Magnetically-Doped III-V Semiconductor Nanostructures

EPSRC: Daniel Blight: EP/ r513131 /1由于硅晶体管的尺寸和其他电路特性正在接近其物理极限，随着引入新工艺节点的时间增加和这些节点的成本效益降低，性能增长已经开始落后于摩尔定律。与此相关的两个关键挑战是：(i)随着更多晶体管和其他器件的加入，硅芯片内产生的热量越来越多，提取这些热量的难度越来越大；（ii）器件的长度尺度达到了量子效应占主导地位并导致器件性能崩溃的极限。因此，人们对替代技术进行了大量研究，以帮助保持设备性能的历史增长速度。自旋电子学是在该领域显示出巨大前景的一个领域，在这个领域中，电子的自旋被用作另一个自由度，为设备增加了新的功能。自旋是一种量子力学性质，电荷载体（如电子）的自旋被定义为“向上”或“向下”。这一特性与硬币的顺时针或逆时针旋转不同，因为量子力学允许电子同时携带“向上”和“向下”，直到进行测量。这提供了利用这一特性来执行当前技术无法实现的复杂计算的机会，同时还可以实现额外的信息存储。重要的是，自旋可以在不需要建立电流的情况下通过材料。因此，这种自旋电流不会通过电阻效应（由欧姆定律描述）产生热量，因此可能为设备中产生热量的问题提供解决方案。几十年来，对能够显示自旋特性和转移等的材料的研究一直是人们关注的焦点。自旋的一个重要特征是它与磁场相互作用，因此在材料中掺杂磁性掺杂剂（如锰）以增强其性能。这在低温下显示了一些令人印象深刻的结果，然而在室温（或更高）下的热效应通常意味着这些效应“消失”。为了克服这个问题，以产生在室温下工作的材料为目标，最近的工作表明，在小结构（纳米级）中，物理限制载流子在接近其“波长”的结构中的作用可以增强相互作用，从而可以在更高的温度下观察到它们。然而，用磁掺杂剂掺杂这种小结构的任务是非常具有挑战性的。该项目将结合多伦多在生产纳米线材料方面的世界领先专业知识，以及曼彻斯特的新材料掺杂能力的开发，使单个离子（原子）能够掺杂到纳米结构中。这将为解决开发适合实现室温自旋基器件的材料这一目标提供新的途径。它还将提供研究量子效应的机会，这在未来可能会提供传统半导体电子（例如量子计算）的替代技术。该职位将为曼彻斯特大学的博士生（Daniel Blight）提供机会，让他在多伦多大学度过一段较长的时间，开发纳米材料生长、设备制造、磁掺杂和表征的协议。这一安排将为相关小组和大学之间更大规模的合作奠定基础，并将作为未来资金申请、联合博士奖学金和小组之间研究人员流动交流的基础，以最大限度地减少获得世界领先专业知识和实验能力的障碍。

EPSRC : Daniel Blight : EP/R513131/1As the size of silicon transistors and other circuit features is approaching their physical limits, performance growth has begun to lag behind Moore's law with the time between the introduction of new process nodes increasing and the cost-effectiveness of these nodes decreasing. Two key challenges exist relating to this: (i) the increasing heat generated within silicon chips as more transistors and other devices are added and the difficulty in extracting this heat, and (ii) length scales in the devices are reaching the limit at which quantum effects become dominant and lead to a breakdown of the device performance.As a result there has been much research into alternative technologies that could help to maintain the historical rate of device performance growth. One field that has shown great promise in that area is the field of spintronics, where the spin of electrons is used as another degree of freedom, adding new capabilities to devices. Spin is a quantum mechanical property and charge carriers (e.g. electrons) possess a spin that is defined as either 'up' or 'down'. This property is not the same as the rotating spin of a coin for example which is either clockwise or anti-clockwise, as quantum mechanics allows the electron to carry both 'up' and 'down' at the same time until a measurement is made. This offers the opportunity to utilise this property to perform complex calculation not feasible by current technologies, whilst also enabling the additional storage of information. Importantly, spins can be 'passed' through a material without needing to establish an electrical current. Such spin currents therefore do not generate heat through the effect of resistance (described by Ohm's law) and therefore may offer a solution to the issue of heat generation in devices.Research into materials which are able to display spin properties and transfer etc. has been the focus of much attention as a result for a number of decades. One important feature of spin is that it interacts with magnetic fields and hence the doping of materials with magnetic dopants (such as manganese) to enhance their properties has been undertaken. This has shown some impressive results at low temperatures, however the effect of heat when at room temperature (or above) typically means these effects are 'lost'.To overcome this issue, with the aim of generating materials which operate at room temperature, recent work has indicated that in small structures (nanoscale) the effect of physically confining charge carriers in a structure close to their 'wavelength' can enhance interactions such that they may be observed at higher temperatures. However, the task of doping such small structures with magnetic dopant is very challenging. This project will combine the world-leading expertise in Toronto in generating nanowire materials with the development of a new materials doping capability at Manchester that enables single ions (atoms) to be doped into nanostructures. This will provide a new route to addressing this goal of developing materials suitable for realising room-temperature spin-based devices. It will also offer the opportunity to study quantum effects which in the future might offer an alternative technology to traditional semiconductor electronics (e.g. quantum computing).The placement will provide the opportunity for a PhD student (Daniel Blight) at the University of Manchester to spend an extended period of time at the University of Toronto to develop the protocols for nanomaterials growth, device fabrication, magnetic doping, and characterisation. The placement will form the basis of a much larger collaboration between the groups and Universities involved and be used as a basis for future funding applications, joint PhD studentships and the fluid exchange of researchers between the groups with minimal barriers to accessing world-leading expertise and experimental capabilities.