TiN薄膜中电子-声子散射介导的各向异性热载流子弛豫
Anisotropic hot carrier relaxation mediated by electron phonon scattering in TiN thin films
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中文总结 AI 辅助
研究TiN薄膜中电子-声子散射介导的热载流子弛豫，结合第一性原理计算与超快光谱，发现其具有各向异性，[111]取向散射寿命长、热电子冷却慢，为调节弛豫提供途径，指导难熔等离子体和能量转换平台设计。
中文摘要 AI 辅助
晶体取向可影响过渡金属氮化物薄膜的超快能量弛豫。本文结合第一性原理计算和超快泵浦-探测瞬态吸收光谱，研究了氮化钛（TiN）薄膜沿[100]、[110]和[111]方向的取向依赖电子-声子（e-ph）介导弛豫。利用最大局域化Wannier函数评估费米能级附近的e-ph准粒子散射寿命，发现明显各向异性：TiN[111]取向的e-ph散射寿命（15.96 fs）长于[100]（13.69 fs）和[110]（11.12 fs），表明本征e-ph散射强度降低。此外，在MgO衬底上生长了准外延、取向可控的TiN薄膜。泵浦-探测测量表明，载流子能级弛豫（热电子冷却）时间也取决于取向，[111]薄膜的衰减（110 fs）明显慢于[100]（90 fs）和[110]（80 fs）。计算的飞秒级散射寿命和测量的几百飞秒级冷却时间分别代表单事件散射和集体冷却，但趋势一致。这些结果表明，晶体取向为调节TiN薄膜中e-ph主导的弛豫提供了实用且有力的途径，为难熔等离子体和能量转换平台提供了重要设计指导。
英文摘要
Crystal orientations can shape the ultrafast energy relaxations of transition-metal nitride thin films. Here, we investigate the orientation-dependent electron-phonon (e-ph) mediated relaxation in titanium nitride (TiN) thin films along the [100], [110], and [111] directions by combining first-principles calculations with ultrafast pump-probe transient absorption spectroscopy. Using maximally localized Wannier functions, we evaluate e-ph quasiparticle scattering lifetimes near the Fermi level and identify a clear anisotropy: The TiN [111] orientation exhibits a longer e-ph scattering lifetime (15.96 fs) than [100] (13.69 fs) and [110] (11.12 fs), indicating reduced intrinsic e-ph scattering strength. Furthermore, we grew quasi-epitaxial, orientation-controlled TiN thin films on MgO substrates. Pump-probe measurements reveals that the population-level relaxation (hot-electron cooling) time also depends on orientations, with [111] films showing a significantly slower decay (110 fs) than [100] (90 fs) and [110] (80 fs). We emphasize that the calculated few-femtosecond scattering lifetimes and the measured few-hundred-femtosecond cooling time respectively represent single-event scattering and collective cooling, yet they exhibit consistent trends. These results demonstrate that crystallographic orientation provides a practical and powerful route to tune e-ph-governed relaxation in TiN thin films, offering essential design guidelines for refractory plasmonic and energy-conversion platforms.
