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Article ; Online: Nonequilibrium Dynamics of Electron Emission from Cold and Hot Graphene under Proton Irradiation.

Yao, Yifan / Kononov, Alina / Metzlaff, Arne / Wucher, Andreas / Kalkhoff, Lukas / Breuer, Lars / Schleberger, Marika / Schleife, André

Nano letters

2024

Abstract: Characteristic properties of secondary electrons emitted from irradiated two-dimensional materials arise from multi-length and multi-time-scale relaxation processes that connect the initial nonequilibrium excited electron distribution with their eventual ...

Abstract	Characteristic properties of secondary electrons emitted from irradiated two-dimensional materials arise from multi-length and multi-time-scale relaxation processes that connect the initial nonequilibrium excited electron distribution with their eventual emission. To understand these processes, which are critical for using secondary electrons as high-resolution thermalization probes, we combine first-principles real-time electron dynamics with irradiation experiments. Our data for cold and hot proton-irradiated graphene show signatures of kinetic and potential emission and generally good agreement for electron yields between experiment and theory. The duration of the emission pulse is about 1.5 fs, which indicates high time resolution when used as a probe. Our newly developed method to predict kinetic energy spectra shows good agreement with electron and ion irradiation experiments and prior models. We find that the lattice temperature significantly increases secondary electron emission, whereas electron temperature has a negligible effect.
Language	English
Publishing date	2024-04-08
Publishing country	United States
Document type	Journal Article
ISSN	1530-6992
ISSN (online)	1530-6992
DOI	10.1021/acs.nanolett.4c00356
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: Non-equilibrium dynamics of electron emission from cold and hot graphene under proton irradiation

Yao, Yifan / Metzlaff, Arne / Wucher, Andreas / Kalkhoff, Lukas / Breuer, Lars / Schleberger, Marika / Schleife, André

2023

Abstract: Secondary electrons that are emitted from materials under electron or ion irradiation can serve as a detailed probe for electron-ion processes within the target material. This requires a thorough understanding of their emission characteristics, including ...

Abstract	Secondary electrons that are emitted from materials under electron or ion irradiation can serve as a detailed probe for electron-ion processes within the target material. This requires a thorough understanding of their emission characteristics, including intensity, duration, and kinetic energy distribution. However, complicated multi-length and time scale relaxation processes connect the initial non-equilibrium excited electron distribution with their eventual emission as secondary electrons. The situation is pushed even further into the non-equilibrium regime e.g. in two-dimensional materials or when using beams with high ion flux. We combine first-principles real-time electron dynamics simulations with modern experiments to characterize the processes that are involved in secondary electron emission for proton-irradiated graphene. From our data we identify signatures of kinetic and potential emission mechanisms, by comparing secondary electron characteristics for the entrance and exit side. Simulated yields on the exit side are higher by a factor of up to 2.75, which agrees with experiment within a factor of two and the simulated yield on the exit side of 0.53 electrons per ion also agrees with a value of 0.4 measured for argon irradiated two-layer graphene. Our simulated kinetic energy spectra match electron and ion irradiation experiments and prior models, and provide detailed insight into the emission dynamics. The duration of the emission pulse is only about 1.5 femto-seconds, pointing at high time resolution when used as a probe. Finally, we show that secondary electron emission is significantly increased from graphene with high lattice temperature, whereas the influence of electronic temperature is negligible.
Keywords	Condensed Matter - Materials Science
Subject code	541
Publishing date	2023-11-30
Publishing country	us
Document type	Book ; Online
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Article: Molecular imaging of biological tissue using gas cluster ions.

Tian, Hua / Wucher, Andreas / Winograd, Nicholas

Surface and interface analysis : SIA

2015 Volume 46, Issue 1, Page(s) 115–117

Abstract: ... An ... ...

Abstract	An Ar
Language	English
Publishing date	2015-07-22
Publishing country	England
Document type	Journal Article
ZDB-ID	2023881-2
ISSN	1096-9918 ; 0142-2421
ISSN (online)	1096-9918
ISSN	0142-2421
DOI	10.1002/sia.5509
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Article ; Online: On the SIMS Ionization Probability of Organic Molecules.

