An Empirical Approach to Calculate the Number of Atoms in Column-Domains by HAADF-STEM Analysis: A Binary Approximation in the Nb₁₆W₁₈O₉₄ Ternary System

Authors: Rendon, L.; Santiago, P.

Source: Journal of Scanning Probe Microscopy, Volume 3, Numbers 1-2, June/December 2008 , pp. 36-41(6)

Publisher: American Scientific Publishers

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Abstract:

We report the observation of atomic column-domains, produced by non-uniformity intercalation of W and Nb atoms along the [001] projection. An ultra thin sample of the complex oxide Nb₁₆W₁₈O₉₄ was observed using a high-angle annular dark field detector. While HRTEM technique is efficient to determine bulk crystallinity and defect structures, HAADF technique is superior in determining surface inhomogeneities and defects in the stoichiometric composition even at atomic resolution because it is possible to determine the chemical specie of the atoms involved by Z-contrast imaging process. An empirical calculation was developed to quantify the number of W atomic sites in excess at a specific column using a binary approximation in the ternary system Nb₁₆W₁₈O₉₄. This theoretical calculation is based on the fact that the profile line intensity in a HAADF image strongly depends on Z^α, where the α coefficient is between 1.5 to 2 (named: Z-contrast) and this effect generates observable column domains in the HAADF image recorder. The study was developed along the [001] zone axis projection. Some atomic columns observed by STEM-HAADF technique showed an excess of W atoms, this effect is directly related to the intensity distribution in the image generated by the HAADF scintillation detector.

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Keywords: HIGH ANGLE ANNULAR DARK FIELD; SCANNING TRANSMISSION ELECTRON MICROSCOPY; Z-CONTRAST; COLUMN DOMAINS

Document Type: Research article

DOI: http://dx.doi.org/10.1166/jspm.2008.002

Publication date: 2008-06-01

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Scanning probe microscopy (SPM) typically covers atomic force microscopy (AFM), scanning tunneling microscopy (STM), near-field scanning optical microscopy (NSOM, or SNOM) and related technologies. Since its invention in early 1980s, SPM has now been regarded as one of the major driving forces for the rapid development of nanoscience and nanotechnology, and the tool of choice in many areas of research. Journal of Scanning Probe Microscopy (JSPM) provides a forum for rapid dissemination of important developments in SPM technology. JSPM offers scientists, engineers and developers timely, peer-reviewed research on SPM science and technology of the highest quality. JSPM publishes original rapid communications, full research papers and timely state-of-the-art reviews (with author's photo and biography) encompassing the fundamental and applied research on SPM in all fields of science, engineering, and medicine.
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