scholarly journals The Determination of Interfacial Structure and Phase Transitions in Al/Cu and Al/Ni Interfaces by Means of Surface Extended X-Ray Absorption Fine Structure

1991 ◽  
Vol 238 ◽  
Author(s):  
E. V. Barrera ◽  
S. M. Heald
Keyword(s):  
Fine Structure ◽  
Room Temperature ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Interfacial Structure ◽  
Reaction Products ◽  
X Ray ◽  
Absorption Fine ◽  
Reaction Zones ◽  
X Ray Absorption

ABSTRACTSurface extended x-ray absorption fine structure (SEXAFS) was used to investigate the interfacial conditions of Al/Cu and Al/Ni shallow buried interfaces. Previous studies using glancing angle extended x-ray absorption fine structure, x-ray reflectivity, photoemission, and SEXAFS produced conflicting results as to whether or not the interfaces between Al and Cu and Al and Ni were reacted upon room temperature deposition. In this study polycrystalline bilayers of Al/Cu and Al/Ni and trilayers of Al/Cu/Al and Al/Ni/Al were deposited on tantalum foil at room temperature in ultra high vacuum and analyzed to evaluate the reactivity of these systems on a nanometer scale. It became overwhelming apparent that the interfacial phase reactions were a function of the vacuum conditions. Samples deposited with the optimum vacuum conditions showed reaction products upon deposition at room temperature which were characterized by comparisons to standards and by least squares fitting to be CuAl2 and NiAl3 respectively. The results of this study showed that the reacted zone thicknesses were readily dependent on the deposition parameters. For both Al on Cu and Al on Ni as well as the metal on Al conditions 10A reaction zones were observed. These reaction zones were smaller than that observed for bilayers of Al on Cu (30Å) and Al on Ni (60Å) where deposition rates were much higher and samples were much thicker. The reaction species are evident by SEXAFS, where the previous photoemission studies only indicated that changes had occurred. Improved vacuum conditions as compared to the earlier experiments is primarily the reason reactions on deposition were seen in this study as compared to the earlier SEXAFS studies.

Formation of Reactive Clusters in Pd-Y Zeolite by Reduction-Reoxidation Treatment

1992 ◽  
Vol 57 (4) ◽  
pp. 817-825 ◽  
Author(s):  
Hiroshige Matsumoto ◽  
Shuji Tanabe
Keyword(s):  
Fine Structure ◽  
Room Temperature ◽  
Reactive Species ◽  
Temperature Programmed Reduction ◽  
Y Zeolite ◽  
X Ray ◽  
Absorption Fine ◽  
Temperature Programmed ◽  
X Ray Absorption

Preparation of a finely dispersed Pd-Y zeolite has been investigated by temperature-programmed reduction (TPR) and extended X-ray absorption fine structure (EXAFS) techniques. Upon the treatment by a sequence of calcination, reduction, and reoxidation, the original Pd(NH3)42+ ions in the zeolite transformed to reactive species, which were reduced with hydrogen at room temperature and characterized as small PdO clusters of about 25 Pd atoms.

Determination of the Sb/Si(111) interfacial structure by back-reflection x-ray standing waves and surface extended x-ray-absorption fine structure

1991 ◽  
Vol 44 (7) ◽  
pp. 3475-3478 ◽  
Author(s):  
J. C. Woicik ◽  
T. Kendelewicz ◽  
K. E. Miyano ◽  
P. L. Cowan ◽  
C. E. Bouldin ◽  
...  
Keyword(s):  
Fine Structure ◽  
Standing Waves ◽  
Interfacial Structure ◽  
X Ray ◽  
Back Reflection ◽  
Absorption Fine ◽  
X Ray Absorption

Unimportance of Siloxene in Luminescent Porous Silicon as Determined by Nexafs & Exafs

