Digital Instruments

Peter Maivald

Virgil B Elings

John A Gurley

This invention is an atomic force microscope having a digitally calculated feedback system which can perform force spectroscopy on a sample in order to map out the local stiffness of the sample in addition to providing the topography of the sample. It consists of a three-dimensional piezoelectric scanner, scanning either the sample or a force sensor. The force sensor is a contact type with a tip mounted on a cantilever and a sensor to detect the deflection of the lever at the tip. The signal from the sensor goes to an A-D convertor and is then processed by high-speed digital electronics to control the vertical motion of the sample or sensor. In operation, the digital electronics raise and lower the piezoelectric scanner during the scan to increase and decrease the force of the tip on the sample and to use the sensor signal to indicate the change in height of the tip to measure the which is the spring constant of the sample. This constant can be determined with nanometer spatial resolution. At the same time, the instrument can determine the topography of the sample with nanometer resolution. In an alternate embodiment, the lever is connected to a separate piezoelectric driver to vary the force on the tip. This improved AFM can also be used to periodically reset the force at which the tip contacts the sample and quickly replace the tip on the sample in the event that the tip loses contact with the surface.

Atomic force microscope

In a scanning probe microscope having a probe moved by a piezoelectric 3-dimensional positioner in perpendicular X and Y directions over the surface of a sample to create a raster scan thereof and feedback controlled and sensed in a Z direction vertical to the surface to gather data about the topography of the surface, this is a method of operating the piezoelectric 3-dimensional positioner to increase the speed of gathering data about a scanning area of the surface being scanned. The method comprises the steps of, causing the positioner to traverse the surface from a first edge of the scanning area with the probe in a +X direction at a first rate of speed while feedback controlling and sensing the Z direction; causing the positioner to lift the probe above the surface a clearance distance at a second edge of the scanning area opposite the first edge in the +X direction; and, causing the positioner to return the probe to the first edge in a -X direction without feedback control thereof at a second rate of speed which is faster than the first rate of speed.

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Goleta, CA, United States of America

Peter Maivald