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Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH <sub/>3</sub> plasma pretreatment
摘要： High quality gallium oxide (Ga2O3) thin films are deposited by remote plasma-enhanced atomic layer deposition (RPEALD) with trimethylgallium (TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga2O3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 ?/cycle at 250 °C, respectively. The increasing of deposition rate is attributed to more hydroxyls (–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga2O3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga2O3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.
关键词： RPEALD,NH3 plasma,Ga-oxide,passivation
更新于2025-09-19 17:15:36
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Preparation and NH3 Gas-Sensing Properties of Double-Shelled Hollow ZnTiO3 Microrods
摘要： A novel double-shelled hollow (DSH) structure of ZnTiO3 microrods was prepared by self-templating route with the assistance of poly(diallyldimethylammonium chloride) (PDDA) in an ethylene glycol (EG) solution, which was followed by calcining. Moreover, the NH3 gas-sensing properties of the DSH ZnTiO3 microrods were studied at room temperature. The morphology and composition of DSH ZnTiO3 microrods films were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The formation process of double-shelled hollow microrods was discussed in detail. The comparative gas-sensing results revealed that the DSH ZnTiO3 microrods had a higher response to NH3 gas at room temperature than those of the TiO2 solid microrods and DSH ZnTiO3 microrods did in the dark. More importantly, the DSH ZnTiO3 microrods exhibited a strong response to low concentrations of NH3 gas at room temperature.
关键词： room-temperature,NH3 gas sensor,ZnTiO3 microrods,Double-shelled hollow
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Probing Molecules Next to Surfaces
摘要： Selective reflection spectroscopy at normal incidence provides signals with sub-Doppler resolution, linear with optical intensity. Frequency modulated (FM) selective reflection probes atomic vapours at distances comparable to the excitation wavelength (~λ/2π) and is used extensively to probe the Casimir-Polder interactions between an excited state atom and a macroscopic surface. Extending selective reflection spectroscopy to molecular gases allows probing a thin layer of molecular gas next to a surface. This is a very attractive prospect that allows envisaging high-resolution molecular spectroscopy and molecular frequency references in a compact and miniaturised apparatus, such as a thin cell [1] or a photonic crystal [2]. Additionally, it paves the way for spectroscopic probing of the Casimir-Polder interaction with molecules. The molecule-surface interaction has been the object of extensive theoretical investigations, focusing on the effects of molecular orientation and chirality. However, experimental tests are few and comparison with theoretical predictions has been challenging [3]. Here, we present selective reflection measurements on polyatomic molecules in gaseous form. We probe rovibrational molecular transitions of NH3 and SF6 using a Quantum Cascade Laser (QCL) at ~10.6μm. Reflection spectroscopy is performed in a vacuum chamber with transparent ZnSe windows. In a separate chamber, we perform simultaneous saturated absorption measurements, to get molecular frequency references in the volume. We also use an auxiliary set-up to lock the QCL laser, either on the derivative (after FM demodulation) of a Doppler linear absorption, or on the wings of the NH3 linear absorption (direct signal). This allows us to eliminate a frequency drift of the QCL source due to temperature fluctuations. By tuning the molecular pressure and therefore the absorption profile, the latter method (lock on the direct signal) allows stable frequency scanning for hundreds of MHz. A system of electronic valves allows us to empty and refill the chamber with molecules within tens of seconds. Detecting the difference between signals, as well as using multiple vibrating mirrors in our set-up, eliminates to about 0.1ppm an interferometric parasitic background, typical in infrared spectroscopy. Fig.1 shows our experimental results obtained for the isolated saP(1) transition of NH3 (Fig. 1a) and a multitude of transitions of SF6, mostly unidentified in molecular databases (Fig. 1b). Linear selective reflection allows us to pinpoint these transitions and easily determine their relative amplitude. At sufficiently low molecular pressure, the frequency resolution of our measurements is limited to ~0.5MHz essentially by laser linewidth. This allows partially resolving the hyperfine structure of NH3. The dotted curves represent theoretical predictions of selective reflection spectra, with transition amplitude adjustments, accounting for FM and laser linewidth. We are working on the fabrication of thin cells using ZnSe windows for rovibrational transmission spectroscopy in the mid-infrared, as well as glass windows, for probing C2H2 at telecommunication wavelengths. Due to the Dicke narrowing effect, thin cells are a step towards compact high-resolution frequency references. Furthermore, achieving, nanometric molecular confinement, defined by cell thickness, instead of wavelength (λ/2π for selective reflection, here ~1.5μm) will allow us to measure the Casimir-Polder interaction with molecules and to study the thermal coupling and energy transfer between rovibrational molecular transitions and surface polaritons [4].
