The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon （CZ-Si） are investigated systemically by using Fourier transform infrared （FTIR） spectrometer and positron annihilation technique （PA...The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon （CZ-Si） are investigated systemically by using Fourier transform infrared （FTIR） spectrometer and positron annihilation technique （PAT）. Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration （[Oi]） in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies （0.1-1.0eV） can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms （O） at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.展开更多
Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usu...Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usually used as the detectors in the positron lifetime spectrometer. In those cases, a long light guide between the detector and the photomultiplier was exclusively necessary for keeping展开更多
Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption s...Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na_5Lu_9F_(32) single crystal. The stimulated emission cross-section of the ~3F_4→~3H_6 transition(～1.8 μm) is 0.35×10^(-20) cm^2 for Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The emission spectra under the excitation of 790 nm laser diode(LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The research results show that the Tm^(3+) doped Na_5Lu_9F_(32) single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm^(3+)doped Na_5Lu_9F_(32) crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.展开更多
A new simple digital positron lifetime spectrometer has been developed. It includes a DRS4 waveform digitizing board and two scintillation detectors based on the XP2020Q photomultiplier tubes and LaBr3 scintillators. ...A new simple digital positron lifetime spectrometer has been developed. It includes a DRS4 waveform digitizing board and two scintillation detectors based on the XP2020Q photomultiplier tubes and LaBr3 scintillators. The DRS4 waveform digitizing can handle small pulses, down to few tens of millivolts, and its time scale linearity and stability are very good. The new system has reached a 206 ps time resolution, which is better than the conventional analog apparatus using the same detectors. These improvements make this spectrometer more simple and convenient in comparison with other spectrometers, and it can be applied to the other scintillation timing measurements with picosecond accuracy.展开更多
A digital three-detector positron lifetime spectrometer was developed.It consists of a DRS4 waveform digitizing board and three La Br3scintillation detectors coupled to XP2020Q photomultiplier tubes.DRS4 waveform digi...A digital three-detector positron lifetime spectrometer was developed.It consists of a DRS4 waveform digitizing board and three La Br3scintillation detectors coupled to XP2020Q photomultiplier tubes.DRS4 waveform digitizing allows data sampling at up to 5 GSPS with high amplitude resolution,with good time scale linearity and stability.In the triple-coincidence,the new system could reach a 195 ps time resolution,which is better than the conventional analog apparatus with the same detectors.This spectrometer can be applied to the other scintillation timing measurements with picoseconds accuracy.展开更多
采用单光子计数法(Time Correlated Single Photon Counting,TCSPC)测量了MEH-PPV和CdS共混薄膜退火处理前后受到超短脉冲激光激发及光生载流子的瞬态衰减过程,得到了MEH-PPV:CdS共混薄膜材料的光生载流子寿命。分析表明,退火处理后MEH-...采用单光子计数法(Time Correlated Single Photon Counting,TCSPC)测量了MEH-PPV和CdS共混薄膜退火处理前后受到超短脉冲激光激发及光生载流子的瞬态衰减过程,得到了MEH-PPV:CdS共混薄膜材料的光生载流子寿命。分析表明,退火处理后MEH-PPV:CdS共混薄膜材料的光生载流子寿命更长,相应的光伏器件(结构为ITO/PEDOT:PSS/MEH-PPV:CdS/Al的有机薄膜光伏器件)也具有较高的光电转换效率。展开更多
The method of analyzing positron annihilation lifetime spectra was used to study molecular structures of raw silicone rubbers with different molecular weights and heat-cured silicone rubbers’s constitutions. The posi...The method of analyzing positron annihilation lifetime spectra was used to study molecular structures of raw silicone rubbers with different molecular weights and heat-cured silicone rubbers’s constitutions. The positron annihilation lifetime spectra were measured using a fast-fast coincidence circuitry positron lifetime spectrometer modified by us from a fast-slow delayed coincidence positron lifetime展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 50872028)the Natural Science Foundation ofHebei Province,China (Grant No E2008000079)the Specialized Research Fund for the Doctoral Program of Higher Educationof China (Grant No 20050080006)
文摘The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon （CZ-Si） are investigated systemically by using Fourier transform infrared （FTIR） spectrometer and positron annihilation technique （PAT）. Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration （[Oi]） in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies （0.1-1.0eV） can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms （O） at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.
基金Project supported by the National Natural Science Foundation of China.
文摘Ⅰ. INTRODUCTION In the past experiments on the magnetic quenching of positronium atom （a hydrogenlike bound state of positron and dectron ）, the plastic scintillator and BaF<sub>2</sub> crystal were usually used as the detectors in the positron lifetime spectrometer. In those cases, a long light guide between the detector and the photomultiplier was exclusively necessary for keeping
基金supported by the National Natural Science Foundation of China(Nos.51472125 and 51272109)the Natural Science Foundation of Zhejiang Province(No.LZ17E020001)K.C. Wong Magna Fund in Ningbo University
文摘Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na_5Lu_9F_(32) single crystal. The stimulated emission cross-section of the ~3F_4→~3H_6 transition(～1.8 μm) is 0.35×10^(-20) cm^2 for Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The emission spectra under the excitation of 790 nm laser diode(LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The research results show that the Tm^(3+) doped Na_5Lu_9F_(32) single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm^(3+)doped Na_5Lu_9F_(32) crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.
基金Supported by National Natural Science Foundation of China(11175171,10835006,11105139,10975133)
文摘A new simple digital positron lifetime spectrometer has been developed. It includes a DRS4 waveform digitizing board and two scintillation detectors based on the XP2020Q photomultiplier tubes and LaBr3 scintillators. The DRS4 waveform digitizing can handle small pulses, down to few tens of millivolts, and its time scale linearity and stability are very good. The new system has reached a 206 ps time resolution, which is better than the conventional analog apparatus using the same detectors. These improvements make this spectrometer more simple and convenient in comparison with other spectrometers, and it can be applied to the other scintillation timing measurements with picosecond accuracy.
基金Supported by the National Natural Science Foundation of China(Nos.11175171,10835006,11105139 and 10975133)
文摘A digital three-detector positron lifetime spectrometer was developed.It consists of a DRS4 waveform digitizing board and three La Br3scintillation detectors coupled to XP2020Q photomultiplier tubes.DRS4 waveform digitizing allows data sampling at up to 5 GSPS with high amplitude resolution,with good time scale linearity and stability.In the triple-coincidence,the new system could reach a 195 ps time resolution,which is better than the conventional analog apparatus with the same detectors.This spectrometer can be applied to the other scintillation timing measurements with picoseconds accuracy.
文摘采用单光子计数法(Time Correlated Single Photon Counting,TCSPC)测量了MEH-PPV和CdS共混薄膜退火处理前后受到超短脉冲激光激发及光生载流子的瞬态衰减过程,得到了MEH-PPV:CdS共混薄膜材料的光生载流子寿命。分析表明,退火处理后MEH-PPV:CdS共混薄膜材料的光生载流子寿命更长,相应的光伏器件(结构为ITO/PEDOT:PSS/MEH-PPV:CdS/Al的有机薄膜光伏器件)也具有较高的光电转换效率。
文摘The method of analyzing positron annihilation lifetime spectra was used to study molecular structures of raw silicone rubbers with different molecular weights and heat-cured silicone rubbers’s constitutions. The positron annihilation lifetime spectra were measured using a fast-fast coincidence circuitry positron lifetime spectrometer modified by us from a fast-slow delayed coincidence positron lifetime
