Structure of complexes responsible for radiation-stimulated softening of silicon single crystals

The rate of the radiation-stimulated change in the microhardness of silicon single crystals exposed to irradiation with a low-intensity flux of beta particles (10⁵ < I < 2.9 × 10⁶ cm^?2 s^?1) is studied as a function of the radiation intensity. The temperature is determined at which the microhardness H = H _τ reached in a time τ under low-intensity beta irradiation regains its initial value H ₀. The results obtained indicate that complexes containing two vacancies play a dominant role in the radiation-stimulated softening of silicon single crystal     

Absolute photon yield from silicon surface under electron and ion irradiation

The characteristics of the optical radiation accompanying the bombardment of silicon surface by electrons and medium-energy ions have been studied. The continuous radiation observed in this case is related to interband electronic transitions. The characteristic radiation (which is present in both cases), in the case of ion bombardment, is emitted by silicon atoms sputtered in the excited state and scattered helium ions; in the case of electron bombardment, this radiation is emitted by desorbed excited atoms and residual atmosphere molecules, which cover the silicon surface under study.     

The influence of low-intensity beta radiation on crack susceptibility under indentation of silicon

The dependence of the lengths of radial cracks formed during indentation of silicon single crystals on the depth of imprint has been studied using electron microscopy. The influence of low-intensity (I = 10⁵ cm⁻² s^–1) beta radiation on the crack susceptibility during indenter penetration to a depth of ∼2.5 μm has been revealed.     

Synchrotron‐based spectroscopy of X‐ray channeling through hollow capillary microchannels inside glass plates

Here, soft X‐ray synchrotron radiation transmitted through microchannel plates is studied experimentally. Fine structures of reflection and XANES Si L‐edge spectra detected on the exit of silicon glass microcapillary structures under conditions of total X‐ray reflection are presented and analyzed. The phenomenon of the interaction of channeling radiation with unoccupied electronic states and propagation of X‐ray fluorescence excited in the microchannels is revealed. Investigations of the interaction of monochromatic radiation with the inner‐shell capillary surface and propagation of fluorescence radiation through hollow glass capillary waveguides contribute to the development of novel X‐ray focusing devices in the future.     

Synchrotron radiation interference in front of the silicon absorption edge for silicon-on-insulator structures

The synchrotron radiation (SR) interference phenomenon has been for the first time observed in a strained silicon nanolayer deposited on a dielectric SiO₂ layer (∼150 nm) on Si (100) single crystalline substrates (silicon-on-insulator (SOI) structures). Strong oscillations of spectra intensity depending on photon energy have been detected in the energy range preceding the elementary silicon Si L _2,3 absorption edge (≤100 eV) at grazing angles of SR smaller than 21° in the X-ray photoeffect quantum yield structure. The phase of the spectra oscillation structure is reversed for small variations of grazing angle in the 4°–21° range. The silicon nanolayer thickness (∼180 nm) has been estimated in the three-layer, Si nanolayer-SiO₂-Si substrate structure with the use of neighbor maxima positions of ultrasoft X-ray radiation interference in XANES (X-ray absorption near edge structure) spectra. A decrease in the crystal lattice parameter of a strained silicon layer along the normal to substrate has been determined by X-ray diffraction. An increase in the Si-Si interatomic distances in the strained silicon nanolayer lattice of SOI structure has been found using ultrasoft X-ray emission spectroscopy data.     

Dynamic thermometry of a solid via optical diffraction method at pulsed irradiation

A method for the fast measurement of the temperature of solids under the action of a high-power light pulse is proposed and demonstrated. This method is based on the application of the Fraunhofer diffraction and is implemented for silicon samples heated to melting temperatures T _melt = 1412°C by a high-power light pulse. The current silicon temperature was determined by measuring the varying diffraction angle of the probing laser beam. The diffraction angle was varied over time because the period of the diffraction grating increased as a result of the dynamic thermal expansion of the crystal. An initial grating was formed on the surface of the silicon plate with a period of d = 4 μm. The radiation beam of a He-Ne laser with λ = 0.6328 μm was used as the probing beam; the measured signal was recorded in the pair of symmetric fifth-order diffraction maxima.     

