Near-surface Layer Of Silicon Research Articles

Changes in the electronic structure of the Si surface as a result of ion implantation

The composition, structure, and physicochemical properties of the surface and near-surface layers of silicon doped with low-energy (E0<5 keV) Ba+ and O2+ ions have been studied using a set of photoelectron and secondary electron spectroscopy methods. It has been established that in the process of ion implantation, chemical bonds are formed between the atoms of the alloying element and the matrix, the width of the energy bands and the density of electronic states in the bands change.

Ultrafast electron transfer through a silicon–vacuum interface induced by the action of an intense femtosecond laser pulse

A theoretical study of the influence of a quasistationary electric field formed during emission separation of charges on ultrafast electron transfer near a silicon–vacuum interface irradiated by femtosecond laser pulses was carried out. The values of the strength of the arising quasistationary field during irradiation by femtosecond pulses with fluences near and above the silicon damage thresholds were estimated. The possibility of the formation of a dynamic optically layered structure in the near-surface layers of silicon irradiated by a femtosecond pulse, resulting from a modification of its optical properties due to the depletion of electrons in the surface layer, was studied. It is suggested that the time-dependent dipole moment induced by the emission separation of charges should lead to the generation of electromagnetic radiation from the terahertz frequency range. The basic properties of this radiation were theoretically investigated.

The Influence of Structural Defects in Silicon on the Formation of Photosensitive Mn4Si7–Si❬Mn❭–Mn4Si7 and Mn4Si7–Si❬Mn❭–M Heterostructures

The effect of the amorphous transition layer at the interface between Mn4Si7 and silicon doped with manganese on the photoelectric properties of heterostructures is considered. It is found that the precipitated Mn atoms on the silicon surface are grouped at high temperatures, forming drops of liquid manganese, which dissolve the near-surface layer of silicon, forming a liquid solution-melt of Mn with Si. As the solution solidifies, Mn4Si7 forms, and the Si–Si bonds under the silicide break due to intense diffusion of Si atoms; an elastically deformed Si region forms, which predetermines the evolution of the formation of photoelectric phenomena in the Mn4Si7–Si❬Mn❭–Mn4Si7 and Mn4Si7–Si❬Mn❭–M heterostructures. The microstructure and chemical composition of doped Si❬Mn❭ samples were studied by means of scanning electron microscopy and X-ray energy dispersive spectrometry using a Quanta 200-3D microscope, and the interface structure of the higher manganese silicide (HMS) and Si❬Mn❭ layer at the nanoscale was refined using the Fourier transform of local zones of high-resolution electron-microscopic images. It is concluded that in the process of diffusion doping of silicon with manganese, broken layers on the surface of the crystal deepen the embedding of manganese atoms, facilitate adsorption, dissolution, and diffusion of Mn in the volume of Si, and also enable the formation of an amorphous layer at the interface of higher manganese silicide and the Si❬Mn❭ layer. The presence of an amorphous transition layer facilitates the process of impact ionization of current carriers upon application of external voltage, as well as the formation of photoelectric phenomena: infrared quenching, temperature quenching, high photosensitivity, and long-term relaxation of residual conductivity.

Influence of Constant Magnetic Fields on Defect Formation under Conditions of Heat Shock in Surface Layers of Silicon

The work is devoted to the study of defect formation processes in the near-surface layers of silicon under thermal shock conditions and to the effect of preliminary exposure in a constant magnetic field on this process. As a result of investigations it was established that dislocation half-loops near the local heat source are formed in the near-surface layers of Si (with a depth of up to 30 μm) after a current pulse of density j> 5.1010 A / m2 passing through the metallized film on the silicon surface. In addition, it was found that preliminary exposure of samples in a constant magnetic field leads to an increase in the dislocation density compared to samples not exposed in a magnetic field.

The Influence of the Surface Neutralization of Active Impurities on the Field-Electron Emission Properties of p-Type Silicon Crystals

Correlation dependences between variations of the structural-phase composition, morphology characteristics, and field-electron-emission (FEE) properties of surface-structured p-type silicon singlecrystalline (100)-oriented wafers have been studied during their stepwise high-dose carbon-ion-beam irradiation. It is established that the stepwise implantation of carbon decreases the FEE threshold and favors an increase in the maximum FEE-current density by more than two orders of magnitude. Physicochemical mechanisms involved in this modification of the properties of near-surface layers of silicon under carbon-ion implantation are considered.

