Atomic-Level Structure Determines Electron–Phonon Scattering Rates in 2-D Polar Metal Heterostructures,ACS Nano

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Atomic-Level Structure Determines Electron–Phonon Scattering Rates in 2-D Polar Metal Heterostructures
ACS Nano ( IF 15.8 ) Pub Date : 2021-10-19 , DOI: 10.1021/acsnano.1c05944
Megan A Steves ₁ , Siavash Rajabpour ₂ , Ke Wang ₃ , Chengye Dong ₄ , Wen He _{5,

6} , Su Ying Quek _{5,

6,

7,

8} , Joshua A Robinson _{4,

9,

10} , Kenneth L Knappenberger ₁

Affiliation

Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Materials Characterization Laboratory, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
2D Crystal Consortium, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive, Singapore 117456, Singapore.
Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117456, Singapore.
Department of Physics, National University of Singapore, Singapore 117456, Singapore.
NUS Graduate School Integrative Sciences and Engineering Programme, National University of Singapore, Singapore 117456, Singapore.
Center for 2D and Layered Materials, Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States.

The electron dynamics of atomically thin 2-D polar metal heterostructures, which consisted of a few crystalline metal atomic layers intercalated between hexagonal silicon carbide and graphene grown from the silicon carbide, were studied using nearly degenerate transient absorption spectroscopy. Optical pumping created charge carriers in both the 2-D metals and graphene components. Wavelength-dependent probing suggests that graphene-to-metal carrier transfer occurred on a sub-picosecond time scale. Following rapid (<300 fs) carrier–carrier scattering, charge carriers monitored through the metal interband transition relaxed through several consecutive cooling mechanisms that included sub-picosecond carrier–phonon scattering and dissipation to the silicon carbide substrate over tens of picoseconds. By studying 2-D In, 2-D Ga, and a Ga/In alloy, we resolved accelerated electron–phonon scattering rates upon alloy formation as well as structural influences on the excitation of in-plane phonon shear modes. More rapid cooling in alloys is attributed to increased lattice disorder, which was observed through correlative polarization-resolved second harmonic generation and electron microscopy. This connection between the electronic relaxation rates, far-field optical responses, and metal lattice disorder is made possible by the intimate relation between nonlinear optical properties and atomic-level structure in these materials. These studies provided insights into electronic carrier dynamics in 2-D crystalline elemental metals, including resolving contributions from specific components of a 2-D metal-containing heterojunction. The correlative ultrafast spectroscopy and nonlinear microscopy results suggest that the energy dissipation rates can be tuned through atomic-level structures.

中文翻译：

原子级结构决定二维极性金属异质结构中的电子-声子散射率

使用近简并瞬态吸收光谱研究原子级薄二维极性金属异质结构的电子动力学，该异质结构由插入六方碳化硅和从碳化硅生长的石墨烯之间的几个结晶金属原子层组成。光泵浦在二维金属和石墨烯组件中都产生了电荷载流子。波长相关探测表明石墨烯到金属载体的转移发生在亚皮秒的时间尺度上。在快速（<300 fs）载流子 - 载流子散射之后，通过金属带间跃迁监测的电荷载流子通过几个连续的冷却机制放松，包括亚皮秒载流子 - 声子散射和耗散到碳化硅衬底数十皮秒。通过研究二维 In、二维 Ga 和 Ga/In 合金，我们解决了合金形成时加速的电子 - 声子散射率以及对平面内声子剪切模式激发的结构影响。合金中更快速的冷却归因于晶格紊乱的增加，这是通过相关的极化分辨二次谐波产生和电子显微镜观察到的。这些材料中非线性光学特性和原子级结构之间的密切关系使电子弛豫率、远场光学响应和金属晶格无序之间的这种联系成为可能。这些研究提供了对二维晶体元素金属中电子载流子动力学的见解，包括解析含有二维金属的异质结的特定成分的贡献。

更新日期：2021-11-23

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