The global supply chain for semiconductor devices is founded on highly specialised and centralised manufacturing facilities. The result is an over-dependence on a handful of companies which may be in geopolitically unstable areas, a high cost for custom designs, and large barriers for innovation. A new decentralised manufacturing paradigm is needed using novel tools to enable low-cost point-of-use microelectronics manufacturing and rapid custom electronics manufacturing. Ideally, such a paradigm will allow the unimpeded heterogeneous integration of emerging quantum and semiconductor materials from the lab directly into real world electronic systems with enhanced performance and unique functionalities, facilitating innovation and industry uptake of novel materials. Manufacturing electronics is conventionally a top-down process where a semiconductor wafer is etched into transistor channels, and modified through the addition of dopants or dielectrics. There, the size and location of each device is defined deterministically. Nevertheless, many novel competing or complementary electronic materials, including quantum materials and novel semiconductor nanostructures, are grown bottom-up by nucleation or deposition processes that are inherently non-deterministic. While the performance of these materials can be extraordinary and enabling for applications in information and communication technologies and quantum technologies, positional accuracy is sacrificed, which is a challenge for traditional deterministic manufacturing methods. Efforts to deterministically define quantum and nanostructures are on-going, but yield remains low. An effectively perfect (100%) yield could be achieved if, instead of a top-down deterministic manufacturing approach, we used an adaptive approach that could select, address and connect the best performing randomly located elements (quantum structures, nanostructures, etc.) into functional systems. By combining computer vision-guided automated microscopy, dynamic circuit design, and advanced optical lithography into a desktop tool, our proposed technique will be used to rapidly manufacture custom electronic and photonic circuits. It will allow the unimpeded integration of new materials from the lab directly to real-world (opto)electronic, photonic and quantum device applications with enhanced performance and unique functionalities, enhancing innovation globally.

This proposal is underpinned by our recent discoveries: out of plane ferroelectricity in hetero-bilayers of atomically thin body (ATB) semiconductors (Science, 2022); and realisation of wafer scale growth of a universal dielectric in the form of hexagonal boron nitride (h-BN) (Nature, 2022). The ground-breaking nature of the proposed work is in realisation of ultra-low power devices - namely ferroelectric field effect transistors (FeFETs) and tunnel electro-magneto-resistance (TEMR) devices - using industrially relevant complementary metal oxide semiconductor (CMOS) compatible processes that can perform both logic and memory functions to increase the energy efficiency of electronics. The carbon footprint (3% of total CO2 emission) of modern electronics is comparable to that of aviation and is expected to rise to ~10% by 2030 because of the von Neumann bottleneck where information is shuttled between the logic and memory devices, which increases energy consumption and reduces the processing speed. One objective of the proposed work is to directly explore and therefore understand the key processes that underpin the stable operation of FeFETs based on ATB semiconductors to significantly accelerate their development. Second objective is to integrate ferroelectric hetero- bilayers as tunnel layers between two ferromagnetic contacts to realise TEMR devices with magneto-resistance of > 1000%. The advantage of TEMR devices is that the tunnelling probability can be tuned with polarisation of the ferroelectric tunnel layer so that very large MR is achievable. In applications that are of strategic importance for the UK, energy efficient electronics are fundamentally important for meeting the net zero by 2050 goal as well as developing resilient local supply chain for semiconductors. We propose to focus on hetero-bilayers of transition metal dichalcogenide (TMD) compounds as a novel class of ferroelectric semiconductors where probing and understanding of device operation can rapidly improve the quality and control of available devices beyond the state-of-the-art, and for which recent work has highlighted significant application potential for high performance electronics. The motivation for such new devices is to address today's most important scientific challenges, namely that of climate change through energy efficient high-performance electronics. The recently published Nation Semiconductor Strategy highlights the need to develop the UK market and local supply chains. Atomically thin semiconductors were pioneered in the UK and this proposal will leverage the local expertise to develop new technology. Specifically, we aim to: (i) Develop methodology for realising ultra-clean semiconductor/dielectric interface using our recent breakthrough in high quality wafer scale chemical vapor deposition (CVD) grown h-BN (Nature, 2022) to eliminate hysteresis due to interface defects. We will also integrate our ultra-clean van der Waals (vdW) contacts on ATBs [enabled via EPSRC funded research (EP/T026200/1) and reported in Nature 2019, 2022] to eliminate defects at metal/semiconductor junctions. (ii) Establish a fundamental understanding of ferro-magnetic (FM) vdW contacts for spin injection and tunnelling behaviour through ATB TMD ferroelectric hetero-bilayers. (iii) Develop an integrated and scalable CMOS compatible fabrication process for ultra-low energy FeFETs and TEMR devices based on wafer scale CVD grown ATB hetero-bilayers using h-BN dielectrics and vdW contacts. (iv) Explore transport properties of FeFETs and TEMR devices that are capable of functioning as both logic and memory devices to establish understanding of fundamental operating mechanisms and energy footprint. Establish new design concepts exploiting the logic and memory functions of FeFETs and TEMR devices for high performance, low power electronics.

