Temperature-Resolved Electrical Transport Response of ZrO x N y Thin Films under Alternating Electrical Perturbation

Cryogenic thermometry based on DC resistance measurements in polycrystalline thin films can be influenced by extrinsic grain-boundary contributions, limiting reproducibility and interchangeability. Here, we investigate zirconium oxynitride (ZrOxNy) thin films using temperature-dependent impedance spectroscopy under an alternating electrical perturbation at zero DC bias. The distribution of relaxation times analysis with Tikhonov regularization was employed to deconvolute the impedance response and distinguish the characteristic relaxation processes associated with bulk grains and grain boundaries. The extracted relaxation frequencies exhibit a smooth and monotonic dependence on temperature, providing a physical basis for their use as thermometric parameters. The bulk capacitance remains nearly temperature independent, while being tunable through deposition conditions. The relaxation dynamics are governed by quantum corrections associated with weak localization, with the observed dimensionality crossover correlated with the crystallite size. Films deposited on polycrystalline alumina additionally exhibit splitting of the bulk relaxation frequencies, consistent with contributions from different grain orientations. These results demonstrate the potential of bulk relaxation frequencies derived from impedance spectroscopy as physically meaningful parameters for impedance-based cryogenic thermometry and related instrumentation.