Positron Annihilation Studies of Vacancy Formation in Tungsten, Chromium, and Niobium

1984 ◽  
Vol 41 ◽  
Author(s):  
L. C. Smedskjaer ◽  
G. D. Loper ◽  
M. K. Chason ◽  
R. W. Siegel
Keyword(s):  
Positron Annihilation ◽  
High Vacuum ◽  
Formation Enthalpy ◽  
Positron Annihilation Spectroscopy ◽  
Ultra High Vacuum ◽  
Vacancy Formation ◽  
Self Diffusion ◽  
Melting Temperatures ◽  
Bcc Metals ◽  
Diffusion Studies

AbstractVacancy formation was studied in the refractory bcc metals, tungsten, chromium, and niobium, using the positron annihilation spectroscopy Doppler broadening technique, between room temperature and the respective melting temperatures, under ultra-high vacuum conditions. Temperatures were measured by optical and infrared pyrometry, a W(Rh) thermocouple, and the power delivered to the sample, with calibrations against known melting temperatures. For W, a trapping-model analysis of the data from the temperature range 300–3633 K yielded a vacancy formation enthalpy of 3.76 ± 0.39 eV. For Cr, a similar fit to the data from 296–2049 K yielded a vacancy formation enthalpy of 2.0 ± 0.2 eV. The results are discussed in relation to previous vacancy formation and self-diffusion studies. Measurements on Nb as a function of temperature and oxygen content are also presented.

Measurements of the vacancy formation enthalpy in aluminum using positron annihilation spectroscopy

1978 ◽  
Vol 17 (9) ◽  
pp. 3444-3455 ◽  
Author(s):  
M. J. Fluss ◽  
L. C. Smedskjaer ◽  
M. K. Chason ◽  
D. G. Legnini ◽  
R. W. Siegel
Keyword(s):  
Positron Annihilation ◽  
Formation Enthalpy ◽  
Positron Annihilation Spectroscopy ◽  
Vacancy Formation

Study Of Al Surface Segregation In Icosahedral A162Cu25.5Fe12.5

1998 ◽  
Vol 553 ◽  
Author(s):  
M. GIL-GAVATZ ◽  
D. Rouxel ◽  
P. Pigeat ◽  
B. Weber ◽  
J.-M. Dubois
Keyword(s):  
Surface Segregation ◽  
Vacuum Chamber ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Spectrometer ◽  
Temperature Dependent ◽  
Self Diffusion ◽  
Different Temperatures ◽  
High Vacuum Chamber

AbstractSurface segregation of aluminium was observed during oxidation experiments of icosahedral A162Cu25.5 Fel12.5, performed in-situ and at different temperatures in the ultra-high vacuum chamber of a scanning Auger electron spectrometer. Two regimes, below and above 770K, were observed in relation with severe segregation of Al atoms at the surface for T > 770K. We postulate that this temperature dependent segregation rate is representative of the aluminium transport towards the surface of the quasicrystal. By analogy with classical diffusion experiments, we can thus determine reasonable estimates of the activation energy for Al self-diffusion in this quasicrystal. The results are consistent with the existence of phason flips below 770K and thermal vacancies above this temperature.

Effect of Hydrogen on Vacancy Formation in Sputtered Cu Films Studied by Positron Annihilation Spectroscopy

2013 ◽  
Vol 52 (4R) ◽  
pp. 046501 ◽  
Author(s):  
Atsushi Yabuuchi ◽  
Teruo Kihara ◽  
Daichi Kubo ◽  
Masataka Mizuno ◽  
Hideki Araki ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Vacancy Formation ◽  
Cu Films

Rutherford Backscattering Spectrometry Analysis of Growth Rate and Activation Energy for Self-formed Ti-rich Interface Layers in Cu(Ti)/Low-k Samples

2009 ◽  
Vol 1156 ◽  
Author(s):  
Kazuyuki Kohama ◽  
Kazuhiro Ito ◽  
Kenichi Mori ◽  
Kazuyoshi Maekawa ◽  
Yasuharu Shirai ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Layer ◽  
Rutherford Backscattering Spectrometry ◽  
High Vacuum ◽  
Formation Enthalpy ◽  
Interface Layer ◽  
Rutherford Backscattering ◽  
Ultra High Vacuum ◽  
Dielectric Layers ◽  
Interface Layers

