Centro de Física de Materiales CSIC-UPV/EHU - Materials Physics Center MPC, Edificio Korta, San Sebastián, Spain.
Ultramicroscopy. 2010 May;110(6):634-8. doi: 10.1016/j.ultramic.2010.02.024. Epub 2010 Feb 23.
Dielectric relaxation (DR) has shown to be a very useful technique to study dielectric materials like polymers and other glass formers, giving valuable information about the molecular dynamics of the system at different length and time scales. However, the standard DR techniques have a fundamental limitation: they have no spatial resolution. This is of course not a problem when homogeneous and non-structured systems are analyzed but it becomes an important limitation for studying the local properties of heterogeneous and/or nano-structured materials. To overcome this constrain we have developed a novel approach that allows quantitatively measuring the local dielectric permittivity of thin films at the nanoscale by means of Electrostatic Force Microscopy. The proposed experimental method is based on the detection of the local electric force gradient at different values of the tip-sample distance. The value of the dielectric permittivity is then calculated by fitting the experimental points using the Equivalent Charge Method. Even more interesting, we show how this approach can be extended in order to obtain quantitative dielectric images of insulating thin films with an excellent lateral resolution.
介电弛豫 (DR) 已被证明是一种非常有用的技术，可用于研究聚合物和其他玻璃形成材料等介电材料，为系统在不同长度和时间尺度下的分子动力学提供有价值的信息。然而，标准的 DR 技术有一个基本的限制：它们没有空间分辨率。当分析均匀和非结构化系统时，这当然不是问题，但对于研究异质和/或纳米结构材料的局部性质，这成为一个重要的限制。为了克服这一限制，我们开发了一种新方法，通过静电场显微镜定量测量纳米尺度薄膜的局部介电常数。所提出的实验方法基于在不同的针尖-样品距离下检测局部电场梯度。然后通过使用等效电荷法拟合实验点来计算介电常数的值。更有趣的是，我们展示了如何扩展这种方法，以便获得具有优异横向分辨率的绝缘薄膜的定量介电图像。
