Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface
Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface
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DOI：
10.1038/nphys4047
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发表时间：
2017-06-01
期刊：
影响因子：
19.6
通讯作者：
Hegmann, Frank A.
中科院分区：
文献类型：
--
作者：
Jelic, Vedran;Iwaszczuk, Krzysztof;Hegmann, Frank A.
原子尺度上的超快电流控制对于纳米电子学的未来创新至关重要。通过将持续皮秒的太赫兹脉冲耦合到金属纳米结构上，可以实现纳米尺度上的极局域瞬态电场。在这里，我们展示了超高真空下的太赫兹扫描隧道显微镜（THz-STM）作为一个新的平台，以原子精度探索超快非平衡隧道动力学。极端太赫兹脉冲驱动的隧道电流比传统STM中的稳态电流大10(7)倍，用于以0.3nm的空间分辨率成像硅表面上的单个原子。在太赫兹频率下，金属状的Si(111)-（7 × 7）表面无法屏蔽来自体体的电场，导致太赫兹隧道电导与稳定状态的电导根本不同。超快太赫兹诱导的带弯曲和表面状态的非平衡充电为体打开了新的传导途径，使极端瞬态隧道电流在尖端和样品之间流动。
Ultrafast control of current on the atomic scale is essential for future innovations in nanoelectronics. Extremely localized transient electric fields on the nanoscale can be achieved by coupling picosecond duration terahertz pulses to metallic nanostructures. Here, we demonstrate terahertz scanning tunnelling microscopy (THz-STM) in ultrahigh vacuum as a new platform for exploring ultrafast non-equilibrium tunnelling dynamics with atomic precision. Extreme terahertz-pulse-driven tunnel currents up to 10(7) times larger than steady-state currents in conventional STM are used to image individual atoms on a silicon surface with 0.3nm spatial resolution. At terahertz frequencies, the metallic-like Si(111)-(7 x 7) surface is unable to screen the electric field from the bulk, resulting in a terahertz tunnel conductance that is fundamentally different than that of the steady state. Ultrafast terahertz-induced band bending and non-equilibrium charging of surface states opens new conduction pathways to the bulk, enabling extreme transient tunnel currents to flow between the tip and sample.