Strained Graphene Field-Effect Transistor - Nano-electro-mechanical transistors for low power applications and locally adjustable electronic properties

对于未来的能源自主系统，需要一种新型的开关，提供几乎为零的待机功耗，并可以在非常小的电压下工作。在这方面，纳米机电系统（NEMS）已经吸引了新的兴趣：纳米继电器的基础上使用电场的纳米级光束偏转目前被认为是超低功率开关的候选人，因为它们表现出极低的关断状态泄漏和突然导通特性。然而，由于在NEMS开关中，实心梁被迫与漏电极机械接触，因此它们易于出现严重的可靠性问题，包括梁静摩擦和接触退化。此外，迄今为止的NEMS开关需要非常大的电压来提供足够的静电吸引力并表现出大的滞后效应。在另一种NEMS器件概念中-悬栅FET -梁是电容耦合的，因此避免了与NEMS继电器相关的许多问题。然而，悬置栅极FET也表现出大的滞后，并且也需要相当大的栅极电压。在目前的建议中，我们将制造和研究纳米机电开关，结合联合收割机CMOS的可靠性，CMOS的导通状态电流与显着较低的关断状态泄漏电流相比，传统的CMOS，利用石墨烯纳米带的压电性能。场效应诱导的致动和场效应本身作用于采用移动和固定栅电极的石墨烯纳米晶体管的导带和价带，从而导致如常规FET中的导带/价带的高能移动，同时导致带隙的改变。因此，这种器件-在下文中称为纳米机电应变石墨烯FET（NEMSGFET）-提供了上级开关行为。由于悬浮机械栅极和固定静电栅极的组合，在NEMSGFET（与悬浮栅极FET相反）中，机械栅极可以调整特定的应变状态，而静电栅极用于晶体管功能。这可以用于例如模拟应用，或者如果由于移动栅极的静摩擦而实现永久应变状态，则可以在同一芯片上紧密接近地实现几个不同的带隙，用于例如多值逻辑或用于实现纳米级光谱仪。

For future energy autonomous systems a novel class of switches is needed that provide almost zero stand-by power consumption and that can be operated at very small voltages. In this respect, nano-electro-mechanical systems (NEMS) have attracted a renewed interest: nanoscale relays based on the deflection of nanoscale beams using an electric field are currently being considered as candidates for ultra-low power switches since they exhibit an extremely low off-state leakage and abrupt turn-on characteristics. However, since in NEMS switches a solid beam is forced into mechanical contact with the drain electrode, they are prone to serious reliability issues including beam stiction and contact degradation. Moreover, NEMS switches to-date require very large voltages to provide sufficient electrostatic attraction and exhibit large hysteresis effects. In an alternative NEMS device concept - the suspended gate FET - the beam is capacitively coupled and thus many of the issues related to NEMS relays are avoided. However, the suspended gate FET also exhibits a large hysteresis and substantial gate voltages are required, too. In the current proposal we will fabricate and investigate nano-electro-mechanical switches that combine CMOS reliability, CMOS on-state currents with significantly lower off-state leakage currents compared to conventional CMOS, exploiting the piezo-electric properties of graphene nanoribbons. Field-effect induced actuation and the field-effect itself act on the conduction and valence bands of a graphene nanoribbon employing a moving and a fixed gate electrode resulting in an energetic movement of the conduction/valence bands as in a conventional FET and a modification of the band gap at the same time. As a result, such a device - called nano-electro-mechanical strained graphene FET (NEMSGFET) in the following offers superior switching behavior. Due to the combination of a suspended mechanical gate and a fixed electrostatic gate, in the NEMSGFET (in contrast to the suspended gate FET) the mechanical gate can adjust a certain strain state while the electrostatic gate is used for transistor functionality. This can be used e.g. for analog applications or, if a permanent strain state is achieved due to stiction of the moving gate, several different band gaps can be realized in close proximity on the same chip for e.g. multi-valued logic or in for the realization of nanoscale spectrometers.