Physics of Thin Films

PES 449 / PHYS 549

Thin Film Characterization - Mechanical Techniques

Ohring Chapter 9 Section 9.2.3, 9.2.4, 9.3.1, 9.4.1, 9.6.5

Internal Stress / Residual Stress - curvature

deposit film on thin, flexible substrate
Tensile stress - film wants to be smaller

Compressive stress - film wants to be larger

Measure curvature of sample:

mechanical measurement

(height at edge vs. height at center)

stylus profilometer

laser methods (angle of reflection)

interference techniques with a flat reference

Microindentation - Nanoindentation

generate stress-strain curves of materials
apply force (0.3 µN resolution)
measure displacement of tip in material (2 Å resolution)

determine hardness, elastic modulus, stress relaxation . . .

typical data:

Web references:

tutorial introduction to nanoindentation: http://spm.aif.ncsu.edu/nanoindentation/intro.html
list of application articles and technical notes: http://www.mts.com/nano/References.htm
application notes: http://www.hysitron.com/webpage2/newpage51.htm
Stanford research group: http://mse.stanford.edu/people/faculty/nix/research/nanoindentation/nanoindentation.html

Friction and Wear Testing:

measuring the force of friction
= friction coefficient x applied Normal force
need to know applied force to determine property of material

measure forces using strain gauges

pin on flat

pin on disk

Adhesion tests

Adhesive tape test
simple, cheap, qualitative

scratch tests

drag stylus of known radius over film
find minimum load on stylus needed to remove film completely

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