A minority carrier lifetime of 25.46 μs in a P-type 4H-SiC epilayer has been attained through sequential thermal oxidation and hydrogen annealing. Thermal oxidation can enhance the minority carrier lifetime in the 4H...A minority carrier lifetime of 25.46 μs in a P-type 4H-SiC epilayer has been attained through sequential thermal oxidation and hydrogen annealing. Thermal oxidation can enhance the minority carrier lifetime in the 4H-SiC epilayer by reducing carbon vacancies. However, this process also generates carbon clusters with limited diffusivity and contributes to the enlargement of surface pits on the 4H-SiC. High-temperature hydrogen annealing effectively reduces stacking fault and dislocation density. Moreover, electron spin resonance analysis indicates a significant reduction in carbon vacancy defects after hydrogen annealing. The mechanisms of the elimination of carbon vacancies by hydrogen annealing include the decomposition of carbon clusters formed during thermal oxidation and the low-pressure selective etching by hydrogen,which increases the carbon content on the 4H-SiC surface and facilitates carbon diffusion. Consequently, the combination of thermal oxidation and hydrogen annealing eliminates carbon vacancies more effectively, substantially enhancing the minority carrier lifetime in P-type 4H-SiC. This improvement is advantageous for the application of high-voltage SiC bipolar devices.展开更多
The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C...The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.展开更多
P-type nitrogen-doped ZnO films are prepared successfully by in-situ thermal oxidation of Zn3N2 films. The prepared films are characterized by x-ray diffraction, non-Rutherford back.scattering （non-RBS） spectroscopy...P-type nitrogen-doped ZnO films are prepared successfully by in-situ thermal oxidation of Zn3N2 films. The prepared films are characterized by x-ray diffraction, non-Rutherford back.scattering （non-RBS） spectroscopy, x- ray photoelectron spectroscopy, and photoluminescence spectrum. The results show that the Zn3N1 films start to transform to ZnO at 400℃ and the total nitrogen content decreases with the increasing annealing temperature. The p-type fihns are achieved at 500℃ with a low resistivity of 6.33Ω.cm and a high hole concentration of ＋8.82 × 10^17 cm-3, as well as a low level of carbon contamination, indicating that the substitutional nitrogen （No） is an effective acceptor in the ZnO：N film. The photoluminescence spectra show clear UV emissions and also indicate the presence of oxygen vacancy （Vo） defects in the ZnO：N films. The p-type doping mechanism is briefly discussed.展开更多
The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found ...The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.展开更多
We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is fou...We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is found that all the samples have wrinkles and the size of the wrinkles increases with the oxidation time increasing. CuO NWs can grow on both the sidehill and hilltop of wrinkle. The CuO NWs on sidehill are longer and denser than those on hilltop. The growth direction of the CuO NWs on sidehill is not vertical to the substrate but vertical to their growth surfaces. The process of wrinkling and CuO NWs growth can be divided into three stages： undulating, voiding, and cracking. The CuO NWs on both sidehill and hilltop grow at the undulating stage. However, only the CuO NWs on sidehill grow and those on hilltop stop growing at the voiding and cracking stages because of the void in hilltop. The local electric field in a wrinkle at undulating stage was calculated, and it is found that the difference of local electric field strengths between hilltop and sidehill is small, which indicates that the predominant driving force for the diffusion of Cu ion during CuO NWs growth is internal stress.展开更多
We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer （OBL） to form an ultrathin GeOx interracial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. T...We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer （OBL） to form an ultrathin GeOx interracial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. The GeOx interfacial layer is formed in oxidation reaction by oxygen passing through the Al2O3 OBL, in which theAl2O3 layer could restrain the oxygen diffusion and suppress the GeO desorption during thermal treatment. The thickness of the GeOx interfacial layer would dramatically decrease as the thickness of Al2O3 OBL increases, which is beneficial to achieving an ultrathin GeOx interfacial layer to satisfy the demand for small equivalent oxide thickness （EOT）. In addition, the thickness of the GeOx interfacial layer has little influence on the passivation effect of the Al2O3/Ge interface. Ge （100） p-channel metal- oxide-semiconductor field-effect transistors （pMOSFETs） using the Al2O3/GeOx/Ge gate stacks exhibit excellent electrical characteristics; that is, a drain current on-off （Ionloft） ratio of above 1 104, a subthreshold slope of - 120 mV/dec, and a peak hole mobility of 265 cm2/V.s are achieved.展开更多
Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importa...Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study, we for the first time experimentally find that all types of strained Si substrates （uniaxial tensile, uniaxial compressive, biaxial tensile, and biaxial compressive） show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.展开更多
Single-crystalline Mn_(3)O_(4)nanoflakes were grown on manganese sheets by one-step thermal oxidation process at 360-500℃in ambient atmosphere.The samples were characterized by scanning electron microscope(SEM),X-ray...Single-crystalline Mn_(3)O_(4)nanoflakes were grown on manganese sheets by one-step thermal oxidation process at 360-500℃in ambient atmosphere.The samples were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),Raman and transmission electron microscope(TEM).The nanoflakes with a size of 15-20 nm in thickness,~60 nm in width,and~210 nm in length are obtained at 360℃for 24 h.A surface diffusion mechanism is proposed to explain the growth of manganese oxide nanostructures via thermal oxidation,which includes two steps:manganese oxide(MnO/Mn_(3)O_(4))layers form firstly,and then Mn_(3)O_(4)nanostructures grow above the upper metal oxide layer to form multi-layered structures,MnO/Mn_(3)O_(4)/Mn_(3)O_(4)-nanoflakes.The nucleation and growth of Mn_(3)O_(4)nanostructures are related to the surface energy and different growth rates along different crystal directions,which are controlled by the diffusion of the metal and gas molecule.展开更多
Thermal oxidation was used to remove the subsurface damage of silicon carbide （SIC） surfaces. The anisotropy of oxidation and the composition of oxide layers on Si and C faces were analyzed. Regular pits were observ...Thermal oxidation was used to remove the subsurface damage of silicon carbide （SIC） surfaces. The anisotropy of oxidation and the composition of oxide layers on Si and C faces were analyzed. Regular pits were observed on the surface after the removal of the oxide layers, which were detrimental to the growth of high quality epitaxial layers. The thickness and composition of the oxide layers were characterized by Rutherford backscattering spectrometry （RBS） and X-ray photoelectron spectroscopy （XPS）, respectively. Epitaxial growth was performed in a metal organic chemical vapor deposition （MOCVD） system. The substrate surface morphology after removing the oxide layer and gallium nitride （GaN） epilayer surface were observed by atomic force microscopy （AFM）. The results showed that the GaN epilayer grown on the oxidized substrates was superior to that on the unoxidized substrates.展开更多
By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-ma...By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched Ino.18Alo.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magni- tude is observed after the thermal oxidation of the Ino.18Alo.82N/GaN heterostructures at 700 ℃. It is confirmed that the reverse leakage current is dominated by the Frenkel-Poole emission, and the main origin of the leakage current is the emis- sion of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAll-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAll-xN surface, which increases the electron emission barrier height.展开更多
Titanium oxide films were prepared by annealing DC magnetron sputtered titanium films in an oxygen ambient. X-ray diffraction （XRD）, Auger electron spectroscopy （AES） sputter profiling, MCs^＋-mode secondary ion m...Titanium oxide films were prepared by annealing DC magnetron sputtered titanium films in an oxygen ambient. X-ray diffraction （XRD）, Auger electron spectroscopy （AES） sputter profiling, MCs^＋-mode secondary ion mass spectrometry （MCs^＋-SIMS） and atomic force microscopy （AFM） were employed, respectively, for the structural, com- positional and morphological characterization of the obtained films. For temperatures below 875 K, titanium films could not be fully oxidized within one hour. Above that temperature, the completely oxidized films were found to be rutile in structure. Detailed studies on the oxidation process at 925K were carried out for the understanding of the underlying mechanism of titanium dioxide （TiO2） formation by thermal oxidation. It was demonstrated that the formation of crystalline TiO2 could be divided into a short oxidation stage, followed by crystal forming stage. Relevance of this recognition was further discussed.展开更多
