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

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

GISAXS study of defects in He implanted silicon

The modifications induced in single-crystal silicon by implanted helium have been investigated by grazing incidence small angle X-ray scattering technique. The samples prepared by implanting 2×1016 cm−2 helium ions at 20 keV in silicon wafers held at 77 K were thermally treated for 2 h in the 100–800°C temperature range. It is shown that implantation produced a film with slightly lower density than that of undamaged single crystal silicon. Further thermal treatment caused shrinking of the film leaving well ordered subsurface layer and damaged film below. Upon annealing at 600°C this structure apparently disappear, to be formed again upon annealing at 800°C

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

GISAXS Studies of Structural Modifications in Ion-beam Amorphized Ge

Grazing incidence small angle scattering of X-rays (GISAXS) was used to analyze structural modifications in implantation-damaged Ge. Samples were implanted by different doses of 74Ge, from 3 × 1012 cm-2 to 3 × 1016 cm-2; at room- or liquid nitrogen-tem

Ion beam synthesis and characterization of Ge nanoparticles in SiO2

Ge quantum dots embedded in SiO2 have been obtained by implantation of Ge ions in the 10(16)-10(17) cm(-2) dose range, followed by post-implantation annealing in the temperature range T-a = 300-1000 degrees C. Using Rutherford back-scattering, grazing incidence X-ray diffraction and grazing incidence small angle X-ray scattering it was found that Ge-QDs are synthesized as discrete, spherical QDs, with radius ranging from 1.7 to 10 nm, depending on dose and T-a. For T-a above 800 degrees C the Ge atom diffusion becomes considerable, leading to a strong increase of both size and size distribution of Ge QDs, but still without sizeable loss of Ge atoms from the implanted layer

Structure of CdS–arachidic acid composite LB multilayers

Langmuir–Blodgett (LB) multilayers of cadmium arachidate were used as precursors to grow semiconducting CdS nanoclusters. The formation of CdS in the multilayers was determined by Fourier transform-infrared (FT-IR), ultraviolet–visible (UV–vis) and Raman spectroscopy. The structural changes occurring as a consequence of CdS formation have been characterized using X-ray reflection (XR) and grazing incidence X-ray diffraction (GIXD) techniques. The CdS containing composite multilayers exhibit the presence of two types of molecular domains, one with close packed herringbone arrangement and the other with tilted molecular chains with no in-plane order. The structural and spectroscopic evidences together suggest that the CdS nanoclusters formed within the arachidic acid LB matrix are quasi two-dimensional in nature with lateral dimension ~5–10 nm and thickness ~1.1 nm.© Elsevie