“New donors” in Czochralski grown silicon annealed at T >= 600 degrees C under compressive stress

Effects of compressive stress on oxygen agglomeration processes in Czochralski grown silicon heat treated at T = 450 degrees C, used as a reference temperature, and T = 600 degrees C to 800 degrees C are investigated in some detail. Compressive stresses of about P = 1 GPa lead to enhanced formation of Thermal Double Donors in materials annealed over a temperature range of T = 450 degrees C - 600 degrees C. It has been shown that the formation of thermal donors at T = 450 degrees C under normal conditions and compressive stress is accompanied with loss of substitutional boron. In contrast, the concentration of the shallow acceptor states of substitutional boron in silicon annealed under stress at T >= 600 degrees C remains constant. An enhancement effect of thermal donor formation is gradually weakened at T >= 700 degrees C. The oxygen diffusivity sensitive to mechanical stress is believed to be responsible for the observed effects in heat-treated silicon

Effect of carbon on oxygen precipitation in Czochralski silicon

Isochronal anneals were performed in Cz-Si samples of high and low carbon concentrations, from room temperature up to 1200 degrees C. We report infrared studies on the thermal evolution of various bands of oxygen precipitates formed in the course of the annealing process. The effect of carbon on their spectral behavior is examined. It was observed that in the carbon-rich material the oxygen impurity appears to anneal out at a lower temperature than in the carbon-lean material, in agreement with earlier reports that carbon enhances the oxygen precipitation process in Si. In relation with that, two bands at 1060 and 1080 cm(-1) attributed to spheroidal precipitates and another band at 1099 cm(-1) related to the dissolution of platelet precipitates and the formation of microprecipitates make appearance in the spectra of carbon-rich Si at slightly lower temperatures and display higher intensities. This indicates that the enhancement of oxygen precipitation Process is due to the effective formation of spheroidal precipitates having the lowest interfacial energy. The role of carbon in the enhanced precipitation process is discussed

The effect of thermal treatments on the annealing behaviour of oxygen-vacancy complexes in irradiated carbon-doped silicon

Cz-grown, carbon-doped silicon samples were irradiated by fast neutrons. We investigated the annealing behaviour of oxygen-related defects, by infrared spectroscopy. We studied the reaction channels leading to the formation of various VmOn defects and in particular the VOn defects formed by the accumulation of oxygen atoms and vacancies in the initially produced by the irradiation VO defects, as the annealing temperature ramps upwards. We mainly focused on bands appearing in the spectra above 450 degrees C. A band at 1005 cm(-1) is found to be the convolution of two bands at 1004 and 1009 cm(-1). The latter band has the same thermal stability with the 983 cm(-1) of the VO4 defect and therefore is also attributed to this defect. The former band has the same thermal stability with three other bands at 965, 1034 and 1048 cm(-1). These four bands may be attributed to VOn (n=5,6) defects, although other VmOn complexes are also potential candidates. Furthermore, we found that pre-treatments of the samples at 1000 degrees C, with or without the application of high hydrostatic pressure lead to an increase in the concentration of the VO2, VO3 and generally VOn defects in comparison with that of the untreated samples

Investigations of the effect of high pressure on the annealing behavior of oxygen related defects in silicon

Infrared and x-ray studies are reported on the effect of high pressure (BP) treatments on the annealing behavior of oxygen-related defects, particularly the VO defect, formed in neutron-irradiated Cz-Si. Upon annealing at 300 degreesC, the VO defect begins to convert to the VO2 defect. The main purpose of this paper is the study of the effect of pressure on the conversion of the VO to the VO2 defect. To this end, isothermal treatments of 45 min duration at a time, were performed at temperatures T-1=325 degreesC and T-2=350 degreesC with and without the application of hydrostatic pressure of 10.5 kbar. The analysis of the IR results indicates that the application of pressure enhances the growth of the VO2 defect and also the growth of the various VnOm complexes, which give rise to satellite bands in the region of the VO band. X-Ray reciprocal space maps and rocking curves received at the end of the annealing sequence reveal the presence of point-like defects, which are more numerous in the stressed samples. These defects could be considered to act as nucleation sites for the oxygen impurity precipitation

Coincident-site lattice matching during van der Waals epitaxy

Van der Waals (vdW) epitaxy is an attractive method for the fabrication of vdW heterostructures. Here Sb(2)Te(3) films grown on three different kind of graphene substrates (monolayer epitaxial graphene, quasi freestanding bilayer graphene and the SiC (6√3 × 6√3)R30° buffer layer) are used to study the vdW epitaxy between two 2-dimensionally (2D) bonded materials. It is shown that the Sb(2)Te(3) /graphene interface is stable and that coincidence lattices are formed between the epilayers and substrate that depend on the size of the surface unit cell. This demonstrates that there is a significant, although relatively weak, interfacial interaction between the two materials. Lattice matching is thus relevant for vdW epitaxy with two 2D bonded materials and a fundamental design parameter for vdW heterostructures

Vacancy-oxygen defects in silicon: the impact of isovalent doping

Silicon is the mainstream material for many nanoelectronic and photovoltaic applications. The understanding of oxygen related defects at a fundamental level is essential to further improve devices, as vacancy-oxygen defects can have a negative impact on the properties of silicon. In the present review we mainly focus on the influence of isovalent doping on the properties of A-centers in silicon. Wherever possible, we make comparisons with related materials such as silicon germanium alloys and germanium. Recent advanced density functional theory studies that provide further insights on the charge state of the A-centers and the impact of isovalent doping are also discussed in detail