By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon ...By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon monocrystal under dry oxygen atmosphere at 1100℃.Compared with their oxidation kinetic curves consisted of three stages,we suggested a mechanism on forming silicon oxide film.According to electron and X-ray diffraction analyses the silicon oxide films consisted of silica with different crystal structure.We also have discussed a stacking fault and a dislocation formed in the Si-Sio_2 interface region simulaneously forming silicon oxide film.展开更多
P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device appl...P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device applications. In this paper,we introduce an alternative route to stabilizing N in the oxidation process, the thermal stability of p-ZnO is significantly improved. Finally, we discuss the limitations of the alternative doping method and provide some prospective outlook of the method.展开更多
Two kinds of NiCrAlY coatings(Ni-25Cr-10Al-0.5Y)were prepared on K417 superalloy using ion plating(AIP)and magnetron sputtering(MS),respectively.The isothermal and cyclic oxidation behaviors of the two NiCrAlY coating...Two kinds of NiCrAlY coatings(Ni-25Cr-10Al-0.5Y)were prepared on K417 superalloy using ion plating(AIP)and magnetron sputtering(MS),respectively.The isothermal and cyclic oxidation behaviors of the two NiCrAlY coatings were evaluated at 1323 K in stair air.The results revealed that the nanocrystalline NiCrAlY coating exhibited better isothermal and cyclic oxidation resistance compared to the conventional NiCrAlY at 1323 K.The mass gain and parabolic rate constant Kp of the nanocrystalline NiCrAlY coating were 45.2%and 44.7%lower than those of the conventional NiCrAlY coating,respectively.During cyclic oxidation,the tendency for spallation of the oxide scale was evidently decreased by nanocrystallization due to the formation of a continuous,compact,adherent,and slow-growing exclusiveα-Al_(2)O_(3)scale.The mechanism responsible for the improvement of the nanocrystalline NiCrAlY coating was discussed.展开更多
In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick....In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick.The forced flow method and infrared imaging method are used to test the permeability and capillary performance of the samples.The effects of different oxidation temperatures on the performance of capillary wick are investigated.The experimental results show that the wetting performance of the oxidized samples is significantly enhanced.With the increase of oxidation temperature,the permeability decreases.The capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary wick.However,the oxidation temperature needs to be adjusted to obtain the best capillary performance.The highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated ones.Comparisons with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer device.This study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.展开更多
The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results sho...The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results showed that the mica improved the thermal properties of the composites,the thermal expansion coefficient decreased,and the liquid phase formation caused the composites to shrink and increase the density.The flexural strength of mica surface modified composites not only increased to 78.64MPa after thermal treatment at 800-1200℃,but reached 83.02 MPa after high temperature treatment at1400℃.The improvement of the mechanical properties of the residual product benefits from the formation of high temperature ceramic phases such as Mo_(2)C and MoB,and the improvement of the shear strength of the composites by the mica.The shear strength of MBm5-2 at room temperature reached 33.08 MPa,indicating that the improvement of the interlayer properties of the composites further improved its mechanical properties.展开更多