Characteristics of the formation of radiation defects in silicon structures

The method of deep-level transient spectroscopy is used to investigate aspects of the formation of radiation defects in silicon p ⁺-n diffusion structures when bombarded by accelerated electrons. It is shown that for base thicknesses of the p ⁺-n structures in the range 0.2–0.6mm a substantial change in the concentration of the radiation defects formed in this way is observed, having a maximum at 0.25 mm. Below 0.2 mm and above 0.6 mm the concentration of radiation defects exhibits a weak dependence on base thickness. The observed effect is explained by variation of the relative concentrations of vacancies and interstitial silicon atoms in the base during formation of p ⁺-n pairs. Zh. Tekh. Fiz. 69, 121–123 (January 1999)     

Condensation of injected electrons and holes in silicon

We report that the condensed electron—hole phase in silicon has been produced by electrical carrier injection. The condensed phase recombination radiation occured at 1.082 ± 0.001 eV with a linewidth of 0.012 eV. Hence the line position and linewidth appear to be independent of whether the semiconductor is excited by optical of electrical injection. Joule heating is shown to be important by analyses of time resolved recombination radiation spectra and double pulse experiments.     

Phase transitions in erbium-doped silicon exposed to laser radiation

The dynamics of phase transitions induced by nanopulsed ruby laser radiation (80 nsec, 2 J/cm²) both in silicon layers doped with erbium ions and in those containing doped erbium and oxygen have been studied by an optical probing method. It is shown that the reflectivity behavior of structures under pulsed irradiation is governed by phase transitions (melting and crystallization) of implanted silicon and also by interference effects at the interfaces of the resulting phases. It is established that the profiles of erbium distribution change under nanosecond laser irradiation and that the dopant is forced out to the surface due to a segregation effect at small implantation doses. As the implanatation dose increases, diffusion deep into the sample tends to prevail over segregation. A considerable increase in the photoluminescence peak intensity at 0.81 eV is found after both the pulsed laser processing and thermal post-annealing of doped samples as opposed to spectra of samples subjected either to thermal annealing or to pulsed laser irradiation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 225–231, March–April, 2009.     

Optical-pyrometric diagnostics of the state of silicon during nanopulsed laser irradiation

The dynamics of the reflectivity at ?? = 0.53 ??m and the IR radiation of silicon in the wavelength range 0.9?C1.2 ??m is studied under the action of nanosecond ruby laser radiation pulses. When radiation energy density W is lower than the threshold of laser-induced melting of the surface of a semiconductor crystal, the major contribution to the IR radiation emitted by this crystal is made by edge photoluminescence. As the melting threshold is exceeded, the nanosecond dynamics of the detected IR radiation changes from photoluminescence to the thermal radiation of the forming Si phase melt with a high reflectivity. The results of pyrometric measurements of the peak melt surface temperature as a function of W obtained at an effective wavelength ?? _e = 1.04 ??m of the detected IR radiation agree with the data of analogous measurements performed at ?? _e = 0.53 and 0.86 ??m.     

Chemical sputtering,a discussion of mechanisms

Sputtering can be defined as the process whereby particles leave the surface as a direct consequence of the presence of incident radiation. When particles leave the surface as a result of receiving momentum from the collision cascade induced by the incident radiation, the process is called “physical sputtering”. If the incoming radiation (ions, electrons, or photons) induces a chemical reaction which leads to the subsequent desorp-tion of particles, the process could be classified as “chemical sputtering”. There are a number of molecules such as CH₄, CF₄, CF₃H, CF₃CI, etc., whose binding energy to a large variety of surfaces is believed to be only a few kcal/mole. Therefore, these molecules will not remain absorbed at room temperature. Consequently, if they are generated from surface atoms by radiation-induced processes, they will almost immediately desorb into the gas phase. This process is one type of chemical sputtering. Recent data obtained in plasma environments suggest that this type of reaction is a widely occurring phenomena: however, few systematic quantitative investigations of the subject have been completed. In this paper we will review the evidence for chemical sputtering and discuss mechanisms based on experimental information obtained for the chemical sputtering of silicon and SiO₂ under argon ion bombardment in the presence of a molecular beam of XeF2. Under these conditions, 25 or more silicon atoms can leave the surface per incident argon ion. About 75% of the silicon is emitted as SiF₄ (gas) and the rest leaves as silicon atoms or SiFx radicals. The total yield (silicon plus fluorine) is greater than 100 atoms/ion. The measured yields are a strong function of XeF₂ flux and a much weaker function of ion energy in the range 500-5000 eV. The chemical-sputtering yield for SiO₂ is smaller than that of silicon by about an order of magnitude, but it is still larger than the physical-sputtering yield. Moreover, SiO₂ is also sputtered by electrons. These results indicate that the incident radiation induces a chemical reaction between silicon and adsorbed fluorine which produces SiF₄, and the SiF4 is subsequently desorbed into the gas phase. We define this process as chemical sputtering. The large yields are probably a consequence of weak binding between the surface and the SiF₄ molecule.     

