The results of plasma-chemical synthesis of nanodiamonds from carbon nanostructures in a microarc discharge are presented. The electrodes used in the experiments were a molybdenum cathode and a copper anode coated with carbon nanostructures, such as carbon nanotubes, fullerene soot, and graphene. The formation of carbon nanostructures on the surface of the copper electrode was carried out in an electric arc embedded in a liquid hydrocarbon. At the next stage, these carbon nanostructures served as a source of atomic carbon from the surface of the anode of the microarc discharge. It was found that carbon nanotubes, graphene, and nanodiamonds are synthesized on the cathode surface. A significant influence on their formation is exerted by both the surrounding gaseous medium, and the electrophysical parameters of the arc discharge (current and electric field intensity distribution). Two types of nanodiamonds of size 50–100 nm and 5–10 nm have been synthesized, with large nanodiamonds being located separately and small ones as a necklace. The time of formation of microdiamonds is several tens of seconds, which differs by orders of magnitude from those obtained by traditional methods of their production.

An original technique for the synthesis of germanium nanostructures in an electric arc argon plasma is described. The plasma–chemical synthesis of germanium nanotubes up to 100 μm long and up to 1 μm in diameter is performed by selecting the strength of the electric current, the pressure of the buffer gas, and the interelectrode distance. Individual nanotubes reach lengths of several mm. Unlike germanium nanotubes grown via CVD, the germanium nanotubes synthesized in this work have distinct shapes and sizes. They are separated from each other and can be easily manipulated. It is shown that this technique allows both germanium nanotubes and germanene to be grown.

The paper presents methods for growing silicon nanotubes using an electric discharge with different values of the electric field strength in the interelectrode gap. It is shown that the shapes of the grown nanomaterials are significantly influenced by both the surrounding gaseous medium and the electric field strength in the interelectrode gap. The silicon nanostructures obtained have been a rather complex and, at the same time, definitely regular configuration and can be widely used in electronics, photovoltaics, batteries, and even as structural elements in composite materials.

A method for the synthesis of microdiamonds from graphite in an argon arc using germanium as a catalyst is presented. Simple microdiamonds and diamonds of complex configuration are obtained. It has been revealed that forms of synthesized nanomaterials are significantly affected by the buffer gas, the electrical and thermal parameters of the arc discharge, and the presence of germanium at the nucleation stage. Microdiamonds are formed within a few tens of seconds, which is much different from time required for their traditional production.

In this reply, we discuss the relative stability of different forms of CiCs complexes. Based on the extended sections of IR absorption spectra reported by Lavrov [J. Appl. Phys. 124, 086101 (2018)] in his comment, we identify that the C form is stabilized transiently in Float-Zone (FZ)-silicon during and just after electron irradiation. For a longer time at room temperature, the C form disappears at the expense of the B form. Nonetheless, the C form was found to be stable up to 280 °C in Czochralski (Cz)-silicon after neutron irradiation [E. N. Sgourou et al., J. Appl. Phys. 113, 113506 (2013)]. We attribute this apparent discrepancy to a vacancy-induced CiCs dissolution mechanism that drives the electron irradiated sample in a non-equilibrium state that differs from the equilibrium state predicted by density functional theory (DFT) calculations [D. Timerkaeva et al., J. Appl. Phys. 123, 161421 (2018)]. In the neutron irradiation experiment, the generated vacancies are trapped by oxygen interstitial allowing the thermodynamics equilibrium to be preserved.

The structure of the CiCs complex in silicon has long been the subject of debate. Numerous theoretical and experimental studies have attempted to shed light on the properties of these defects that are at the origin of the light emitting G-center. These defects are relevant for applications in lasing, and it would be advantageous to control their formation and concentration in bulk silicon. It is therefore essential to understand their structural and electronic properties. In this paper, we present the structural, electronic, and optical properties of four possible configurations of the CiCs complex in bulk silicon, namely, the A-, B-, C-, and D-forms. The configurations were studied by density functional theory and many-body perturbation theory. Our results suggest that the C-form was misinterpreted as a B-form in some experiments. Our optical investigation also tends to exclude any contribution of A- and B-forms to light emission. Taken together, our results suggest that the C-form could play an important role in heavily carbon-doped silicon.

The impact of a heavy doping on oxygen diffusion at 350 degrees C-700 degrees C is widely discussed in literature, however, the retardation/enhancement mechanisms remains unclear at that temperature range. In this paper, we study the impact of heavy doping on the oxygen diffusion coefficient in silicon by using density functional theory calculations. While it is known that the lowering of temperature induces a switch in the diffusion mechanism from monomer mediated diffusion to dimer one, we have discovered that the reported enhanced oxygen diffusion in p-doped silicon is driven by a switch back from the dimer to monomer. We base our claim on extensive calculations of both pre-exponential factors and activation energies in various doping and stress conditions. We show that the stress has a negligible effect and we attribute the switch back to monomer diffusion at low temperatures in p-doped materials, to a charge assisted mechanism that reduces the migration energy of the monomer of 0.4 eV, while the diffusion rate is kept high thanks to the pre-exponential factor. We also provide comparisons to n-doped and isovalent cases.

