AlN was used as a host material and doped with Eu grown on Si substrate by pulsed laser deposition (PLD) with low substrate temperature. The X-ray diffraction (XRD) data revealed the orientation and the composition of...AlN was used as a host material and doped with Eu grown on Si substrate by pulsed laser deposition (PLD) with low substrate temperature. The X-ray diffraction (XRD) data revealed the orientation and the composition of the thin film. The surface morphology was studied by scanning electron microscope (SEM). While raising the annealing temperatures from 300˚C to 900˚C, the emission was observed from AlN: Eu under excitation of 260 nm excitation. The photoluminescence (PL) was integrated over the visible light wavelength shifted from the blue to the red zone in the CIE 1931 chromaticity coordinates. The luminescence color coordination of AlN: Eu depending on the annealing temperatures guides the further study of Eu-doped nitrides manufacturing on white light emitting diode (LED) and full color LED devices.展开更多
Solid electrolytes for all solid sodium-ion batteries have been attracting much attention as an alternative energy storage system, which have the advantage of being extremely safe because it can be charged quickly and...Solid electrolytes for all solid sodium-ion batteries have been attracting much attention as an alternative energy storage system, which have the advantage of being extremely safe because it can be charged quickly and is nonflammable. We have synthesized anti-perovskite type Na<sub>3</sub>OX (X = Br, and I) electrolytes with high purity, by reactions of halogen mixtures with sodium oxides. After mixing, it was filled in an alumina crucible and heated for 6 hours at 330°C. It was confirmed that a large crystal strain was introduced by eutectication, which might reduce the activation energy of Na ion conduction and lead to an improvement of the conductivity. A relatively higher ionic conductivity of σ = 1.55 × 10<sup>-7</sup> S/cm at 60°C has been obtained for Na<sub>3</sub>OBr<sub>0.6</sub>I<sub>0.4</sub>, which is about three orders higher than that in literature. A different ratio of X (X = Br, I) ions was added into sodium oxide to make the Na<sub>3</sub>OX crystal. The influence of strain introduction on optimizing the bottleneck and improving the conductivity was discussed.展开更多
Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to ro...Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to room temperature. It is shown that the immersing process is valid to dope Er in high concentration in porous Si. Time resolved study of the Er-doped porous Si revealed that the doped Er3+ ions are excited by energy transfer from photo-generated electron-hole pairs in the host. The energy back transfer process from the excited 4f electrons in the Er3+ion to the host is not a dominant factor to quench the Er-related emission in porous Si. Ourresults are well explained by a proposed model in which an intermediate state was introduced.展开更多
The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during ...The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during high-temperature Ar annealing. In particular, for a reconstructed Si(110) surface, characteristic line-shaped oxidation occurs at preferential oxidation sites appearing in pentagonal pairs in the directions of Si[-112] and/or [-11-2]. We previously reported that the roughness increase of reconstructed Si(110) due to reflow oxidation can be restrained by replacing Ar gas with H2 gas at 1000°C during the cooling to 100°C after high-temperature Ar annealing. It was speculated that preferential oxidation sites on reconstructed Si(110) were eliminated by H2 gas etching and hydrogen termination of dangling bonds. Thus, it is necessary to investigate the effect of H2 gas etching and hydrogen termination behavior on the reconstructed Si(110) surface structure. In this study, we evaluated in detail the relationship between the temperature at which the H2 gas replaces the Ar in high-temperature Ar annealing and the reconstructed Si(110) surface structure. The maximum height of the roughness on the reconstructed surface was the same as if Ar gas was used when the H2 gas introduction temperature was 200°C, although the amount of reflow oxidation was decreased to 70% by hydrogen termination. Furthermore, line-shaped oxidation still occurs when H2 gas replaces Ar at this low temperature. Therefore, we conclude that oxidation is caused by slight Si etching at low temperatures, and thus the preferential oxidation sites on the reconstructed structure must be eliminated by hydrogen etching in order to form an atomically smooth Si(110) surface.展开更多