Popczun, Nicholas J / Breuer, Lars / Wucher, Andreas / Winograd, Nicholas

Journal of the American Society for Mass Spectrometry

2017 Volume 28, Issue 6, Page(s) 1182–1191

Abstract: The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is ... ...

Abstract	The prospect of improved secondary ion yields for secondary ion mass spectrometry (SIMS) experiments drives innovation of new primary ion sources, instrumentation, and post-ionization techniques. The largest factor affecting secondary ion efficiency is believed to be the poor ionization probability (α
Language	English
Publishing date	2017-03-06
Publishing country	United States
Document type	Journal Article
ZDB-ID	1073671-2
ISSN	1879-1123 ; 1044-0305
ISSN (online)	1879-1123
ISSN	1044-0305
DOI	10.1007/s13361-017-1624-0
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Zs.A 4618: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 241: Show issues

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Article ; Online: Dynamic Reactive Ionization with Cluster Secondary Ion Mass Spectrometry.

Tian, Hua / Wucher, Andreas / Winograd, Nicholas

Journal of the American Society for Mass Spectrometry

2016 Volume 27, Issue 2, Page(s) 285–292

Abstract: Gas cluster ion beams (GCIB) have been tuned to enhance secondary ion yields by doping small gas molecules such as CH4, CO2, and O2 into an Ar cluster projectile, Arn + (n = 1000–10,000) to form a mixed cluster. The ‘tailored beam’ has the potential to ... ...

Abstract	Gas cluster ion beams (GCIB) have been tuned to enhance secondary ion yields by doping small gas molecules such as CH4, CO2, and O2 into an Ar cluster projectile, Arn + (n = 1000–10,000) to form a mixed cluster. The ‘tailored beam’ has the potential to expand the application of secondary ion mass spectrometry for two- and three-dimensional molecular specific imaging. Here, we examine the possibility of further enhancing the ionization by doping HCl into the Ar cluster. Water deposited on the target surface facilitates the dissociation of HCl. This concerted effect, occurring only at the impact site of the cluster, arises since the HCl is chemically induced to ionize to H+ and Cl– , allowing improved protonation of neutral molecular species. This hypothesis is confirmed by depth profiling through a trehalose thin film exposed to D2O vapor, resulting in ~20-fold increase in protonated molecules. The results show that it is possible to dynamically maintain optimum ionization conditions during depth profiling by proper adjustment of the water vapor pressure. H–D exchange in the trehalose molecule M was monitored upon deposition of D2O on the target surface, leading to the observation of [Mn* + H]+ or [Mn* + D]+ ions, where n = 1–8 hydrogen atoms in the trehalose molecule M have been replaced by deuterium. In general, we discuss the role of surface chemistry and dynamic reactive ionization of organic molecules in increasing the secondary ion yield.
MeSH term(s)	Deuterium Oxide/chemistry ; Hydrochloric Acid/chemistry ; Ice ; Spectrometry, Mass, Secondary Ion/methods ; Trehalose/chemistry
Chemical Substances	Ice ; Trehalose (B8WCK70T7I) ; Deuterium Oxide (J65BV539M3) ; Hydrochloric Acid (QTT17582CB)
Language	English
Publishing date	2016-02
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	1073671-2
ISSN	1879-1123 ; 1044-0305
ISSN (online)	1879-1123
ISSN	1044-0305
DOI	10.1007/s13361-015-1283-y
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Zs.A 4618: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 241: Show issues

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Article ; Online: Reducing the Matrix Effect in Organic Cluster SIMS Using Dynamic Reactive Ionization.

Tian, Hua / Wucher, Andreas / Winograd, Nicholas

Journal of the American Society for Mass Spectrometry

2016 Volume 27, Issue 12, Page(s) 2014–2024

Abstract: Dynamic reactive ionization (DRI) utilizes a reactive molecule, HCl, which is doped into an Ar cluster projectile and activated to produce protons at the bombardment site on the cold sample surface with the presence of water. The methodology has been ... ...

