnO contact behavior for application-oriented research and the development on ZnO nanostructures. Herein, we explain the phenomenon for how Au–ZnO contact could be rectifying or non-rectifying. Growth method-dependent defect engineering was exploited to explain the change in Schottky barrier heights at the Au–ZnO interface, and the change in device characteristics from Schottky to Ohmic and vice versa. The ZnO nanorods were fabricated via aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. For further investigations, one ACG sample was doped with Ga, and another was subjected to oxygen plasma treatment (OPT). The ACG and Ga-doped ACG samples showed a quasi-Ohmic and Ohmic behavior, respectively, because of a high surface and subsurface level donor defect-centric Schottky barrier pinning at the Au–ZnO interface. However, the ACG-OPT and MAG samples showed a more pronounced Schottky contact because of the presence of low defect-centric carrier concentration via MAG, and the removal of the surface accumulation layer via the OPT process.
关键词： oxygen plasma treatment,nanorod,ZnO,crystal defects,microwave,metal-semiconductor contact
更新于2025-09-23 15:22:29
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Recent Advances in β-Ga2O3–Metal Contacts
摘要： Ultra-wide bandgap beta-gallium oxide (β-Ga2O3) has been attracting considerable attention as a promising semiconductor material for next-generation power electronics. It possesses excellent material properties such as a wide bandgap of 4.6–4.9 eV, a high breakdown electric field of 8 MV/cm, and exceptional Baliga’s figure of merit (BFOM), along with superior chemical and thermal stability. These features suggest its great potential for future applications in power and optoelectronic devices. However, the critical issue of contacts between metal and Ga2O3 limits the performance of β-Ga2O3 devices. In this work, we have reviewed the advances on contacts of β-Ga2O3 MOSFETs. For improving contact properties, four main approaches are summarized and analyzed in details, including pre-treatment, post-treatment, multilayer metal electrode, and introducing an interlayer. By comparison, the latter two methods are being studied intensively and more favorable than the pre-treatment which would inevitably generate uncontrollable damages. Finally, conclusions and future perspectives for improving Ohmic contacts further are presented.
关键词： Intermediate semiconductor layer,Metal stacks,Contacts,β-Ga2O3
更新于2025-09-23 15:22:29
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Monodisperse Six-Armed Starbursts based on Truxene-Cored Multibranched Oligofluorenes: Design, Synthesis, and Stabilized Lasing Characteristics
摘要： A series of monodisperse six-armed conjugated starbursts (Tr1F, Tr2F and Tr3F) containing a truxene core and multibranched oligofluorene bridges capped with diphenylamine (DPA) units has been designed, synthesized, and investigated as robust gain media for organic semiconductor lasers (OSLs). The influence of electron-rich DPA end-groups on their optoelectronic characteristics has been discussed at length. DPA cappers effectively raise HOMO levels of the starbursts, thus enhancing the hole injection and transport ability. Solution-processed electroluminescence devices based on the resulting six-armed starbursts exhibited efficient deep-blue electroluminescence with clear reduced turn-on voltages (3.2~3.5 V). Moreover, the resulting six-armed molecules showed stabilized electroluminescence and amplified spontaneous emission with low thresholds (27.4~63.9 nJ pulse-1), high net gain coefficients (80.1~101.3 cm-1), and small optical loss (2.6~4.4 cm-1). Distributed feedback OSLs made from Tr3F exhibited low lasing threshold of 0.31 kW/cm2 (at 465 nm). The results suggest that the construction of truxene-centered six-armed conjugated starbursts with the incorporation of DPA units can effectively enhance EL properties by precisely regulating the HOMO energy levels, and further optimizing their optical gain properties.
关键词： Organic gain media,Organic light-emitting diodes (OLEDs),Conjugated starburst molecules,Organic semiconductor lasers (OSLs),HOMO levels
更新于2025-09-23 15:22:29