Evanescent Microwave Spectroscopy for nanoscale measurements - feasibility study

扫描消逝微波显微镜(SEMM)是一种在小(纳米)尺度上确定材料电学性质的技术。空间分辨率取决于仪器的几何形状，并且明显小于微波激励的波长。SEMM探头可以扫描样品表面，以获得介电常数或电导率等材料参数的图像。研究的主要目的是量化响应。器件结构的微型化需要新的询问功能方法。例如，在过去，复杂介电性能的测量依赖于使用谐振腔测量尺寸为毫米的介电材料圆柱体。在这里，介电常数和损耗可以很容易地以良好的精度进行测量。电阻率的测量依赖于触点的应用，尽管其尺寸小于毫米，以便进行测量。随着微米和纳米级结构的发展，对功能的测量提出了特殊的困难。该方案旨在利用微波光谱技术来解决这一问题，探头发射微波能量，但由于探头的特征尺寸比波长小得多，这种能量是以逝去波的形式存在的，即场强呈指数衰减。这提供了较高的空间分辨率。探头可以采用谐振器中的孔、同轴传输线的开口端或短导体的形式。孔径法和开放式同轴电缆方法的信噪比很低，因为很难在不影响空间分辨率的情况下将足够的能量耦合到样品上。

Scanning Evanescent Microwave Microscopy (SEMM) is a technique for determining the electrical properties of materials on small (nm) length scales. The spatial resolution depends on the geometry of the instrument, and is significantly smaller than the wavelength of the microwave excitation. The SEMM probe may be scanned across the surface of a sample to give an image of material parameters such as dielectric constant or conductivity.The main aim of the research is to quantify the response.Miniaturisation of structures for devices demands new ways of interrogating function. In the past measurement of complex dielectric properties for example, has relied on the measurement of a cylinder of dielectric material with dimensions of millimetres using resonant cavities. Here the permittivity and the loss can easily be measured with good accuracy. Measurement of resisitivity has relied on the application of contacts, albeit at sub millimetre dimensions, in order to make measurements. With the drive towards structures at micrometer and nanometre scale measurement of function poses special difficulties. This proposal is aimed at providing a solution to such problems by using evanescent microwave spectroscopy.The probe emits microwave energy, but because the characteristic dimension of the probe is much smaller than a wavelength this energy is in the form of an evanescent wave i.e. the field intensity decays exponentially. This gives high spatial resolution. The probe may take the form of an aperture in a resonator, the open end of a coaxial transmission line, or a short conductor. The aperture and open coaxial cable methods can suffer from poor signal-to-noise ratio, as it is difficult to couple sufficient energy to the sample without compromising spatial resolution.