• Fornasier, H.
• Ott, Vincent
• Lee, S.
• Gerdes, B.
• Short, M.
• Rupp, T.
• Köhler, U.
• Woll, K.
• Kirchlechner, C.
• Stüber, M.
• Müller, J.

Abstract

A new method applied to the sensor proposed by Zhang et al. in 2018 is demonstrated in this paper that combines the benefits of this design with the fast heating possible with nanocalorimetry. By applying a PID regulated pulse instead of a constant wattage, we unlock an accessible method to sense morphological changes occurring over short time periods that would be invisible to methods based only on heat capacity. In this study, multilayer Ni/Al thin films were linearly heated at 25, 50, 100, and 200 K/s to over 700°C, showing two distinct peaks in resistance change with activation energies of 554 and 747 kJ/mol, respectively. Through Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray Analysis (EDX) analysis on cross sections taken ex situ from samples quenched before and after the peaks of interest, we find strong evidence that peak 1 corresponds to Ni diffusing through Al grain boundaries forming intermetallic phases that essentially block the highly conductive Al pathway. This presents the potential to design and calibrate novel heterogeneous structures in a high throughput manner.

Topics

• impedance spectroscopy
• grain
• phase
• thin film
• transmission electron microscopy
• forming
• activation
• Energy-dispersive X-ray spectroscopy
• intermetallic
• heat capacity