Theoretical and experimental study of second order dynamic effects in nanocomposite thin film thermocouples affected by substrate roughness

Thin-film thermocouples (TFTCs) are crucial for transient temperature measurement; however, their oscillatory response remains inadequately understood and controlled. This study develops a second-order transient heat transfer model to analyze the impact of substrate roughness on the damping ratio and dynamic performance of TFTCs. Theoretical analysis reveals that adjusting substrate roughness modulates the damping ratio. To validate these findings, TFTCs with varying substrate roughness were fabricated and characterized using pulsed laser excitation and frequency response analysis. The results confirm that TFTCs exhibit nanosecond-scale second-order dynamic behavior, with a 59 ns oscillation period. Lower substrate roughness enhances phase margin and stability, while higher roughness mitigates oscillatory behavior by increasing damping. By fine-tuning substrate roughness, the dynamic performance of TFTCs can be tailored to optimize sensitivity and stability in transient temperature measurements. This study establishes a novel framework for tuning TFTC dynamic performance through substrate roughness control, providing valuable insights for optimizing sensitivity and stability in transient temperature measurements and advancing high-precision sensing technologies.