The excitation process of rare-earth ions in oxide semiconductors for optical emission is thought to be related to defect levels within the band-gap of the host material. In order to improve understanding of the role ...The excitation process of rare-earth ions in oxide semiconductors for optical emission is thought to be related to defect levels within the band-gap of the host material. In order to improve understanding of the role defect levels play in the energy transfer process, junction spectroscopy techniques can be used to investigate the electrically active emission centres. It has been reported that TiO<sub>2</sub> is sensitive to humidity at low temperatures, such as those employed when conducting junction spectroscopy measurements. However, there are not many discussions how to prevent this effect and to improve the quality of measurements. After optimization of samples such as fabrication of flat surface and encupsulant for preventing external effect, temperature dependent-capacitance measurements (C-T) were carried out to characterise shallow traps formed within TiO<sub>2</sub> band-gap. TiO<sub>2</sub> and Sm-doped TiO<sub>2</sub> thin films were deposited on SrTiO<sub>3</sub> (100) templates by laser ablaton and rectifying Ruthenium Oxide Schottky diodes deposited on the TiO<sub>2</sub> surface by laser ablation. A Sm or Sm-related shallow trap was observed in the Arrhenius plot of TiO<sub>2</sub>:Sm. In this paper, we show the optimized sample fabrication/preparation process that stabilizes the junction spectroscopy measurements, even in the presence of humidity and we present initial results obtained on samples using these optimized processing techniques.展开更多
Most accidents of centrifugal compressors are caused by fluid pulsation or unsteady fluid excitation.Rotating stall,as an unstable flow phenomenon in the compressor,is a difficult point in the field of fluid machinery...Most accidents of centrifugal compressors are caused by fluid pulsation or unsteady fluid excitation.Rotating stall,as an unstable flow phenomenon in the compressor,is a difficult point in the field of fluid machinery research.In this paper,a stack denoising kernel autoencoder neural network method is proposed to study the early warning of rotating stall in a centrifugal compressor.By collecting the pressure pulsation signals of the centrifugal compressor under different flow rates in engineering practice,a double hidden layer sparse denoising autoencoder neural network is constructed.According to the output labels of the network,it can be judged whether the rotation stall occurs.At the same time,the Gaussian kernel is used to optimize the loss function of the whole neural network to improve the signal feature learning ability of the network.From the experimental results,it can be seen that the flow state of the centrifugal compressor is accurately judged,and the rotation stall early warning of the centrifugal compressor at different speeds is realized,which lays a foundation for the research of intelligent operation and maintenance of the centrifugal compressor.展开更多
Reconstruction of Quaternary environments,late Cenozoic geodynamics and evaluation of volcanic hazards,all depend on the precise delineation of eruptive stages.In recent years,laser 40Ar/39Ar dating methods have been ...Reconstruction of Quaternary environments,late Cenozoic geodynamics and evaluation of volcanic hazards,all depend on the precise delineation of eruptive stages.In recent years,laser 40Ar/39Ar dating methods have been widely used for dating young volcanic rocks,given their stable automated testing process,very low background level and high sensitivity,which meet the requirements for precise dating of young samples.This paper applied high-precision laser 40Ar/39Ar dating to the main volcanic units in the Tengchong area and obtained ages in the range of 0.025–5.1 Ma using conventional data processing methods.However,conventional dating highlighted issues related to very low radiogenic 40Ar content,accidental errors and poor data stability,which led to huge age deviations.Moreover,lacking a unified timescale,conventional methods were unable to strictly define the stages of the Tengchong volcanic eruptions,leading to ongoing controversy.In this study,we applied a Gaussian mathematical model to deal with all 378 original ages from 13 samples.An apparent age-probability diagram,consisting of three independent waveforms,have been obtained.The corresponding isochron ages of these three waveforms suggest there were three volcanic eruptive stages,namely during the Pliocene(3.78±0.04 Ma),early Middle Pleistocene(0.63±0.03 Ma)and late Middle Pleistocene to early Late Pleistocene(0.139±0.005 Ma).These results accurately define eruptive stages in the Tengchong area.展开更多
文摘AlN was used as a host material and doped with Eu grown on Si substrate by pulsed laser deposition (PLD) with low substrate temperature. The X-ray diffraction (XRD) data revealed the orientation and the composition of the thin film. The surface morphology was studied by scanning electron microscope (SEM). While raising the annealing temperatures from 300˚C to 900˚C, the emission was observed from AlN: Eu under excitation of 260 nm excitation. The photoluminescence (PL) was integrated over the visible light wavelength shifted from the blue to the red zone in the CIE 1931 chromaticity coordinates. The luminescence color coordination of AlN: Eu depending on the annealing temperatures guides the further study of Eu-doped nitrides manufacturing on white light emitting diode (LED) and full color LED devices.