1993 ◽  
Vol 298 ◽  
Author(s):  
S.L. Friedman ◽  
M.A. Marcus ◽  
D.L. Adler ◽  
Y.-H. Xie ◽  
T.D. Harris ◽  
...  
Keyword(s):  
Fine Structure ◽  
Porous Silicon ◽  
Room Temperature ◽  
Emission Spectra ◽  
Porous Si ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
Room Temperature Luminescence ◽  
Combined Data

AbstractNear-edge-- and extended--x-ray absorption fine structure measurements, as well as luminescence excitation and emission spectra, were obtained from samples of porous Si and siloxene. Contrary to a recently proposed explanation for the room temperature luminescence in porous Si, the combined data indicate that siloxene is not principally responsible for the observed effect.

scholarly journals High-temperature treatments of niobium under high vacuum, dilute air- and nitrogen-atmospheres as investigated by in situ X-ray absorption spectroscopy

2021 ◽  
Vol 28 (1) ◽  
pp. 266-277
Author(s):  
Jonas Klaes ◽  
Patrick Rothweiler ◽  
Benjamin Bornmann ◽  
Ralph Wagner ◽  
Dirk Lützenkirchen-Hecht
Keyword(s):  
Fine Structure ◽  
Structural Changes ◽  
High Vacuum ◽  
Heat Treatments ◽  
Niobium Nitride ◽  
X Ray ◽  
Absorption Fine ◽  
Reactive Gases ◽  
X Ray Absorption

Niobium metal foils were heat-treated at 900°C under different conditions and in situ investigated with time-resolved X-ray absorption fine-structure (EXAFS and XANES) measurements. The present study aims to mimic the conditions usually applied for heat treatments of Nb materials used for superconducting radiofrequency cavities, in order to better understand the evolving processes during vacuum annealing as well as for heat treatments in controlled dilute gases. Annealing in vacuum in a commercially available cell showed a substantial amount of oxidation, so that a designated new cell was designed and realized, allowing treatments under clean high-vacuum conditions as well as under well controllable gas atmospheres. The experiments performed under vacuum demonstrated that the original structure of the Nb foils is preserved, while a detailed evaluation of the X-ray absorption fine-structure data acquired during treatments in dilute air atmospheres (10−5 mbar to 10−3 mbar) revealed a linear oxidation with the time of the treatment, and an oxidation rate proportional to the oxygen (air) pressure. The structure of the oxide appears to be very similar to that of polycrystalline NbO. The cell also permits controlled exposures to other reactive gases at elevated temperatures; here the Nb foils were exposed to dilute nitrogen atmospheres after a pre-conditioning of the studied Nb material for one hour under high-vacuum conditions, in order to imitate typical conditions used for nitrogen doping of cavity materials. Clear structural changes induced by the N2 exposure were found; however, no evidence for the formation of niobium nitride could be derived from the EXAFS and XANES experiments. The presented results establish the feasibility to study the structural changes of the Nb materials in situ during heat treatments in reactive gases with temporal resolution, which are important to better understand the underlaying mechanisms and the dynamics of phase formation during those heat treatments in more detail.

Local structure around Mn atoms in room-temperature ferromagnetic (In,Mn)As thin films probed by extended x-ray absorption fine structure

2004 ◽  
Vol 84 (4) ◽  
pp. 481-483 ◽  
Author(s):  
Y. L. Soo ◽  
S. Kim ◽  
Y. H. Kao ◽  
A. J. Blattner ◽  
B. W. Wessels ◽  
...  
Keyword(s):  
Thin Films ◽  
Fine Structure ◽  
Local Structure ◽  
Room Temperature ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption

Structure of magnetic thin films and nanostructures studied by extended X-ray absorption fine structure

2000 ◽  
Vol 454-456 ◽  
pp. 723-728 ◽  
Author(s):  
H. Magnan ◽  
P. Le Fèvre ◽  
A. Midoir ◽  
D. Chandesris ◽  
H. Jaffrès ◽  
...  
Keyword(s):  
Thin Films ◽  
Fine Structure ◽  
Magnetic Thin Films ◽  
X Ray ◽  
Absorption Fine ◽  
X Ray Absorption
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