Thermal response of an in-situ STEM MEMS chip under rapid pulse heating

Abstract: In-situ rapid solidification studies demand measurements of thermal histories with high temporal resolution. We present a simple, effective setup to quantify the cooling response of an uncoated commercial Protochips Fusion MEMS chip in an in-situ scanning transmission electron microscopy (STEM) context. We drive user-defined temperature programs via an arbitrary waveform generator (AWG), while recording the voltage drops across a series shunt to reconstruct chip resistance and temperature at sub-millisecond resolution. We confirm the response times inferred from the current; however, the temperature obtained from the physically linked resistance, $T(R)$, evolves more slowly. Analysis of the maximum cooling step reveals an exponential-like relaxation with time constant $τ=1.80$ ms, consistent with reported thermal lag constants for fast scanning calorimetry. From the time to reach $95\%$ of the temperature difference $ΔT$, we measure an average cooling rate of $\approx 7.9\times 10<sup>{4}$ K/s. Robustness checks include repeated $R(T)$ measurements (revealing a modest downward drift approaching an asymptote), a 10 k$Ω$ test load, and characterization of small off-duty arbitrary waveform generator leakage/offsets. These findings define practical bounds on achievable thermal-path rates when planning in-situ electron microscopy experiments with this chip platform.