A.K. Fedotov

Grain boundary structure and electrical activity in shaped silicon

Abstract Crystalline structure, recombination activity, and electron transport properties have been investigated in boron-doped, thin-walled crystals of silicon obtained from hexagons grown by the EFG process (a modification of Stepanovs method). All grain boundaries (GBs) can be divided into special (Σ3, Σ9), near coincidence, highly deviated (Σ3, Σ9, Σ13), and general (i.e., non-special) GBs. Special GBs are electrically inactive to both minority and majority carriers. Near coincidence GBs are active to minority but inactive to majority carriers. General and highly deviated GBs are very active to both minority and majority carriers. The observed classification of GB activity is explained on the basis of a phenomenological model.

Capacitive properties of nanocomposite (FeCoZr)x(PZT)(100-x) produced by sputtering with the use of argon and oxygen ions beam

The paper established that, the hopping mechanism of the charge exchange for the (FeCoZr)64.4(PZT)35.6 nanocomposite and the additional polarization of tested sample occurs. As frequency increases two frequency areas where capacitance decreases can be observed. Correlation between the conductivity increase and the capacitance decrease has been observed for the both stages of their variability. Voltage resonance phenomenon for the studied material was observed. The zero crossing in the frequency dependence of phase difference transition is accompanied with this phenomenon, which is reflected by a sharp minimum in the capacitance versus frequency characteristics.

Formation of the buried insulating SixNy layer in the region of radiation defects created by hydrogen implantation in silicon wafer

The radiation defects in 10 Ω⋅cm p-type and 4.5 Ω⋅cm n-type Cz Si were created at depth of 0.8-1 µm using 100 keV 2⋅1016 at/cm2 hydrogen implantation at room temperature. Then the introduction of nitrogen into silicon and its diffusion were carried out at different thermodynamic conditions. Finally, the samples were vacuum annealed at 800 oС during 2 h. The state of sample surfaces was studied by SEM. The depth and thickness of SixNy layer and also defect numbers were estimated by RBS method in the channeling mode. The electrical properties of the obtained structures were characterized by the transversal conductance measurements with the keep of a standard LCR-meter at a frequency of 1 MHz using the two-probe method. Our experiments have shown that the above-described method enables one to form the buried SiхNy layer with dielectric properties and the number of defects and nitrogen atoms on the silicon surface and in the near-surface region are comparable with those for the initial silicon wafers.

Gettering of Oxygen onto Buried Defect Layer in Hydrogen Implanted Silicon Wafers after Low Temperature Surface Saturation by Oxygen and Vacuum Annealing

The 10 Ω⋅cm boron-doped Cz-Si wafers were implanted by 100 keV H + and He ions with doses (2.0 ÷4.0)⋅10 cm and then subjected to low-temperature saturation by oxygen from DC plasma source and annealing in vacuum at 250 C or 500 C for 4 h. SIMS measurements have shown that oxygen plasma pre-treatment of H -implanted silicon wafers and their subsequent vacuum low-temperature annealing result in gettering of oxygen from the surface onto the buried defect layer. Measurements in the scanning electron beam induced volt age mode of SEM have exhibited the formation of inhomogeneously distributed contrast, induced by the presence of the buried electrically active extended defects at depths close to a maximal oxygen content. This contrast represents a system of dark spots with a more or less ordered structure the dimensions of that are dependent on the dose of H + pre-implantation.

Electric properties of composite ZnO-based ceramics doped with Fe

This work is focused on the analysis of phase structure and temperature dependences of electric resistivity ρ(Т) in ZnO-based composite ceramics (ZnO)90(FexOy)10, doped with Fe by the addition of 10 wt.% of one of the iron oxides FexOy. Streszczenie. Praca koncentruje się na analizie struktury fazowej oraz zależności temperaturowych rezystywności elektrycznej ρ(Т) kompozytów ceramicznych (ZnO)90(FexOy)10 opartych o ZnO, domieszkowanych Fe poprzez dodanie 10% wag. jednego z tlenków żelaza FexOy. (Własności elektryczne ceramiki kompozytowej na bazie ZnO domieszkowanej Fe)

