Phonon gated electronics: Changing the electrical transport in molecular devices with vibrations generated via magnetic power absorption

由于材料科学和制造工艺的进步，电子设备的尺寸和速度在过去几十年中呈指数级增长。尽管如此，这些更小更快的组件正在推动量子力学的基本边界，这将很快导致过度加热，有缺陷的元件和/或受损的处理。此外，性能限制不是传统电子设备的唯一问题。人们越来越关注对环境和健康的影响，因为我们生活的几乎每个方面都依赖于电子产品，产品范围和市场基础不断扩大。电子设备中使用的许多材料都是有害的，其制造过程中使用的浪费方法，以及每隔几年电子设备的不可阻挡的更新意味着产生大量的有害废物。分子电子学与传统的半导体器件相比具有优势，这些器件的固有尺寸小，并且具有潜在的生物降解成分。然而，到目前为止，研究的重点是模拟标准器件和p-n结的操作，而不是基于分子结构的独特性质开发新的功能。再加上金属-分子接触问题，以及有机结构在操作过程中经历的化学和结构降解，分子器件仍然落后于传统结构的效率和耐用性。因此，电子行业无法从采用新一代混合电子产品中获利。该项目旨在通过利用分子的固有特性和分子动力学来解决这些缺点，而不是模仿半导体器件。为了使分子电子学成为一个具有内在特征的独立领域，需要在混合电子学中进行定性的概念性步骤。分子动力学，其中原子由于热能而以特征频率振动，通常被认为是旨在模拟半导体结构的分子器件的麻烦。然而，分子中丰富的振动特性范围，从低频呼吸模式到超快氢键振动，如果我们能够在不改变宏观温度的情况下在选定的化学键处产生甚至人工控制振动，则开发新的范例是一种有吸引力的可能性。为此目的，我们可以使用磁性材料在暴露于交变磁场期间耗散的功率，以在功能化到磁体或与磁体接触的分子中产生或淬灭简正模。该功率取决于外部DC磁场、AC磁场的频率和磁各向异性，这些参数可以通过外部场或修改材料成分或形状来控制。这将使我们能够通过控制电压和振动光谱来研究电子输运和分子动力学之间的相互作用。从电子器件的应用角度来看，我提出的方法不仅可以改变系统的温度，而且不会受到与分子结构变化和电极宏观冷却相关的长弛豫时间的阻碍。这是因为声子将通过不与电极接触的第三绝缘磁性端子直接注入分子。与简单地用微波场照射分子相比，该技术还将使我们能够克服有机分子的低微波吸收，并将操作扩展到任意分子系统，在那里我们将在暴露于微波场的光学范围内产生振动模式。然后，我们可以制造在分子尺度上工作的晶体管，并在几GHz的频率下驱动磁场。

The size and speed of electronic appliances have improved exponentially in the last few decades thanks to the advances in materials science and fabrication processes. Nonetheless, these ever smaller and faster components are pushing at the fundamental boundaries of quantum mechanics, which will soon result in excessive heating, defective elements and/or impaired processing. Furthermore, performance limitations are not the only problem for conventional electronics. There is an increasing concern about the environmental and health repercussions for a society that depends on electronics in almost every aspect of our life, with an ever-expanding product range and market base. Many of the materials used in electronic devices are harmful, and the wasteful methods employed for their fabrication, together with the unstoppable updating of electronic gadgets every few years mean that large amounts of hazardous waste is produced.Molecular electronics has the advantages over conventional semiconducting devices of small intrinsic size and potentially biodegradable components. However, the research has so far focused in emulating the operation of standard devices and p-n junctions, rather than developing new functionalities based on the unique properties of molecular structures. Added to metal-molecular contact problems, and the chemical and structural degradation that organic structures undergo during operation, molecular devices still lag the efficiency and durability of conventional structures. Therefore, the electronics industry cannot profit from adopting a new generation of hybrid electronics. This project aims to address these drawbacks by using the intrinsic properties of molecules and molecular dynamics, instead of mimicking semiconductor devices.To bring molecular electronics to fruition as an independent field with intrinsic features, a qualitative conceptual step in hybrid electronics is required. Molecular dynamics, where the atoms vibrate at a characteristic frequency due to the thermal energy, are usually considered a nuisance for molecular devices aiming to emulate semiconducting structures. However, the rich range of vibrational properties in molecules, from low-frequency breathing modes to ultrafast hydrogen bond vibrations, is an attractive possibility to develop new paradigms if we could generate or even artificially control the vibrations at chosen chemical bonds without changing the macroscopic temperature. For this purpose, we can use the power dissipated by magnetic materials during exposure to alternating magnetic fields to generate or quench normal modes in molecules functionalized to, or in contact with the magnet. This power is dependent on an external DC magnetic field, the frequency of the AC magnetic field and the magnetic anisotropy, parameters which can be controlled by external fields or modifying the material composition or shape. This will allow us to study the interaction between electronic transport and molecular dynamics by having control over both voltage andvibrational spectrum.From the point of view of applications to electronic devices, rather than just changing the temperature of the system, the method I put forward will not be hampered by the long relaxation times associated with structural changes in the molecules and the macroscopic cooling of the electrodes. This is because the phonons will be injected directly to the molecules through a third insulating magnetic terminal not in contact with the electrodes. As compared with simply irradiating the molecules with microwave fields, the technique will also allow us to overcome the low microwave absorption of organic molecules, and extend the operation to arbitrary molecular systems, where we will generate vibrational modes in the optical range with exposure to microwave fields. We can then fabricate transistors operating at the molecular scale and with driving magnetic fields at frequencies of several GHz.