关键词： SF6,Casimir-Polder interactions,molecular gases,Quantum Cascade Laser,NH3,Selective reflection spectroscopy
更新于2025-09-16 10:30:52
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High ammonia sensitive ability of novel Cu12Sb4S13 quantum dots@reduced graphene oxide nanosheet composites at room temperature
摘要： In the work, rGO nanosheet is synthesized using the typical Hummer’s method, then Cu12Sb4S13 quantum dots@rGO composites are prepared by solvent thermal method, and Cu12Sb4S13 quantum dots with the average size of 5 nm are densely distributed on the surface of rGO sheet. NH3 gas response of Cu12Sb4S13 quantum dots@rGO nanosheet composites at room temperature of 25 oC is enhanced compared with the pure Cu12Sb4S13 quantum dots and rGO nanosheet, and the composites possess an excellent stability during the humidity range of 45%-80% with a low detection limit of 1 ppm, which is related with the intrinsic hydrophobicity characteristic of Cu12Sb4S13 quantum dots. It also proves that Cu12Sb4S13 quantum dots@rGO nanosheet composites have a quite high selectivity towards ammonia compared with ethanol, methanol, acetone and toluene at room temperature. The gas sensing mechanism of the composites is discussed primarily
关键词： Gas response,Room temperature,Cu12Sb4S13 quantum dots@rGO nanosheet composites,NH3
更新于2025-09-16 10:30:52
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Rydberg-State-Resolved Resonant Energy Transfer in Cold Electric-Field-Controlled Intrabeam Collisions of NH <sub/>3</sub> with Rydberg He Atoms
摘要： The resonant transfer of energy from the inversion sublevels in NH3 to He atoms in triplet Rydberg states with principal quantum number n = 38 has been controlled using electric fields below 15 V/cm in intrabeam collisions at translational temperatures of ～1 K. The experiments were performed in pulsed supersonic beams of NH3 seeded in He at a ratio of 1:19. The He atoms were prepared in the metastable 1s2s 3S1 level in a pulsed electric discharge in the trailing part of the beams. The velocity slip between the heavy NH3 and the lighter metastable He was exploited to perform collision studies at center-of-mass collision speeds of ～70 m/s. Resonant energy transfer in the atom?molecule collisions was identified by Rydberg-state-selective electric-field ionization. The experimental data have been compared to a theoretical model of the resonant dipole?dipole interactions between the collision partners based on the impact parameter method.
关键词： NH3,resonant energy transfer,cold collisions,electric-field control,Rydberg states,He
更新于2025-09-12 10:27:22
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Additive‐Free Non‐Fullerene Organic Solar Cells
摘要： CeMnOx catalyst was synthesized by the combustion method, and the supported Ti/CeMnOx catalyst was subsequently prepared by wetness impregnation. Ti/CeMnOx catalyst exhibited higher N2 selectivity than CeMnOx catalyst in the selective catalytic reduction of NO by NH3 (NH3-SCR), and the generation of side products including in N2O and NO2 were discussed. N2 adsorption/desorption, X-ray di?raction (XRD), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (TPR), NH3 temperature-programmed desorption (TPD), and in situ di?use re?ectance infrared Fourier transform spectroscopy (DRIFTS) were carried out to reveal the promotion e?ect of TiO2 on the N2 selectivity of CeMnOx catalyst. Results indicated that loading TiO2 weakened the redox ability and enhanced the NH3 adsorption ability of CeMnOx catalyst, and thus inhibited NO/NH3 oxidation and facilitated the Eley?Rideal reaction pathways even at higher temperature.
关键词： TiO2,NH3 adsorption,redox ability,CeMnOx catalyst,N2 selectivity,NH3-SCR
更新于2025-09-11 14:15:04
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Optimization Algorithms of Neural Networks for Traditional Time-Domain Equalizer in Optical Communications
摘要： Herein we report an e?ective Ru(NH3)6 3+/Ru(NH3)6 2+-mediated photoelectrochemical-chemical-chemical (PECCC) redox cycling ampli?cation (RCA) strategy toward enhanced triple signal ampli?cation for advanced split-type PEC immunoassay application. Speci?cally, alkaline phosphatase (ALP) label was con?ned via a sandwich immunorecognition to convert 4-aminophenyl phosphate to the signal reporter 4-aminophenol (AP), which was then directed to interact with Ru(NH3)6 2+ as a redox mediator and tris (2-carboxyethyl) phosphine (TCEP) as reducing agent in the detection bu?er. Upon illumination, the system was then operated upon the oxidation of Ru(NH3)6 2+ by the photogenerated holes on the Bi2S3/BiVO4 photoelectrode, starting the chain reaction in which the Ru(NH3)6 2+ was regenerated by Ru(NH3)6 3+-enabled oxidization of AP to p-quinoneimine, which was simultaneously recovered by TCEP. Exempli?ed by interleukin-6 (IL-6) as the analyte, the Ru(NH3)6 3+/Ru(NH3)6 2+-mediated, AP-involved PECCC RCA coupled with ALP enzymatic ampli?cation could achieve triple signal ampli?cation toward the ultrasensitive PEC IL-6 immunoassay. This protocol can be extended as a general basis for other numerous targets of interest. Besides, we believe this work could o?er a new perspective for the further exploration of advanced RCA-based PEC bioanalysis.