The process of translating new materials into practical devices of benefit to society typically requires substantial time and capital investment. By virtue of their unique geometries and material properties, devices based on nanomaterial structures have unique (opto)electronic characteristics enabling applications not possible with conventional bulk materials. When creating a device based on an individual nanostructure, that structure's exact position needs to be known. Fabricating and measuring nanoscale devices is notoriously labour-intensive, involving searching and alignment before manual routing of electrode layout, or manually performing pick-and-place to transfer these nanostructures onto existing electrode configurations. In a research setting, this need for human intervention is a significant bottleneck that slows the development of new nanomaterials-enabled technologies. Worse still, the slow throughput of this approach precludes its application in any manufacturing setting. We have developed a three-pronged approach - together known as NanoMation - to remove the human intervention required during inspection, research and manufacturing. The first is a system of fiducial markers, "LithoTags", which are optimised for lithography processing - photo-, electron beam-, or nanoimprint lithography. These markers can be easily read by automated microscopy processes. The second is a computer-vision system that can find, sort and filter nanostructures depending on desired properties. Third is a system of computer-adjustable electrode designs where a machine-learning algorithm automatically routes the supporting electrodes to form an entire circuit. These processes will enable a rapid transition from individual prototype devices to high performance integrated systems (e.g. single-unit nanomaterial photodetectors, transistors, or LEDs respectively - to image sensors, integrated circuits, and displays).

The high performance, at relatively low energy cost in today's field effect transistors (FETs), is achieved by decades long optimization of electrical contacts that has allowed the miniaturization of the semiconductor channel down to nanoscale dimensions. However, decreasing dimensions of the devices leads to power dissipation in the off state (leakage current) and other detrimental consequences that are collectively referred to as short channel effects. Emergent semiconductors, such as MoS2, that are naturally atomically thin can in principle mitigate several concerns related to short channel effects. In FETs with atomically thin body (ATB) channels, the charge carriers are confined within the sub 1nm thick semiconductor so that application of gate voltage influences all the carriers uniformly. This prevents leakage currents and allows the FETs to be sharply turned on or off. The fact that atomically thin individual layers of bulk-layered materials can be isolated necessitates the absence of dangling bonds in 2D semiconductors, which means that surface roughness effects are minimized. Recent research in FETs suggests that such ATB materials could be one pathway towards future energy efficient electronics that can operate down to milli volts using the current CMOS manufacturing platform. While the benefits of 2D semiconductor FETs in addressing short channel effects are obvious, they still possess lower performance compared to state-of-the-art silicon and III-V semiconductor analogues due the high contact resistance. To reap the benefits of ultra-short channel (sub 10 nm node) and tunnel FETs, contact resistances must be reduced down to the quantum limit. The contact resistance acts as a severe source-choke. This leads to degradation in the performance of the transistor, because the current depends very strongly on the effective gate voltage at the source injection point. The high contact resistance between metals and 2D semiconductors is a major barrier to their implementation in high performance short channel electronics. This proposal aims to pioneer low electrical resistance contacts on atomically thin body (ATB) transition metal dichalcogenide (TMD) semiconductors to enable the exploration of fundamental phenomena that is currently limited by poor contacts - with the motivation to understand key processes that underpin the behavior of short channel and tunnel field effect transistors so that devices with unprecedented energy efficiency and performance can be realized. The proposal builds on the our recent breakthrough on van der Waals contacts on ATB semiconductors published in