The examination of the merits of a new type of sampling structure for performing enhanced Raman s... more The examination of the merits of a new type of sampling structure for performing enhanced Raman scattering is presented here. These structures typically consist of 50 A of SiO$\sb2$ sputtered on Ag or Au island films, all coated on a lithographically defined opening in a masked SiO$\sb2$ substrate and use internal reflection in the SiO$\sb2$ substrate to excite plasma resonances in the island films with higher incident field strengths than possible with external excitation. Enhanced scattering from adsorbate molecules adsorbed on top of the SiO$\sb2$ overlayer is driven by the long ranged electromagnetic enhancement provided by the resonantly driven island film particles. Evidence for the long range enhancement comes from chemical passivation, scanning Auger, and distance dependence experiments, as well as comparing enhanced Raman scattering signals obtained from coated and uncoated Au island films. The dependence of the scattering on the excitation angle on incidence can be interpr...
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Vibrational spectroscopy as a tool for ultrathin organic film structural investigations is consid... more Vibrational spectroscopy as a tool for ultrathin organic film structural investigations is considered. The application of total-internal-reflection-excited surface Raman spectroscopy to self-assembled and Langmuir-Blodgett monolayers and multilayer structures is described. The substrate is fused silica upon which a metallic mask has been deposited. Laser excitation is on-coupled from the rear through the ~100-μm opening in the mask. A metal island film (Ag or Au) of ~50-Å thickness is evaporated onto the substrate and is then covered with a sputtered dielectric layer. Typical results for a quaternary ammonium cationic amphiphile are shown. Two types of information can be obtained from the spectrum. The depolarization ratios can be used, at least in principle, to determine the orientation of the polarizability ellipsoid of the molecule, and spectral interpretation can be used just as in bulk systems
The ability of certain reptiles to adhere to vertical (and hang from horizontal) surfaces has bee... more The ability of certain reptiles to adhere to vertical (and hang from horizontal) surfaces has been attributed to the presence of specialized adhesive setae on their feet. Structural and compositional studies of such adhesive setae will contribute significantly towards the design of biomimetic fibrillar adhesive materials. The results of electron microscopy analyses of the structure of such setae are presented, indicating their formation from aggregates of proteinaceous fibrils held together by a matrix and potentially surrounded by a limiting proteinaceous sheath. Microbeam X-ray diffraction analysis has shown conclusively that the only ordered protein constituent in these structures exhibits a diffraction pattern characteristic of β-keratin. Raman microscopy of individual setae, however, clearly shows the presence of additional protein constituents, some of which may be identified as α-keratins. Electrophoretic analysis of solubilized setal proteins supports these conclusions, indi...
ABSTRACT A critical examination of the use of ATR-IR for the examination of surface composition a... more ABSTRACT A critical examination of the use of ATR-IR for the examination of surface composition and orientation in uniaxially drawn poly(ethyleneterephthalate) (PET) films has been performed. This work has identified the band at 1410 cm−1 as a satisfactory reference band in ATR-IR analyses for surface composition and orientation analyses in oriented PET films. Other commonly used reference bands at 790 and 1510 cm−1 have been shown to be influenced by both incident infrared polarization and orientation within the polymer films. Control of sample clamping pressure in a conventional ATR-IR clamp has been shown to afford optimized sample contact, needed in conjunction with the use of valid reference bands to obtain reproducible in-plane surface dichroism measurements of films with varying degrees of orientation.
ABSTRACT This review addresses the special problems associated with the micro-structural characte... more ABSTRACT This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.
Interfacial Aspects of Multicomponent Polymer Materials, 1997
ABSTRACT Design and development of today's high performance, original equipment manufact... more ABSTRACT Design and development of today's high performance, original equipment manufacturer (OEM) paints and coatings requires the ability to do surface and interface analysis, as well as depth profiling. Obtaining compositional information as a function of ...
Tools for effective surface/near-surface and interface/interphase characterization, as well as de... more Tools for effective surface/near-surface and interface/interphase characterization, as well as depth profiling, are critical for effective development of current and future automotive coating systems, including those targeted for original equipment manufacturer (OEM) and refinish ...