High-efficient rubber antioxidants for enhanced heat resistance without compromising mechanical properties remain an enormous and long-term challenge for the rubber industry.Herein,we employed the in-situ growth of Ce...High-efficient rubber antioxidants for enhanced heat resistance without compromising mechanical properties remain an enormous and long-term challenge for the rubber industry.Herein,we employed the in-situ growth of Ce-doped Co-metal-organic framework(Ce Co-MOF)in dendritic mesoporous organosilica nanoparticles(DMONs@Ce Co-MOF,denoted as DCCM)to prepare a novel antioxidant that exhibit outstanding thermal stability.Dendritic mesoporous organosilica nanoparticles(DMONs)effectively alleviated the incompatibility of Ce Co-MOF in the polymer matrix,and the effective scavenging of free radicals was attributed to the various oxidation states of metal ions in Ce Co-MOF.Surprising,by adding only0.5 phr(parts per hundred of rubber)of DMONs@Ce Co-MOF to silicone rubber,(SR),the retention rate of tensile strength increased from 37.3%to 61.6%after aging 72 h at 250℃,and the retention rate of elongation at break of DCCM/SR1 composites reached 68%,which was 5.43 times of SR.The strategy of anchoring MOFs on the surface of silica also provides a viable method for preparing effective compound functionalized rubber antioxidant.展开更多
This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carb...This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.展开更多
The ZnO layer with thickness of 1.6 jim in ZnO/ZnGa2O4 composite structure was grown by the thermal oxidation of ZnS sub- strate with gallium. The optical property of the ZnO thick layer was investigated by time-resol...The ZnO layer with thickness of 1.6 jim in ZnO/ZnGa2O4 composite structure was grown by the thermal oxidation of ZnS sub- strate with gallium. The optical property of the ZnO thick layer was investigated by time-resolved photoluminescence. A single UV emission around 375 nm with short lifetime was observed at room temperature while the visible emission was absolutely quenched. The UV emission band was composed of the neutral donor bound exciton （D^0X） and donor-acceptor pair （DAP） emission peaks with large full-width at half-maximums （FWHMs） at 3.367 and 3.318 eV, respectively, at 10 K. However, the intensity of the D^0X emission was stronger than that of the DAP emission at measuring temperatures of 10-300 K.展开更多
A novel approach for the fabrication of a metal oxide semiconductor（MOS） structure was reported.The process comprises electrochemical deposition of aluminum and zinc layers on a base of nickel-chromium alloy. This t...A novel approach for the fabrication of a metal oxide semiconductor（MOS） structure was reported.The process comprises electrochemical deposition of aluminum and zinc layers on a base of nickel-chromium alloy. This two-layer structure was thermally oxidized at 400℃for 40 min to produce thin layers of aluminum oxide as an insulator and zinc oxide as a semiconductor on a metallic substrate.Using deposition parameters,device dimensions and SEM micrographs of the layers,the device parameters were calculated.The resultant MOS structure was characterized by a C-V curve method.From this curve,the device maximum capacitance and threshold voltage were estimated to be about 0.74 nF and -2.9 V,respectively,which are in the order of model-based calculations.展开更多
基金Project supported by the National Key Research and Development Program of China (Grant Nos. 2023YFB3609500 and 2023YFB3609502)the National Natural Science Foundation of China (Grant No. 62274137)+1 种基金the Natural Science Foundation of Jiangxi Province, China (Grant No. 20232BAB202043)the Science and Technology Project of Fujian Province of China (Grant No. 2020I0001)。
文摘A minority carrier lifetime of 25.46 μs in a P-type 4H-SiC epilayer has been attained through sequential thermal oxidation and hydrogen annealing. Thermal oxidation can enhance the minority carrier lifetime in the 4H-SiC epilayer by reducing carbon vacancies. However, this process also generates carbon clusters with limited diffusivity and contributes to the enlargement of surface pits on the 4H-SiC. High-temperature hydrogen annealing effectively reduces stacking fault and dislocation density. Moreover, electron spin resonance analysis indicates a significant reduction in carbon vacancy defects after hydrogen annealing. The mechanisms of the elimination of carbon vacancies by hydrogen annealing include the decomposition of carbon clusters formed during thermal oxidation and the low-pressure selective etching by hydrogen,which increases the carbon content on the 4H-SiC surface and facilitates carbon diffusion. Consequently, the combination of thermal oxidation and hydrogen annealing eliminates carbon vacancies more effectively, substantially enhancing the minority carrier lifetime in P-type 4H-SiC. This improvement is advantageous for the application of high-voltage SiC bipolar devices.