Structural properties of the formation of zinc-containing nanoparticles obtained by ion implantation in Si (001) and subsequent thermal annealing

This work deals with the study of structural transformations in the near-surface layers of silicon after ion beam synthesis of zinc-containing nanoparticles. Phase formation after implantation of Zn+ ions and two-stage implantation of O+ and Zn+ ions with subsequent thermal annealing in an atmosphere of dry oxygen has been considered. We heated the substrate to 350°C during the implantation to avoid amorphization. After implantation, the specimens were annealed for 1h in a dry oxygen atmosphere at 800°C. Investigation of the structure of surface silicon layers has been carried out by X-ray diffractometry and transmission electron microscopy.We show that a damaged layer with a large concentration of radiation induced defects forms near the surface as a result of the implantation of Zn+ ions with an energy of 50keV. In the as-implanted state, nanoparticles of metallic Zn with a size of about 25nm form at a depth of 40nm inside the damaged silicon layer. Subsequent annealing at 800°C in a dry oxygen atmosphere leads to structural changes in the defect layer and the formation of Zn2SiO4 nanoparticles at a depth of 25nm with an average size of 3nm, as well as oxidation of the existing Zn particles to the Zn2SiO4 phase. The oxidation of the metallic Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core-shell” structure. Analysis of the phase composition of the silicon layer after two-stage implantation with O+ and Zn+ ions showed that Zn and Zn2SiO4 particles form in the as-implanted state. Subsequent annealing at 800°C in a dry oxygen atmosphere leads to an increase in the particle size but does not change the phase composition of the near-surface layer. ZnO nanoparticles were not observed under these experimental conditions of ion beam synthesis.

Formation of ordered nano- and mesostructures in silicon irradiated with a single femtosecond laser pulse in different environments

We report on a new class of ordered nano- and mesostructures, including distinct structured areas with subnanoscale roughness, produced by interaction of single tightly focused femtosecond laser pulses with a monocrystalline silicon surface under different environments. The environment was found to have a significant effect on the final morphology of near-surface layers of silicon.

Silicon Photodiode for Visible Spectral Region

Photodiodes with high sensitivity in the short-wavelength portion of the visible region of the spectrum, fabricated based on high-ohmic silicon, are widely used in scintillation devices for visualization of gamma radiation and x-radiation in nuclear physics and medicine [1]. The following have been used to improve collection of minority charge carriers generated by short-wavelength photons in the immediate vicinity of the silicon surface: a shallow p-n junction with a vertical [2] or a horizontal [3, 4] structure, a graded p-n junction formed by diffusion of boron through the lattice of a thin layer of silicon oxide on the substrate surface [5], and an inversion layer photodiode [6]. The use of an inversion layer photodiode is limited by the narrow range of linearity typical of the spectral responsivity. A general disadvantage of photodiodes formed by boron diffusion into n-type silicon is the presence in the near-surface layer of silicon of a barrier layer under the oxide, preventing electrons generated by light in the p-region of the silicon from crossing into the p-n junction [7]. Photodiodes based on n-p junctions formed by diffusion of phosphorus or arsenic are more stable in the short-wavelength portion of the visible region of the spectrum [8, 9]. Their sensitivity at O 1 [12]. This allows us to ensure the minimum depth for the non-photoactive zone on the silicon surface. Arsenic is selected because of the following considerations. Its low diffusion coeffi cient makes it possible to form shallow junctions. The depth of the arsenic-doped n-region in our case is 0.2 om. Due to the relatively low atomic weight and the similar size of the ionic radii for silicon and arsenic, mechanical strains arising when doping with arsenic are relatively small, which lets us decrease the number of defects in the n-region and reduce the effect of recombination processes compared with the phosphorus-doped n + -regions [13]. The ohmic contact to the n-region is formed on the periphery of the arsenic-doped n-region. A guard ring reduces the surface component of the dark current. It is designed to be combined with the ohmic contact to the substrate. The dimensions of the photosensitive region of the photodiode are 5 × 5 mm. A two-layer SiO2/Si3N4 antirefl ective coating is formed on the photosensitive surface of the n-i-p junction.

Dislocation Self-Organization Processes in Silicon during High-Temperature Oxidization

The dislocation self-organization processes in near-surface silicon layers of Si-SiO2 during high temperature oxidization have been investigated. It was observed the complex destruction of these layers caused by relaxation of mechanical stresses. We have proposed the defect formation mechanism of near-surface layers in Si-SiO2 structure. For self-organization processes to be explained, the synergetic method was applied. It was shown that the formation of periodical dislocation structures at the interface is a consequence of the spatial instability of the dislocation distribution in the crystal, their self-organization due to correlation effects between the oxygen diffusing along structural defects and an ensemble of dislocations.

A distribution of Ga+ ions in a silicon substrate for nano-dimensional masking

A nano-dimensional doping method of near-surface silicon layers using the focused ion beam was studied by software tools based on mathematical calculations of ion ranges in crystals. The sizes of local doping regions and concentrations of impurity atoms as function of real process parameters of the nano-dimensional exposure to the ion gallium beam are calculated. Theoretical boundaries of process doping parameters, taking silicon sputtering into consideration are determined.

