This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a ...This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.展开更多
Undoped ZnO and doped ZnO films were deposited on the MgO（111） substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection hig...Undoped ZnO and doped ZnO films were deposited on the MgO（111） substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction（XRD）. The film roughness was measured by atomic force microscopy, which was correlated with the grain sizes determined by XRD. Synchrotron-based x-ray absorption spectroscopy was performed to study the doping effect on the electronic properties of the ZnO films, compared with density functional theory calculations.It is found that, nitrogen doping would hinder the growth of thin film, and generate the NOdefect, while magnesium doping promotes the quality of nitrogen-doped ZnO films, inhibiting（N_2）Oproduction and increasing nitrogen content.展开更多
ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption ...ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption spectroscopy. The negative integer charge transfer energy level is determined to be 4.00 ± 0.05 eV below the vacuum level, and the ionization potential is 5,75 ±0.10 eV. The molecules predominantly have the face-on orientation on inert substrates as long as the surfaces of the substrates are not too rough. These results provide the physical understanding of the high performance of ITIC-based solar ceils, which also afford implications to design more advanced photovoltaic small molecules.展开更多
Fe-doped ZnO film has been grown by laser molecular beam epitaxy（L-MBE） and structurally characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）,all of which reveal the high quality of the ...Fe-doped ZnO film has been grown by laser molecular beam epitaxy（L-MBE） and structurally characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）,all of which reveal the high quality of the film.No secondary phase was detected.Resonant photoemission spectroscopy（RPES） with photon energies around the Fe 2p-3d absorption edge is performed to detect the electronic structure in the valence band.A strong resonant effect at a photon energy of 710 eV is observed.Fe3＋ is the only valence state of Fe ions in the film and the Fe 3d electronic states are concentrated at binding energies of about 3.8 eV and 7 eV～8 eV.There are no electronic states related to Fe near the Fermi level.Magnetic measurements reveal a typical superparamagnetic property at room temperature.The absence of electronic states related to Fe near the Fermi level and the high quality of the film,with few defects,provide little support to ferromagnetism.展开更多
The effect of temperature on the electronic structure of Nb-doped SrTiO3（100） surface is investigated by highresolution synchrotron radiation photoemission spectroscopy.According to the x-ray photoemission spectrosc...The effect of temperature on the electronic structure of Nb-doped SrTiO3（100） surface is investigated by highresolution synchrotron radiation photoemission spectroscopy.According to the x-ray photoemission spectroscopy（XPS）results,at an annealing temperature of less than 700 ℃,the adsorbed carbon and hydroxyl on the STO surface could be removed,to expose the fresh intrinsic surface with a constant ratio of Ti/O.It is obvious that the STO would be doped by Ca^＋ impurities of bulks and O vacancies in the surface after annealing at 920 ℃ for one hour.展开更多
Surfactant-assisted Co film epitaxy growth on Cu(111)using Pb as a surfactant was studied by means of Auger electron spectra and synchrotron radiation photoemission spectra.The results reveal that with increasing the ...Surfactant-assisted Co film epitaxy growth on Cu(111)using Pb as a surfactant was studied by means of Auger electron spectra and synchrotron radiation photoemission spectra.The results reveal that with increasing the Co thickness most of the Pb atoms always float on the surface.Compared with 0.7ML(monolayer)Pb,the Co film with 1.5 ML Pb surfactant has more layer-by-layer growth on Cu(111).The predeposited Pb layer can suppress the intralayer diffusion on the Cu(111)surface and effectively increase the Co island density at the initial stage of Co growth.On the contrary,a Pb-Co surface alloy was found during the Co film growth;this may hinder the interlayer diffusion of the deposited Co atoms,which is unfavorable to the layer-by-layer growth.The Pb-Co is also considered to be the main reason why some Pb atoms have been buried in the Co films.展开更多
The reactions of superthin Pb Hlms on a Cu(111)surface with respect to the coverage of Pb and annealing have been studied by synchrotron radiation photoemission.The submonolayer Pb atoms deposited at room temperature ...The reactions of superthin Pb Hlms on a Cu(111)surface with respect to the coverage of Pb and annealing have been studied by synchrotron radiation photoemission.The submonolayer Pb atoms deposited at room temperature are distributed on the Cu(111)surface as two-dimensional(2D)islands.Annealing to 200℃ gives rise to Pb-Cu surface alloy formation.Analyses show that the surface alloy occurs only in the first layer of the Cu(111)surface.As a surfactant,Pb can promote 2D layer-by-layer growth of thin Hlms on Cu(111),but the Pb~Cu surface alloying may have an unfavorable effect on the activation process.展开更多
The electronic structure of fcc Fe/Cu{111}interface has been studied by angle-resolved photoemission with synchrotron radiation.The existence of the interface state and absence of intermixture between Fe and Cu atoms ...The electronic structure of fcc Fe/Cu{111}interface has been studied by angle-resolved photoemission with synchrotron radiation.The existence of the interface state and absence of intermixture between Fe and Cu atoms in the Fe/Cu{111}interface show that the Fe/Cu{111}system has an abrupt and ordered interface.展开更多
