Nature and parameters of radiation defects in dislocated silicon

The radiation defect production and annealing processes in dislocated silicon are analysed. The character of the effect of dislocations on the radiation defect parameters is shown to depend on their nature. Taking into account the dependence determined a scheme is suggested in accordance with which the electrically active defects in Si are divided into four groups. This is useful when identifying defects of unknown nature.     

From compact point defects to extended structures in silicon

We show that in contrast to the 1d Frenkel-Kontorova (FK) chain known to obey the Fourier law of heat conduction and several 2d models which show logarithmic dependence of conductivity on system size, a scalar 2d FK lattice with commensurate structure exhibits anomalous heat conduction, whose thermal conductivity displays a power law behavior. The dependence of thermal gradient on bulk temperature and noise correlation is critically analyzed. A dynamical contribution to conductivity when the system attains a nonequilibrium steady state of thermal conduction has been identified.     

Concentrations of radiation defects with almost isoenergetical levels in silicon

Isochronous annealing of radiation defects with almost isoenergetical levels (indistinguishable from each other by means of temperature dependence of the majority charge carriers concentration) in silicon is studied. The concentrations of G- and A-centres with a level E _c?0.17 eV in n-Si and some (unidentified) vacancy-type and V₂+B complexes with a level E _v+0.22 eV in p-Si are determined.     

The efficiency of direct annihilation of resistivity silicon primary radiation defects in high-resistivity silicon

Abstract

The change of charge-carrier concentration and lifetime in high-resistivity float-zone n- and p-Si with equilibrium concentrations of electrons n₀=(2 to 30)× 10¹² cm^?3 and holes p₀=(5 to 30)× 10¹¹ cm^?3 when irradiating by ⁶⁰Co γ-rays (T= 330 K) is studied. There is a drastic increase of the initial charge- carrier removal rate and the coefficient for the radiation variation of their lifetime. The results obtained are explained on the assumption of the dependence of the annihilation probability of Frenkel pairs on the charge state of vacancy (V) and interstitial Si atom (I).The energetic position of the levels separating the states I⁰/I⁺⁺ and V^?/V⁰ which are at E_c ?(0.43?0.45) eV and E_c ?(0.47?0.54) eV, respectively, is estimated.     

Modification of silicon waveguide structures using ion implantation induced defects

The structure of re-crystallized silicon films is investigated using transmission electron microscopy, spectroscopic ellipsometry and positron annihilation spectroscopy. Samples were prepared via amorphization of the silicon overlayer of silicon-on-insulator substrates, and subsequent thermal annealing. For an annealing temperature of 650 °C we show that the silicon film has a poly-crystalline structure. Its refractive index measured at 1550 nm is comparable to that of crystalline silicon following re-crystallization at 750 °C. Positron measurements indicate a high concentration of open-volume point defects in the re-crystallized films. We discuss the potential importance of these structures with regard to defect engineering for silicon photonic devices.     

The mechanism of formation and properties of stratified-inhomogeneity defects in silicon

The mechanism of formation and properties of stratified-inhomogeneity defects in single-crystal and epitaxial silicon wafers are studied using currently available investigation methods. The mechanism of formation of these defects is found to be due to the layered structure of silicon wafers. The type of defects and conditions of impurity precipitation are determined. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–7, March, 2006.     

Efficiency of the formation of radiation defects in heat-treated dislocation-free zone n-silicon

A study was made of processes involved in the formation of radiation defects (RD) in n-type dislocation-free silicon subjected to high-temperature heat treatment at T_t = 600–1300°C. It was established that the effectiveness of introducing compensating RDs changes significantly with an increase in T_t. It is proposed that interstitital inclusions present in the crystal are transformed during heat treatment, these inclusions creating strain fields around themselves and thus influencing the efficiency with which radiation defects are formed.A. N. Sevchenko Scientific Research Institute of Applied Physical Problems. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 93–95, November, 1993.     

The formation of defects in Si under the radiation enhanced diffusion conditions

A review is given of recent developments in the study of magnetic (localized) photo-excitations in ionic solids. Emphasis will be on three topics: (i) the importance of magnetic properties in the structural characterization of defects, (ii) photo-chemical reactions as revealed from magnetic interactions in point defects, and (iii) energy and phase relaxation dynamics in photo-excited colour centres as probed from magnetic transients. In our survey we will focus on defects photo-excited to phosphorescent triplet states. In discussing a number of dynamical processes, some attention is given to the application of (optical-microwave) coherence spectroscopy which holds considerable promise for future work.     

