Papers by Author: Barbara Surma

Abstract: High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to determining the properties and concentrations of radiation defect centers formed in FZ silicon single crystals subjected to doping with phosphorus in neutron transmutation processes. The studies were performed immediately after the neutron irradiation on the samples with the resistivity of the order of 10⁵ Ωcm. The preset target resistivity was around 2000 Ωcm. The N-doping effect on the material radiation damage has been demonstrated. It is shown that in the N-enriched material, the radiation defect centers with activation energies of 81, 125, 160, 185, and 390 meV are not observed and the concentrations of the defect centers with activation energies of 46, 84, 133, 140, 265, 300, 380, 460, and 546 meV are significantly lower than those in the N-free material. We also show that the majority of defect centers produced by the irradiation of FZ silicon with fast neutrons are also observed after neutron transmutation doping.

Abstract: Creation and transformation of defects in single crystalline (001) oriented Si-Ge with about 5.6 at. % Ge content, containing oxygen interstitials, Oi’s, at 9x1017cm-3 level, were investigated, after processing for 5 h at up to 1400 K (HT) under Ar pressure to 1.1 GPa (HP), by X-ray, synchrotron, infrared and photoluminescence methods. To create nucleation centres for Oi’s precipitation, some samples were pre-annealed for 10 h at 1000 K under 105 Pa. HT-HP treatment at 1230/1400 K results in improved sample homogeneity and crystallographic perfection. HT-HP induced changes in Si-Ge are related mainly to HP-stimulated diffusivity of Ge.

Abstract: The effect of hydrostatic argon pressure equal to 105 Pa and 1.1 GPa applied to processing at up to 1270 K (HT) of Si:Cr samples prepared by Cr+ implantation (dose 1x1015 cm-2, 200 keV) into (001) oriented Czochralski silicon, has been investigated by Secondary Ion Mass Spectrometry, photoluminescence, X-ray and SQUID methods. Cr+ implantation at this energy and dosage produces amorphous silicon (a-Si) near the implanted ions range. Solid phase epitaxial re-growth (SPER) of a-Si takes place at HT. The Cr profile does not depend markedly on HP applied during processing at 723 K. Si:Cr processed at up to 723 K indicates magnetic ordering. Annealing under 105 Pa at 873 K, 1070 K and 1270 K results in a marked diffusion of Cr toward the sample surface. In the case of processing under 1.1 GPa this diffusion is less pronounced, SPER of a-Si is retarded and the a-Si/Si interface becomes enriched with Cr. The Cr concentration in Si:Cr sample processed at 1270 K under 1.1 GPa forms two distinct maxima, the deeper one at 0.35 μm depth.

Abstract: The effect of treatment at up to 1400 K (HT) under enhanced hydrostatic pressure (HP, up to 1.2 GPa) on helium implanted single crystalline silicon (Si:He, He ion dose up to 6x1017cm-2, energy up to 300 keV) has been investigated by transmission electron microscopy, secondary ion mass spectrometry, photoluminescence and X-Ray methods. The treatment of Si:He at ≤ 920 K - HP results in a formation of buried nano-structured layers containing helium filled cavities/bubbles and numerous extended defects; many less dislocations are created at ≥ 1270 K in Si:He treated under HP. HP affects the recrystallization of amorphous Si, diffusivity of implanted He and of implantation-induced defects and thus promotes the creation of more but smaller He-filled cavities/bubbles as well as other defects near the range of implanted He+.

Abstract: Effect of hydrostatic pressure (HP) on out – annealing of defects in self – implanted silicon (Si:Si, Si+ doses 5x1016 cm-2 and 1x1017 cm-2, energies 50 keV and 160 keV), treated for 1 – 10 h at up to 1400 K (HT) under HP ≤ 1.4 GPa, has been investigated by photoluminescence, X-ray and related methods. Applied at 720 – 1270 K enhanced pressure does not affect or affects adversely Si:Si structure while at 1400 K assists in its improvement. HP – dependent transformations in Si:Si at HT are related to effect of HP on diffusion of point defects, such as silicon interstitials and vacancies produced at implantation. Out - annealing of defects in self - implanted silicon is dependent also on spatial position of damaged areas in Si substrate.

Abstract: Oxygen precipitation and creation of defects in Czochralski grown silicon with interstitial oxygen concentration 9.4·1017 cm-3, subjected to irradiation with neutrons (5 MeV, dose 1x1017 cm-2) and subsequently treated for 5 h under atmospheric and high hydrostatic pressures (HP, up to 1.1 GPa) at 1270 / 1400 K, were investigated by spectroscopic and X - Ray methods. Point defects created by neutron irradiation stimulate oxygen precipitation and creation of dislocations under HP, especially at 1270 K. The effect of pressure treatment is related to changed concentration and mobility of silicon interstitials and vacancies as well as of the VnOm – type defects.

Abstract: The effect of annealing under enhanced hydrostatic pressure (HT-HP treatment) on the structural evolution of nano-structured buried He-enriched layers in silicon was investigated by photoluminescence and TEM methods. It has been stated that the HT-HP treatment can affect the defect structure of nano-structured He-containing layer. Enhanced creation of helium bubbles during the HP-HT treatment takes place at HT £ 600oC. Annealing at HT ³ 800oC results in the accumulation (gettering) of oxygen atoms in the He implanted layer in Czochralski grown silicon. HP treatment stimulates this effect.