Scanning probe microscopy tips composed of nanoparticles and methods to form same

Abstract

A structure and method for improving the spatial resolution of a scanning probe microscope (SPM) tip, which has been coated with a layer of chemically-synthesized nanoparticles. The nanoparticles are either single-species or heterogeneous, such that the single-species nanoparticles can be either ferromagnetic, paramagnetic, superparamagnetic, antiferromagnetic, ferrimagnetic, magneto-optic, ferroelectric, piezoelectric, superconducting, semiconducting, magnetically-doped semiconducting, insulating, fluorescent, or chemically catalytic. The layer of nanoparticles is at least two nanoparticles thick, or alternatively, is a single layer of nanoparticles thick, or alternatively, is a single layer of nanoparticles thick and covers only the tip apex portion of the tip, or alternatively, only a single nanoparticle is affixed to the tip apex. Alternatively, the layer of nanoparticles is transformed into an electrically-continuous magnetic film by annealing at a high temperature.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 10 / 039,635 filed Jan. 2, 2002, the complete disclosure of which, in its entirety, is herein incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to scanning probe microscopy (SPM) and more particularly to a scanning probe microscope tip with improved spatial resolution using chemically-synthesized nanoparticles. [0004] 2. Description of the Related Art [0005] In scanning probe microscopy, specimens are imaged by scanning a sharp probe tip in close proximity to the specimen surface. Data acquired from the probe tip is plotted as a function of the location of the probe tip in the plane of the specimen surface. [0006] Magnetic force microscopy is one of numerous scanning probe microscopy (SPM) techniques. Magnetic force microscopy is a probe to image magnetic fields in magnetic thin films. In the ...

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Benefits of technology

[0013] In view of the foregoing and other problems, disadvantages, and drawbacks of the conventional material compositions of the probe tips of scanning probe microscopes, the present invention has been devised, and it is an object of the present invention to provide a structure and method to improve the spatial resolution of a scanning probe microscope.

[0014] In order to attain the object suggested above, there is provided, according to one aspect of the invention a structure and method for improving the spatial resolution of a magnetic force microscope (MFM) tip, which has been coated with a layer of chemically-synthesized nanoparticles. The nanoparticles may be either single-species or heterogeneous, such that the single-species nanoparticles may be either ferromagnetic, paramagnetic, superparamagnetic, antiferromagnetic or ferrimagnetic. A heterogeneous coating may contain nanoparticles of one or more sizes and may comprise a mixture of one or more of the above-mentioned types of nanoparticles, or nanoparticles with one or more types of organic coats. The layer of nanoparticles is at least two nanoparticles thick, or alternatively, is a single layer of nanoparticles thick, or alternatively, is a single layer of nanoparticles thick and covers only the apex portion of the tip, or alternatively, only a single nanoparticle is affixed to the tip apex. Additionally, the layer of nanoparticles may be annealed at a high temperature to change the crystal structure of the nanoparticles, or to strengthen the adhesion of the nanoparticles to the tip, or to orient uniformly the magnetic axes of ferromagnetic nanoparticles.

Problems solved by technology

MFM sensors fabricated in this manner are limited in resolution by two main factors: 1) the film thickness of the magnetic coating layer increases the tip radius-of-curvature, thus decreasing resolution; and 2) the size of the magnetic domains in such a continuous thin-film also limits the resolution.

Both of these techniques are quite labor-intensive and are difficult to implement in a parallel manner.

However, nanoparticles have not been used in SPM before because there did not exist a good method for attaching nanoparticles to SPM tips.

Furthermore, magnetic nanoparticles have not been used in MFM before because, until recently, high-quality magnetic nanoparticles were unavailable (S. H. Sun, C. B. Murray, D. Weller, L. Folks, A. Moser, Science 287, 1989 (2000)).

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