John S. Villarrubia

Bio: John S. Villarrubia is an academic researcher from National Institute of Standards and Technology. The author has contributed to research in topics: Metrology & Dimensional metrology. The author has an hindex of 26, co-authored 92 publications receiving 3227 citations. Previous affiliations of John S. Villarrubia include IBM.

Algorithms for Scanned Probe Microscope Image Simulation, Surface Reconstruction , and Tip Estimation

Abstract: To the extent that tips are not perfectly sharp, images produced by scanned probe microscopies (SPM) such as atomic force microscopy and scanning tunneling microscopy are only approximations of the specimen surface. Tip-induced distortions are significant whenever the specimen contains features with aspect ratios comparable to the tip’s. Treatment of the tip-surface interaction as a simple geometrical exclusion

Nanoindentation of polymers: an overview

Abstract: In this paper, the application of instrumented indentation devices to the measurement of the elastic modulus of polymeric materials is reviewed. This review includes a summary of traditional analyses of load-penetration data and a discussion of associated uncertainties. Also, the use of scanning probe microscopes to measure the nanoscale mechanical response of polymers is discussed, particularly with regard to the associated limitations. The application of these methods to polymers often leads to measurements of elastic modulus that are somewhat high relative to bulk measurements with potentially artificial trends in modulus as a function of penetration depth. Also, power law fits to indentation unloading curves are often a poor representation of the actual data, and the power law exponents tend to fall outside the theoretical range. These problems are likely caused by viscoelasticity, the effects of which have only been studied recently. Advancement of nanoindentation testing toward quantitative characterization of polymer properties will require materialindependent calibration procedures, polymer reference materials, advances in instrumentation, and new testing and analysis procedures that account for viscoelastic and viscoplastic polymer behavior.

Formation of Si(111)-(1×1)Cl

Abstract: Using scanning tunneling microscopy, we have studied the structural modifications induced by Cl upon reaction with Si(111)-(7\ifmmode\times\else\texttimes\fi{}7). At low coverages, reacted and unreacted sites are distinguishable in both current-voltage curves and topographs. At saturation coverage, annealing produces extensive mass transport in which most of the adatom layer is stripped away and accumulated in pyramidal Si structures, permitting the complete underlying Si rest-atom layer to be imaged. Much of this layer initially exists as nearly-adatom-free Cl-stabilized 7\ifmmode\times\else\texttimes\fi{}7 domains, but further annealing converts it slowly to the more favorable bulklike 1\ifmmode\times\else\texttimes\fi{}1 structure. Structures intermediate between the 7\ifmmode\times\else\texttimes\fi{}7 and 1\ifmmode\times\else\texttimes\fi{}1 are observed.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Gwyddion: an open-source software for SPM data analysis

Abstract: In this article, we review special features of Gwyddion—a modular, multiplatform, open-source software for scanning probe microscopy data processing, which is available at http://gwyddion.net/. We describe its architecture with emphasis on modularity and easy integration of the provided algorithms into other software. Special functionalities, such as data processing from non-rectangular areas, grain and particle analysis, and metrology support are discussed as well. It is shown that on the basis of open-source software development, a fully functional software package can be created that covers the needs of a large part of the scanning probe microscopy user community.