A systematic investigation of oxidation on a superconductive Fe Te_（0.5）Se_（0.5）thin film,which was grown on Nb-doped SrTiO_3（001） by pulsed laser deposition,has been carried out.The sample was exposed to ambien...A systematic investigation of oxidation on a superconductive Fe Te_（0.5）Se_（0.5）thin film,which was grown on Nb-doped SrTiO_3（001） by pulsed laser deposition,has been carried out.The sample was exposed to ambient air for one month for oxidation.Macroscopically,the exposed specimen lost its superconductivity due to oxidation.The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy（PES） and x-ray absorption spectroscopy（XAS） measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air.By the spectroscopic measurements,we found that the as-grown FeTe_（0.5）Se_（0.5）superconductive thin film experienced an element selective substitution reaction.The oxidation preferentially proceeds through pumping out the Te and forming Fe–O bonds by O substitution of Te.In addition,our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials.展开更多
The in situ valence band photoemission spectrum （PES） and X-ray absorption spectrum （XAS） at V LⅡ-LⅢ edges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal–insul...The in situ valence band photoemission spectrum （PES） and X-ray absorption spectrum （XAS） at V LⅡ-LⅢ edges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal–insulator transition （MIT） temperature （TMIT=67 ℃）. The spectra show evidence for changes in the electronic structure depending on temperature. Across the TMIT, pure V 3d characteristic d‖ and O 2p-V 3d hybridization characteristic πpd, σpd bands vary in binding energy position and density of state distributions. The XAS reveals a temperature-dependent reversible energy shift at the V LⅢ-edge. The PES and XAS results imply a synergetic energy position shift of occupied valence bands and unoccupied conduction band states across the phase transition. A joint inspection of the PES and XAS results shows that the MIT is not a one-step process, instead it is a process in which a semiconductor phase appears as an intermediate state. The final metallic phase from insulating state is reached through insulator–semiconductor, semiconductor–metal processes, and vice versa. The conventional MIT at around the TMIT=67 ℃ is actually a semiconductor–insulator transformation point.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 102750770)
文摘This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by X-ray absorption near edge structure spectra and X-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11204253,U1332105,61227009,and 91321102)the Fundamental Research Funds for Central Universities,China(Grant No.20720160020)the National High Technology Research and Development Program of China(Grant No.2014AA052202)
文摘Undoped ZnO and doped ZnO films were deposited on the MgO（111） substrates using oxygen plasma-assisted molecular beam expitaxy. The orientations of the grown ZnO thin film were investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction（XRD）. The film roughness was measured by atomic force microscopy, which was correlated with the grain sizes determined by XRD. Synchrotron-based x-ray absorption spectroscopy was performed to study the doping effect on the electronic properties of the ZnO films, compared with density functional theory calculations.It is found that, nitrogen doping would hinder the growth of thin film, and generate the NOdefect, while magnesium doping promotes the quality of nitrogen-doped ZnO films, inhibiting（N_2）Oproduction and increasing nitrogen content.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374258 and 11079028)
文摘ITIC is the milestone of non-fullerene small molecule acceptors used in organic solar cells. We study the electronic states and molecular orientation of ITIC film using photoelectron spectroscopy and x-ray absorption spectroscopy. The negative integer charge transfer energy level is determined to be 4.00 ± 0.05 eV below the vacuum level, and the ionization potential is 5,75 ±0.10 eV. The molecules predominantly have the face-on orientation on inert substrates as long as the surfaces of the substrates are not too rough. These results provide the physical understanding of the high performance of ITIC-based solar ceils, which also afford implications to design more advanced photovoltaic small molecules.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10775126 and 10975138)
文摘Fe-doped ZnO film has been grown by laser molecular beam epitaxy（L-MBE） and structurally characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）,all of which reveal the high quality of the film.No secondary phase was detected.Resonant photoemission spectroscopy（RPES） with photon energies around the Fe 2p-3d absorption edge is performed to detect the electronic structure in the valence band.A strong resonant effect at a photon energy of 710 eV is observed.Fe3＋ is the only valence state of Fe ions in the film and the Fe 3d electronic states are concentrated at binding energies of about 3.8 eV and 7 eV～8 eV.There are no electronic states related to Fe near the Fermi level.Magnetic measurements reveal a typical superparamagnetic property at room temperature.The absence of electronic states related to Fe near the Fermi level and the high quality of the film,with few defects,provide little support to ferromagnetism.