Specific features and mechanisms of photoluminescence of nanostructured silicon carbide films grown on silicon in vacuum

The light-emitting properties of cubic silicon carbide films grown by vacuum vapor phase epitaxy on Si(100) and Si(111) substrates under conditions of decreased growth temperatures (T _gr ∼ 900–700°C) have been discussed. Structural investigations have revealed a nanocrystalline structure and, simultaneously, a homogeneity of the phase composition of the grown 3C-SiC films. Photoluminescence spectra of these structures under excitation of the electronic subsystem by a helium-cadmium laser (λ_excit = 325 nm) are characterized by a rather intense luminescence band with the maximum shifted toward the ultraviolet (∼3 eV) region of the spectral range. It has been found that the integral curve of photoluminescence at low temperatures of measurements is split into a set of Lorentzian components. The correlation between these components and the specific features of the crystal structure of the grown silicon carbide layers has been analyzed.     

Oxidation of the porous silicon surface under the action of a pulsed ionic beam: XPS and XANES studies

The changes in the electronic structure and phase composition of porous silicon under action of pulsed ionic beams have been studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) using synchrotron radiation. The Si 2p and O 1s core photoemission spectra for different photoelectron collection angles, valence band photoemission spectra, and X-ray absorption near-edge fine structure spectrain the region of Si L _2,3 edges of the initial and irradiated samples have been analyzed. It has been found that, as a result of the irradiation, a thin oxide film consisting predominantly of higher oxide SiO₂ is formed on the porous silicon surface, which increases the energy gap of the silicon oxide. Such film exhibits passivation properties preventing the degradation of the composition and properties of porous silicon in contact with the environment.     

一种基于PIN结的硅基微型核电池研究

针对PN结式微型核电池由于衬底掺杂浓度较大而造成的少子寿命短,收集效率低等缺点,提出使用硅基PIN结作为微型核电池的换能结构,构建了PIN换能结构的电学模型,并对其性能影响因素进行了分析和仿真,优化了换能结构参数.完成换能结构加工之后,分别使用⁶³Ni,¹⁴⁷Pm和²⁴¹Am对换能结构进行了辐照实验.实验结果表明,PIN换能结构通过增加耗尽层宽度来增大电子空穴对的收集空间,通过使用保护环来降低漏电流,能够有效提高短路电流和开路电压,最终提升能量转换效率. 关键词： 微型核电池 辐射伏特 微机电系统 PIN结     

Structural Anisotropy of Amorphous Silicon Films Modified by Femtosecond Laser Pulses

It is demonstrated that the surface-relief orientation in the form of one-dimensional gratings with a period of 1.20 ± 0.02 μm formed under processing of hydrogenated-silicon films by femtosecond laser pulses (1.25 μm) with an energy density of 0.15 J/cm² is determined by the direction of the polarization vector of the radiation and total laser exposure. Based on the results of the analysis of Raman spectra, the presence of a nanocrystalline phase of silicon with a volume fraction between 15 and 67% (depending on processing conditions) is detected. The observed processes of micro- and nanostructuring are caused by excitation of the surface plasmon–polaritons and nanocrystallization in the near-surface region in the field of high-power femtosecond laser pulses, respectively. In addition, formation of polymorph modifications of silicon Si-III and Si-XII under femtosecond laser processing with a number of pulses exceeding 500 is discovered. Anisotropy of the Raman signal for the above polymorph modifications is revealed.     

