Deconvolution processing for increasing the resolution of magnetic force microscopy measurements

Abstract

Magnetic force microscopy (MFM) is a widely used form of scanning probe microscopy (SPM) that is used for obtaining a magnetic image from a surface with nanoscale resolution. Currently, the resolution of MFM is limited to approximately 20 nm due to the long-range nature of magnetic interactions between the MFM probe's tip and the magnetic medium. This paper describes an optimal signal processing solution to the problem of achieving high resolution MFM with the goal of significantly exceeding the level at which MFM metrology currently performs, thus providing metrologists with a means of resolution increase that is believed will enable, for example, the rapid development of high-density magnetic recording media (>100 Gbit in−2). This is achieved by using focused-ion beam trimming of a conventional tip to create a probe tip of predictable magnetic characteristics and then, provided that the sample could be approximated as a thin-film, using knowledge of this tip's sensitivity field for performing a deconvolution on the measured signal to better estimate the magnetic state of the surface under study. Stated differently, as the MFM measured signal is modelled as the convolution of the magnetized surface and the tip's sensitivity field, we exploit knowledge of the tip's properties to increase the resolution of the MFM image. Details of the deconvolution approach as well as images resulting from this processing are the focus of this paper.