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RBS/Channeling and TEM Study of Damage Buildup in Ion Bombarded GaN

100%

Pągowska K., Ratajczak R., Stonert A., Turos A., Nowicki L., Sathish N., Jóźwik P., Muecklich A.

Acta Physica Polonica A

2011

vol. 120

issue 1

153-155

A systematic study on structural defect buildup in 320 keV Ar-ion bombarded GaN epitaxial layers has been reported, by varying ion fluences ranged from 5 × 10^{12} to 1 × 10^{17} at./cm^2. 1 μm thick GaN epitaxial layers were grown on sapphire substrates using the metal-organic vapor phase epitaxy technique. Rutherford backscattering/channeling with 1.7 MeV^4He beam was applied for analysis. As a complementary method high resolution transmission electron microscopy has been used. The later has revealed the presence of extended defects like dislocations, faulted loops and stacking faults. New version of the Monte Carlo simulation code McChasy has been developed that makes it possible to analyze such defects on the basis of the bent channel model. Damage accumulation curves for two distinct types of defects, i.e. randomly displaced atoms and extended defects (i.e. bent channel) have been determined. They were evaluated in the frame of the multistep damage accumulation model, allowing numerical parameterization of defect transformations occurring upon ion bombardment. Displaced atoms buildup is a three-step process for GaN, whereas extended defect buildup is always a two-step process.

Analysis of Crystal Lattice Deformation by Ion Channeling

81%

Jóźwik P., Sathish N., Nowicki L., Jagielski J., Turos A., Kovarik L., Arey B., Shutthanandan S., Jiang W., Dyczewski J., Barcz A.

Acta Physica Polonica A

2013

vol. 123

issue 5

828-830

A model of dislocations has been developed for the use in Monte Carlo simulations of ion channeling spectra obtained for defected crystals. High resolution transmission electron microscopy micrographs show that the dominant type of defects in the majority of ion irradiated crystals are dislocations. The RBS/channeling spectrum is then composed of two components: one is due to direct scattering on randomly displaced atoms and the second one is related to beam defocussing on dislocations, which produce predominantly crystal lattice distortions, i.e. bent channels. In order to provide a correct analysis of backscattering spectra for the crystals containing dislocations we have modified the existing Monte Carlo simulation code "McChasy". A new version of the code has been developed by implementing dislocations on the basis of the Peierls-Nabarro model. Parameters of the model have been determined from the high resolution transmission electron microscopy data. The newly developed method has been used to study the Ar-ion bombarded SrTiO_3 samples. The best fit to the Rutherford backscattering/channeling spectra has been obtained by optimizing the linear combination of two kinds of defects: displaced atoms and bent channels. The great virtue of the Monte Carlo simulation is that unlike a traditional dechanneling analysis it allows quantitative analysis of crystals containing a mixture of different types of defects.

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2 Acta Physica Polonica A

1 2013

1 2011

2 Jóźwik P.

2 Nowicki L.

2 Sathish N.

2 Turos A.

1 Arey B.

1 Barcz A.

1 Dyczewski J.

1 Jagielski J.

1 Jiang W.

1 Kovarik L.

1 Muecklich A.

1 Pągowska K.

1 Ratajczak R.

1 Shutthanandan S.

1 Stonert A.

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RBS/Channeling and TEM Study of Damage Buildup in Ion Bombarded GaN

Analysis of Crystal Lattice Deformation by Ion Channeling