Comparative Method To Quantify Dielectric Constant at Nanoscale Using Atomic Force Microscopy

We propose a comparative method to measure the quasi-static dielectric constant of relatively thick dielectric films (approximately 500 nm or thicker) with comparatively low dielectric permittivity (1 < ε_r < 10) at nanoscale by using the force spectroscopy technique of atomic force microscopy (AFM). Based on the relevance of analytical expression of the force spectroscopy on the dielectric susceptibility, the dielectric constant could be estimated by comparing with a reference sample of comparable dielectric permittivity. The validity of the approach was verified by good agreement between the reported values in the literature and the experimental results obtained on different materials, such as muscovite mica, SiO₂ film, poly­(methyl methacrylate) (PMMA), and polystyrene (PS). The comparative scheme avoids the complex simulation involving irregular shape of AFM tips, providing a facile approach for quantitative analysis of dielectric properties of a number of materials at the nanometer scale.