Thermoelectric response from grain boundaries and lattice distortions in crystalline gold devices
Thermoelectric response from grain boundaries and lattice distortions in crystalline gold devices
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DOI：
10.1073/pnas.2002284117
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
Charlotte I. Evans;Rui Yang;Lucia T. Gan;M. Abbasi;Xifan Wang;R. Traylor;Jonathan A. Fan;D. Natelson
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文献类型：
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作者：
Charlotte I. Evans;Rui Yang;Lucia T. Gan;M. Abbasi;Xifan Wang;R. Traylor;Jonathan A. Fan;D. Natelson
扫描光电热测量，使用激光光斑作为一个可移动的热源，揭示了各种材料的热电响应的本地信息。这项工作适用于研究令人惊讶的热电变化，在名义上简单的单晶金以及晶体之间的个别晶界。晶界突变对热电响应影响不大。相反，塞贝克响应与晶体缺陷和应变相关的单晶内的取向不良，通过电子背散射衍射检测。退火降低了这些热电签名，大概是通过晶格畸变的弛豫。这些测量结果表明，在其他单晶材料中的微小结构缺陷可以容易地检测到热电后果，这一结果对许多设备和材料系统都有影响。导体中的电子塞贝克响应涉及电荷载流子的能量依赖的平均自由程，并且受到晶体结构、来自边界和缺陷的散射以及应变的影响。以前的光电（PTE）的研究表明，多晶金属纳米线的热电性能与晶粒结构，虽然直接的证据连接到PTE响应的晶体微结构是很难阐明。在这里，我们表明，室温扫描的PTE测量是敏感的探针，可以检测到微妙的变化，在当地的塞贝克系数的金与底层的缺陷和应变，介导晶体变形。这种连接是通过结合扫描PTE和电子显微镜测量的单晶和双晶金微尺度设备。出乎意料的是，光电压图强烈相关的逐渐变化的晶体学的电子背散射衍射检测到的取向差。单个晶界和不同的晶粒取向对PTE信号的影响是最小的。这种扫描PTE技术显示出识别纳米材料和器件中微小结构扭曲的希望。
Significance Scanning photothermoelectric measurements, using a laser spot as a moveable heat source, have revealed local information about thermoelectric response in various materials. This work applies this to examine surprising thermoelectric variation in nominally simple single crystals of gold as well as individual grain boundaries between crystals. Abrupt grain boundaries have little effect on thermoelectric response. Instead, the Seebeck response correlates with crystallographic defects and strain associated with misorientation within the single crystals, detected via electron backscatter diffraction. Annealing reduces these thermoelectric signatures, presumably via relaxation of lattice distortions. These measurements show that minor structural defects in otherwise single-crystalline materials can have readily detectable thermoelectric consequences, a result with implications for many devices and material systems. The electronic Seebeck response in a conductor involves the energy-dependent mean free path of the charge carriers and is affected by crystal structure, scattering from boundaries and defects, and strain. Previous photothermoelectric (PTE) studies have suggested that the thermoelectric properties of polycrystalline metal nanowires are related to grain structure, although direct evidence linking crystal microstructure to the PTE response is difficult to elucidate. Here, we show that room temperature scanning PTE measurements are sensitive probes that can detect subtle changes in the local Seebeck coefficient of gold tied to the underlying defects and strain that mediate crystal deformation. This connection is revealed through a combination of scanning PTE and electron microscopy measurements of single-crystal and bicrystal gold microscale devices. Unexpectedly, the photovoltage maps strongly correlate with gradually varying crystallographic misorientations detected by electron backscatter diffraction. The effects of individual grain boundaries and differing grain orientations on the PTE signal are minimal. This scanning PTE technique shows promise for identifying minor structural distortions in nanoscale materials and devices.