EXTRAORDINARY MAGNETORESISTANCE NANO SENSORS - FUNDAMENTAL ISSUES AND APPLICATIONS

该提案是两所英国大学帝国理工学院和兰开斯特大学之间的合作，他们希望将努力和专业知识结合起来，以开发和利用特殊磁阻（EMR）效应。EMR效应是当半导体靠近金属界面时对其电性能的四端测量。传感器的特性是由于在金属和半导体这两种材料的界面上形成的混合器件具有非常不同的导电性。磁阻提升是由于在低磁场下电流流过金属分流器，在高磁场下电流流过半导体而产生的。升力是一种几何效应，磁通率取决于材料迁移率的平方。我们的工作将与EMR的发明者Stuart Solin教授直接合作（他目前是EPSRC资助EP/C511816的访问学者，截止日期为08年8月）。Solin教授已经证明，如果传感器以某种特定的方式加工到纳米级，则会引入侧壁散射，从而使半导体保持在扩散极限（平均自由程小于器件长度），从而保留上述器件概念。如果移除侧壁散射，我们预计该器件将在弹道极限（平均自由程大于器件尺寸）中运行，并且将观察到完全不同的传感器特性。我们希望研究的正是这种交叉，我们有兴趣了解侧壁散射对不同晶圆设计的材料迁移率的影响程度，以及最大化MR效应的精确条件。该提案的重点将是发展对单个纳米传感器的全面理解，并开发新型成像纳米阵列，这将对高分辨率、快速数据采集成像工具产生影响，对广泛的科学领域至关重要。这也是一个基础科学研究的机会，因为EMR杂化结构的输运性质在纳米尺度上的研究很少，特别是在扩散和弹道输运之间的交叉状态下。

This proposal is a collaboration between two UK universities Imperial College and Lancaster who wish to combine efforts and expertise in order to develop and utilise the Extraordinary Magnetoresistance (EMR) effect. The EMR effect is a four terminal measurement of electrical properties of a semiconductor when in close proximity to a metal interface. The sensor properties result from the hybrid device formed at the interface between these two materials metal and semiconductor with very different electrical conductivity magnitude. The magnetoresistance boost come about due to fact that at low field the electrical current flows through the metal shunt and at high magnetic field it flows through the semiconductor. The boost is know as a geometric effect and the MR depends on the square of the mobility of the material. Our work will be in direct collaboration with the inventor of EMR, Prof Stuart Solin (who is currently supported as a visiting Fellow to Imperial through an EPSRC grant EP/C511816 end date Aug 08). Prof Solin has shown that if the sensor is processed down to the nanoscale but in a certain particular way, side wall scattering is introduced and this keeps the semiconductor in the diffusive limit (mean free path less than device length) where these device concepts described above are retained. If the side wall scattering is removed we anticipate that the device will operate in the ballistic limit (mean free path greater than the device dimensions) and entirely different sensor properties will be observed. It is this cross over that we wish to study and we are interested to understand how much the side wall scattering impairs the mobility of the material for different wafer designs and the precise conditions to maximise the MR effect. The emphasis of the proposal will be to develop a comprehensive understanding of single nanosensors and develop new types of imaging nanoarrays which will have impact as a high resolution, fast data acquisition imaging tool pivotal for a wide range of scientific areas. There is also a basic science opportunity because the transport properties of EMR hybrid structures have been little studied at the nanoscale particularly in the crossover regime between diffusive and ballistic transport.