Opposed-flow ignition and flame spread over melting polymers with Navier-Stokes gas flow

A numerical model is constructed to predict transient opposed-flow flame spread behaviour in a channel flow over a melting polymer. The transient flame is established by initially applying a high external radiation heat flux to the surface. This is followed by ignition, transition and finally steady opposed-flow flame spread. The physical phenomena under consideration include the following: gas phase: channel flow, thermal expansion and injection flow from the pyrolyzed fuel; condensed phase: heat conduction, melting, and discontinuous thermal properties (heat capacity and thermal conductivity) across the phase boundary; gas-condensed phase interface: radiation loss. There is no in-depth gas radiation absorption in the gas phase. It is necessary to solve the momentum, species, energy and continuity equations in the gas along with the energy equation(s) in the liquid and solid. Agreement is obtained between the numerical spread rate and a flame spread formula. The influence of the gas flow is explored by comparing the Navier-Stokes (NS) and Oseen (OS) models. An energy balance analysis describes the flame-spread mechanism in terms of participating heat transfer mechanisms.     

X‐ray absorption near‐edge structure anomalous behaviour in structures with buried layers containing silicon nanocrystals

Substructure and phase composition of silicon suboxide films containing silicon nanocrystals and implanted with carbon have been investigated by means of the X‐ray absorption near‐edge structure technique with the use of synchrotron radiation. It is shown that formation of silicon nanocrystals in the films' depth (more than 60 nm) and their following transformation into silicon carbide nanocrystals leads to abnormal behaviour of the X‐ray absorption spectra in the elementary silicon absorption‐edge energy region (100–104 eV) or in the silicon oxide absorption‐edge energy region (104–110 eV). This abnormal behaviour is connected to X‐ray elastic backscattering on silicon or silicon carbide nanocrystals located in the silicon oxide films depth.     

Contribution to the problem of observing thermal nonuniformities in a two-layer plate consisting of opaque solid materials

The theoretical problem of determining the sizes δ of defects under opaque surface coatings according to the phase shift of the signals from a photodetector with two ring-shaped p-n junctions that detects radiation from a concentric surface heat wave excited in the sample by harmonically-varying low-power probe radiation is studied. The problem is solved for the signal amplitude in the first approximation in the small parameter δ and for the phase in the second approximation. An expression is derived for the resolution of the method for detecting defects. Zh. Tekh. Fiz. 67, 129–131 (October 1997)     

Cosmological evolution of interacting dark energy in Lorentz violation

The cosmological evolution of an interacting scalar-field model in which the scalar field interacts with dark matter, radiation, and baryons via Lorentz violation is investigated. We propose a model of interaction through the effective coupling, [`(b)]\bar{\beta} . Using dynamical system analysis, we study the linear dynamics of an interacting model and show that the dynamics of critical points are completely controlled by two parameters. Some results can be mentioned as follows. Firstly, the sequence of radiation, the dark matter, and the scalar-field dark energy exist and baryons are subdominant. Secondly, the model also allows for the possibility of having a universe in the phantom phase with constant potential. Thirdly, the effective gravitational constant varies with respect to time through [`(b)]\bar{\beta} . In particular, we consider the simple case where [`(b)]\bar{\beta} has a quadratic form and has a good agreement with the modified ΛCDM and quintessence models. Finally, we also calculate the first post-Newtonian parameters for our model.     

Synchrotron investigations of the specific features in the electron energy spectrum of silicon nanostructures

The Si L _{2, 3} x-ray absorption near-edge structure (XANES) spectra of porous silicon nanomaterials and nanostructures with epitaxial silicon layers doped by erbium or containing germanium quantum dots are measured using synchrotron radiation for the first time. A model of photoluminescence in porous silicon is proposed on the basis of the results obtained. According to this model, the photoluminescence is caused by interband transitions between the energy levels of the crystalline phase and oxide phases covering silicon nanocrystals. The stresses generated in surface silicon nanolayers by Ge quantum dots or clusters with incorporated Er atoms are responsible for the fine structure of the spectra in the energy range of the conduction band edge and can stimulate luminescence in these nanostructures.