A test apparatus includes a movable stage to support a sample, tips above the stage that have different shapes and alternately perform profiling and milling on the sample, a tip stage connected to a cantilever coupled to the tips, the tip stage to adjust a position of the cantilever, a position sensor to obtain information about a positional relationship between the tips and the sample, a stage controller to control movements of the stage and the tip stage, based on the information about the positional relationship, and a tip controller to select the tips for performing the profiling or milling and to determine conditions for performing milling, wherein a depth of the sample being processed by the milling in the first direction is controlled based on a relationship between a distance between the tips and the sample and a force between the tips and the sample.

A method for optimizing loop gain of an atomic force microscope (AFM) apparatus includes determining a change in gain of the physical system and adjusting a controller frequency response of the controller in an AFM loop to compensate for the determined change in gain. The AFM loop has a corresponding loop response that includes the product of the controller frequency response and a physical system response of the physical system.

The present invention relates to a method for measuring the dielectric properties of a sample with a scanning probe microscope. In particular, the invention relates to highly-localized optical imaging and spectroscopy on a sample surface using an atomic force microscope (AFM) probe mechanically driven at two oscillation frequencies, referred to herein as active bimodal operation, and a modulated source of electromagnetic radiation.