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9-2-2010

Systems for Assessing and Enhancing the Performance of ScanningElectron Microscopes by Quantifying and Enforcing Symmetriesand Periodicities in Two DimensionsPeter MoeckPortland State University, [email protected]

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Citation DetailsMoeck, Peter. "Systems for assessing and enhancing the performance of scanning probe microscopes by quantifying and enforcingsymmetries and periodicities in two dimensions." U.S. Patent No. 8,196,216. 5 Jun. 2012.

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US 20100223697A1

(12) Patent Application Publication (10) Pub. No.: US 2010/0223697 A1 (19) United States

Moeck (43) Pub. Date: Sep. 2, 2010

(54) SYSTEMS FOR ASSESSING AND ENHANCING THE PERFORMANCE OF SCANNING PROBE MICROSCOPES BY QUANTIFYING AND ENFORCING SYMMETRIES AND PERIODICITIES IN TWO DIMENSIONS

(75) Inventor: Peter Moeck, Portland, OR (U S)

Correspondence Address: KLARQUIST SPARKMAN, LLP 121 SW SALMON STREET, SUITE 1600 PORTLAND, OR 97204 (US)

(73) Assignees: State of Oregon acting by and through the State Board of Higher Education on behalf of; Portland State University

(21) App1.No.: 12/660,422

(22) Filed: Feb. 25, 2010

Related US. Application Data

(60) Provisional application No. 61/208,782, ?led on Feb. 27, 2009, provisional application No. 61/228,463, ?led on Jul. 24, 2009.

Publication Classi?cation

(51) Int. Cl. G01Q 40/00 (2010.01) G06K 9/54 (2006.01)

(52) US. Cl. ......................................... .. 850/19; 382/307

(57) ABSTRACT

Scanning probe microscope (SPM) images are enhanced by enforcing one or more symmetries that can be selected based on suitable Fourier coef?cient amplitude or phase angle residuals, and/ or geometric Akaike information criteria, and/ or cross correlation techniques. Alternatively, this selection can be based on prior knowledge of specimen characteristics. In addition, a scanning microscope point spread function is obtained based on the evaluation of a calibration image by enforcing at least one symmetry and can be applied to other image acquisitions.

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US 2010/0223697 A1

SYSTEMS FOR ASSESSING AND ENHANCING THE PERFORMANCE OF SCANNING PROBE MICROSCOPES BY QUANTIFYING AND ENFORCING

SYMMETRIES AND PERIODICITIES IN TWO DIMENSIONS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the bene?t of US. Provi sional Patent Applications 61/208,782, ?led Feb. 27, 2009 and 61/228,463, ?led Jul. 24, 2009, and is related to US. Pat. No. 7,472,576, issued Jan. 6, 2009, all ofWhich are incorpo rated herein by reference.

BACKGROUND

[0002] Scanning probe microscopy (SPM) is a relatively neW form of microscopy that is used to image surfaces and small objects that are supported by surfaces. Scanning probe microscopes (SPMs) use a very small probe, frequently a sharp tip that may be attached to a cantilever, to gather infor mation about surfaces and small objects. This probe is scanned laterally, very close to the surface or objects, While interactions betWeen the probe and surface or objects are measured. The “images” formed by SPMs are plots of the measured value of these interactions as a function of position along the surface or object. In a generaliZed sense, scanning electron microscopes (SEMs) and scanning transmission electron microscopes (STEMs) can also be considered as being part of the SPM type family of microscopes Where the scanning probe is a ?ne beam of electrons. [0003] SPMs are categoriZed by the type(s) of interaction that they measure and plot. The tWo most common types of SPMs are the scanning tunneling microscope (STM) and the atomic force microscope (AFM). STMs measure tunneling currents betWeen the probe and surface. AFMs, in contrast, measure quantum-physical forces betWeen the probe and sur face or object. Exemplary forms of scanning probe micros copy are listed in the folloWing table:

Acronym Name

AFM atomic force microscopy EFM electrostatic force microscope ESTM electrochemical scanning tunneling microscope FMM force modulation microscopy KPFM Kelvin probe force microscopy MFM magnetic force microscopy MRFM magnetic resonance force microscopy NSOM near-?eld scanning optical microscopy PFM pieZo force microscopy PSTM photon scanning tunneling microscopy PTMS photothennal rnicrospectroscopy/microscopy SECM scanning electrochemical microscopy SCM scanning capacitance microscopy SGM scanning gate microscopy SICM scanning ion-conductance microscopy SNOM scanning near-?eld optical microscopy (same as NSOM) SPSM spin polarized scanning tunneling microscopy SThM scanning thermal microscopy STM scanning tunneling microscopy SPSTM spin-polarized scanning tunneling microscopy SVM scanning voltage microscopy SHPM scanning Hall probe microscopy CDSPM critical dimension scanning probe microscope

Sep. 2, 2010

-continued

Acronym Name

SEM scanning electron microscope STEM scanning transmission electron microscope

Certain types of SPMs can be used to image surfaces or objects at atomic resolution. In principle, SPMs can resolve individual atoms, groups of atoms, molecules, and arrays of molecules (at a fraction of the nanometer length scale). HoW ever, the accuracy of the performance of SPMs is limited by the accuracy of the tWo-dimensional (2D) scanning mecha nism (i.e., the accuracy With Which tWo-dimensional posi tions along the surface can be controlled and measured), among other limitations such as the ?nite siZe of the SPM probe tip. Thus, there is a need for improved systems for assessing the performance, calibrating, and enhancing SPMs.

SUMMARY

[0004] The present disclosure pertains to systems, appara tus, methods, kits, and softWare for assessing and enhancing the performance and/or calibrating scanning probe micro scopes. [0005] Methods of improving the performance of an SPM microscope and/or images that are recorded With it comprise collecting an SPM image of a calibration sample having a known 2D or 1D periodicity and high 2D or 1D symmetry using the SPM. The SPM image is processed to determine the prevalent point spread function of the Whole microscopical imaging process (and its inverse function) and its/ (their) Fou rier transform(s), as Well as the characteristic point spread functions that represent certain physical disturbances of the imaging process and their Fourier transforms in addition to the most likely symmetry and periodicity of the calibration sample. [0006] The selected point spread function or its inverse function in either Fourier space or direct space is applied to one or more images recorded from other samples With the same microscope under essentially the same or similar experimental conditions and With the same or a similar scan ning probe tip. In some examples, the other samples for Which the SPM images are to be improved possess the same period icity Whereby the Fourier transform of these SPM images is divided by the selected point spread function in Fourier space and the result of this operation is Fourier back-transformed into direct space. In other examples, the other samples for Which the SPM images are to be improved possess either no periodicity or a different periodicity than the calibration sample, Whereby the Fourier transform of the selected inverse point spread function is ?rst Fourier back-transformed into direct space, Where it is then convolved With the SPM images. [0007] In other examples, methods comprise collecting an SPM image of a calibration sample having a knoWn symme try and periodicity, and processing the SPM image to deter mine the most likely symmetry and periodicity of the calibra tion sample. The SPM microscope is con?gured to manually and/or automatically repeat the steps of collecting and pro cessing until a most likely symmetry and periodicity is selected. In some examples, a correspondence betWeen the mo st likely symmetry and periodicity and a knoWn symmetry and periodicity is assessed by computing a combined ?gure of merit. In other embodiments, the correspondence betWeen

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