X-ray reflectivity study of hydrogen implanted silicon

The X-ray reflectivity (XRR) technique was used to study monocrystalline silicon samples implanted with H-2 ions at an energy of 31 keV and to the dose of 2 x 1016 hydrogen atoms/cm(2). All samples were subsequently isochronally annealed in vacuum at different temperatures in the range from 100 to 900 degrees C. Although the hydrogen depth distribution was expected to be smooth initially, fringes in the XRR spectra were observed already in the implanted but not annealed sample, revealing the presence of a well-defined film-like structure. Annealing enhances the film top to bottom interface correlation due to structural relaxation, resulting in the appearance of fringes in the larger angular range, already at low annealing temperatures. The thickness of the film decreases slowly up to 350 degrees C where substantial changes in the roughness are observed, probably due to the onset of larger clusters formation. Further annealing at higher temperatures restores the high correlation of the film interfaces, while the thickness decreases with the temperature more rapidly. (c) 2006 Elsevier B.V. All rights reserved

GISAXS study of structural relaxation in amorphous silicon

The structural changes induced in single crystal silicon implanted with silicon ions above the amorphisation threshold were studied by Grazing Incidence Small Angle X-ray Scattering technique. Silicon samples were implanted with silicon ions at 30 keV to the dose of 5 x 10(15) atoms/cm(2). A well-defined layer of amorphous silicon, thick about 40 nm was formed below the surface. As implanted samples were subsequently relaxed by thermal annealing at 350 degreesC. The analysis have shown that the amorphous layer exhibits a granular structure that develops with annealing. A model will be presented for the film structure changes obtained by data evaluation based on the distorted wave Born approximation. (C) 2002 Elsevier Science B.V. All rights reserved

Grazing incidence small-angle X-ray scattering study of defects in deuterium implanted monocrystalline silicon

Grazing incidence small-angle X-ray scattering was used to study monocrystalline silicon samples implanted with deuterium ions at an energy of 24 keV and to the dose of 2 x 10(16) ions/cm(2). Samples were annealed isochronally at different temperatures in the range from 393 to 973 K. Due to the relaxation of the defects structures, i.e. redistribution of vacancies and deuterium, strong particle like contribution is observed in addition to the rough surface scattering, already at 393 K annealing. During the annealing, this particles (agglomerations of vacancies) are gradually dissolved till 623 K annealing temperature. Another agglomeration mechanism takes over at about 773 K when a different type of particle growth is observed, and these are dissolved again at about 973 K. The sizes of detected particles are in 2-3 nm range. Also, the interference type of scattering from a film of about 30 nm thickness (the top layer, mostly unaffected by implantation) is observed. This film is gradually getting thinner with the increasing annealing temperature, due to the redistribution of the defects and the structure relaxation

Early stages of bubble formation in helium-implated (100) silicon

Early stages of bubble formation in Czochralski grown, (100)-oriented silicon are investigated by implanting 2 x 10(16) He+ cm(-2) at 20 keV and treating the samples in the temperature range 100-450 degreesC. Elastic recoil detection is used to measure the helium content and depth distribution, while the gas release is studied by thermal desorption spectrometry. To evidence the radiation damage evolution and the defect behavior, the results from Rutherford backscattering spectrometry in channeling conditions, cross sectional transmission electron microscopy, and grazing incidence small angle X-ray scattering are critically analyzed and compared. The study leads to the identification of the steps followed by the defects during annealing and suggests that critical condition for the production of stable bubbles is the presence at low temperature of agglomerates composed of more than four vacancies decorated by helium. This kind of defect offers helium the room necessary to transform into gas phase and confer thermal stability to the bubble embryos

Direct ion beam synthesis of II-VI nanocrystals

Abstract We have studied the direct synthesis of nanoparticles formed by dual implantation of large and equal doses of Cd + S, Zn + Te, Cd + Te or Pb + Te ions into SiO 2 substrate. Grazing incidence small angle X-ray scattering (GI-SAXS), transmittance measurements and Raman spectroscopy were used to investigate implanted composites. The 2D GISAXS patterns suggest the synthesis of nanoparticles already during ion implantation, performed either at 300 or at 77 K, while annealing at higher T causes an increase of the fraction and the average size of synthesized nanoparticles. After high-T annealing both optical methods detected nanocrystals of compound semiconductors CdS, ZnTe or CdTe through the appearance of the respective first optical gaps, E g , in transmittance measurements and characteristic LO peaks in Raman spectra. It is proposed that at high ion doses a fraction of implanted atoms synthesize already during implantation into amorphous aggregates of compound semiconductor, which transform into crystalline nanoparticles after annealing

The evolution of the morphology of Ge nanocrystals formed by ion implantation in SiO2

Grazing incidence small angle X-ray scattering was applied to study the synthesis and growth of Ge quantum dots in Ge-implanted SiO2. Ge ion doses were up to 10(17)/cm(2), and subsequent annealing temperatures up to T-a = 1000 degrees C. Results suggest that ordered and correlated Ge QDs can be achieved by high-dose implantation followed by medium-T annealing