Publications

Displaying 1 - 25 of 77

Raman spectroscopic measurements and imaging on sub-newton Berkovich and spherical imprints in fused silica

January 6, 2024

Author(s)

Yvonne Gerbig, Chris A. Michaels

This paper lays out a general approach for evaluating and optimizing a Raman spectroscopy setup to ensure the collection of reliable spectral data and/or Raman images on indented glasses. The Raman spectroscopic measurements and imaging were conducted on

In-situ Raman spectroscopic measurements of the deformation region in indented glasses

February 15, 2020

Author(s)

Yvonne B. Gerbig, Chris A. Michaels

This paper describes the design and integration of a custom-built optical instrument for in- situ Raman microscopy suitable for collecting high-quality spectroscopic data during the indentation of glass materials. It will further show that the reported

Stress measurements in alumina by optical fluorescence: revisited

August 27, 2019

Author(s)

Robert F. Cook, Chris A. Michaels

Stress measurements in single crystal and polycrystalline alumina are revisited using a recently-developed optical fluorescence energy shift method. The method simultaneously utilizes the R1 and R2 Cr-related ruby line shifts in alumina to determine two

Residual Stress in Polycrystalline Alumina: Comparison of Two-Dimensional Maps and Integrated Scans in Fluorescence-Based Measurements

August 18, 2018

Author(s)

Chris A. Michaels, Robert F. Cook

The spatially heterogeneous residual stress fields in a series of three polycrystalline alumina materials are compared using two fluorescence-based measurement techniques. In the first technique, 18 hyperspectral arrays of the Cr-based R1 and R2 ruby

Review: Coefficients for Stress, Temperature, and Composition Effects in Fluorescence Measurements of Alumina

December 13, 2017

Author(s)

Robert F. Cook, Chris A. Michaels

The numerical coefficients linearly relating the effects of stress (including pressure), temperature, and composition to shifts in the energies of the Cr-related fluorescence in alumina (Al2O3) are reviewed. The primary focus is the shift of the R1 and R2

Two-Dimensional Strain-Mapping by Electron Backscatter Diffraction and Confocal Raman Spectroscopy

November 27, 2017

Author(s)

Andrew J. Gayle, Lawrence Henry Friedman, Ryan Beams, Brian G. Bush, Yvonne B. Gerbig, Chris A. Michaels, Mark D. Vaudin, Robert F. Cook

The strain field surrounding a spherical indentation in silicon is mapped in two dimensions (2- D) using electron backscatter diffraction (EBSD) cross-correlation and confocal Raman spectroscopy techniques. The 200 mN indentation created a 4 m diameter

Determination of Residual Stress Distributions in Polycrystalline Alumina using Fluorescence Microscopy

June 30, 2016

Author(s)

Chris A. Michaels, Robert F. Cook

Maps of residual stress distributions arising from anisotropic thermal expansion effects in a polycrystalline alumina are generated using fluorescence microscopy. The shifts of both the R1 and R2 ruby fluorescence lines of Cr in alumina are used to create

In situ observations of Berkovich indentation induced phase transitions in crystalline silicon films

April 19, 2016

Author(s)

Yvonne B. Gerbig, Chris A. Michaels, Robert F. Cook

The pressure induced phase transitions of crystalline Si films was studied in situ under a Berkovich probe using the Raman spectroscopy-enhanced instrumented indentation technique. The observations suggested strain and time as important parameters in the

Quantitative Mapping of Stress Heterogeneity in Polycrystalline Alumina using Hyperspectral Fluorescence Microscopy

January 15, 2016

Author(s)

Grant A. Myers, Chris A. Michaels, Robert F. Cook

The microstructurally-induced heterogeneous stress fields arising in a series of Cr-doped polycrystalline alumina materials are mapped with sub-micrometer sub-grain size resolution using fluorescence microscopy. Analysis of the hyperspectral data sets

In situ spectroscopic study of the plastic deformation of amorphous silicon under non-hydrostatic conditions

December 17, 2015

Author(s)

Yvonne B. Gerbig, Chris A. Michaels, Robert F. Cook, Jodie E. Bradby

Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by in situ Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique (IIT). The

In situ observation of the spatial distribution of crystalline phases during pressure-induced transformations of indented silicon thin films

February 14, 2015

Author(s)

Yvonne B. Gerbig, Chris A. Michaels, Robert F. Cook

Indentation-induced phase transformation processes were studied by in situ Raman imaging of the deformed contact region of silicon, employing a Raman spectroscopy-enhanced instrumented indentation technique. This is, to our knowledge, the first sequence of

Raman spectroscopy-enhanced IIT: In situ analysis of mechanically stressed polycrystalline Si thin films

July 8, 2014

Author(s)

Yvonne B. Gerbig, Chris A. Michaels, Robert F. Cook

Exposed to mechanical stress, semiconductor materials may phase transform, resulting in changes of crystallographic structure and material properties, rather than deform by plastic flow. As a consequence, prediction of the state and distribution of strain

Stress mapping of micromachined polycrystalline silicon devices via confocal Raman microscopy

June 15, 2014

Author(s)

Grant A. Myers, Siddharth Hazra, Maarten de Boer, Chris A. Michaels, Stephan J. Stranick, Ryan P. Koseski, Robert F. Cook, Frank W. DelRio

Stress mapping of micromachined polycrystalline silicon devices with components in various levels of uniaxial tension was performed. Confocal Raman microscopy was used to form two-dimensional maps of Raman spectral shifts, which exhibited variations on the

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