V. Smentkowski - Academia.edu (original) (raw)

Papers by V. Smentkowski

The Journal of Physical Chemistry, 1988

ABSTRACT The catalytic oxidation of dimethyl methylphosphonate (DMMP) has been studied on a Mo(11... more ABSTRACT The catalytic oxidation of dimethyl methylphosphonate (DMMP) has been studied on a Mo(110) single-crystal surface. Molecular beam dosing methods delivering a 1:2 DMMP/oxygen flux to the crystal were used, with mass spectrometer sampling of the desorbing products. Under steady-state conditions at 898 K, continuous catalytic production of CO and phosphorus oxide gas-phase species is observed as DMMP is oxidized on the Mo(110) surface. Only surface oxygen is present at measurable coverage on the Mo(110) surface during the catalytic oxidation process. Both CO and phosphorus oxide gas evolution rates are enhanced by heating to temperatures of the order of 1050 K, compared to the rates observed at 898 K. For DMMP decomposition at 898 K on Mo(110) in the absence of oxygen, surface phosphorus is the dominant stable surface component present. This is the first report of the sustained catalytic destruction of compounds in this class, in which catalyst deactivation was not observed after long exposure.

2010 35th IEEE Photovoltaic Specialists Conference, 2010

We present results of chemical composition analysis across CdTe/CdS interfaces using depth profil... more We present results of chemical composition analysis across CdTe/CdS interfaces using depth profiling in Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS). The analysis of these buried interfaces is typically challenging due to significant interface broadening due to CdTe initial roughness and developing roughness during depth profiling. We have developed two alternative methods for sample preparation, namely chemical etching and mechanical polishing, and we will present S conc. profiles obtained using both methods in samples grown with variable CdTe temperature. AES depth profiling near bottom of CdTe solar cells showed widening of S conc. profiles for the hottest CdTe as compared to the coldest CdTe. In addition, the peak S conc. decreases from the coldest to the hottest sample, suggesting that S out-diffusion from CdS is also temperature dependent. Finally we employ focused ion beam cross-sectioning and scanning electron microscopy to measure layer thicknesses, evaluate the success of the sample preparation methods, and to discuss the effects of interface roughness on S conc. profiles and Te-S interdiffusion.

Thin Solid Films, 1995

Diamond and diamond-like carbon have properties which in principle make them ideally suited to a ... more Diamond and diamond-like carbon have properties which in principle make them ideally suited to a wide variety of thin-film applications. The widespread use of diamond thin films, however, has been limited for a number of reasons related largely to the lack of understanding and control of the nucleation and growth processes. Real-time, in-situ studies of the surface of the growing diamond film are experimentally difficult because these films are normally grown under a relatively high pressure of hydrogen, and conventional surface analytical methods require an ultrahigh vacuum environment. Pulsed ion beam based analytical methods with differentially pumped ion sources and particle detectors are able to characterize the uppermost atomic layer of a film during growth at ambient pressures in the range 0.7-27 Pa (4-6 orders of magnitude higher than other surface-specific analytical methods). We describe here a system which has been developed for the purpose of determining the hydrogen concentration and bonding sites on diamond surfaces as a function of sample temperature and ambient hydrogen pressure under hot-filament chemical vapor deposition (CVD) growth conditions. It is demonstrated that as the hydrogen partial pressure increases the saturation hydrogen coverage of the surface of a CVD diamond film increases, but that the saturation level depends on the atomic hydrogen concentration and substrate temperature. At the highest temperatures studied (700 "C), it was found that the surface hydrogen concentration did not exceed l/4 monolayer.

