FNR - Fundamentals of Negative Capacitance: Towards New Low Power Electronics

构成我们日常电子产品的晶体管等电子元件的持续小型化，一直是这些设备性能不断提高的核心。然而，继续这一趋势带来了越来越复杂的挑战，需要新的材料解决方案，而不是目前的硅技术。其中一大挑战是功耗和散热--随着晶体管变得越来越小，越来越多的晶体管被封装在芯片上，它们产生的热量变得越来越难以管理。一种可能的解决方案是用铁电材料取代用于控制晶体管中半导体沟道导电性的栅电介质。铁电材料是在一定温度下自发获得电极化的材料，已经被广泛应用于从超声波换能器到非易失性随机存取存储器的许多应用中。在铁电材料的许多令人着迷的特性中，目前吸引半导体界注意的一个特性是，在特定条件下，它能够表现为具有负电容的电容器，即与普通电容器相反的充电方式。这种负电容行为可以被用来放大晶体管内部的内部电势，使其能够在较低的电压下运行。然而，尽管在过去的几年里，对负电容器件的研究有了惊人的增长，但这种现象的基本物理学仍然知之甚少。到目前为止，关于负电容的内在机制、它的全部电势和局限性、如何在实验上最好地描述这种现象、如何优化材料参数和器件几何形状以获得最佳性能，人们还知之甚少。这个项目的目的是利用实验技术和最先进的理论模拟相结合来解决这些基本问题。

Continued miniaturisation of electronic components such as transistors that make up our everyday electronics has been at the heart of the ever-improving performance of these devices. Yet continuing this trend presents ever more complex challenges that require new materials solutions, beyond current silicon technology. One of the big challenges is power consumption and heat dissipation--as transistors get smaller and more of them are packed on a chip, the heat they produce becomes increasingly unmanageable. One possible solution is to replace the gate dielectric, which is used to control the conductivity of the semiconducting channel in the transistor, with a ferroelectric material. Ferroelectrics are materials that spontaneously acquire an electrical polarisation at some temperature and are already widely used in many applications ranging from ultrasound transducers to non-volatile random access memories. Among the many fascinating properties of ferroelectrics, the one that is currently captivating the attention of the semiconductor community is its ability to behave, under certain conditions, as a capacitor with a negative capacitance, i.e. one that charges up in the opposite sense to an ordinary capacitor. Such negative capacitance behaviour can be exploited to amplify the internal potential inside a transistor, allowing it to operate at lower voltages. However, despite an incredible increase in research on negative capacitance devices over the last few years, the fundamental physics of this phenomenon is still very poorly understood. As yet, little is known about the intrinsic mechanism of negative capacitance, its full potential and limitations, how to best characterise this phenomenon experimentally, and how to optimise the materials parameters and device geometries for the best performance. The aim of this project is to address these fundamental questions using a combination of experimental techniques and state-of-the-art theoretical simulations.