Department of Physics, Georgetown University, Washington, Washington DC 20057, USA.
US Naval Research Laboratory, Washington, Washington DC 20375, USA.
Nat Nanotechnol. 2016 Apr;11(4):335-8. doi: 10.1038/nnano.2015.303. Epub 2016 Jan 4.
Light absorption in graphene causes a large change in electron temperature due to the low electronic heat capacity and weak electron-phonon coupling. This property makes graphene a very attractive material for hot-electron bolometers in the terahertz frequency range. Unfortunately, the weak variation of electrical resistance with temperature results in limited responsivity for absorbed power. Here, we show that, due to quantum confinement, quantum dots of epitaxial graphene on SiC exhibit an extraordinarily high variation of resistance with temperature (higher than 430 MΩ K(-1) below 6 K), leading to responsivities of 1 × 10(10) V W(-1), a figure that is five orders of magnitude higher than other types of graphene hot-electron bolometer. The high responsivity, combined with an extremely low electrical noise-equivalent power (∼2 × 10(-16) W Hz(-1/2) at 2.5 K), already places our bolometers well above commercial cooled bolometers. Additionally, we show that these quantum dot bolometers demonstrate good performance at temperature as high as 77 K.
石墨烯的光吸收会导致电子温度发生很大变化，这是由于其电子热容低和电子-声子耦合弱。这种特性使得石墨烯成为太赫兹频率范围内热电子量热器中非常有吸引力的材料。不幸的是，电阻随温度的微弱变化导致吸收功率的响应率有限。在这里，我们表明，由于量子限制，SiC 上外延石墨烯的量子点表现出随温度变化的电阻的异常高变化（在 6K 以下高于 430MΩK(-1)），导致响应率为 1×10(10)V W(-1)，比其他类型的石墨烯热电子量热器高出五个数量级。高响应率，再加上极低的电噪声等效功率（在 2.5K 时约为 2×10(-16)W Hz(-1/2)），已经使我们的量热器远远超过了商用制冷量热器。此外，我们还表明，这些量子点量热器在高达 77K 的温度下也具有良好的性能。
