In situ nanoelectromechanical characterization of phase transformation in Si phononic crystal during nanoindentation

The size dependence of Young’s modulus and the critical pressure for phase transformation from the diamond structure at ambient pressure to a metallic β-Sn structure at high pressure was studied in a Si phononic crystal. We used dynamic mechanical analysis and in situ electrical characterization with an electrically conducting diamond nanoindentation tip. Experiments on several phononic periodic sizes enabled us to establish that the Young’s modulus and critical phase-transformation pressure decreased as the neck width (periodic structure) of the phononic crystal shrank. The finding enables us to understand the reduction in the thermal conductivity of the Si phononic crystal at the local neck between the nanoholes.