Liu, Xianping (1994) Fidelity study in surface measurements in nanometre metrology. PhD thesis, University of Warwick.

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Abstract

The object of this Ph.D work is to evaluate fidelity in surface measurements in nanometric
metrology for both contact and non-contact methods, namely stylus instruments and scanning
tunnelling microscopy. Fidelity is defined, in this thesis, as a measure to which an instrument
system reproduces the surface features and thus the parameters of interest. High fidelity
measurement has two meanings; less distortion in the measured result and less disturbance to the
surface being measured. Interaction at the interface between the probe and the surface is the source
of failure to achieve high fidelity.

No instrument measures surface topography alone: all instruments measure a convolution of
topography and the geometrical and physical interaction of the measured probe and the surface. In
the case of a mechanical stylus, factors extraneous to the topography include (a) the shape and size
of the stylus, (b) mechanical properties of the stylus and the specimen such as elastic moduli and
hardness, (c) frictional force of the sliding pair. and (d) dynamic interaction forces during the
sliding. For the scanning tunnelling microscope, factors which affect measurement in addition to
topography include the geometry of the tip, the electronic properties of the surface and mechanical
deformation due to electrostatic forces and contamination.

'These factors have been investigated in great detail, particularly for the stylus instruments. A
specially designed electro-magnetic force actuator has been developed to give a better control on
loading force during the experiments. Tracking force effects were evaluated by profiling statistical
parameters, and scanning electron microscopy. Friction between a stylus and specimen has been
measured for different loading force, sliding speed, material and surface finish. Improvement on
dynamic characteristics of a stylus system has been achieved by active damping control. An optimal
damping ratio for stylus instruments is found to be within 0.5-0.7. Through the study, the tracking
force and traversing speed are found to be the crucial factors to be tackled so that high fidelity
measurement can be obtained. A similar investigation has been also made on two home-built
scanning tunnelling microscopes to explore the potential applications of STM on nanometric
metrology.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Library of Congress Subject Headings (LCSH):	Nanotechnology -- Research, Nanostructured materials, Metrology
Official Date:	November 1994
Dates:	Date Event November 1994 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Chetwynd, D. G. (Derek G.), 1948- ; Smith, S. T. (Stuart T.), 1961-
Extent:	xx, 262 leaves : illustrations
Language:	eng

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