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Atomic Force Microscopy of Ammonium Perchlorate

Published online by Cambridge University Press:  15 February 2011

Minsun Yoo
Affiliation:
Department of Physics, University of Texas, Austin, TX 78712-I081, USA
Seokwon Yoon
Affiliation:
Department of Physics, University of Texas, Austin, TX 78712-I081, USA
Alex De Lozanne
Affiliation:
Department of Physics, University of Texas, Austin, TX 78712-I081, USA
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Abstract

We have studied the (210) surface of ammonium perchlorate (NH4ClO4) with an atomic force microscope (AFM) in air. Large scale images show monomoreculat steps that are often aligned with major crystalline directions. Surface modification is clearly observed with forces as low as 30 nN, but is usually limited to the bottom and the sides of the field of view, where the tip scans for a long time and where it turns around, respectively. At the molecular scale we have observed structures with substantial order, with minimum lateral sizes of 3 Å. The identification of these features is difficult due to the large unit cell of this compound (40 atoms per unit cell), and the lack of perfect order in the images. We use the SARCH/LATUSE progrmn developed by Van Hove and Hermann to analyze this structure. Ammonium perchlorate is hygroscopic; it is therefore possible that surface modification is enhanced by the moisture present in air. Experiments in a dry atmosphere have confirmed this explanation. We have therefore designed and built a UHV (ultra-high vacuum) AFM for these studies. The first images from this instrument are presented here.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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