... Polarized Surface Raman Scattering DJ Walls and PW Bohn* Department of Chemistry, University ... more ... Polarized Surface Raman Scattering DJ Walls and PW Bohn* Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61 801 (Received: July 12, 1989; In Final Form: October 4, 1989) ... Phys. 1986, 85, 2429. (24) Lalama, S. J.; Garito, A. F. Phys. Rev. ...
ABSTRACT This review addresses the special problems associated with the micro-structural characte... more ABSTRACT This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.
... 10 T. Subbiah, GS Bhat, RW Tock, S. Parameswaran, SS Ramkumar, J. Appl. Polym. Sci. 2005, 96,... more ... 10 T. Subbiah, GS Bhat, RW Tock, S. Parameswaran, SS Ramkumar, J. Appl. Polym. Sci. 2005, 96, 557. ... 11 S. Ramakrishna, K. Fujihara, WE Teo, T. Yong, Z. Ma, R. Ramaseshan, Mater. Today 2006, 9, 40. ... 12 R. Murugan, S. Ramakrishna, Tissue Eng. 2006, 12, 435. ...
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
ABSTRACT The authors investigated moisture permeation for Al2O3 barrier films grown by atomic lay... more ABSTRACT The authors investigated moisture permeation for Al2O3 barrier films grown by atomic layer deposition (ALD) on the two individual chemically distinct surfaces of a commercial (DuPont Teijin Films, Chester, VA) polyethylene terephthalate (PET) film. One surface is “bare” PET polymer, whereas the opposite surface is coated with a low friction “slip” layer to facilitate winding and unwinding of the polymer film on a roll. For early stage Al2O3 film growth (<8 nm), the authors found that moisture permeation was less on the bare polymer side than the slip side but converged to same instrument limited value (∼1 × 10-4 g H2O/m2 day) for thicker films. However, thicker barrier films grown on the slip side experienced abrupt permeation breakthrough in longer-term Ca-testing at 60 °C/85% RH, whereas equivalently grown barrier films on the bare PET-side were stable. Mildly etching the slip side in Ar, before depositing Al2O3, resulted in permeation performance equivalent to barriers grown on the bare polymer side. The authors present evidence that the etch pretreatment reduced incorporation of hydroxide during early stage growth of Al2O3 by ALD, and this was critical for long-term, stable, low moisture permeation barrier films.
The examination of the merits of a new type of sampling structure for performing enhanced Raman s... more The examination of the merits of a new type of sampling structure for performing enhanced Raman scattering is presented here. These structures typically consist of 50 A of SiO$\sb2$ sputtered on Ag or Au island films, all coated on a lithographically defined opening in a masked SiO$\sb2$ substrate and use internal reflection in the SiO$\sb2$ substrate to excite plasma resonances in the island films with higher incident field strengths than possible with external excitation. Enhanced scattering from adsorbate molecules adsorbed on top of the SiO$\sb2$ overlayer is driven by the long ranged electromagnetic enhancement provided by the resonantly driven island film particles. Evidence for the long range enhancement comes from chemical passivation, scanning Auger, and distance dependence experiments, as well as comparing enhanced Raman scattering signals obtained from coated and uncoated Au island films. The dependence of the scattering on the excitation angle on incidence can be interpr...
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Vibrational spectroscopy as a tool for ultrathin organic film structural investigations is consid... more Vibrational spectroscopy as a tool for ultrathin organic film structural investigations is considered. The application of total-internal-reflection-excited surface Raman spectroscopy to self-assembled and Langmuir-Blodgett monolayers and multilayer structures is described. The substrate is fused silica upon which a metallic mask has been deposited. Laser excitation is on-coupled from the rear through the ~100-μm opening in the mask. A metal island film (Ag or Au) of ~50-Å thickness is evaporated onto the substrate and is then covered with a sputtered dielectric layer. Typical results for a quaternary ammonium cationic amphiphile are shown. Two types of information can be obtained from the spectrum. The depolarization ratios can be used, at least in principle, to determine the orientation of the polarizability ellipsoid of the molecule, and spectral interpretation can be used just as in bulk systems
The ability of certain reptiles to adhere to vertical (and hang from horizontal) surfaces has bee... more The ability of certain reptiles to adhere to vertical (and hang from horizontal) surfaces has been attributed to the presence of specialized adhesive setae on their feet. Structural and compositional studies of such adhesive setae will contribute significantly towards the design of biomimetic fibrillar adhesive materials. The results of electron microscopy analyses of the structure of such setae are presented, indicating their formation from aggregates of proteinaceous fibrils held together by a matrix and potentially surrounded by a limiting proteinaceous sheath. Microbeam X-ray diffraction analysis has shown conclusively that the only ordered protein constituent in these structures exhibits a diffraction pattern characteristic of β-keratin. Raman microscopy of individual setae, however, clearly shows the presence of additional protein constituents, some of which may be identified as α-keratins. Electrophoretic analysis of solubilized setal proteins supports these conclusions, indi...