Surface Science, 1995

The interaction of atomic deuterium with diamond (100) has been studied by X-ray photoelectron sp... more The interaction of atomic deuterium with diamond (100) has been studied by X-ray photoelectron spectroscopy (XPS). Reproducible cleaning and conditioning procedures have been developed using atomic hydrogen exposure and heating to 1450 K in ultrahigh vacuum. As the clean diamond surface is exposed to atomic deuterium, the FWHM of the C ls transition initially broadens for low atomic deuterium exposures. Increasing the atomic deuterium exposure results in a sharpening of the C ls transition. This is essentially reversible by stepwise heating to desorb the deuterium. The C Is broadening/sharpening phenomenon may be due to the electronic inhomogeneity caused by partial deuteration of the surface region sampled by XPS. Complete deuteration leads to a more homogeneous chemical environment and thus the C ls line sharpens. These results suggest that deep deuteration of diamond (100) may take place upon exposure to atomic deuterium. The inhomogeneity of the surface region caused by Ar + ion bombardment has a similar broadening effect on the C ls line. Charging effects were found to be insignificant. Deuteration of the diamond (100) surface by atomic deuterium results in apparent shifts of the C Is binding energy, dependent (in sign) upon n-type or p-type doping in the diamond. This is consistent with band bending effects in the surface region caused by the removal of the surface state by deuterium adsorption. It is demonstrated that graphite overlayers on diamond cannot be removed with atomic D or molecular oxygen at high temperatures.

Surface Science, 1989

The direct detection of :CCl, desorption from the thermal dissociation of adsorbed Ccl, on Fe(ll0... more The direct detection of :CCl, desorption from the thermal dissociation of adsorbed Ccl, on Fe(ll0) is reported at 177 K. The process is expected to be thermodynamically favored and represents an unusual low temperature surface process.

Surface and Interface Analysis, 2009

ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data s... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data sets with a tremendous quantity of data. Multivariate statistical analysis (MVA) tools are being used to reduce the massive amount of chemical information into a smaller set of components that are easier to interpret and understand as a result of species association. Standard principal component analysis (PCA) is the most heavily used MVA algorithm in the ToF-SIMS community, and is frequently computed using the singular value decomposition (SVD). Other algorithms such as multivariate curve resolution (MCR) have also gained popularity over the past few years. In this work, we compare the as-measured ToF-SIMS spectrum and ion images with four MVA data analysis protocols: standard PCA, image-rotated SVD, spectra-rotated SVD, and a PCA-based MCR procedure. Image-rotated SVD and spectra-rotated SVD are closely connected to PCA and involve abstract rotations of the singular vectors that naturally arise during computation of the principal components via SVD. These rotations are designed to enhance either spatial contrast or spectral contrast in the components, respectively. We will show that the four MVA protocols provide essentially the same information, but accentuate different aspects of the sample's composition and lateral distribution, and that taken together these methods provide a more complete understanding of the sample. We will demonstrate that the component spectra estimated by MVA protocols assist the analyst in discovering minor constituents and understanding species correlation that would have been difficult, if not impossible, using univariate analysis protocols. For the data set described here, MVA tools identified unexpected species, which were not obvious in the as-measured data. Copyright © 2008 John Wiley & Sons, Ltd.

Surface and Interface Analysis, 2008

Cluster LMIGs are now regarded as the standard primary ion guns on time-of-flight secondary ion m... more Cluster LMIGs are now regarded as the standard primary ion guns on time-of-flight secondary ion mass spectrometers (ToF-SIMS). The ToF-SIMS analyst typically selects a bombarding species (cluster size and charge) to be used for material analysis. Using standard data collection protocols where the analyst uses only a single primary bombarding species, only a fraction of the ion-beam current generated by the LMIG is used. In this work, we demonstrate for the first time that it is possible to perform ToF-SIMS analysis when all of the primary ion intensity (clusters) are used; we refer to this new data analysis mode as non-mass-selected (NMS) analysis. Since each of the bombarding species has a different mass-to-charge ratio, they strike the sample at different times, and as a result, each of the bombarding species generates a spectrum. The resulting NMS ToF-SIMS spectrum contains contributions from each of the bombarding species that are shifted in time. NMS spectra are incredibly complicated and would be difficult, if not impossible, to analyze using univariate methodology. We will demonstrate that automated multivariate statistical analysis (MVSA) tools are capable of rapidly converting the complicated NMS data sets into a handful of chemical components (represented by both spectra and images) that are easier to interpret since each component spectrum represents a unique and simpler chemistry.