Synthesis and properties of doped ZnO ceramics

In our work, we studied zinc oxide ceramic samples doped with aluminum and gallium. Structure peculiarities of ceramics depending on their synthesis regime were investigated by the SEM, EDX, XRD, and Raman spectroscopy methods. It was demonstrated that at some technological conditions the formation of indesirable phases of zinc aluminate or gallate may occur preventing an uniform material doping and reducing quality of samples. Single-phase ZnO ceramics were produced when the nanostructured alumina powders were used as a dopant source. The correlations between the synthesis regimes of ZnO ceramics and their electrophysical parameters essential for thermoelectric figure-of-merit (electrical conductivity and Seebeck coefficient) have been established. The best electrophysical characteristics were obtained when the nanostructured alumina produced by combustion in isopropyl alcohol was used as a dopant. Conductivity and Seebeck coefficient of such ceramics are equal to 3·10 S/m and -0.27 mV/K, respectively, corresponding to the power factor of 2.2·10 W/(m·K). Streszczenie. W naszej pracy zbadaliśmy próbki ceramiki tlenku cynku domieszkowanej aluminium oraz galem. Specyfikę struktury ceramiki zależącą od warunków syntezy zbadano metodami SEM, EDX, XRD oraz spektroskopią Ramana. Zaprezentowano, że dla niektórych warunków technologicznych tworzą się niepożądane fazy glinianu cynku lub galusanu zapobiegając jednolitemu domieszkowaniu materiału oraz zmniejszając jakość próbek. Jednofazowa ceramika ZnO została uzyskana w czasie, gdy nanostrukturalny proszek tlenku aluminium był używany jako źródło domieszki. Określono powiązania pomiędzy warunkami otrzymywania ceramiki ZnO oraz jej elektro-fizycznymi parametrami niezbędnymi do termoelektrycznego współczynnika jakości (przewodnictwo elektryczne oraz współczynnik Seebeck`a). Najlepsze elektrofizyczne charakterystyki otrzymano, gdy używano jako domieszkę nanostrukturalny tlenek aluminium produkowany poprzez spalanie w alkoholu izopropylowym. Przewodność oraz współczynnik Seebeck`a tego typu ceramik wynosi odpowiednio 3·10 S/m oraz -0.27 mV/K, co odpowiada współczynnikowi mocy równemu 2.2·10 W/(m·K). (Synteza i właściwości domieszkowanej ceramiki ZnO).

Low-temperature conductivity of silicon doped with antimony

A detailed analysis of the experimental temperature dependences of the resistivity of silicon doped with arsenic with a concentration of 1018 cm−3 is performed for the region 1.8 K < T < 25 K. It is shown that, as a result of cooling to a temperature lower than 4.5 K, a transition from the Mott mode with variable hopping length to the mode of hopping conduction via nearest neighbors is observed, while, at T < 2.5 K, a transition to the Shklovskii-Efros mechanism is possible. A model for such a temperature crossover is suggested; the model is based on simplified solution of the percolation problem with the use of an interpolation expression for the density of states. Performed estimates show that the model is in satisfactory agreement with experimental data when the minimum number of adjustable parameters are used.

Buried Insulating Layer Formation in Cz Si Wafers after Helium Implantation, Nitrogen Plasma Treatment and Annealing

Standard p-type 12 cm Cz Si wafers were implanted by helium ions. The implanted and nonimplanted samples were subsequently subjected to nitrogen plasma treatment and final vacuum annealing. SEM studies have shown the absence of large-scale defects on the top wafer surface and the presence of a layer revealing contrast with surrounding silicon on the cleavage surface at a depth corresponding to the projected range Rp. Scanning over a crater formed by ion sputtering has exposed no defects to the depth of Rp and beyond. At the same time, at a depth of Rp there is a layer with the morphology (structure) significantly different from the surrounding defect-free areas. The measurements of transverse conductivity have shown that the wafer with the formed nitrogen-contained layer possesses dielectric properties with a breakdown voltage up to 15 V.

Influence of Low-Temperature Argon Ion-Beam Treatment on the Photovoltage Spectra of Standard Cz Si Wafers

The main goal of this work is to investigate the influence of low-temperature argon ionbeam treatment on the electric and structural properties of a near-surface region of the standard commercial p-type Cz Si wafers, and to compare the effects of Ar+ and H+ ion-beam treatment. The measurements of thermo-EMF have shown that both Ar+ and H+ ion-beam treatment with the ion energy 200 eV and current density 0.15 mA/cm2 at a temperature of 30 oC during 30 min leads to the p-to-n −type overcompensation of the near-surface layer of silicon wafers. The measurements of photovoltage spectra have shown that (i) Ar+ and H+ treatments in like manner lead to the appearance of a photovoltage signal over a wide spectral region due to the formation of p-n-junction on the treated surface, and (ii) photosensitivity of the Ar+ ion-beam treated wafers in the ultraviolet (UV) spectral region (200-400 nm) is much greater as compared to the wafers subjected to H+ ion beam treatment in the same conditions. The main difference in the Ar+ and H+ ion-beam treatment effects is the formation of a thin (5-20 nm) oxygen-containing dielectric layer on the surface of hydrogenated samples and the absence of such layer in case of Ar+ ion-beam treatment.

SEM Investigation of Surface Defects Arising at the Formation of a Buried Nitrogen-Containing Layer in Silicon

The main goal of this work is to demonstrate the correlation between the density and type of surface defects arising during the formation of a buried nitrogen-containing layer in Si wafers, and the number of buried defects formed by different dose hydrogen preimplantation. Standard commercial 12 ⋅cm boron-doped and 4.5 ⋅cm phosphorous-doped Cz Si wafers were subjected to hydrogen ion implantation at room temperature with the energy 100 keV and doses 1⋅1015 - 4⋅1016 at/cm2. Then nitrogen was introduced into silicon from a DC plasma source at a temperature of 300 oС. Finally, all samples were subjected to 2 h vacuum annealing at 900 oС. The experiments have shown that the density and type of the surface defects depend significantly on the dose of hydrogen implantation, parameters of N+-plasma treatment, and conductivity type of silicon. Optimization of the above-mentioned parameters makes it possible to create the substrates containing a buried dielectric SixNy layer and having a practically defect-free surface.