文摘Solid electrolytes for all solid sodium-ion batteries have been attracting much attention as an alternative energy storage system, which have the advantage of being extremely safe because it can be charged quickly and is nonflammable. We have synthesized anti-perovskite type Na<sub>3</sub>OX (X = Br, and I) electrolytes with high purity, by reactions of halogen mixtures with sodium oxides. After mixing, it was filled in an alumina crucible and heated for 6 hours at 330°C. It was confirmed that a large crystal strain was introduced by eutectication, which might reduce the activation energy of Na ion conduction and lead to an improvement of the conductivity. A relatively higher ionic conductivity of σ = 1.55 × 10<sup>-7</sup> S/cm at 60°C has been obtained for Na<sub>3</sub>OBr<sub>0.6</sub>I<sub>0.4</sub>, which is about three orders higher than that in literature. A different ratio of X (X = Br, I) ions was added into sodium oxide to make the Na<sub>3</sub>OX crystal. The influence of strain introduction on optimizing the bottleneck and improving the conductivity was discussed.
文摘Er was doped into porous Si by immersing the porous Si sample in a saturated ErCl3,ethanol solution. Sharp and intense 1.54 μm photoluminescence caused by intra-4f-shefl transitions in Er3+ ions was observed up to room temperature. It is shown that the immersing process is valid to dope Er in high concentration in porous Si. Time resolved study of the Er-doped porous Si revealed that the doped Er3+ ions are excited by energy transfer from photo-generated electron-hole pairs in the host. The energy back transfer process from the excited 4f electrons in the Er3+ion to the host is not a dominant factor to quench the Er-related emission in porous Si. Ourresults are well explained by a proposed model in which an intermediate state was introduced.
文摘The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during high-temperature Ar annealing. In particular, for a reconstructed Si(110) surface, characteristic line-shaped oxidation occurs at preferential oxidation sites appearing in pentagonal pairs in the directions of Si[-112] and/or [-11-2]. We previously reported that the roughness increase of reconstructed Si(110) due to reflow oxidation can be restrained by replacing Ar gas with H2 gas at 1000°C during the cooling to 100°C after high-temperature Ar annealing. It was speculated that preferential oxidation sites on reconstructed Si(110) were eliminated by H2 gas etching and hydrogen termination of dangling bonds. Thus, it is necessary to investigate the effect of H2 gas etching and hydrogen termination behavior on the reconstructed Si(110) surface structure. In this study, we evaluated in detail the relationship between the temperature at which the H2 gas replaces the Ar in high-temperature Ar annealing and the reconstructed Si(110) surface structure. The maximum height of the roughness on the reconstructed surface was the same as if Ar gas was used when the H2 gas introduction temperature was 200°C, although the amount of reflow oxidation was decreased to 70% by hydrogen termination. Furthermore, line-shaped oxidation still occurs when H2 gas replaces Ar at this low temperature. Therefore, we conclude that oxidation is caused by slight Si etching at low temperatures, and thus the preferential oxidation sites on the reconstructed structure must be eliminated by hydrogen etching in order to form an atomically smooth Si(110) surface.
