Proportional Analysis of Composite Polycrystalline Specimens by Electron Diffraction

Abstract

Selected area electron diffraction patterns have been obtained from vacuum-evaporated thin films of aluminium, copper, nickel and silver both single and in combinations of aluminium-copper, aluminium-nickel and silver-copper. The relative integrated intensities of the diffraction patterns from both single and composite specimens were measured by microdensitometry. Selected pairs of maxima were taken from both single-specimen patterns and compositespecimen patterns in order to deduce whether their relative intensity ratios were consistent with the kinematic or with the dynamic theories of electron diffraction. For single specimens, it was found that both kinematic and dynamic conditions can occur, but the kinematic condition dominated. For the composite specimens, it was shown that the expression relating the intensity ratios (t'1/t'2) to the thickness ratios (t 1/t 2) and the fraction of electrons“diffracted into I'1 and I'2, (k'1/k'2)namely I'1/I'2 = (k'1 /K'2).  (t1/t2),  could be used to determine (t,/t ), provided (i) that k,- and K'2, were given by the kinematic theory of electron diffraction, (1i) the crystallite size was less than the extinction distance and (iii) the average interplanar spacing of the two diffraction maxima was greater than about 1.4Aο (for aluminium copper)and about 2.0Aο~ (for aluminium-nickel).