Identification of Vacancy-Like Defects in High-Rate Grown a-Si Before and After Light Soaking by Vepas

1998 ◽  
Vol 507 ◽  
Author(s):  
X. Zou ◽  
Y. C. Chan ◽  
D. P. Webb ◽  
Y. W. Lam ◽  
S. H. Lin ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Structural Changes ◽  
Positron Annihilation Spectroscopy ◽  
High Rate ◽  
Light Illumination ◽  
Vacancy Clusters ◽  
Before And After ◽  
New Type ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous

ABSTRACTWe show how positron annihilation can distinguish vacancies in undoped hydrogenated amorphous silicon by performing Variable Energy Positron Annihilation Spectroscopy experiments before and after light soaking. We find that vacancy clusters, di-vacancies and a new type of single vacancies are created in undoped as-grown a-Si:H thin film by light illumination. The fact that the vacancy clusters are eliminated by the thermal annealing suggests that the Staebler-Wronski effect is closely related to vacancy clusters in a-Si:H material. The creation of vacancy clusters and redistribution of di-vacancies and even single vacancies probably result in photo-induced structural changes in this material.

Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

2012 ◽  
Vol 331 ◽  
pp. 41-52 ◽  
Author(s):  
Andreas Wagner ◽  
Wolfgang Anwand ◽  
Maik Butterling ◽  
Thomas E. Cowan ◽  
Fine Fiedler ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Linear Accelerator ◽  
Electron Accelerator ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Electron Linear Accelerator ◽  
Positron Annihilation Lifetime ◽  
Electron Bremsstrahlung ◽  
New Type ◽  
Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

Micro Structural Changes in Welded AlCuLi-Alloys by Positron Annihilation Spectroscopy, SAXS and DSC

2016 ◽  
Vol 877 ◽  
pp. 387-392
Author(s):  
Danny Petschke ◽  
Torsten E.M. Staab
Keyword(s):  
Positron Annihilation ◽  
Structural Changes ◽  
Base Material ◽  
Positron Annihilation Spectroscopy ◽  
Weld Nugget ◽  
Scanning Calorimetry ◽  
Positron Annihilation Lifetime ◽  
Friction Stir ◽  
X Ray Scattering ◽  
Type Size

We follow changes in the micro structure at several distances from the weld nugget of friction stir welded AlCuLi-alloy (AA2198) plates occurring due to the tool movement and the created heat by employing different methods: Small Angle X-ray Scattering (SAXS), giving information on type, size and density of precipitates, Differential Scanning Calorimetry (DSC), giving information on formed precipitates by their dissolution signal, and positron annihilation lifetime spectroscopy (PALS), being sensitive to vacancies and dislocations as well as to the formation and growth of precipitates. We start by characterizing the base material as a reference and proceed via the heat-affected zone to the weld nugget. By the use of complementary methods, we obtain information on structure, kind and distribution of precipitates and correlate this with hardness measurements.

High-Deposition-Rate a-Si:H Through VHF-CVD of Argon-Diluted Silane

1997 ◽  
Vol 467 ◽  
Author(s):  
H. Meiling ◽  
J. Bezemer ◽  
R. E. I. Schropp ◽  
W. F. Van Der Weg
Keyword(s):  
Deposition Rate ◽  
Thin Film Transistors ◽  
Hydrogenated Amorphous Silicon ◽  
High Rate ◽  
High Deposition Rate ◽  
Rf Power ◽  
Bonding Configuration ◽  
Before And After ◽  
Configuration Changes ◽  
Hydrogenated Amorphous

ABSTRACTWe discuss various ways to produce hydrogenated amorphous silicon, a-Si:H, at a high deposition rate. We also present results of our recent study on the structural properties of a-Si:H films deposited at high rates using argon (Ar) dilution of silane in a 50-MHz glow discharge. The results of the depositions with Ar dilution are compared to films deposited from pure silane, SiH4. The deposition rate rd is changed by varying the rf power Prf into the discharge. We focus on the Prf-dependence of the hydrogen (H) bonding configuration and total H content in the film. It is observed that rd saturates at 14 Å/s for pure SiH4, and at 22 Å/s for Ar-diluted SiH4 deposition. Upon increase of Prf the H bonding configuration changes from mostly isolated H to mostly clustered H, and back to mostly isolated H. It is argued that Ar* metastable atoms play an important role in the growth mechanism at intermediate Prf, whereas at high Prf ion bombardment through Ar+ and ions becomes crucial. Two high-rate a-Si:H films are incorporated in thin-film transistors, TFTs. We present their characteristics before and after illumination with calibrated light. It is shown that a-Si:H TFTs with a saturation mobility of 0.7 cm2/Vs can be fabricated, with the complete intrinsic layer deposited at 20 Å/s.

