Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally anal...Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally analyzed to determine the molecular constants. The excited states exhibit highly irregular variations in terms of isotopic shifts, vibrational intervals, and rotational constants. Twenty-six bands attributed to [Ω=0, 1]-X3∑o transitions have been tentatively grouped into five vibrational progressions. Furthermore, dispersed fluorescence and lifetimes of the strong bands have also been measured.展开更多
Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spect...Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spectroscopy （AES）. We find that the surface of relatively thick （more than tens of nanometers） Bi2Te3 NPs is oxidized in the air and forms a bump under heating with moderate laser power, as revealed by the emergence of Raman lines characteristic of Bi2O3 and TeO2 and characterization by AFM and EDS. Further increase of laser power burns holes on the surface of the NPs. Thin （thicknesses less than 20 nm） NPs with stoichiometry different from Bi2Te3 were also studied. Raman lines from non-stoichiometric NPs are different from those of stoichiometric ones and display characteristic changes with the increase of Bi concentration. Thin NPs with the same thickness but different stoichiometries show different color contrast compared to the substrate in the optical image. This indicates that the optical absorption coefficient in thin Bi-Te NPs strongly depends on their stoichiometry.展开更多
By using the surface photovoltage (SPV) technique based on a lock-in amplifier, surface states located 3.1 eV below the conduction band of TiO_(2) have been detected in TiO_(2) nanotube arrays prepared by anodization ...By using the surface photovoltage (SPV) technique based on a lock-in amplifier, surface states located 3.1 eV below the conduction band of TiO_(2) have been detected in TiO_(2) nanotube arrays prepared by anodization of titanium foil in fluoride-based ethylene glycol solution. The photo-induced charge transportation behavior of TiO_(2) nanotube arrays was also studied by quali- tatively analyzing their SPV phase spectra measured under different external bias. When a negative bias was applied, carriers excited from surface states have the same transportation properties as those excited from the valence band; in contrast, when a positive bias was applied, these two kinds of photo-excited carriers exhibit different transportation behavior..展开更多
文摘Laser-induced fluorescence excitation spectra of NiO have been recorded in the wavelength region of 510-650 nm under supersonic molecular beam conditions. More than fifty bands have been observed and rotationally analyzed to determine the molecular constants. The excited states exhibit highly irregular variations in terms of isotopic shifts, vibrational intervals, and rotational constants. Twenty-six bands attributed to [Ω=0, 1]-X3∑o transitions have been tentatively grouped into five vibrational progressions. Furthermore, dispersed fluorescence and lifetimes of the strong bands have also been measured.
文摘Bi-Te nanoplates （NPs） grown by a low pressure vapor transport method have been studied by Raman spectroscopy, atomic force microscopy （AFM）, energy- dispersive X-ray spectroscopy （EDS）, and Auger electron spectroscopy （AES）. We find that the surface of relatively thick （more than tens of nanometers） Bi2Te3 NPs is oxidized in the air and forms a bump under heating with moderate laser power, as revealed by the emergence of Raman lines characteristic of Bi2O3 and TeO2 and characterization by AFM and EDS. Further increase of laser power burns holes on the surface of the NPs. Thin （thicknesses less than 20 nm） NPs with stoichiometry different from Bi2Te3 were also studied. Raman lines from non-stoichiometric NPs are different from those of stoichiometric ones and display characteristic changes with the increase of Bi concentration. Thin NPs with the same thickness but different stoichiometries show different color contrast compared to the substrate in the optical image. This indicates that the optical absorption coefficient in thin Bi-Te NPs strongly depends on their stoichiometry.
基金supported by the National Basic Research Program of China (973 Program,2007CB613303)the National Natural Science Foundation of China (20873053)
文摘By using the surface photovoltage (SPV) technique based on a lock-in amplifier, surface states located 3.1 eV below the conduction band of TiO_(2) have been detected in TiO_(2) nanotube arrays prepared by anodization of titanium foil in fluoride-based ethylene glycol solution. The photo-induced charge transportation behavior of TiO_(2) nanotube arrays was also studied by quali- tatively analyzing their SPV phase spectra measured under different external bias. When a negative bias was applied, carriers excited from surface states have the same transportation properties as those excited from the valence band; in contrast, when a positive bias was applied, these two kinds of photo-excited carriers exhibit different transportation behavior..
