Atomic force microscope and method for imaging surfaces with atomic resolution

#This invention relates to a method for imaging surfaces of objects with atomic resolution, and to an atomic force microscope which employs that method.

#Conventional optical microscopes have a resolution limit which is determined by the aperture of the object lens, and a resolution better than about one-half the wavelength of the light used can principally not be achieved. In copending U.S. application, Ser. No. 06/563,722, filed Dec. 20, 1983, an optical near-field scanning microscope is disclosed which circumvents the resolution limit through the use of an aperture with an entrance pupil diameter that is small compared to the wavelength, and arranged at a distance from the object smaller than the wavelength. This microscope achieves a resolution on the order of one tenth of the wavelength, i.e., in the neighborhood of 50 nm.

#Electron microscopes typically have resolutions of 20 nm vertical and 1 nm lateral, but their known disadvantage is that because of the high energies of the electron beam required in achieving a high resolution, most surfaces are severely damaged.

#Details of preferred embodiments of the invention will hereafter be described, by way of example, with reference to the accompanying drawings in which:

#FIG. 1 illustrates the configuration of the essential parts of the atomic force microscope embodying the invention;

#FIG. 2 illustrates a preferred embodiment of the atomic force microscope of FIG. 1; and

#Referring to FIG. 1, the basic configuration of the atomic force microscope embodying the invention comprises a rigid base 1 which may, for example, consist of an aluminum block. Mounted to an arm 2 of base 1 is an xyz-drive 3 which permits a sample 4 to be displaced in x, y, and z directions with respect to a stationary point 5. Point 5 is supported on an arm 6 protruding from base 1 and carrying a cantilever which in the preferred embodiment takes the form of a leaf spring 7 with point 5 fixed to the upper end of said spring.

#Facing the back of spring 7 is a tunnel tip 8 supported by a z-drive 9. Z-drive 9 permits tunnel tip 8 to advance or retract with respect to spring 7 and is supported on an arm 10 extending from base 1.

#Since this instrument is intended to investigate surfaces at extreme magnifications, it is necessary to provide means for eliminating all ambient vibrations, such as building vibrations. Toward this end, cushions 11, 12 of Viton rubber separate the drives 3 and 9 from the arms 2 and 10 of base 1. (Viton is a trademark of E. I. duPont de Nemours & Co. for its brand of damping material.)