Hydrogen diffusion in amorphous Cu50Ti50 studied by positron-annihilation spectroscopy

1988 ◽  
Vol 66 (6) ◽  
pp. 476-477 ◽  
Author(s):  
R. A. Dunlap ◽  
A. M. Putnam ◽  
D. S. Vardy
Keyword(s):  
Amorphous Alloy ◽  
Positron Annihilation ◽  
Momentum Distribution ◽  
Hydrogen Diffusion ◽  
Positron Annihilation Spectroscopy ◽  
Crystalline Alloy ◽  
Hydrogenated Amorphous ◽  
Trapping Sites

Positron-annihilation spectroscopy has been used to study the density of trapping sites in amorphous and crystalline Cu50Ti50. The effects of hydrogenation on the positron-annihilation spectrum in the amorphous alloy are also investigated. It is shown that the amorphous alloy has a higher concentration of trapping sites than the crystalline alloy and that in the hydrogenated amorphous alloy, the positrons are annihilated by electrons having a momentum distribution that is very nearly the same as in the crystalline alloy.

Study of Defects Generated by Standard- and Plasma-Implantation of Nitrogen Atoms in 4H-SiC Epitaxial Layers

2012 ◽  
Vol 725 ◽  
pp. 41-44 ◽  
Author(s):  
Laurent Ottaviani ◽  
Michel Kazan ◽  
Stephane Biondo ◽  
Filip Tuomisto ◽  
Frédéric Milesi ◽  
...  
Keyword(s):  
Optical Axis ◽  
Positron Annihilation Spectroscopy ◽  
Epitaxial Layers ◽  
Extended Defects ◽  
Dopant Distribution ◽  
Plasma Process ◽  
Vacancy Clusters ◽  
Lower Point ◽  
Before And After ◽  
P Type

A comparison is made between two kinds of Nitrogen implantations for the formation of thin n+p junctions in p-type Silicon Carbide (SiC) epitaxial layers. The standard beam ion implantations and PULSIONTM processes were performed at two distinct energies (700 eV and 7 keV) and the subsequent annealing was held at 1600°C in a resistive furnace specifically adapted to SiC material. Positron Annihilation Spectroscopy (PAS) and unpolarized infrared reflectivity (IR) measurements were carried out before and after the annealing, respecively. Despite the presence of deep vacancy clusters near the as-implanted sample surfaces, no extended defects were detected after the annealing. Plasma implanted samples prove to contain a lower point defect concentration than beam implanted samples. The concentration of these defects (resulting from plasma process) is higher in the plane parallel to the optical axis, which denotes an energy spreading alongside the dopant distribution.

Change in the Positron Annihilation Lifetime of Vacancy Clusters Containing Hydrogen Atoms in Electron-Irradiated F82H

2021 ◽  
Vol 1024 ◽  
pp. 71-78
Author(s):  
Koichi Sato ◽  
Yohei Kondo ◽  
Masakiyo Ohta ◽  
Qiu Xu ◽  
Atsushi Yabuuchi ◽  
...  
Keyword(s):  
Theoretical Calculation ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Vacancy Cluster ◽  
Hydrogen Atoms ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Hydrogen Charging ◽  
Trapping Effect ◽  
Before And After

The change in the positron annihilation lifetime (PAL) of vacancy clusters before and after electrolysis hydrogen charging was determined using PAL measurements in electron-irradiated F82H. The experimental change indicated 8 hydrogen atoms were trapped in vacancy clusters; whereas the theoretical calculation resulted in approximately 14 atoms. As the samples were left at room temperature for 5 min until the start of the PAL measurements, the de-trapping effect of hydrogen atoms was also considered; approximately 13 hydrogen atoms were captured at each vacancy cluster. The PAL decreased after annealing at 148 K, which could not be explained theoretically. Therefore, further experiments and discussions are needed to obtain a precise change in the PAL of vacancy clusters containing hydrogen atoms in F82H.

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