Optimizing mechanical resonator sensitivity for thin film internal friction and shear modulus measurements

The double-paddle oscillator is a mechanical resonator with an extremely high qualty factor at liquid helium temperatures, enabling sensitivie measurements of the internal friction and shear modulus of thin film materials. Since its development more than twenty years ago, several energy loss mechanisms that establish its background quality factor have been identified and quantitatively modeled, including thermoelastic dissipation and attachment loss. Building on work that led to the successful design of a companion resonator (one that measures Young’s modulus), here we use Finite Element Modeling (FEM) of variations on resonator geometry to seek lower thermoelastic and attachement losses as well as to increase the frequency-space separation of resonaont modes. Four candidate resonator geometries were identiified and fabricated. We compare measurements of these designs to that of the standard resonator geometry.