Apparatus for combined nanoscale gravimetric, stress, and thermal measurements

Abstract

We present an apparatus that allows for the simultaneous measurement of mass change, heat evolution, and stress of thin film samples deposited on quartz crystal microbalances (QCMs). We show device operation at 24.85 ± 0.05 °C under 9.31 ± 0.02 bars of H as a reactive gas. Using a 335 nm palladium film, we demonstrate that our apparatus quantifies curvature changes of 0.001 m. Using the QCM curvature to account for stress induced frequency changes, we demonstrate the measurement of mass changes of 13 ng/cm in material systems exhibiting large stress fluctuations. We use a one-state nonlinear lumped element model to describe our system with thermal potentials measured at discrete positions by three resistance temperature devices lithographically printed on the QCM. By inputting known heat amounts through lithographically defined Cr/Al wires, we demonstrate a 150 W calorimetric accuracy and 20W minimum detectable power. The capabilities of this instrument will allow for a more complete characterization of reactions occurring in nanoscale systems, such as the effects of hydrogenation in various metal films and nanostructures, as well as allow for direct stress compensation in QCM measurements.

Dynamic Optical Properties of Metal Hydrides

“…To overcome these challenges, we perform measurements in a modified version of our environmental chamber described in Murray et al, which maintains the sample at a constant pressure and temperature while varying the hydrogen partial pressure. 28 This system monitors the mass change of thin films via a QCM. A specially designed ellipsometry lid provides optical access to the sample with fused silica windows set normal to our desired optical measurement angles to prevent extraneous Fresnel effects (polarization dependent transmission magnitude and phase) in the measurement (see Methods for further details on the ellipsometry measurement scheme, accounting for stress-induced residual retardation in the optical measurement, and correcting for artifacts in QCM measurements).…”

“…For each deposition, at least two QCMs are included: the first for the optical and in situ loading measurement and the second for a more precise and complete loading measurement in a separate environmental chamber which incorporates stress compensation (see Murray et al for details). 28 Having the samples deposited in the same run ensures the similarity of the metals on each QCM for comparison of loading. With each deposition, a lithographically defined 1 cm x 1 cm square is included for determining the sample height via atomic force microscopy (AFM) (Cypher, Asylum Research).…”

“…The loading is calculated as outlined in Murray et al, where the stress of the QCM amongst other extraneous effects are corrected for in the loading calculation. 28 To obtain the loading data of the optically measured sample, we first subtract away the frequency change due to the changes of gas partial pressures in the chamber. We then offset and normalize the recorded frequency change.…”

In Situ Optical and Stress Characterization of Alloyed PdxAu1–xHydrides

“…The stress values reported in this work use an adapted method from EerNisse’s double resonator model . Instead of using two separate cuts of QCMs, we measure the curvature of the sample and use the curvature to frequency relation detailed by Murray et al . to find the change in QCM frequency due to stress in the sample.…”

“…The hydrogen-loading and stress measurements were taken in a separate environmental chamber equipped with an interferometer using the metal alloy films on the QCM as one of the mirrors. The loading value for each alloy is calculated with the method outlined by Murray et al, 32 which compensates the total QCM frequency change with effects from stress along with environmental effects, such as changes in gas composition.…”