P. Romanowski

Structural and magnetic properties of the molecular beam epitaxy grown MnSb layers on GaAs substrates

The structural and magnetic properties of MnSb layers grown on two differently oriented GaAs substrates are reported. The MnSb compounds grow nonhomogenously both on GaAs (111) B and on GaAs (100) substrates. In x-ray diffraction studies the formation of two epitaxial domains is observed depending on the crystallographic orientation of the substrate. The observed diffusion of Ga atoms from the substrate to the layers results in the formation of an additional Mn-rich cubic phase of GaMnSb. In the case of the (100) oriented substrate, the diffusion of Mn into the substrate was additionally found. Traces of other phases were also noticed. The complex morphology of the layers is found to influence their magnetic properties. Magnetic force microscopy images revealed an inhomogenous distribution of the magnetic force gradient on the surface and the formation of magnetic domains in the samples. X-ray absorption studies of the chemical bonding and local atomic structure around Mn atoms confirmed high structural and chemical disorder in the samples. The chemical bonding of the dominating fraction of Mn atoms is found, however, similar to that in the reference MnSb powder. The x-ray magnetic circular dichroism measurements reveal an enhanced orbital moment and a reduced spin moment, which is most likely caused by the presence of different phases and a Mn-rich surface in the investigated samples

Structure of Magnetically Ordered Si:Mn

The structure studies of single crystalline silicon implanted at 340 K or 610 K with Mn+ ions (Si:Mn) and subsequently processed under atmospheric and enhanced hydrostatic pressure at up to 1270 K are reported. The defect structure was determined by an analysis of X-ray diffuse scattering around the 004 reciprocal lattice point and by electron microscopy. High resolution X-ray diffraction techniques based on the conventional source of radiation were used for this purpose. The crystal structure of Si:Mn and the Si1-xMnx precipitates in the implantation – disturbed layer were studied by synchrotron radiation diffraction in the grazing incidence geometry. Processing of Si:Mn results in crystallization of amorphous Si within the buried implantation – disturbed layer and in formation of Mn4Si7 precipitates. Structural changes are dependent both on temperature of the Si substrate at implantation and on processing parameters.

Variation of strain in granular GaAs:MnAs layers

Granular GaAs(MnAs) layers with different Mn concentration and various layer thickness were grown by MBE method and subjected to annealing at 500°C under ambient and enhanced hydrostatic pressure. Distinct influence of hydrostatic pressure applied during annealing on strain state of layers as well as on hexagonal MnAs inclusions was found. Pressure induced strain of inclusions is related to different bulk moduli of GaAs and of hexagonal MnAs. Formation of hexagonal inclusions depends on concentration of Mn in interstitial position in as-grown samples.

Solid Phase Epitaxial Re-Growth of Amorphous Layer in Si:Si Annealed under Enhanced Hydrostatic Pressure

Solid phase epitaxial regrowth (SPER) of amorphized layer in Czochralski grown silicon (Cz-Si) created by self-implantation (Si+ dose 2x1016 cm-2, energy 150 keV), subsequently annealed for 5 h at up to 1400 K under Ar pressure up to 1.4 GPa, was investigated by Secondary Ion Mass Spectrometry (SIMS) and X-ray methods. Annealing of Cz-Si:Si resulted in pressure-dependent SPER with a marked carbon and oxygen gettering within regrown region. Depth profiling of carbon and oxygen contaminants provides useful information concerning SPER in implanted single crystalline silicon.

Structure of self-implanted silicon annealed under enhanced hydrostatic pressure

Implantation of any ions at a sufficiently high dose and energy (E) into single-crystalline Si leads to the creation of amorphous Si (aSi), with damages peaking near the projected range (R p) of implanted species. Enhanced hydrostatic pressure (HP) at a high temperature (HT) influences the recrystallization of aSi. The structure of self-implanted Czochralski silicon (Si+ dose, D=2×1016 cm−2, E=150 keV, R p=0.22 μm) processed for 5 h at 1400 or 1520 K under HPs up to 1.45 GPa was investigated by X-ray, secondary ion mass spectrometry and photoluminescence methods. The implantation of Si produces vacancies (V) and self-interstitials (Sii). Vacancies and Siis form complex defects at HT–HP, also with contaminants (e.g. oxygen, always present in Czochralski silicon). The mobility and recombination of V and Sii as well as the kinetics of recrystallization are affected by HP, thus processing at HT–HP affects the recovery of aSi.

Hydrogen Gettering within Processed Oxygen-Implanted Silicon

Hydrogen gettering by implantation-disturbed buried layers in oxygen-implanted silicon (Si:O, prepared by O2+ implantation at energy 200 keV and doses 1014 cm-2 and 1017 cm-2) was investigated after annealing of Si:O at up to 1570 K, also under enhanced hydrostatic pressure, up to 1.2 GPa. Depending on processing conditions, buried layers containing SiO2-x clusters and/or precipitates were formed. To produce Si:O,H, Si:O samples were subsequently treated in RF hydrogen plasma. As determined by Secondary Ion Mass Spectrometry, hydrogen was accumulated at the sample surface and within implantation-disturbed areas. It was still present in Si:O,H (D=1017 cm–2) even after subsequent annealing at up to 873 K. Hydrogen accumulation within disturbed areas of Si:O as well as of SOI can be used for recognition of defects in such structures.