基金Project(51072165)supported by the National Natural Science Foundation of ChinaProject(201305)supported by the Fund of State Key Laboratory of Solidification Processing,ChinaProjects(2013JK0921,2013JK0922)supported by Shaanxi Provincial Education Department of China
文摘The SiCf/SiC composites containing PyC interphase were prepared by chemical vapor infiltration process. The influences of thermal oxidation on the complex permittivity and microwave absorption properties of Si Cf/Si C composites were investigated in the frequency range of 8.2-12.4 GHz. Both the real and imaginary parts of the complex permittivity decreased after thermal oxidation. The composites after 100 h thermal oxidation showed that reflection loss exceeded-10 d B in the frequency of 9.7-11.9 GHz and the minimum value was-11.4 d B at 11.0 GHz. The flexural strength of composites decreased but fracture behavior was improved obviously after thermal oxidation. These results indicate that the SiCf/SiC composites containing PyC interphase after thermal oxidation possess good microwave absorbing property and fracture behavior.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10775033 and 11075038
文摘P-type nitrogen-doped ZnO films are prepared successfully by in-situ thermal oxidation of Zn3N2 films. The prepared films are characterized by x-ray diffraction, non-Rutherford back.scattering （non-RBS） spectroscopy, x- ray photoelectron spectroscopy, and photoluminescence spectrum. The results show that the Zn3N1 films start to transform to ZnO at 400℃ and the total nitrogen content decreases with the increasing annealing temperature. The p-type fihns are achieved at 500℃ with a low resistivity of 6.33Ω.cm and a high hole concentration of ＋8.82 × 10^17 cm-3, as well as a low level of carbon contamination, indicating that the substitutional nitrogen （No） is an effective acceptor in the ZnO：N film. The photoluminescence spectra show clear UV emissions and also indicate the presence of oxygen vacancy （Vo） defects in the ZnO：N films. The p-type doping mechanism is briefly discussed.
文摘The rare earth-containing composite elastomer was obtained by the reaction of vinyl pyridine-SBR (PSBR) latex with rare earth alkoxides, and its thermal oxidation resistance was studied. After aging test, it is found that its retention rate of mechanical properties is far higher than that of the control sample. The results of thermogravimetric analysis show that its thermal-decomposing temperature rises largely. The analysis of oxidation mechanisms indicates that the main reasons for thermal oxidation resistance are that rare earth elements are of the utility to discontinue autoxidation chain reaction and that the formed complex structure has steric hindrance effect on oxidation.
文摘We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is found that all the samples have wrinkles and the size of the wrinkles increases with the oxidation time increasing. CuO NWs can grow on both the sidehill and hilltop of wrinkle. The CuO NWs on sidehill are longer and denser than those on hilltop. The growth direction of the CuO NWs on sidehill is not vertical to the substrate but vertical to their growth surfaces. The process of wrinkling and CuO NWs growth can be divided into three stages： undulating, voiding, and cracking. The CuO NWs on both sidehill and hilltop grow at the undulating stage. However, only the CuO NWs on sidehill grow and those on hilltop stop growing at the voiding and cracking stages because of the void in hilltop. The local electric field in a wrinkle at undulating stage was calculated, and it is found that the difference of local electric field strengths between hilltop and sidehill is small, which indicates that the predominant driving force for the diffusion of Cu ion during CuO NWs growth is internal stress.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CBA00605 and 2011CBA00607)the National Natural Science Foundation of China(Grant No.61204103)the National Science & Technology Major Project of China(Grant No.2011ZX02708-003)
文摘We propose a modified thermal oxidation method in which an Al2O3 capping layer is used as an oxygen blocking layer （OBL） to form an ultrathin GeOx interracial layer, and obtain a superior Al2O3/GeOx/Ge gate stack. The GeOx interfacial layer is formed in oxidation reaction by oxygen passing through the Al2O3 OBL, in which theAl2O3 layer could restrain the oxygen diffusion and suppress the GeO desorption during thermal treatment. The thickness of the GeOx interfacial layer would dramatically decrease as the thickness of Al2O3 OBL increases, which is beneficial to achieving an ultrathin GeOx interfacial layer to satisfy the demand for small equivalent oxide thickness （EOT）. In addition, the thickness of the GeOx interfacial layer has little influence on the passivation effect of the Al2O3/Ge interface. Ge （100） p-channel metal- oxide-semiconductor field-effect transistors （pMOSFETs） using the Al2O3/GeOx/Ge gate stacks exhibit excellent electrical characteristics; that is, a drain current on-off （Ionloft） ratio of above 1 104, a subthreshold slope of - 120 mV/dec, and a peak hole mobility of 265 cm2/V.s are achieved.