AbstractA new fabrication technique to prepare ultra-thin barrier layers for nano-scale Cu wires was proposed in our previous studies. Ti-rich layers formed at the Cu(Ti)/dielectric-layer interfaces consisted of crystalline TiC or TiSi and amorphous Ti oxides. The primary control factor for Ti-rich interface layer composition was the C concentration in the dielectric layers rather than the formation enthalpy of the Ti compounds. To investigate Ti-rich interface layer growth in Cu(Ti)/dielectric-layer samples annealed in ultra high vacuum, Rutherford Backscattering Spectrometry (RBS) was employed in the present study. Ti peaks were obtained only at the interface for all the samples. Molar amounts of Ti atoms segregated to the interface (n) were estimated from Ti peak areas. The n value was defined by n = Z·exp(-E/RT) · tm, where Z is a preexponential factor and E the activation energy for the reaction. The Z, E, and m values were estimated from plots of log n vs log t and log n vs 1/T. The m values are similar in all the samples. The E values for Ti atoms reacting with the dielectric layers containing carbon (except SiO2) tended to decrease with decreasing C concentration (decreasing k), while reaction rate coefficients (Z·exp(-E/RT)) were insensitive to C concentration in the dielectric layers. These factors lead to conclusion that growth of the Ti-rich interface layers is controlled by chemical reactions of the Ti atoms with the dielectric layers represented by the Z and E values, rather than diffusion in the Ti-rich interface layers.

The vacancy formation enthalpy in Ni determined by positron annihilation

1981 ◽  
Vol 11 (11) ◽  
pp. 2221-2230 ◽  
Author(s):  
L C Smedskjaer ◽  
M J Fluss ◽  
D G Legnini ◽  
M K Chason ◽  
R W Siegel
Keyword(s):  
Positron Annihilation ◽  
Formation Enthalpy ◽  
Vacancy Formation

The composition dependence of the effective vacancy formation enthalpy in copper-rich brass as deduced from the threshold temperature for positron trapping in vacancies

1978 ◽  
Vol 56 (8) ◽  
pp. 1077-1083 ◽  
Author(s):  
P. J. Schultz ◽  
T. E. Jackman ◽  
J. Fabian ◽  
E. A. Williams ◽  
J. R. MacDonald ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Positron Annihilation ◽  
Composition Dependence ◽  
Formation Enthalpy ◽  
Vacancy Formation ◽  
Threshold Temperature ◽  
Α Phase ◽  
Linear Decrease ◽  
Zn Concentration ◽  
Bcc Structure

The temperature dependence of the Doppler-broadened positron annihilation lineshape has been measured for 13 brass specimens with compositions varying from 0 to 48% by weight of Zn. The vacancy formation enthalpy deduced from these measurements shows a linear decrease of 22% with increasing Zn concentration through the α phase and a further 31% decrease on changing from fcc to bcc structure.

Estimating the Activation Enthalpy for Defect Formation in 5754 Alloys by Using Nuclear, Electrical and Mechanical Methods

2012 ◽  
Vol 329 ◽  
pp. 29-33 ◽  
Author(s):  
Alaa M. Ibrahim ◽  
E.M. Hassen ◽  
M. A. Abdel-Rahman ◽  
Emad A. Badawi
Keyword(s):  
Positron Annihilation ◽  
Defect Formation ◽  
Activation Enthalpy ◽  
Formation Enthalpy ◽  
Quenching Rate ◽  
Positron Annihilation Lifetime ◽  
Self Diffusion ◽  
Mechanical Methods ◽  
Positron Annihilation Study ◽  
Induced Defects

The Positron Annihilation Lifetime Technique (PALT) Is One of the Most Important Nuclear Non-Destructive Techniques. it Was Used to Study the Activation Enthalpy for Defect Formation in 5754 Alloy. Quenching Experiments Were Usually Performed on Thin Specimens to Ensure a Uniform Quenching Rate throughout the Specimen. from such Measurements, it Is Possible to Deduce the Vacancy Formation Enthalpy which, in Combination with the Results of Self-Diffusion Measurements, Gives a Value for the Migration Enthalpy of the Vacancy. these Are Very Important Quantities in the Study of the Annealing of Irradiation-Induced Defects. the Use of the Quenching Technique in the Positron Annihilation Study Has the Advantage that it Allows a Distinction to Be Made between Vacancies and Dislocations. Correlations between Nuclear, Electrical and Mechanical Methods Have Been Carried Out after Quenching.

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