Application of a novel nonperiodic grating in scanning probe microscopy drift measurement

A technique based on two-dimensional nonperiodic grating is proposed to quantitatively measure the drift of scanning probe microscopy (SPM) instruments. Cross-correlation image analysis is adopted in determining the drift. The grating, named as zero-reference mark (ZRM), has specially designed codes and arrangement of the elements can be optimized to have maximum ratio of maximum peak to second maximum of the image correlation matrix. Design considerations of ZRM for drift measurement are discussed theoretically. Advantages of applying ZRM are analyzed by numerical simulation. Comparisons between ZRM and periodic grating show that ZRM has a sharper, less ambiguous correlation function. Adopting ZRM is much more insensitive to drift larger than one element width. Measurement sensitivity is improved by almost one order of magnitude. These characteristics of ZRM imply that it is suitable to be severed as a reference mark for SPM drift measurement.