关键词： photoelectrochemical-chemical-chemical (PECCC) redox cycling ampli?cation (RCA),triple signal ampli?cation,Bi2S3/BiVO4 photoelectrode,Ru(NH3)6 3+/Ru(NH3)6 2+-mediated,PEC immunoassay
更新于2025-09-11 14:15:04
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Simultaneous two cross-sectional measurements of NH<sub>3</sub> concentration in bent pipe flow using CT-tunable diode laser absorption spectroscopy
摘要： Urea Selective Catalytic Reduction (urea SCR) system is widely used for diesel engine to reduce the emission of NOx by NH3 which is provided by a hydrolysis of urea water. Concentration distribution of NH3 in an exhaust pipe is an important factor for improvement of the SCR efficiency and prevention of NH3 slip and urea deposit. Therefore, it is necessary to measure two-dimensional (2D) concentration of NH3 in detail. The purpose of this study is to develop the real-time two cross-sectional measurements technology of NH3 concentration using the computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS). Theoretical NH3 concentration distribution which was reconstructed by CT agreed to CFD results and quadruple pipe’s results showed good resolution by 14th order reconstruction. Therefore, this method has enough resolution and accuracy for measuring the concentration distribution of NH3. And this method was employed in a bent pipe model demonstrated a urea SCR system. The experimental results of two cross-sectional 2D concentration of NH3 show differences of the concentration distribution of NH3 each cross-section and flow pattern like swirl flow. It was found that CT-TDLAS was an effective method to measure concentration distribution of NH3 and observe characteristics of flow. In addition, observing flow pattern enable to validate CFD results, and it helps to improve efficiency of after treatment system.
关键词： Urea selective catalytic reduction,NH3 concentration measurement,Exhaust aftertreatment,CT tunable diode laser absorption spectroscopy,Measurement and instrumentation
更新于2025-09-11 14:15:04
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Investigation of carrier density and mobility variations in graphene caused by surface adsorbates
摘要： Conductivity, carrier concentration and carrier mobility in graphene were investigated as a function of time in response to ionized donor and acceptor adsorbates. While a reduction in conductivity and hole density in graphene was observed upon exposure to a weak electron donor NH3, the carrier mobility was found to increase monotonically. The opposite behavior is observed upon exposure to NO2, which is expected based on its typical electron withdrawing property. Upon exposure to C9H22N2, a strong donor, it resulted in the transformation of graphene from p-type to n-type, although the inverse variation of carrier concentration and mobility was still observed. The variational trends remained unaltered even after intentional introduction of defects in graphene through exposure to oxygen plasma. The responses to C9H22N2, NH3 and NO2 exposures underline a strong influence by ionized surface adsorbates that we explained via a simple model considering charged impurity scattering of carriers in graphene.
关键词： Carrier density,Gas molecule adsorption,Graphene,Graphene mobility,NH3,NO2
更新于2025-09-10 09:29:36
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First-Principle Study of Ammonia Decomposition and Nitrogen Incorporation on the GaN Surface in Metal Organic Vapor Phase Epitaxy
摘要： Based on the density functional theory (DFT), we theoretically investigate the growth mechanism of GaN (0001) using the Metal-Organic Vapor-Phase Epitaxy (MOVPE). We first identify the structure of the growing Ga rich GaN (0001) surface, then study the adsorption of NHx (x = 0-3) on such surface. We find that NH2 and NH units spontaneously intervene in the Ga-Ga weak bonds on the Ga-rich GaN (0001) surface. A reaction pathway of decomposition of NH3 on Ga rich surface is revealed. During reaction, N is found to incorporate in the weak Ga-Ga bond and form - Ga - (NH) - Ga - structure. The activation barrier of NH3 is surprisingly small, just 0.63eV. We also explore the decomposition of NH2 to N to form Ga-N network and find the plausible reaction pathway with the energy barrier of 2 eV. Taking into account the chemical potential of an H2 molecule in the gas phase at the growth temperature, we find that this reaction can be overcome. This NH3 decomposition mechanism and the N incorporation on GaN is a new growth mechanism catalyzed by the growing surface.
关键词： NH3 decomposition,DFT,N incorporation,MOVPE,GaN
更新于2025-09-10 09:29:36