基金supported by the National Key Basic Research Project of China(Grant No.2011CBA00607)the National Natural Science Foundation of China(Grant Nos.61106089 and 61376097)the Program B for Outstanding Ph.D.Candidate of Nanjing University,China(Grant No.201301B005)
文摘Strained Si is recognized as a necessary technology booster for modem integrated circuit technology. However, the thermal oxidation behaviors of strained Si substrates are not well understood yet despite their importance. In this study, we for the first time experimentally find that all types of strained Si substrates （uniaxial tensile, uniaxial compressive, biaxial tensile, and biaxial compressive） show smaller thermal oxidation rates than an unstrained Si substrate. The possible mechanisms for these retarded thermal oxidation rates in strained Si substrates are also discussed.
基金the National Natural Science Foundation(Nos.51264013 and 21005034)Science Foundation of Jiangxi Provincial Education Development(Nos.GJJ14442 and GJJ14448)the Doctoral Program of Jiangxi University of Science and Technology(No.jxxjbs13017)。
文摘Single-crystalline Mn_(3)O_(4)nanoflakes were grown on manganese sheets by one-step thermal oxidation process at 360-500℃in ambient atmosphere.The samples were characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),Raman and transmission electron microscope(TEM).The nanoflakes with a size of 15-20 nm in thickness,~60 nm in width,and~210 nm in length are obtained at 360℃for 24 h.A surface diffusion mechanism is proposed to explain the growth of manganese oxide nanostructures via thermal oxidation,which includes two steps:manganese oxide(MnO/Mn_(3)O_(4))layers form firstly,and then Mn_(3)O_(4)nanostructures grow above the upper metal oxide layer to form multi-layered structures,MnO/Mn_(3)O_(4)/Mn_(3)O_(4)-nanoflakes.The nucleation and growth of Mn_(3)O_(4)nanostructures are related to the surface energy and different growth rates along different crystal directions,which are controlled by the diffusion of the metal and gas molecule.
基金supported by the National Natural Sci-ence Foundation of China (No. 50721002)Program for New Century Excellent Talents in University
文摘Thermal oxidation was used to remove the subsurface damage of silicon carbide （SIC） surfaces. The anisotropy of oxidation and the composition of oxide layers on Si and C faces were analyzed. Regular pits were observed on the surface after the removal of the oxide layers, which were detrimental to the growth of high quality epitaxial layers. The thickness and composition of the oxide layers were characterized by Rutherford backscattering spectrometry （RBS） and X-ray photoelectron spectroscopy （XPS）, respectively. Epitaxial growth was performed in a metal organic chemical vapor deposition （MOCVD） system. The substrate surface morphology after removing the oxide layer and gallium nitride （GaN） epilayer surface were observed by atomic force microscopy （AFM）. The results showed that the GaN epilayer grown on the oxidized substrates was superior to that on the unoxidized substrates.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60444007,11174008,60325413,and 10774001)
文摘By using temperature-dependent current-voltage, variable-frequency capacitance-voltage, and Hall measurements, the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched Ino.18Alo.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magni- tude is observed after the thermal oxidation of the Ino.18Alo.82N/GaN heterostructures at 700 ℃. It is confirmed that the reverse leakage current is dominated by the Frenkel-Poole emission, and the main origin of the leakage current is the emis- sion of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAll-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAll-xN surface, which increases the electron emission barrier height.