Science, 1996

A facile method for chemically functionalizing diamond surfaces has been developed using x-ray ir... more A facile method for chemically functionalizing diamond surfaces has been developed using x-ray irradiation of perfluoroalkyl iodide layers on the surface. Perfluoroalkyl radicals chemically bond to the diamond surface and can be thermally decomposed to produce strongly bound surface C-F bonds that are stable at high temperatures.

The authors have developed a mass spectrometer capable of surface analysis using the techniques o... more The authors have developed a mass spectrometer capable of surface analysis using the techniques of secondary ion mass spectroscopy (SIMS) and mass spectroscopy of recoiled ions (MSRI). For SIMS, an energetic ion beam creates a collision cascade which results in the ejection of low kinetic energy secondary ions from the surface being analyzed. The low kinetic energy SIMS ions are very susceptible to charge neutralization with the surface, and as a result, the SIMS ion yield varies by orders of magnitude depending on the chemical state of the surface. SIM spectra contain elemental ions, and molecular ions. For MSRI, a pulsed ion beam induces a binary collision with the surface being analyzed and the surface species are recoiled into the forward scattering direction with a large kinetic energy. The violence of the binary collision results in complete molecular decomposition, and only elemental ions are detected. The high kinetic energy MSRI ions are much less susceptible to charge neut...

Microscopy and Microanalysis, 2007

Microscopy and Microanalysis, 2010

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Microscopy and Microanalysis, 2010

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Microscopy and Microanalysis, 2006

Time of flight secondary ion mass spectrometry (ToF-SIMS) has a number of desirable characteristi... more Time of flight secondary ion mass spectrometry (ToF-SIMS) has a number of desirable characteristics for surface analysis including: high surface specificity (analysis of the top 0.3 to 1.0 nm of samples), high sensitivity (ppb for most elements), high mass resolution (M/∆ M > 10,000), high (< 100 nm) lateral resolution, and the ability to detect all elements (including hydrogen) plus intact, high mass species during a single measurement [1]. Commercial ToF-SIMS instruments can operate in a spectroscopy mode, an imaging mode, or a depth profile mode. At each pixel in an image (or each depth in a depth profile) an entire mass spectrum is saved, ToF-SIMS data sets are very large and contain a wealth of information regarding the sample being analyzed.

Langmuir, 1990

Quantitative adsorption studies, temperature-programmed desorption, Auger spectroscopy, and sputt... more Quantitative adsorption studies, temperature-programmed desorption, Auger spectroscopy, and sputter depth profile methods have been used to study the interaction of CC1, with Fe(ll0) at 90 and 300 K. At 90 K, molecular CC1, adsorption occurs and produces the following desorption products in the temperature range 90-1050 K: CC1, from the multilayer and the monolayer, :CCl,, CCl,, C,Cl,, C,C1,, FeCl,, and a high-temperature iron chloride species with cracking products FeCl,, FeC1, and Fe. Evidence for FeCl, and :CCl, formation at surface defect sites has been obtained. Irreversible dissociative adsorption of CC1, occurs at 300 K, and the only desorption product which is observed is the high-temperature iron chloride species. Auger spectroscopy shows that small coverages of chlorine remain on the surface of the crystal even after heating to >lo70 K while the carbon diffuses into the bulk of the crystal at -600 K. Correlations between the observed surface processes and tribology (the study of friction and wear) investigations are presented.

Langmuir, 1995

This work describes the preparation of octadecanethiol-based monolayers on single crystal InP sur... more This work describes the preparation of octadecanethiol-based monolayers on single crystal InP surfaces. The quality and nature of the monolayer are characterized by contact angle measurements, photocurrent measurements, ellipsometry, and X-ray photoelectron spectroscopy.