基金supported by the Funds from the Chinese Academy of Sciences(Grant No.1G2009312311750101)the National Natural Science Foundation of China(Grant No.11375228)
文摘The effect of temperature on the electronic structure of Nb-doped SrTiO3（100） surface is investigated by highresolution synchrotron radiation photoemission spectroscopy.According to the x-ray photoemission spectroscopy（XPS）results,at an annealing temperature of less than 700 ℃,the adsorbed carbon and hydroxyl on the STO surface could be removed,to expose the fresh intrinsic surface with a constant ratio of Ti/O.It is obvious that the STO would be doped by Ca^＋ impurities of bulks and O vacancies in the surface after annealing at 920 ℃ for one hour.
基金Supported by the National Natural Science Foundation of China under Grant Nos.19890310 and 19874003.
文摘Surfactant-assisted Co film epitaxy growth on Cu(111)using Pb as a surfactant was studied by means of Auger electron spectra and synchrotron radiation photoemission spectra.The results reveal that with increasing the Co thickness most of the Pb atoms always float on the surface.Compared with 0.7ML(monolayer)Pb,the Co film with 1.5 ML Pb surfactant has more layer-by-layer growth on Cu(111).The predeposited Pb layer can suppress the intralayer diffusion on the Cu(111)surface and effectively increase the Co island density at the initial stage of Co growth.On the contrary,a Pb-Co surface alloy was found during the Co film growth;this may hinder the interlayer diffusion of the deposited Co atoms,which is unfavorable to the layer-by-layer growth.The Pb-Co is also considered to be the main reason why some Pb atoms have been buried in the Co films.
基金Supported by the National Natural Sciences Foundation of China under Grant Nos.19890310 and 19874003.
文摘The reactions of superthin Pb Hlms on a Cu(111)surface with respect to the coverage of Pb and annealing have been studied by synchrotron radiation photoemission.The submonolayer Pb atoms deposited at room temperature are distributed on the Cu(111)surface as two-dimensional(2D)islands.Annealing to 200℃ gives rise to Pb-Cu surface alloy formation.Analyses show that the surface alloy occurs only in the first layer of the Cu(111)surface.As a surfactant,Pb can promote 2D layer-by-layer growth of thin Hlms on Cu(111),but the Pb~Cu surface alloying may have an unfavorable effect on the activation process.
基金Supported by the Chinese Academy of Sciences under No.KJ951-A1-401Doctoral Program Foundation from the State Education Committee。
文摘The electronic structure of fcc Fe/Cu{111}interface has been studied by angle-resolved photoemission with synchrotron radiation.The existence of the interface state and absence of intermixture between Fe and Cu atoms in the Fe/Cu{111}interface show that the Fe/Cu{111}system has an abrupt and ordered interface.
基金Project supported by the Chinese Academy of Sciences(Grant No.1G2009312311750101)the National Natural Science Foundation of China(Grant Nos.11375228,11204303,and U1332105)
文摘A systematic investigation of oxidation on a superconductive Fe Te_（0.5）Se_（0.5）thin film,which was grown on Nb-doped SrTiO_3（001） by pulsed laser deposition,has been carried out.The sample was exposed to ambient air for one month for oxidation.Macroscopically,the exposed specimen lost its superconductivity due to oxidation.The specimen was subjected to in situ synchrotron radiation photoelectron spectroscopy（PES） and x-ray absorption spectroscopy（XAS） measurements following cycles of annealing and argon ion etching treatments to unravel what happened in the electronic structure and composition after exposure to air.By the spectroscopic measurements,we found that the as-grown FeTe_（0.5）Se_（0.5）superconductive thin film experienced an element selective substitution reaction.The oxidation preferentially proceeds through pumping out the Te and forming Fe–O bonds by O substitution of Te.In addition,our results certify that in situ vacuum annealing and low-energy argon ion etching methods combined with spectroscopy are suitable for depth element and valence analysis of layered structure superconductor materials.
基金Project supported by the Natural Science Foundation of the Chinese Academy of Sciences(Grant No.H91G750Y21)
文摘The in situ valence band photoemission spectrum （PES） and X-ray absorption spectrum （XAS） at V LⅡ-LⅢ edges of the VO2 thin film, which is prepared by pulsed laser deposition, are measured across the metal–insulator transition （MIT） temperature （TMIT=67 ℃）. The spectra show evidence for changes in the electronic structure depending on temperature. Across the TMIT, pure V 3d characteristic d‖ and O 2p-V 3d hybridization characteristic πpd, σpd bands vary in binding energy position and density of state distributions. The XAS reveals a temperature-dependent reversible energy shift at the V LⅢ-edge. The PES and XAS results imply a synergetic energy position shift of occupied valence bands and unoccupied conduction band states across the phase transition. A joint inspection of the PES and XAS results shows that the MIT is not a one-step process, instead it is a process in which a semiconductor phase appears as an intermediate state. The final metallic phase from insulating state is reached through insulator–semiconductor, semiconductor–metal processes, and vice versa. The conventional MIT at around the TMIT=67 ℃ is actually a semiconductor–insulator transformation point.
