Nanotribology of thin films in a lithium niobate optical waveguide modulator <inline-formula><math display="inline" overflow="scroll"><msub><mi>LiNbO</mi><mrow><mstyle mathvariant="normal"><mtext>3</mtext></mstyle></mrow></msub><mi>-Ti(20</mi><mo> </mo><mi>nm)-Pt(10</mi><mo> </mo><mi>nm)-Au(100</mi><mo> </mo><mi>nm)-Au(10</mi><mo> </mo><mi>μ</mi><mstyle mathvariant="normal"><mtext>m</mtext></mstyle><mo>)</mo></math></inline-formula> using depth-sensing nanoindentation and scratching techniques

Abstract

Nanotribology of thin films in a LiNbO 3 /Ti/Pt/Au/Au integrated optical waveguide modulator (OWM) was studied using a depth-sensing diamond nanoindentation technique. Several nanoindentation tests have been conducted using a Berkovich tip and average measured values of hardness (H) and elastic modulus (E) are given. Thin film's mechanical properties are increasingly affected by the substrate properties as the diamond penetration depth exceeds 20% of the film thickness. In addi- tion, we observed discontinuities in the load-displacement curves that were found to be in indirect relationship with the substrate/films practical adhesion. We also studied the practical adhesion of thin films by the scratch technique using a cube-corner diamond tip. The scratch tests consisted of three failure modes: ductile; ductile to brittle transition; and brittle, which were in correlation with the film's practical adhesion. Both nanoindentation and scratch tests proved that a use of platinum on top of titanium to blockade the diffusion of the gold film into the substrate rela- tively reduces the practical adhesion strength at the substrate/titanium interface. © 2001 Society of Photo-Optical Instrumentation Engineers.