文摘Titanium oxide films were prepared by annealing DC magnetron sputtered titanium films in an oxygen ambient. X-ray diffraction （XRD）, Auger electron spectroscopy （AES） sputter profiling, MCs^＋-mode secondary ion mass spectrometry （MCs^＋-SIMS） and atomic force microscopy （AFM） were employed, respectively, for the structural, com- positional and morphological characterization of the obtained films. For temperatures below 875 K, titanium films could not be fully oxidized within one hour. Above that temperature, the completely oxidized films were found to be rutile in structure. Detailed studies on the oxidation process at 925K were carried out for the understanding of the underlying mechanism of titanium dioxide （TiO2） formation by thermal oxidation. It was demonstrated that the formation of crystalline TiO2 could be divided into a short oxidation stage, followed by crystal forming stage. Relevance of this recognition was further discussed.
文摘By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon monocrystal under dry oxygen atmosphere at 1100℃.Compared with their oxidation kinetic curves consisted of three stages,we suggested a mechanism on forming silicon oxide film.According to electron and X-ray diffraction analyses the silicon oxide films consisted of silica with different crystal structure.We also have discussed a stacking fault and a dislocation formed in the Si-Sio_2 interface region simulaneously forming silicon oxide film.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474076)
文摘P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device applications. In this paper,we introduce an alternative route to stabilizing N in the oxidation process, the thermal stability of p-ZnO is significantly improved. Finally, we discuss the limitations of the alternative doping method and provide some prospective outlook of the method.
基金financially supported by the National Natural Science Foundation of China(No.52101075)China Postdoctoral Science Foundation(Nos.2021M700557,2022M723272)+1 种基金Postdoctoral Scienceof Chongqing Natural Science Foundation(Nos.cstc2021jcyj-bshX0053,cstc2021jcyj-bshX0039)Scientific Research Foundation of Chongqing University of Technology(No.2020ZDZ004)。
文摘Two kinds of NiCrAlY coatings(Ni-25Cr-10Al-0.5Y)were prepared on K417 superalloy using ion plating(AIP)and magnetron sputtering(MS),respectively.The isothermal and cyclic oxidation behaviors of the two NiCrAlY coatings were evaluated at 1323 K in stair air.The results revealed that the nanocrystalline NiCrAlY coating exhibited better isothermal and cyclic oxidation resistance compared to the conventional NiCrAlY at 1323 K.The mass gain and parabolic rate constant Kp of the nanocrystalline NiCrAlY coating were 45.2%and 44.7%lower than those of the conventional NiCrAlY coating,respectively.During cyclic oxidation,the tendency for spallation of the oxide scale was evidently decreased by nanocrystallization due to the formation of a continuous,compact,adherent,and slow-growing exclusiveα-Al_(2)O_(3)scale.The mechanism responsible for the improvement of the nanocrystalline NiCrAlY coating was discussed.
基金financial support for this research from the National Natural Science Foundation of China (52006040 and 51876044)the Natural Science Foundation of Guangdong Province(2019B090905005)the International Science and Technology Projects of Huangpu District of Guangzhou City(2020GH08)。
文摘In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal oxidation.It is used to improve the performance of the capillary wick.The forced flow method and infrared imaging method are used to test the permeability and capillary performance of the samples.The effects of different oxidation temperatures on the performance of capillary wick are investigated.The experimental results show that the wetting performance of the oxidized samples is significantly enhanced.With the increase of oxidation temperature,the permeability decreases.The capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary wick.However,the oxidation temperature needs to be adjusted to obtain the best capillary performance.The highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated ones.Comparisons with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer device.This study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.
基金Funded by the National Natural Science Foundation of China(Nos.52171045,52162013,and 51932006)。
文摘The surface of MoSi2-SiB6/phenolic resin matrix composites was modified by mica,and the thermal oxidation behavior of the composites and the mechanical properties of the pyrolysis products were studied.The results showed that the mica improved the thermal properties of the composites,the thermal expansion coefficient decreased,and the liquid phase formation caused the composites to shrink and increase the density.The flexural strength of mica surface modified composites not only increased to 78.64MPa after thermal treatment at 800-1200℃,but reached 83.02 MPa after high temperature treatment at1400℃.The improvement of the mechanical properties of the residual product benefits from the formation of high temperature ceramic phases such as Mo_(2)C and MoB,and the improvement of the shear strength of the composites by the mica.The shear strength of MBm5-2 at room temperature reached 33.08 MPa,indicating that the improvement of the interlayer properties of the composites further improved its mechanical properties.