The Journal of Physical Chemistry, 1988

ABSTRACT The catalytic oxidation of dimethyl methylphosphonate (DMMP) has been studied on a Mo(11... more ABSTRACT The catalytic oxidation of dimethyl methylphosphonate (DMMP) has been studied on a Mo(110) single-crystal surface. Molecular beam dosing methods delivering a 1:2 DMMP/oxygen flux to the crystal were used, with mass spectrometer sampling of the desorbing products. Under steady-state conditions at 898 K, continuous catalytic production of CO and phosphorus oxide gas-phase species is observed as DMMP is oxidized on the Mo(110) surface. Only surface oxygen is present at measurable coverage on the Mo(110) surface during the catalytic oxidation process. Both CO and phosphorus oxide gas evolution rates are enhanced by heating to temperatures of the order of 1050 K, compared to the rates observed at 898 K. For DMMP decomposition at 898 K on Mo(110) in the absence of oxygen, surface phosphorus is the dominant stable surface component present. This is the first report of the sustained catalytic destruction of compounds in this class, in which catalyst deactivation was not observed after long exposure.

2010 35th IEEE Photovoltaic Specialists Conference, 2010

We present results of chemical composition analysis across CdTe/CdS interfaces using depth profil... more We present results of chemical composition analysis across CdTe/CdS interfaces using depth profiling in Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS). The analysis of these buried interfaces is typically challenging due to significant interface broadening due to CdTe initial roughness and developing roughness during depth profiling. We have developed two alternative methods for sample preparation, namely chemical etching and mechanical polishing, and we will present S conc. profiles obtained using both methods in samples grown with variable CdTe temperature. AES depth profiling near bottom of CdTe solar cells showed widening of S conc. profiles for the hottest CdTe as compared to the coldest CdTe. In addition, the peak S conc. decreases from the coldest to the hottest sample, suggesting that S out-diffusion from CdS is also temperature dependent. Finally we employ focused ion beam cross-sectioning and scanning electron microscopy to measure layer thicknesses, evaluate the success of the sample preparation methods, and to discuss the effects of interface roughness on S conc. profiles and Te-S interdiffusion.

Thin Solid Films, 1995

Diamond and diamond-like carbon have properties which in principle make them ideally suited to a ... more Diamond and diamond-like carbon have properties which in principle make them ideally suited to a wide variety of thin-film applications. The widespread use of diamond thin films, however, has been limited for a number of reasons related largely to the lack of understanding and control of the nucleation and growth processes. Real-time, in-situ studies of the surface of the growing diamond film are experimentally difficult because these films are normally grown under a relatively high pressure of hydrogen, and conventional surface analytical methods require an ultrahigh vacuum environment. Pulsed ion beam based analytical methods with differentially pumped ion sources and particle detectors are able to characterize the uppermost atomic layer of a film during growth at ambient pressures in the range 0.7-27 Pa (4-6 orders of magnitude higher than other surface-specific analytical methods). We describe here a system which has been developed for the purpose of determining the hydrogen concentration and bonding sites on diamond surfaces as a function of sample temperature and ambient hydrogen pressure under hot-filament chemical vapor deposition (CVD) growth conditions. It is demonstrated that as the hydrogen partial pressure increases the saturation hydrogen coverage of the surface of a CVD diamond film increases, but that the saturation level depends on the atomic hydrogen concentration and substrate temperature. At the highest temperatures studied (700 "C), it was found that the surface hydrogen concentration did not exceed l/4 monolayer.

