Positron annihilation studies of mesoporous silica films using a slow positron beam

2006 ◽  
Vol 252 (9) ◽  
pp. 3221-3227 ◽  
Author(s):  
Chunqing He ◽  
Makoto Muramatsu ◽  
Toshiyuki Ohdaira ◽  
Atsushi Kinomura ◽  
Ryoichi Suzuki ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Positron Annihilation ◽  
Positron Beam ◽  
Silica Films ◽  
Slow Positron

Study of mesoporous silica films by positron annihilation based on a slow positron beam: Effects of preparation conditions on pore size and open porosity

2007 ◽  
Vol 331 (2-3) ◽  
pp. 213-218 ◽  
Author(s):  
Chunqing He ◽  
Ryoichi Suzuki ◽  
Toshiyuki Ohdaira ◽  
Nagayasu Oshima ◽  
Atsushi Kinomura ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Pore Size ◽  
Positron Annihilation ◽  
Open Porosity ◽  
Positron Beam ◽  
Silica Films ◽  
Slow Positron ◽  
Preparation Conditions

Ortho-Positronium Reemission Yield and Energy in Surfactant-Templated Mesoporous Silica Films

2008 ◽  
Vol 607 ◽  
pp. 30-33 ◽  
Author(s):  
Laszlo Lizkay ◽  
C. Corbel ◽  
P. Perez ◽  
P. Desgardin ◽  
Marie France Barthe ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Pore Size ◽  
Positron Annihilation ◽  
Time Of Flight ◽  
Positron Beam ◽  
High Porosity ◽  
Silica Layer ◽  
Silica Films ◽  
Gamma Energy ◽  
Positron Energy

Positron annihilation gamma energy distribution, lifetime spectroscopy and time-of-flight method were used to study surfactant-templated mesoporous silica films deposited on glass. The lifetime depth profiling was correlated to Doppler broadening and 3γ annihilation fraction measurements to determine the annihilation characteristics inside the films. A set of consistent fingerprints for positronium annihilation, o-Ps reemission into vacuum, and pore size was directly determined. The lifetime measurements were performed in reflection mode with a specially designed lifetime spectrometer mounted on a slow positron beam system. The intensity of the 142 ns vacuum lifetime component was recorded as a function of the energy of the positron beam. In a film with high porosity a reemission efficiency of as high as 40 % was found at low positron energy. Positron lifetime in samples capped by a thin silica layer was used to determine the pore size. The energy of the reemitted o-Ps fraction was measured by a time-of-flight detector, mounted on the same system, allowing determination of both o-Ps re-emission efficiency and energy in the same sample. We demonstrate the potential of the simultaneous use of different positron annihilation techniques in the study of thin porous films.

Tunable pores in mesoporous silica films studied using a pulsed slow positron beam

2007 ◽  
Vol 76 (2) ◽  
pp. 204-208 ◽  
Author(s):  
Chunqing He ◽  
Makoto Muramatsu ◽  
Toshiyuki Ohdaira ◽  
Nagayasu Oshima ◽  
Atsushi Kinomura ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Positron Beam ◽  
Silica Films ◽  
Slow Positron ◽  
Tunable Pores

scholarly journals Study of Microvoids in High-Rate a-Si:H Using Positron Annihilation

1997 ◽  
Vol 467 ◽  
Author(s):  
X. Zou ◽  
D. P. Webb ◽  
S. H. Lin ◽  
Y. W. Lam ◽  
Y. C. Chan ◽  
...  
Keyword(s):  
Thin Films ◽  
Positron Annihilation ◽  
Surface Region ◽  
Positron Beam ◽  
High Rate ◽  
Doppler Broadening ◽  
Slow Positron ◽  
Depth Profiles ◽  
Vacancy Type Defect ◽  
Low Rate

ABSTRACTIn this paper, we have carried out the positron annihilation measurement on high-rate and low-rate a-Si:H thin films deposited by PECVD. By means of the slow positron beam Doppler-broadening technique, the depth profiles of microvoids in a-Si:H have been determined. We have also studied the vacancy-type defect in the surface region in high-rate grown a-Si:H, making comparison between high-rate and low-rate a-Si:H. By plotting S and W parameters in the (S, W) plane, we have shown that the vacancies in all of the high-rate and low-rate deposited intrinsic samples, and in differently doped low-rate samples are of the same nature.

Positron spectroscopy of bulk and near-surface defects in semiconductors

1989 ◽  
Vol 67 (8) ◽  
pp. 813-817
Author(s):  
P. Hautojārvi
Keyword(s):  
Positron Annihilation ◽  
Positron Lifetime ◽  
Surface Defects ◽  
Positron Beam ◽  
Near Surface ◽  
Slow Positron ◽  
Positron Spectroscopy ◽  
Positron Lifetime Spectroscopy ◽  
Defects In Semiconductors ◽  
Ion Implanted

The use of positron annihilation to study defects in semiconductors is discussed. Positron-lifetime spectroscopy reveals As vacancies in as-grown GaAs and gives information on ionization levels. The vacancy profiles in ion-implanted Si are investigated by slow positron beam.

scholarly journals Development of Positron Microbeam in AIST

2008 ◽  
Vol 607 ◽  
pp. 238-242 ◽  
Author(s):  
Nagayasu Oshima ◽  
Ryoichi Suzuki ◽  
Toshiyuki Ohdaira ◽  
Atsushi Kinomura ◽  
T. Narumi ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Spatial Resolution ◽  
Transport System ◽  
Linear Accelerator ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Beam Size ◽  
Electron Linear Accelerator ◽  
Slow Positron ◽  
Magnetic Transport

To improve the spatial resolution of positron annihilation spectroscopy (PAS), a system to produce an intense positron microbeam was developed in AIST. A slow positron beam, which was produced by an electron linear accelerator, was focused by a lens onto a remoderator to enhance its brightness. The brightness-enhanced beam with an intensity of ≈1 × 106 e+/s was extracted from the remoderator and focused onto the sample by a lens. The beam size at the sample was 25 μm, which is more than two and half orders of magnitude smaller than that in the magnetic transport system (≈10 mm). Hence, the spatial resolution of PAS with an AIST positron microbeam can be drastically improved relative to PAS using conventional methods.

Disordered Structures of Adsorbed Hydrogens on Ni(111) Surface Studied by Slow Positron Beam and LEED

2008 ◽  
Vol 607 ◽  
pp. 114-116
Author(s):  
S. Komagata ◽  
K. Hirota ◽  
S. Arii ◽  
S. Honda ◽  
H. Takaishi ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Beam ◽  
Slow Positron ◽  
Disordered Structures ◽  
Γ Ray

The positron annihilation γ-ray spectra emitted from hydrogen-adsorbed Ni(111) surface in some conditions were measured. We have discussed the disordered structures of adsorbed-hydrogens on Ni(111) through analyzing the positron annihilation spectra.

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