基金support from the Beijing Natural Science Foundation(No.JQ23035)。
文摘High-efficient rubber antioxidants for enhanced heat resistance without compromising mechanical properties remain an enormous and long-term challenge for the rubber industry.Herein,we employed the in-situ growth of Ce-doped Co-metal-organic framework(Ce Co-MOF)in dendritic mesoporous organosilica nanoparticles(DMONs@Ce Co-MOF,denoted as DCCM)to prepare a novel antioxidant that exhibit outstanding thermal stability.Dendritic mesoporous organosilica nanoparticles(DMONs)effectively alleviated the incompatibility of Ce Co-MOF in the polymer matrix,and the effective scavenging of free radicals was attributed to the various oxidation states of metal ions in Ce Co-MOF.Surprising,by adding only0.5 phr(parts per hundred of rubber)of DMONs@Ce Co-MOF to silicone rubber,(SR),the retention rate of tensile strength increased from 37.3%to 61.6%after aging 72 h at 250℃,and the retention rate of elongation at break of DCCM/SR1 composites reached 68%,which was 5.43 times of SR.The strategy of anchoring MOFs on the surface of silica also provides a viable method for preparing effective compound functionalized rubber antioxidant.
基金funded by the Innovative Research Group project of the National Natural Science Foundation of China(52373003).
文摘This study investigates the long-term thermal-oxidative stability and mechanical properties of phenolcontaining phthalonitrile monomer(PN75)and dicyanate ester of bisphenol-A(DCBA)composites reinforced with short carbon fibers T700SC(SCF)within a temperature range of 330375℃.The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content,examining mass loss and changes in flexural strength after thermal aging for 50 h(h).Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength,both at room temperature and after thermal aging.The introduction of the SCF significantly improves the composites'thermal stability and mechanical retention,with higher SCF content correlating to better performance.Notably,after aging at 350℃,the SCF-reinforced composites based(30%(mass)SCF)retained 88.8%of its flexural strength,compared to 61.1%for the neat blend.Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces,the overall composite structure maintains good mechanical properties up to 350℃.At 375℃,significant degradation occurs,yet the composites still retain flexural strengths above 78 MPa.This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications,establishing their upper-temperature limit for long-term use in oxidative environments.
基金supported by the National Natural Science Foundation of China(Grant No.51202191)Natural Science Basic Research Plan in Shaanxi Province of China(Grant No.2012JQ6002)Scientific Research Program Funded by Shaanxi Provincial Education Department of China(Grant No.12JK0427)
文摘The ZnO layer with thickness of 1.6 jim in ZnO/ZnGa2O4 composite structure was grown by the thermal oxidation of ZnS sub- strate with gallium. The optical property of the ZnO thick layer was investigated by time-resolved photoluminescence. A single UV emission around 375 nm with short lifetime was observed at room temperature while the visible emission was absolutely quenched. The UV emission band was composed of the neutral donor bound exciton （D^0X） and donor-acceptor pair （DAP） emission peaks with large full-width at half-maximums （FWHMs） at 3.367 and 3.318 eV, respectively, at 10 K. However, the intensity of the D^0X emission was stronger than that of the DAP emission at measuring temperatures of 10-300 K.
文摘A novel approach for the fabrication of a metal oxide semiconductor（MOS） structure was reported.The process comprises electrochemical deposition of aluminum and zinc layers on a base of nickel-chromium alloy. This two-layer structure was thermally oxidized at 400℃for 40 min to produce thin layers of aluminum oxide as an insulator and zinc oxide as a semiconductor on a metallic substrate.Using deposition parameters,device dimensions and SEM micrographs of the layers,the device parameters were calculated.The resultant MOS structure was characterized by a C-V curve method.From this curve,the device maximum capacitance and threshold voltage were estimated to be about 0.74 nF and -2.9 V,respectively,which are in the order of model-based calculations.