Surface Science, 1995

The interaction of atomic deuterium with diamond (100) has been studied by X-ray photoelectron sp... more The interaction of atomic deuterium with diamond (100) has been studied by X-ray photoelectron spectroscopy (XPS). Reproducible cleaning and conditioning procedures have been developed using atomic hydrogen exposure and heating to 1450 K in ultrahigh vacuum. As the clean diamond surface is exposed to atomic deuterium, the FWHM of the C ls transition initially broadens for low atomic deuterium exposures. Increasing the atomic deuterium exposure results in a sharpening of the C ls transition. This is essentially reversible by stepwise heating to desorb the deuterium. The C Is broadening/sharpening phenomenon may be due to the electronic inhomogeneity caused by partial deuteration of the surface region sampled by XPS. Complete deuteration leads to a more homogeneous chemical environment and thus the C ls line sharpens. These results suggest that deep deuteration of diamond (100) may take place upon exposure to atomic deuterium. The inhomogeneity of the surface region caused by Ar + ion bombardment has a similar broadening effect on the C ls line. Charging effects were found to be insignificant. Deuteration of the diamond (100) surface by atomic deuterium results in apparent shifts of the C Is binding energy, dependent (in sign) upon n-type or p-type doping in the diamond. This is consistent with band bending effects in the surface region caused by the removal of the surface state by deuterium adsorption. It is demonstrated that graphite overlayers on diamond cannot be removed with atomic D or molecular oxygen at high temperatures.

Surface Science, 1989

The direct detection of :CCl, desorption from the thermal dissociation of adsorbed Ccl, on Fe(ll0... more The direct detection of :CCl, desorption from the thermal dissociation of adsorbed Ccl, on Fe(ll0) is reported at 177 K. The process is expected to be thermodynamically favored and represents an unusual low temperature surface process.

Surface and Interface Analysis, 2009

ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data s... more ABSTRACT Time-of-flight secondary ion mass spectrometry (ToF-SIMS) instruments produce raw data sets with a tremendous quantity of data. Multivariate statistical analysis (MVA) tools are being used to reduce the massive amount of chemical information into a smaller set of components that are easier to interpret and understand as a result of species association. Standard principal component analysis (PCA) is the most heavily used MVA algorithm in the ToF-SIMS community, and is frequently computed using the singular value decomposition (SVD). Other algorithms such as multivariate curve resolution (MCR) have also gained popularity over the past few years. In this work, we compare the as-measured ToF-SIMS spectrum and ion images with four MVA data analysis protocols: standard PCA, image-rotated SVD, spectra-rotated SVD, and a PCA-based MCR procedure. Image-rotated SVD and spectra-rotated SVD are closely connected to PCA and involve abstract rotations of the singular vectors that naturally arise during computation of the principal components via SVD. These rotations are designed to enhance either spatial contrast or spectral contrast in the components, respectively. We will show that the four MVA protocols provide essentially the same information, but accentuate different aspects of the sample&amp;#39;s composition and lateral distribution, and that taken together these methods provide a more complete understanding of the sample. We will demonstrate that the component spectra estimated by MVA protocols assist the analyst in discovering minor constituents and understanding species correlation that would have been difficult, if not impossible, using univariate analysis protocols. For the data set described here, MVA tools identified unexpected species, which were not obvious in the as-measured data. Copyright © 2008 John Wiley &amp;amp; Sons, Ltd.

Surface and Interface Analysis, 2008

Cluster LMIGs are now regarded as the standard primary ion guns on time-of-flight secondary ion m... more Cluster LMIGs are now regarded as the standard primary ion guns on time-of-flight secondary ion mass spectrometers (ToF-SIMS). The ToF-SIMS analyst typically selects a bombarding species (cluster size and charge) to be used for material analysis. Using standard data collection protocols where the analyst uses only a single primary bombarding species, only a fraction of the ion-beam current generated by the LMIG is used. In this work, we demonstrate for the first time that it is possible to perform ToF-SIMS analysis when all of the primary ion intensity (clusters) are used; we refer to this new data analysis mode as non-mass-selected (NMS) analysis. Since each of the bombarding species has a different mass-to-charge ratio, they strike the sample at different times, and as a result, each of the bombarding species generates a spectrum. The resulting NMS ToF-SIMS spectrum contains contributions from each of the bombarding species that are shifted in time. NMS spectra are incredibly complicated and would be difficult, if not impossible, to analyze using univariate methodology. We will demonstrate that automated multivariate statistical analysis (MVSA) tools are capable of rapidly converting the complicated NMS data sets into a handful of chemical components (represented by both spectra and images) that are easier to interpret since each component spectrum represents a unique and simpler chemistry.