Abstract	Dynamic reactive ionization (DRI) utilizes a reactive molecule, HCl, which is doped into an Ar cluster projectile and activated to produce protons at the bombardment site on the cold sample surface with the presence of water. The methodology has been shown to enhance the ionization of protonated molecular ions and to reduce salt suppression in complex biomatrices. In this study, we further examine the possibility of obtaining improved quantitation with DRI during depth profiling of thin films. Using a trehalose film as a model system, we are able to define optimal DRI conditions for depth profiling. Next, the strategy is applied to a multilayer system consisting of the polymer antioxidants Irganox 1098 and 1010. These binary mixtures have demonstrated large matrix effects, making quantitative SIMS measurement not feasible. Systematic comparisons of depth profiling of this multilayer film between directly using GCIB, and under DRI conditions, show that the latter enhances protonated ions for both components by 4- to ~15-fold, resulting in uniform depth profiling in positive ion mode and almost no matrix effect in negative ion mode. The methodology offers a new strategy to tackle the matrix effect and should lead to improved quantitative measurement using SIMS. Graphical Abstract ᅟ.
MeSH term(s)	Ions ; Polymers ; Protons ; Spectrometry, Mass, Secondary Ion ; Trehalose
Chemical Substances	Ions ; Polymers ; Protons ; Trehalose (B8WCK70T7I)
Language	English
Publishing date	2016-09-22
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	1073671-2
ISSN	1879-1123 ; 1044-0305
ISSN (online)	1879-1123
ISSN	1044-0305
DOI	10.1007/s13361-016-1492-z
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Zs.A 4618: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (2.OG) ab Jg. 2022: Lesesaal (EG)
Zs.MO 241: Show issues

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Article ; Online: Reduce the matrix effect in biological tissue imaging using dynamic reactive ionization and gas cluster ion beams.

Tian, Hua / Wucher, Andreas / Winograd, Nicholas

Biointerphases

2016 Volume 11, Issue 2, Page(s) 02A320

Abstract: In the context of a secondary ion mass spectrometry (SIMS) experiment, dynamic reactive ionization (DRI) involves introducing a reactive dopant, HCl, into an Ar gas cluster primary ion beam along with a source of water to enable dissociation of HCl to ... ...

Abstract	In the context of a secondary ion mass spectrometry (SIMS) experiment, dynamic reactive ionization (DRI) involves introducing a reactive dopant, HCl, into an Ar gas cluster primary ion beam along with a source of water to enable dissociation of HCl to free protons. This concerted effect, precisely occurring at the impact site of the cluster beam, enhances the protonation of molecular species. Here, the authors apply this methodology to study the hippocampus and cerebellum region of a frozen-hydrated mouse brain section. To determine the degree of enhancement associated with DRI conditions, sequential tissue slices were arranged in a mirrored configuration so that comparable regions of the tissue could be explored. The results show that the protonated lipid species are increased by ∼10-fold, but that the normally prevalent salt adducts are virtually unaffected. This observation is discussed as a novel approach to minimizing SIMS matrix effects in complex materials. Moreover, the chemical images of protonated lipid ions exhibit clearer features in the cerebellum region as compared to images acquired with the pure Ar cluster beam.
MeSH term(s)	Animals ; Cerebellum/anatomy & histology ; Cerebellum/chemistry ; Hippocampus/anatomy & histology ; Hippocampus/chemistry ; Lipids/analysis ; Mice ; Optical Imaging/methods ; Salts/analysis ; Specimen Handling/methods ; Spectrometry, Mass, Secondary Ion/methods
Chemical Substances	Lipids ; Salts
Language	English
Publishing date	2016-06-08
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2234510-3
ISSN	1559-4106 ; 1559-4106
ISSN (online)	1559-4106
ISSN	1559-4106
DOI	10.1116/1.4941366
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Article ; Online: A mixed cluster ion beam to enhance the ionization efficiency in molecular secondary ion mass spectrometry.

Wucher, Andreas / Tian, Hua / Winograd, Nicholas

Rapid communications in mass spectrometry : RCM

2014 Volume 28, Issue 4, Page(s) 396–400

Abstract: Rationale: Chemical modification of a rare gas cluster ion beam (GCIB) to increase the intensity of desorbed molecular ions in secondary ion mass spectrometry experiments relative to the pure Ar cluster.: Methods: Doping of the GCIB by mixing small ... ...

