Surface-state enhancement of tunneling thermopower on the Ag(111) surface.
Surface-state enhancement of tunneling thermopower on the Ag(111) surface.
复制标题
Ag(111) 表面隧道热电势的表面态增强。
作者：
P. Maksymovych;S. Kelly;J. Cerdá
隧道结中的热电效应在冷却和能量收集应用中的前景，以及作为电子输运的敏感探针，目前正在重新审视。这些影响的定量解释要求在理论和实验方面取得进展，特别是关于电子传输概率跨越隧道势垒编码的能量依赖性和隧穿热电势的大小。使用贵金属表面作为清洁的模型系统，我们展示了一个比较简单的和定量的方法，直接测量实验的传输概率。重要的是，我们不仅估计热电压，而且还估计其能量和温度依赖性。因此，我们已经解决了热电压的表面态增强，这表现为10倍的增强热功率的梯田的Ag（111）表面相比，单原子的步骤网站和表面支持的纳米粒子。为了证实实验分析，将该方法应用于从三种贵金属（111）表面的第一性原理计算获得的传输概率，发现总体趋势之间具有良好的一致性。表面态效应本身指出，与分子结相比，全金属隧道结有可能实现具有竞争力的性能。在同一时间，这里提出的方法开辟了可能性，调查名义上掺杂或门控热电隧道结的性能以及纳米间隙中的温度梯度。
Thermoelectric effects in tunnel junctions are currently being revisited for their prospects in cooling and energy harvesting applications, and as sensitive probes of electron transport. Quantitative interpretation of these effects calls for advances in both theory and experiment, particularly with respect to the electron transmission probability across a tunnel barrier which encodes the energy dependence and the magnitude of tunneling thermopower. Using noble metal surfaces as clean model systems, we demonstrate a comparatively simple and quantitative approach where the transmission probability is directly measured experimentally. Importantly, we estimate not only thermovoltage, but also its energy and temperature dependencies. We have thus resolved surface-state enhancement of thermovoltage, which manifests as 10-fold enhancement of thermopower on terraces of the Ag(111) surface compared to single-atom step sites and surface-supported nanoparticles. To corroborate experimental analysis, the methodology was applied to the transmission probability obtained from first-principles calculations for the (111) surfaces of the three noble metals, finding good agreement between overall trends. Surface-state effects themselves point to a possibility of achieving competitive performance of all-metal tunnel junctions when compared to molecular junctions. At the same time, the approach presented here opens up possibilities to investigate the properties of nominally doped or gated thermoelectric tunnel junctions as well as temperature gradient in nanometer gaps.