Nature (April 2019) and strategic investments in the Materials for Energy-Efficient ICT theme at Cambridge through the Sir Henry Royce Institute. Our ambition is to realize low resistance contacts on ATB semiconductors that will allow a broad range of device communities to address and overcome the long-standing challenge of making good electrical contacts on low dimensional materials. The proposed work will underpin and impact ongoing programmes and initiatives aligned with several EPSRC priority areas. This includes adaptation of low resistance contacts for in operando characterization of battery materials using microelectrochemical cells and low resistance contacts for organic semiconductors and perovskites. This proposal aims to bring a step-change and establish an internationally leading programme in low resistance contacts for high-performance electronics based on ATB semiconductors that will add value and connect a broad range of communities. The proposed work will open up new pathways for achieving in-depth fundamental knowledge of physics of novel devices based on ATB materials to accelerate their development towards technological readiness and commercialization in higher value-added products.

The next generation of MEMS is NEMS - nano-electro-mechanical systems, and the most promising candidate for NEMS membranes are graphene and 2-dimensional (2-D) materials. 2-D materials exhibit a unique combination of superlative properties such as high stiffness, low bending modulus, high elasticity, low mass per unit area, low thickness and high electrical conductivity. This allows for the development of NEMS membranes that can achieve behaviour that are typically considered conflicting in traditional MEMS devices and membranes, such as both high resonance frequency and high deflection amplitude. A number of 2-D NEMS devices have been demonstrated on the lab scale, including pressure, touch and mass sensors, microphones, self-sustained oscillators, quantum Hall devices, RF front-end filters, switches, photonic modulators and more. These novel NEMS devices will find applications in future robotics, electronics, healthcare, automotive, aerospace and more. The transition from lab-scale devices to large-scale manufacturing of 2-D NEMS has to overcome a number of critical challenges. Some of these challenges, such as minimising nanoscale defects and improving device yield and performance, have been addressed by employing few-layer graphene or graphene-polymer heterostructure membranes. However, there is still one key outstanding challenge in the future manufacturing of novel 2-D NEMS devices. It is well known that 2-D layers possess significant built-in tensile and compressive stresses which are both arbitrarily distributed as well as difficult to control. These arise both from the way that they are grown and the the way that they are transferred from one surface to another during NEMS manufacturing. In the nano-manufacturing of 2-D NEMS devices, it is essential that these built-in stresses are rendered uniformly within each device and across all devices. This will be accomplished in this project by developing a new process that will apply a well-controlled biaxial tensile strain to the 2-D membrane during the transfer from the parent to the target NEMS substrate. Not only will this strain ensure that the suspended membranes are uniform across all devices, the resulting pre-tension will also increase the stiffness of the membrane, and consequently the resonance quality factor of the resulting NEMS device. Furthermore, the static and dynamic sensitivity of the device and its resonance frequency can be tuned by controlling the pre-tension. It is also essential that this applied strain, and the residual strain in the resulting membrane, are monitored in real-time. In this project, we will implement in-situ strain monitoring based on the fact that the strain in 2-D materials can be detected as shifts in their signature Raman spectroscopy peaks. This project will enable the UK to take the lead in wafer-scale and roll-to-roll 2-D NEMS manufacturing, building on the UK's existing strengths in MEMS foundries, printed electronics, 2-D material production, and sensors and actuators. This in turn will strongly reinforce the health of a wide range of other manufacturing sectors including sensors, healthcare, communications, automotive and aerospace. 2-D NEMS will enable various next-generation devices and technologies that will transform our society to be more productive, connected, healthy and resilient.