Abstract	Rationale: Chemical modification of a rare gas cluster ion beam (GCIB) to increase the intensity of desorbed molecular ions in secondary ion mass spectrometry experiments relative to the pure Ar cluster. Methods: Doping of the GCIB by mixing small concentration levels (1-3% relative partial pressure) of CH4 into the Ar gas driving the cluster ion source. Results: Mass spectra measured on a trehalose film using the doped GCIB exhibit enhanced molecular ion signals. From depth profiling experiments, the results are shown to arise from an increase in the ionization efficiency of the sputtered molecules rather than a change in the sputtering yield of neutral species. Conclusions: Tuning of the chemistry of mixed clusters is suggested as a general approach to enhancing the ionization probability of sputtered molecules.
MeSH term(s)	Gases ; Ions/chemistry ; Methane/chemistry ; Spectrometry, Mass, Secondary Ion/methods ; Trehalose
Chemical Substances	Gases ; Ions ; Trehalose (B8WCK70T7I) ; Methane (OP0UW79H66)
Language	English
Publishing date	2014-01-06
Publishing country	England
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	58731-x
ISSN	1097-0231 ; 0951-4198
ISSN (online)	1097-0231
ISSN	0951-4198
DOI	10.1002/rcm.6793
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Article: Retrospective sputter depth profiling using 3D mass spectral imaging.

Zheng, Leiliang / Wucher, Andreas / Winograd, Nicholas

Surface and interface analysis : SIA

2013 Volume 43, Issue 1-2

Abstract: A molecular multilayer stack composed of alternating Langmuir-Blodgett films was analyzed by ToF-SIMS imaging in combination with intermediate sputter erosion using a focused ... ...

Abstract	A molecular multilayer stack composed of alternating Langmuir-Blodgett films was analyzed by ToF-SIMS imaging in combination with intermediate sputter erosion using a focused C
Language	English
Publishing date	2013-12-17
Publishing country	England
Document type	Journal Article
ZDB-ID	2023881-2
ISSN	1096-9918 ; 0142-2421
ISSN (online)	1096-9918
ISSN	0142-2421
DOI	10.1002/sia.3509
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Article ; Online: Molecular sputter depth profiling using carbon cluster beams.

Wucher, Andreas / Winograd, Nicholas

Analytical and bioanalytical chemistry

2009 Volume 396, Issue 1, Page(s) 105–114

Abstract: Sputter depth profiling of organic films while maintaining the molecular integrity of the sample has long been deemed impossible because of the accumulation of ion bombardment-induced chemical damage. Only recently, it was found that this problem can be ... ...

Abstract	Sputter depth profiling of organic films while maintaining the molecular integrity of the sample has long been deemed impossible because of the accumulation of ion bombardment-induced chemical damage. Only recently, it was found that this problem can be greatly reduced if cluster ion beams are used for sputter erosion. For organic samples, carbon cluster ions appear to be particularly well suited for such a task. Analysis of available data reveals that a projectile appears to be more effective as the number of carbon atoms in the cluster is increased, leaving fullerene ions as the most promising candidates to date. Using a commercially available, highly focused C (60) (q+) cluster ion beam, we demonstrate the versatility of the technique for depth profiling various organic films deposited on a silicon substrate and elucidate the dependence of the results on properties such as projectile ion impact energy and angle, and sample temperature. Moreover, examples are shown where the technique is applied to organic multilayer structures in order to investigate the depth resolution across film-film interfaces. These model experiments allow collection of valuable information on how cluster impact molecular depth profiling works and how to understand and optimize the depth resolution achieved using this technique.
MeSH term(s)	Carbon/chemistry ; Mass Spectrometry ; Organic Chemicals ; Silicon/chemistry ; Surface Properties
Chemical Substances	Organic Chemicals ; Carbon (7440-44-0) ; Silicon (Z4152N8IUI)
Language	English
Publishing date	2009-08-04
Publishing country	Germany
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S. ; Review
ZDB-ID	201093-8
ISSN	1618-2650 ; 0016-1152 ; 0372-7920
ISSN (online)	1618-2650
ISSN	0016-1152 ; 0372-7920
DOI	10.1007/s00216-009-2971-x
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