Science, 1996

A facile method for chemically functionalizing diamond surfaces has been developed using x-ray ir... more A facile method for chemically functionalizing diamond surfaces has been developed using x-ray irradiation of perfluoroalkyl iodide layers on the surface. Perfluoroalkyl radicals chemically bond to the diamond surface and can be thermally decomposed to produce strongly bound surface C-F bonds that are stable at high temperatures.

The authors have developed a mass spectrometer capable of surface analysis using the techniques o... more The authors have developed a mass spectrometer capable of surface analysis using the techniques of secondary ion mass spectroscopy (SIMS) and mass spectroscopy of recoiled ions (MSRI). For SIMS, an energetic ion beam creates a collision cascade which results in the ejection of low kinetic energy secondary ions from the surface being analyzed. The low kinetic energy SIMS ions are very susceptible to charge neutralization with the surface, and as a result, the SIMS ion yield varies by orders of magnitude depending on the chemical state of the surface. SIM spectra contain elemental ions, and molecular ions. For MSRI, a pulsed ion beam induces a binary collision with the surface being analyzed and the surface species are recoiled into the forward scattering direction with a large kinetic energy. The violence of the binary collision results in complete molecular decomposition, and only elemental ions are detected. The high kinetic energy MSRI ions are much less susceptible to charge neut...

Microscopy and Microanalysis, 2007

Microscopy and Microanalysis, 2010

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Microscopy and Microanalysis, 2010

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Microscopy and Microanalysis, 2006

Time of flight secondary ion mass spectrometry (ToF-SIMS) has a number of desirable characteristi... more Time of flight secondary ion mass spectrometry (ToF-SIMS) has a number of desirable characteristics for surface analysis including: high surface specificity (analysis of the top 0.3 to 1.0 nm of samples), high sensitivity (ppb for most elements), high mass resolution (M/∆ M > 10,000), high (< 100 nm) lateral resolution, and the ability to detect all elements (including hydrogen) plus intact, high mass species during a single measurement [1]. Commercial ToF-SIMS instruments can operate in a spectroscopy mode, an imaging mode, or a depth profile mode. At each pixel in an image (or each depth in a depth profile) an entire mass spectrum is saved, ToF-SIMS data sets are very large and contain a wealth of information regarding the sample being analyzed.

Langmuir, 1990

Quantitative adsorption studies, temperature-programmed desorption, Auger spectroscopy, and sputt... more Quantitative adsorption studies, temperature-programmed desorption, Auger spectroscopy, and sputter depth profile methods have been used to study the interaction of CC1, with Fe(ll0) at 90 and 300 K. At 90 K, molecular CC1, adsorption occurs and produces the following desorption products in the temperature range 90-1050 K: CC1, from the multilayer and the monolayer, :CCl,, CCl,, C,Cl,, C,C1,, FeCl,, and a high-temperature iron chloride species with cracking products FeCl,, FeC1, and Fe. Evidence for FeCl, and :CCl, formation at surface defect sites has been obtained. Irreversible dissociative adsorption of CC1, occurs at 300 K, and the only desorption product which is observed is the high-temperature iron chloride species. Auger spectroscopy shows that small coverages of chlorine remain on the surface of the crystal even after heating to >lo70 K while the carbon diffuses into the bulk of the crystal at -600 K. Correlations between the observed surface processes and tribology (the study of friction and wear) investigations are presented.

Langmuir, 1995

This work describes the preparation of octadecanethiol-based monolayers on single crystal InP sur... more This work describes the preparation of octadecanethiol-based monolayers on single crystal InP surfaces. The quality and nature of the monolayer are characterized by contact angle measurements, photocurrent measurements, ellipsometry, and X-ray photoelectron spectroscopy.