We introduce an atomistic description of the kinetic Mass Action Law to predict concentrations of defects and complexes. We demonstrate in this paper that this approach accurately predicts carbon/oxygen related defect concentrations in silicon upon annealing. The model requires binding and migration energies of the impurities and complexes, here obtained from density functional theory (DFT) calculations. Vacancy-oxygen complex kinetics are studied as a model system during both isochronal and isothermal annealing. Results are in good agreement with experimental data, confirming the success of the methodology. More importantly, it gives access to the sequence of chain reactions by which oxygen and carbon related complexes are created in silicon. Beside the case of silicon, the understanding of such intricate reactions is a key to develop point defect engineering strategies to control defects and thus semiconductors properties.

Since many years, silicon is the primary semiconductor material in electronic andphotovoltaic industry. Intensively studied through decades, its properties are essentiallyknown, however new questions keep arising. We need to achieve deep insightinto the numerous possible defects and impurities properties as well as their impacton the performances of the Si based devices. This work covers a range of problemsrelated with point defects interaction of both types long range and short range bymeans of parameter free first principles calculations.The former refers to the impact of heavy doping on diffusivity of interstitialoxygen species. The obtained diffusion coefficients as a function of temperature arein a very good agreement with experimental results that demonstrates the validityof the applied methodology. We showed that the enhanced diffusivity in B-dopedsilicon occurs through a charge transfer mechanism from the p-type dopantThe latter accounts for the various point defect complexes and their thermodynamic,kinetic, and optical properties. Formation of these complexes can beinduced by electron irradiation of Czochralski silicon. This aspect is of extremeimportance for particular operational environment. Here, we performed a combinedexperimental-theoretical investigation to identify the impact of isovalent doping (C,Ge) and co-doping (C-Ge, C-Sn, C-Pb) on the production of different complexes(VOi, CiOi, CiCs, etc.), which are electrically and optically active.Finally, particular attention is addressed to the carbon-carbon defect pair and itsproperties. Recently, it was established that heavily carbon doped silicon elucidateslasing properties. Here we aimed to revisit the possible forms of the complex andtheir properties, in order to associate one of them with light emitting G-centre,observed in experiments.v

We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

Isovalent doping is an important process for the control of point defects in Si. Here, by means of infrared spectroscopy, we investigated the properties of the two main radiation-induced defects in Czochralski-Si (Cz-Si) the oxygen-vacancy (VO) and the carbon-oxygen (CiOi) centres. In particular, we investigated the effect of isovalent doping on the production, the thermal evolution, and the thermal stability of the VO and the CiOi defects. Additionally, we studied the reactions that participate upon annealing and the defects formed as a result of these reactions. Upon annealing VO is converted to VO2 defect although part of the CiOi is converted to CsO2i complexes. Thus, we studied the conversion ratios [VO2]/[VO] and [CsO2i]/[CiOi] with respect to the isovalent dopant. Additionally, the role of carbon in the above processes was discussed. A delay between the temperature characterizing the onset of the VO decay and the temperature characterizing the VO2 growth as well the further growth of VO2 after the complete disappearance of VO indicate that the VO to VO2 conversion is a complex phenomenon with many reaction processes involved. Differences exhibited between the effects of the various dopants on the properties of the two defects were highlighted. The results are discussed in view of density functional theory calculations involving the interaction of isovalent dopants with intrinsic defects, the oxygen and carbon impurities in Si.

We investigate the impact of isovalent (in particular lead (Pb)) doping on the production and thermal stability of the vacancy-related (VO) and the interstitial-related (CiOi and CiCs) pairs in 2 MeV electron irradiated Si samples. We compare the Cz-Si samples with high and low carbon concentration, as well as with Pb-C and Ge-C codoped samples. Using Fourier Transform Infrared Spectroscopy (FTIR), we first determine that under the examined conditions the production of VO decreases with the increase of the covalent radius of the prevalent dopant. Moreover, the production of the VO, CiOi, and CiCs pairs is quite suppressed in Pb-doped Si. In addition, we conclude to an enhanced trapping of both Ci and Cs by Pb impurity under irradiation. The results are further discussed in view of density functional theory calculations. The relative thermodynamic stability of carbon and interstitial related complexes was estimated through the calculations of binding energies of possible defect pairs. This allows to investigate the preferred trapping of vacancies in Pb-doped samples and interstitials in the Ge-doped samples. The different behavior is revealed by considering the analysis of the ratio of vacancy-related to interstitial-related clusters derived from the FTIR measurements. The presence of PbV complexes is confirmed due to the mentioned analysis.

Oscillations of an electric arc in a plasmatron with the fixed arc in wide ranges of currents and air flow rates have been investigated. The distribution functions of arc oscillations have been obtained for various currents, gas flow rates, and distances from a cathode.