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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

curvature under tensile stress

Compressive stress - film wants to be larger

curvature of compressive stress

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 . . .

nanoindenter schematic

typical data:

nanoindenter data: force vs. displacement

Web references:

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 flat friction test

pin on disk

pin on disk friction test

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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© Thomas M. Christensen