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.     

Colloidal particles of silicon dioxide for the formation of opal-like structures

The conditions of synthesis of silicon dioxide particles with a high degree of monodispersity have been investigated. The particles have been synthesized using both the hydrolysis of tetraethoxysilane in the presence of L-arginine and a combination of this technique with the traditional Stöber method. It has been shown that the use of SiO₂ particles synthesized by the heterogeneous hydrolysis of tetraethoxysilane in the presence of the amino acid for their further growth according to the Stöber method makes it possible to obtain particles 100 nm and more in size with a narrow size distribution (the deviation of the diameter is less than 3%), a nearly perfect spherical shape, and a smooth surface.     

Particle track phenomena and radiation power effects at the formation of radiation defects in ionic crystals

The mechanisms of the radiation defect formation in alkali halide crystals are studied in an extremely wide range of the absorbed radiation dose rate (10¹–10¹² Gy/s). It is found that the power dependence of color centers accumulation is described by a curve with a maximum at a dose rate of about 10¹⁰ Gy/s. The electron and proton track parameters for ionic crystals are calculated in the context of the theory of ionization losses of charged-particle energy. Proceeding from the concept of the charged-particle track overlap, the theoretical relations are obtained that explain the radiation power effect in all dielectric materials including alkali halide crystals. The suppression of color center accumulation in these crystals under high-power electron irradiation is due to a more regular topography of the radiation defect formation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 10–21, February, 2007.     

The kinetics of formation and the parameters of radiation defect clusters in silicon

An approximate analytic solution of the system of equations describing the kinetics of formation and the parameters of radiation defect clusters in crystals is obtained. A model corresponding to the real parameters of Si is assumed as a basis for calculation and it is shown that two types of secondary radiation defect clusters may be realized corresponding to the congealing and spreading of the initial vacancy clusters. The cluster type depends on the incident energy of the particle which creates the effects and on the physical parameters of the crystal under irradiation. For a congealing cluster most of the initial vacancies react within the original volume of the damage cascade and for a spreading cluster the final concentration of divacancies and A-centres within the original cascade volume is much less than the initial vacancy concentration, i.e. most of the vacancies form divacancies and A-centres dispersed throughout the crystal volume.

The definition of the concept “threshold energy of cluster formation” as the minimum primarily displaced atom energy for the creation of a “congealing” vacancy cluster is proposed.

It is shown that A-centres form a belt surrounding a central divacancy cluster.     

Study of the atomic and electronic structures of amorphous silicon nitride and defects in it

The structure of amorphous silicon nitride obtained by cooling from a melt has been simulated by Car-Parinello molecular dynamics. Several types of Si-Si defect coordination have been revealed. It has been found that, in addition to normal Si-Si bonds, numerous double Si-Si bonds (Si-Si-Si defects) are present in the amorphous structure.     

Point defects,diffusion processes,and swirl defect formation in silicon

The paper consists of three parts. In the first part we review the basic experimental and theoretical results which shaped our present knowledge on point defects and diffusion processes in silicon. These results concern on one side oxidation effects which established that silicon self-interstitials and vacancies coexist in silicon and on the other side diffusion of gold into dislocation-free silicon which allowed to determine the self-interstitial contribution to silicon self-diffusion and to estimate the corresponding vacancy contribution. In the second part we discuss topics for which an understanding is just emerging within the framework of coexisting self-interstitials and vacancies: reaching of local dynamical equilibrium between self-interstitials and vacancies; rough estimates of the thermal equilibrium concentrations of self-interstitials and vacancies and their respective diffusivities, and finally, various possibilities to generate an undersaturation of self-interstitials. In the third part we examine swirl defect formation in silicon in terms of vacancies and self-interstitials.     

Role of masking oxide on the silicon surface on defect formation in SIMOX structures

The properties of Si/SiO₂ structures produced by oxygen implantation into silicon (SIMOX technology) are investigated by the high-frequency C-V method and by the electroluminescence (EL) method. The existence of electrically active and luminescence centers in the oxide layer near the interface is established. The effect of a SiO₂ masking layer on the silicon surface on defect formation in the SIMOX structure is elucidated. The dependence of the concentration of the electrically active and luminescence centers on the thickness of the masking layer is found.