Annihilation-Line Doppler broadening spectroscopy Doppler effect electron momentum in propagation direction of 511 keV y-ray leads to Doppler broadening of annihilation line 1.0 e annihilation e5 Sr in GaAs 0.8 Y2 0.6 0.4 FWHM2.6 keV FWHM=1.4 keV ■Technique 0.2 22-Na source 0.0 506 508510 512514516 518520 Sample Stabilizer MCA Y-ray energy [keV] Ge e Detector Y←Y ADC Memory E1-E2=PLC 511 keV 511 kev E1,E2-energy of y quanta LN PDF文件使用"pdfFactory”试用版本创建iw.fineprint.cn
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defect-rich 1.0 e annihilation in GaAs 85 Sr 0.8 defect- free 0.6 FWHM≈2.6keV FWHM=1.4 keV 0.4 0.2 ● 0.0 506 508 510 512 514 516 518 520 Y-ray energy [keV] PDF文件使用"pdfFactory”试用版本创建iw.fineprint.cn
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Doppler broadening spectroscopy Data Treatment GaAs 513514515 Line Parameters .Plastically deformed A Reference “Shape"parameter Eo+E s=4,A=NE E-E "Wing"parameter 504 506 508 510 512 514 516 y-ray energy [keV] Both S and W are sensitive to the concentration and defect type W is sensitive to chemical surrounding of the annihilation site,due to high momentum of core electrons participating in annihilation PDF文件使用"pdfFactory”试用版本创建.fineprint..cn
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The W parameter is more sensitive to the chemical surrounding of the annihilation site than the S parameter,because the core electrons having a high momentum are contributing mainly in the region of large energy deviations from the annihilation energy of 511 keV. Both the S and W parameters are sensitive to the concentration and kind of the defect.In order to obtain the defect concentration,a new parameter,R, can be defined,which depends only on the defect type,but not on the concentration: R= S-Sp Sa-Sp W-W。 W-W。 PDF文件使用"pdfFactory”试用版本创建i.fineprint.cn
n The W parameter is more sensitive to the chemical surrounding of the annihilation site than the S parameter, because the core electrons having a high momentum are contributing mainly in the region of large energy deviations from the annihilation energy of 511 keV. n Both the S and W parameters are sensitive to the concentration and kind of the defect. In order to obtain the defect concentration, a new parameter, R, can be defined, which depends only on the defect type, but not on the concentration: PDF 文件使用 "pdfFactory" 试用版本创建 ÿwww.fineprint.cn ÿÿ
the graphic presentation of S=S(W)gives R for one defect type as the slope of the straight line through (W,S)and (Wd,Sa). Such S versus W plots (Clement et al.1996: Liszkay et al.1994)for differently treated samples,e.g.after annealing,may show the presence of more than one defect type (for more details on the R parameter and S versus W plots) PDF文件使用"pdfFactory”试用版本创建i.fineprint.cn
n the graphic presentation of S = S(W) gives R for one defect type as the slope of the straight line through (Wb , Sb ) and (Wd , Sd ). Such S versus W plots (Clement et al. 1996; Liszkay et al.1994) for differently treated samples, e.g. after annealing, may show the presence of more than one defect type (for more details on the R parameter and S versus W plots). PDF 文件使用 "pdfFactory" 试用版本创建 ÿwww.fineprint.cn ÿÿ