Theoretical study of sorption and diffusion of lithium atoms on the surface of crystalline silicon and inside it

The energy of the sorption and diffusion of lithium atoms on the reconstructed (4 × 2) (100) silicon surface in the process of their transport into near-surface layers, as well as inside crystalline silicon, at various lithium concentrations have been investigated within the density functional theory. It has been shown that single lithium atoms easily migrate on the (100) surface and gradually fill the surface states (T3 and L) located in channels between silicon dimers. The diffusion of lithium into near-surface silicon layers is hampered because of high potential barriers of the transition (1.22 eV). The dependences of the binding energy, potential barriers, and diffusion coefficient inside silicon on distances to the nearest lithium atoms have also been examined. It has been shown that an increase in the concentration of lithium to the Li0.5Si composition significantly reduces the transition energy (from 0.90 to 0.36 eV) and strongly increases (by one to three orders of magnitude) the lithium diffusion rate.

Pulsed nanosecond annealing of magnesium-implanted silicon

Single-crystalline silicon is implanted by magnesium ions at room temperature and then subjected to pulsed ion-beam annealing. The surface morphology, crystallinity, and optical properties of the implanted silicon are studied before and after annealing. It is shown that ion implantation makes a near-surface layer of silicon about 0.1 m thick amorphous. Pulsed nanosecond ion-beam annealing results in silicon recrystallization and the formation of crystalline magnesium silicide precipitates. Optimal values of the implantation dose and pulse energy density for the formation of magnesium silicide precipitates in the near-surface layer of silicon are found.

Influence of structural defects on thermostability and radiation sensitivity of Si MOSFET dosimeters

The metal oxide semiconductor field effect transistor (MOSFET) dosimeters have recently become commercially available. For this reason, it is not surprising that the study of radiation interactions with MOS materials, devices, and circuits has been a major theme of many articles. The purpose of this study was to investigate the influence of structural defects on thermostability and radiation sensitivity of Si MOSFET dosimeters. It was shown that the near-surface layers of silicon have a complex defective structure which consists from the disordered layer of silicon and the layer of dislocation networks. Grain boundaries of disordered layer form additional energy levels close to the midgap of silicon. These states are ionized under radiation effect and form positive charge. This positive radiation-induced charge becomes additional to the oxide charge and it changes (increases) radiation sensitivity of Si MOSFET detectors. However, these states are the additional source of charge carriers under temperature increasing and lead to changing of detector’s parameters.

Molecular-beam epitaxy of GaAs/Si(001) structures for high-performance tandem A III B V/Si-solar energy converters on an active silicon substrate

In the present study, a method of low-temperature atomic layer epitaxy of GaAs at the initial stage of formation of a GaAs/Si heterojunction is used for growing GaAs films with a low density of threading defects. It was shown that growth of GaAs films can take place bypassing the stage of formation of islands, provided the first monolayer of GaAs is formed by atomic layer epitaxy at low temperature (200–350°C). A regime was found for growing the GaAs/Si films with a density of threading dislocations less than 106 cm–2, which corresponds to the best world achievements. In this mode, the GaAs/Si and Al0.2Ga0.8As/Si structures were grown for solar-energy converters, the devices were produced, and their characteristics were measured. It is shown that during the growth of the GaAs/Si heterojunction, a p–n-junction is formed in the near-surface layer of silicon. This allows one to produce high-performance cascade converters of solar energy based on the A III B V compounds on the active Si substrate in a single growth cycle.

Complex destruction of near-surface silicon layers of Si-SiO2 structure

Complex destruction of near-surface silicon layers of Si-SiO2 structure

Generation Activity and Structural Defects in Near-Surface Silicon Layers

A correlation between the formation of regions of anomalous generation in MOS-structures of silicon and the lattice disturbances of its near-surface layer is studied using the method of relaxation of nonequilibrium capacitance in combination with metallography. It is found that these regions can be formed with a wide range of surface concentrations and charge carrier generation times depending on the oxidation time. The superposition of selective etching patterns and generation-time distribution of a preset wafer segment shows that the formation of regions of anomalous generation is due to the structural lattice disturbances revealed by the Sirtl-etchant as dome-like figures.

Investigation of the Near-Surface Silicon Layers in SiO2–Si Structures

The regularities of formation of the near-surface silicon layers in the SiO2–Si structures are established using currently available investigation methods. The structural and impurity compositions of the layers are determined. The results can be used for studying the dynamics of postirradiation boosting charge storage in the silicon–silicon oxide structures and photoluminescent properties of silicon with a developed surface.

Surface hydrogen content and passivation of silicon deposited by plasma induced chemical vapor deposition from silane and the implications for the reaction mechanism

A systematic study of the enhanced concentration of hydrogen in the near surface layer of silicon deposited from silane by plasma induced chemical vapor deposition is presented as a function of temperature and ion bombardment of the surface during growth. The passivation effect of the chemisorbed hydrogen towards oxidation of the surface is documented, and a possible explanation is suggested in terms of a donatorlike effect of that hydrogen to underlying silicon. It is shown that the rate limiting step in the composite reaction mechanism of the deposition of high-quality silicon films is the ion bombardment induced dehydrogenation of the surface of the growing film. A critical value of substrate bias of −100 eV with respect to the floating potential at which radiation induced damage of the growing film commences is found experimentally. The corresponding ion impact energy agrees very well with Monte Carlo calculations using the TRIM code.