APPLICATION OF PHOTOELECTRON SPECTROSCOPY IN INORGANIC AND ORGANIC MATERIAL SYSTEMS

Author(s):  
Sudipta Seal ◽  
Tery L. Barr
2018 ◽  
Vol 51 (3) ◽  
pp. 719-727 ◽  
Author(s):  
Yasumasa Takagi ◽  
Tomoya Uruga ◽  
Mizuki Tada ◽  
Yasuhiro Iwasawa ◽  
Toshihiko Yokoyama

1960 ◽  
Vol Original Series, Volume 54 (3) ◽  
pp. 209-219
Author(s):  
K.- A. Omnell ◽  
B. Lindstrom ◽  
F. C. Hoh ◽  
E. Hammarlund-Essler

2020 ◽  
Author(s):  
Graham Purvis ◽  
Cees van der Land ◽  
Naoko Sano ◽  
Peter Cumpson ◽  
Neil Gray

<p>The procedures for detecting fossils on Mars can be derived from the methods that are already used in terrestrial paleobiology (Cady et al., 2003). Here fossils preserving regions are visually located, then inspected for morphological features that might imply fossilised biology (Cady and Noffke, 2009; Westall et al., 2015). Morphological evidence of microfossils on its own is not a completely reliable biosignature (García Ruiz et al., 2002).  However, evidence of biological activity may be implanted within the molecular and isotopic composition of organic compounds, which can serve as biosignatures (Summons et al., 2008). Thus, combining both morphological with organo-geochemical evidence could strengthen any argument that a given geological feature could be associated with biological activity. The results from the simultaneous morphological and geochemical analysis of geobiological structures on Earth could provide evidence that any comparable structures that may be observed on Mars, are potentially connected to biological activity, and therefore, may be suitable for collection for return to the Earth, for further analysis.</p><p>As a proof of concept, the distribution of the organic material that is associated with distinctive microtubules in the glassy volcaniclastic shards within tuff, that have been suggested to be putative ichnofossils (Banergee and Muehlenbachs, 2003), these were analysed by us using X-ray photoelectron spectroscopy, nanoSIMS and the Ionoptika J105 time of flight secondary ion mass spectrometer, with  an argon gas cluster ion beam. This indicated that nitrogenous organic material occurred in regions of the sample that were rich in microtubule textures and in the surrounding microfractures (Sano et al., 2016). </p><p>These results demonstrated that the J105 ToF-SIMS combined with XPS and GC/MS analysis is able to match geomorphological features with their organic and inorganic composition at the µm scale, which may be a useful approach for the identification of fossilised life on Mars.</p><p><strong>References:</strong></p><p>Banerjee et al., (2003). Geochemistry, Geophysics, Geosystems, 4(4).</p><p>Cady et al., (2003). Astrobiology, 3(2), pp.351-368.</p><p>Cady et al., (2009). GSA Today, 19(11).</p><p>García Ruiz et al., (2002). Astrobiology, 2(3), pp.353-369.</p><p>Summons et al., (2008) Astrobiology, 90, 1151–1154.</p><p>Westall, F., et al., (2015). Astrobiology, 15(11), pp.998-1029.</p><p>Sano, N et al., (2016). J. of Vac Sci & Tech A: 34(4), p.041405</p>


1960 ◽  
Vol 54 (3) ◽  
pp. 209-219 ◽  
Author(s):  
K.-Å. Omnell ◽  
B. Lindstrom ◽  
F. C. Hoh ◽  
E. Hammarlund-Essler

Author(s):  
C. C. Baker ◽  
A. A. Voevodin ◽  
J. S. Zabinski

Chameleon coatings are nanocomposite systems that adapt their tribological performance to changes in environmental conditions such as humidity and temperature. In this research we have investigated the tribological properties of two nanocomposite “chameleon” coatings and compared their properties. The two material systems of interest included: (i) Diamond like carbon (DLC) matrix with nanocrystalline WC and WS2 inclusions, and (ii) Yttrium Stabilized Zirconia (YSZ) in an Au matrix with DLC and MoS2 nanoparticle inclusions. The coating design approach included formation of nanocrystalline hard carbide or oxide particles for wear resistance, embedding them into an amorphous matrix for toughness enhancement, and inclusion of nanocrystalline and/or amorphous solid lubricants for friction adaptation to different environments. The coatings were produced using a combination of laser ablation and magnetron sputtering. Chemical and structural analysis of the coatings included x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and micro-Raman spectroscopy. Mechanical properties such as coating hardness and toughness were investigated using nanoindentation, scratch, and indentation adhesion tests. It was observed that both YSZ and WC are valuable in enhancing film toughness. The chemical analysis was used to ascertain a correlation between chemical bonding of species and frictional properties. Friction measurements were studied by cycling between humid air and dry nitrogen conditions. The graphitic carbon component imparted low friction in humid air, MoS2 and WS2 were excellent for dry N2 conditions, and Au was valuable for low friction at elevated temperatures. The direct comparison among coatings demonstrates that similar “chameleon” behavior can be achieved with different material systems, validating the universal nature of the design approach.


1999 ◽  
Vol 598 ◽  
Author(s):  
Norbert Koch ◽  
Egbert Zojer ◽  
Aparna Rajagopal ◽  
Jacques Ghijsen ◽  
Robert L. Johnson ◽  
...  

ABSTRACTThe application of ele ctroactive organic materials in devices (light emitting diodes, photovoltaic cells) often requires electrodes with a low workfunction. Commonly, aluminum or alkaline earth metals are used, which usually exhibit strong interaction with the organic material, such as the formation of new covalent bonds or doping. This results in a strong modification of the electronic structure of the organic/metal interface, and in most cases does not yield the energy level alignment expected for the unreacted interface. As a n alternative to the above-mentioned metals we propose the use of samarium, with a workfunction of 2.7 eV, for the following reason: we have studied the interface formation between Sm and p -sexiphenyl (6P, which exhibits intense blue electroluminescence), with ultraviolet photoelectron spectroscopy. Sm was deposited stepwise onto thin films of 6P in ultrahigh vacuum, and the photoelectron spectra were recorded after each step. We did not find any indication for a strong interaction between the two materials. Metallic Sm is formed instantaneously and the valence electronic structure of 6P remains unchanged upon the metal deposition. The weak interaction at this interface allows one to determine the energy level alignment between a metal and an organic material in a direct manner from the photoelectron spectra, without the need for making any assumptions on the workfunction or ionization potential.


Author(s):  
M.P. Thomas ◽  
A.R. Waugh ◽  
M.J. Southon ◽  
Brian Ralph

It is well known that ion-induced sputtering from numerous multicomponent targets results in marked changes in surface composition (1). Preferential removal of one component results in surface enrichment in the less easily removed species. In this investigation, a time-of-flight atom-probe field-ion microscope A.P. together with X-ray photoelectron spectroscopy XPS have been used to monitor alterations in surface composition of Ni3Al single crystals under argon ion bombardment. The A.P. has been chosen for this investigation because of its ability using field evaporation to depth profile through a sputtered surface without the need for further ion sputtering. Incident ion energy and ion dose have been selected to reflect conditions widely used in surface analytical techniques for cleaning and depth-profiling of samples, typically 3keV and 1018 - 1020 ion m-2.


Author(s):  
A. M. Bradshaw

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).


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