文摘The excitation process of rare-earth ions in oxide semiconductors for optical emission is thought to be related to defect levels within the band-gap of the host material. In order to improve understanding of the role defect levels play in the energy transfer process, junction spectroscopy techniques can be used to investigate the electrically active emission centres. It has been reported that TiO<sub>2</sub> is sensitive to humidity at low temperatures, such as those employed when conducting junction spectroscopy measurements. However, there are not many discussions how to prevent this effect and to improve the quality of measurements. After optimization of samples such as fabrication of flat surface and encupsulant for preventing external effect, temperature dependent-capacitance measurements (C-T) were carried out to characterise shallow traps formed within TiO<sub>2</sub> band-gap. TiO<sub>2</sub> and Sm-doped TiO<sub>2</sub> thin films were deposited on SrTiO<sub>3</sub> (100) templates by laser ablaton and rectifying Ruthenium Oxide Schottky diodes deposited on the TiO<sub>2</sub> surface by laser ablation. A Sm or Sm-related shallow trap was observed in the Arrhenius plot of TiO<sub>2</sub>:Sm. In this paper, we show the optimized sample fabrication/preparation process that stabilizes the junction spectroscopy measurements, even in the presence of humidity and we present initial results obtained on samples using these optimized processing techniques.
基金supported through the Joint Funds of the National Natural Science Foundation of China (Grant No.U1808214)National Key Research and Development Project (Grant No.2020YFB2010800)the National Natural Science Foundation of China (Grant No.92060105).
文摘Most accidents of centrifugal compressors are caused by fluid pulsation or unsteady fluid excitation.Rotating stall,as an unstable flow phenomenon in the compressor,is a difficult point in the field of fluid machinery research.In this paper,a stack denoising kernel autoencoder neural network method is proposed to study the early warning of rotating stall in a centrifugal compressor.By collecting the pressure pulsation signals of the centrifugal compressor under different flow rates in engineering practice,a double hidden layer sparse denoising autoencoder neural network is constructed.According to the output labels of the network,it can be judged whether the rotation stall occurs.At the same time,the Gaussian kernel is used to optimize the loss function of the whole neural network to improve the signal feature learning ability of the network.From the experimental results,it can be seen that the flow state of the centrifugal compressor is accurately judged,and the rotation stall early warning of the centrifugal compressor at different speeds is realized,which lays a foundation for the research of intelligent operation and maintenance of the centrifugal compressor.
基金supported by the Geological Survey Project of the China Geological Survey Bureau(Grant No.1212113013700).
文摘Reconstruction of Quaternary environments,late Cenozoic geodynamics and evaluation of volcanic hazards,all depend on the precise delineation of eruptive stages.In recent years,laser 40Ar/39Ar dating methods have been widely used for dating young volcanic rocks,given their stable automated testing process,very low background level and high sensitivity,which meet the requirements for precise dating of young samples.This paper applied high-precision laser 40Ar/39Ar dating to the main volcanic units in the Tengchong area and obtained ages in the range of 0.025–5.1 Ma using conventional data processing methods.However,conventional dating highlighted issues related to very low radiogenic 40Ar content,accidental errors and poor data stability,which led to huge age deviations.Moreover,lacking a unified timescale,conventional methods were unable to strictly define the stages of the Tengchong volcanic eruptions,leading to ongoing controversy.In this study,we applied a Gaussian mathematical model to deal with all 378 original ages from 13 samples.An apparent age-probability diagram,consisting of three independent waveforms,have been obtained.The corresponding isochron ages of these three waveforms suggest there were three volcanic eruptive stages,namely during the Pliocene(3.78±0.04 Ma),early Middle Pleistocene(0.63±0.03 Ma)and late Middle Pleistocene to early Late Pleistocene(0.139±0.005 Ma).These results accurately define eruptive stages in the Tengchong area.
