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Energy‐filtered transmission electron microscopy of multilayers in semiconductors
Author(s) -
CP Liu,
C. B. Boothroyd,
C. J. Humphreys
Publication year - 1999
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.1999.00459.x
Subject(s) - materials science , resolution (logic) , semiconductor , doping , dopant , scanning transmission electron microscopy , atomic number , optics , transmission electron microscopy , secondary electrons , electron , image resolution , optoelectronics , analytical chemistry (journal) , atomic physics , physics , nanotechnology , chemistry , quantum mechanics , artificial intelligence , chromatography , computer science
Quantitative analysis of novel semiconductors with wide or ultrathin multilayers of atomic dimensions is very important in order to control electronic and optical properties, but rather difficult due to the limited resolution in most techniques. In this paper we attempt to assess how effectively the total As dopant concentration in ultrathin As doped layers in InP and the Ti atomic fraction in a Ti x Al 1− x N multilayer can be analysed quantitatively using energy‐filtered imaging. These two materials have characteristic edges located at widely different energy losses, with the L edge of As being above 1000 eV, while that of Ti is around 450 eV. We have quantified the As concentration using the three‐window technique and theoretical cross‐sections and we find that the resolution limit is dominated by the signal‐to‐noise ratio in this delta‐doped specimen. However, the accuracy of the Ti atomic fraction in Ti x Al 1− x N can be as good as 10 at% for specimens of uniform thickness made by focused ion beam milling. We will compare our results with measurements of the composition made using Fresnel contrast, high resolution imaging and high angle annular dark field techniques.