Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6.
Nat Commun. 2017 May 31;8:15491. doi: 10.1038/ncomms15491.
Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e-h charging energy asymmetry). We parameterize the e-h transport asymmetry by the ratio of the hole and electron charging energies η. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, η reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV.
利用单壁碳纳米管量子晶体管中的双极性输运，单个器件可以同时作为量子点和弹道导体，或者作为两个具有不同充电能的量子点来工作。在这里，我们报告了具有大电子-空穴输运不对称性的超清洁 10 到 100nm 尺度的悬浮纳米管晶体管。这些器件由裸露的纳米管通道与退火金覆盖的管段接触组成。退火金充当 n 型掺杂的顶栅，允许相干量子输运，并能产生纳米级尖锐的势垒。这些隧道势垒定义了一个单一的量子点，其中添加一个电子或空穴的充电能相差很大（电子-空穴充电能不对称性）。我们通过空穴和电子充电能的比值 η 来参数化电子-空穴输运的不对称性。这种不对称性在短通道和小带隙管中最大化。在一个小带隙器件中，我们演示了一种双功能量子器件的制造，该器件作为空穴的量子点和电子的长得多的量子线。在一个 14nm 长的通道中，对于一个带隙为 270meV 的器件，η 高达 2.6。这个器件中的充电能超过 100meV。
