Vendroux, Guillaume (1994) Scanning tunneling microscopy in micromechanics investigations. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-06162005-104436
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A new experimental method is proposed for studying deformations of micromechanical material systems at the submicron scale. To that end, a Scanning Tunneling Microscope (STM) was designed and built to allow placement on a mechanically deforming specimen. Operating in constant current mode, this digitally controlled STM records detailed topographies of specimen surfaces with a resolution of 10.15 nm in-plane and [...] out-of-plane, over a [...] area.
A pattern recognition type algorithm was written to extract the 3-D displacement field from topographies of a given specimen area but under different loading conditions. This Digital Image Correlation (DIC) scheme was found to have very robust convergence characteristics and a higher resolution than that of the images it compares. The accuracy of the DIC code on STM scans was assessed by measuring displacement fields resulting from a translation of the specimen under the microscope. Two major causes of noise were identified, namely drifting of the specimen during scan acquisition and hysteresis distortion of the scan grid. An experimental procedure was devised to limit the occurrence of such perturbations and under these guidelines the resolution of the DIC scheme was found to be 4.8 nm for in-plane displacement measurements and 1.5 nm for out-of plane's.
A micromechanical study of the deformation mechanism of PolyVinylChloride (PVC) was undertaken. Analysis of STM scans revealed that, upon first loading the surface of PVC specimens is deformed irreversibly even at low strain levels. The size of the strain induced topographic changes suggests that, at the scale of [...], a continuum type constitutive modeling of PVC may not be appropriate. This investigation also uncovered the present limitations of the STM-DIC scheme in measuring displacement fields consistently at the nanometer scale.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||16 December 1993|
|Author Email:||Famille.vendroux (AT) laposte.net|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||16 Jun 2005|
|Last Modified:||26 Dec 2012 02:53|
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