ABSTRACT A critical examination of the use of ATR-IR for the examination of surface composition a... more ABSTRACT A critical examination of the use of ATR-IR for the examination of surface composition and orientation in uniaxially drawn poly(ethyleneterephthalate) (PET) films has been performed. This work has identified the band at 1410 cm−1 as a satisfactory reference band in ATR-IR analyses for surface composition and orientation analyses in oriented PET films. Other commonly used reference bands at 790 and 1510 cm−1 have been shown to be influenced by both incident infrared polarization and orientation within the polymer films. Control of sample clamping pressure in a conventional ATR-IR clamp has been shown to afford optimized sample contact, needed in conjunction with the use of valid reference bands to obtain reproducible in-plane surface dichroism measurements of films with varying degrees of orientation.
ABSTRACT This review addresses the special problems associated with the micro-structural characte... more ABSTRACT This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.
Interfacial Aspects of Multicomponent Polymer Materials, 1997
ABSTRACT Design and development of today's high performance, original equipment manufact... more ABSTRACT Design and development of today's high performance, original equipment manufacturer (OEM) paints and coatings requires the ability to do surface and interface analysis, as well as depth profiling. Obtaining compositional information as a function of ...
Tools for effective surface/near-surface and interface/interphase characterization, as well as de... more Tools for effective surface/near-surface and interface/interphase characterization, as well as depth profiling, are critical for effective development of current and future automotive coating systems, including those targeted for original equipment manufacturer (OEM) and refinish ...
... Polarized Surface Raman Scattering DJ Walls and PW Bohn* Department of Chemistry, University ... more ... Polarized Surface Raman Scattering DJ Walls and PW Bohn* Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61 801 (Received: July 12, 1989; In Final Form: October 4, 1989) ... Phys. 1986, 85, 2429. (24) Lalama, S. J.; Garito, A. F. Phys. Rev. ...
ABSTRACT This review addresses the special problems associated with the micro-structural characte... more ABSTRACT This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.
... 10 T. Subbiah, GS Bhat, RW Tock, S. Parameswaran, SS Ramkumar, J. Appl. Polym. Sci. 2005, 96,... more ... 10 T. Subbiah, GS Bhat, RW Tock, S. Parameswaran, SS Ramkumar, J. Appl. Polym. Sci. 2005, 96, 557. ... 11 S. Ramakrishna, K. Fujihara, WE Teo, T. Yong, Z. Ma, R. Ramaseshan, Mater. Today 2006, 9, 40. ... 12 R. Murugan, S. Ramakrishna, Tissue Eng. 2006, 12, 435. ...
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
ABSTRACT The authors investigated moisture permeation for Al2O3 barrier films grown by atomic lay... more ABSTRACT The authors investigated moisture permeation for Al2O3 barrier films grown by atomic layer deposition (ALD) on the two individual chemically distinct surfaces of a commercial (DuPont Teijin Films, Chester, VA) polyethylene terephthalate (PET) film. One surface is “bare” PET polymer, whereas the opposite surface is coated with a low friction “slip” layer to facilitate winding and unwinding of the polymer film on a roll. For early stage Al2O3 film growth (<8 nm), the authors found that moisture permeation was less on the bare polymer side than the slip side but converged to same instrument limited value (∼1 × 10-4 g H2O/m2 day) for thicker films. However, thicker barrier films grown on the slip side experienced abrupt permeation breakthrough in longer-term Ca-testing at 60 °C/85% RH, whereas equivalently grown barrier films on the bare PET-side were stable. Mildly etching the slip side in Ar, before depositing Al2O3, resulted in permeation performance equivalent to barriers grown on the bare polymer side. The authors present evidence that the etch pretreatment reduced incorporation of hydroxide during early stage growth of Al2O3 by ALD, and this was critical for long-term, stable, low moisture permeation barrier films.
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