Role of an oxide layer in the long-range effect upon irradiation of silicon by light and ions with medium energy

Correlations between the modes of silicon irradiation with light, as well as the thickness of an oxide layer on the surface of the sample, and the character of changes in the microhardness in the long-range effect are experimentally established. The results are interpreted from the standpoint of the effect of processes that take place in the oxide layer upon irradiation and cause the generation of two types of hypersonic waves that determine the regularities of the effect. It is shown that an oxide layer on the irradiated silicon surface is a mandatory condition for manifestation of the long-range effect not only in the case of irradiation with light, but also upon ion irradiation.     

Oscillations in the frequency dependence of long-range correlations of waves

We predict new oscillations in the frequency dependence of the intensity autocorrelation functions of waves for a tube geometry. We have performed numerical simulations which clearly confirm the existence of new long-range correlations.     

Hydrogen action in the surface space charge region of highly doped silicon

The action of atomic hydrogen on clean cleaved (1 1 1) surfaces of highly doped silicon samples, both phosphorus ([n] = 2 × 10¹⁹ cm^-3) and boron ([p] = 4 × 10¹⁹ cm^-3) doped has been compared to the case of lightly doped samples ([n] = 1 × 10¹⁴ cm^-3). Once cleaved under ultra high vacuum, the samples were exposed to increasing doses of atomic hydrogen up to saturation. Before and after each hydrogen exposure, the Si(1 1 1) 2 × 1 surface was studied by low energy electron diffraction (LEED) and photoemission yield spectroscopy (PYS). The compared PYS measurements show that H atoms adsorbed on the Si(1 1 1) surface at room temperature do totally compensate the shallow-acceptor impurities (boron) and only partially the shallow-donor impurities (phosphorus) in the space charge region. They also remove the surface dangling bond states. These effects are reversible upon heating under vacuum. Both surface stresses and space charge electric field play a role in this compensation effect.     

X-ray reflectometry and its application to studying the laser evaporation of an oxide film from the silicon surface

An analysis of the published data on X-ray reflectometry is carried out. The potentialities of X-ray reflectometry are demonstrated with the laser evaporation of an oxide film from a silicon surface.     

Oscillations of light absorption in 2D macroporous silicon structures with surface nanocoatings

We investigated the near-IR light absorption oscillations in 2D macroporous silicon structures with microporous silicon layers and CdTe, ZnO surface nanocrystals. The electro-optical effect was taken into account within the strong electric field approximation. Well-separated oscillations were observed in the spectral ranges of the surface bonds of macroporous silicon structures with surface nanocrystals. The model of the resonant electron scattering on impurity states in electric field of heterojunction “silicon-nanocoating” on macropore surface as well as realization of Wannier-Stark effect on the randomly distributed surface bonds were considered. The Wannier-Stark ladders are not broken by impurities because of the longer scattering lifetime as compared with the period of electron oscillations in an external electric field, in all spectral regions considered for macroporous silicon structures with CdTe and ZnO surface nanocrystals.     

Growth and structure of Ge nanoislands on an atomically clean silicon oxide surface

Experimental data on the formation of self-organized Ge islands on an atomically clean oxidized Si(100) surface are presented. On the oxidized silicon surface, the Volmer-Weber growth mechanism is operative rather than the Stranski-Krastanow mechanism, which operates in the case of Ge growth on a clean silicon surface. The Ge growth is accompanied by a significant change (as large as 7%) in the surface unit cell size of the Ge lattice with respect to that for silicon. For Ge films up to five monolayers thick, the nanoisland dimensions at the bottom are smaller than 10 nm and the island density is higher than 2×10¹² cm^?2.     

Space charge and surface state characteristics of the silicon/electrolyte interface

The essentially blocking nature of the silicon/electrolyte (S/E) interface enables charge to be induced electrostatically at the interface by an applied bias. The use of pulsed rather than DC biases provides a fairly detailed picture of the silicon interface. The results reported here concern the silicon space-charge layer, localized states at the S/E interface and charge leakage across the interface. As to the first, evidence is presented that strong, quantized accumulation layers of excess surface-electron densities as high as 10¹⁴ cm⁻² can be induced at the Si surface, an order of magnitude larger that can be attained in Si inversion layers in MOS structures. The localized states are of total density of about 10¹² cm⁻² and of capture cross sections around 5 × 10⁻¹⁸ cm². The nature of these states is not known; they are probably fast surface states at the silicon surface. The charge leakage occurs under strong accumulation conditions, very likely by electron tunneling from the silicon electrode into the electrolyte. It takes place practically instantaneously, but the leaked charge remains stored near the interface for a considerable time. Some suggestions concerning this unexpected behavior are put forward.     

Plasma enhanced atomic layer deposition of gallium oxide on crystalline silicon: demonstration of surface passivation and negative interfacial charge

Herein we report on the passivation of crystalline silicon by gallium oxide (Ga₂O₃) using oxygen plasma as the oxidizing reactant in an atomic layer deposition (ALD) process. Excess carrier lifetimes of 2.1 ms have been measured on 1.75 Ω cm p‐type silicon, from which a surface recombination current density J₀ of 7 fA cm^–2 is extracted. From high frequency capacitance‐voltage (HF CV) measurements it is shown that, as in the case of Al₂O₃, the presence of a high negative charge density Q_tot/q of up to –6.2 × 10¹² cm^–2 is one factor contributing to the passivation of silicon by Ga₂O₃. Defect densities at midgap on the order of ～5 × 10¹¹ eV^–1 cm^–2 are extracted from the HF CV data on samples annealed at 300 °C for 30 minutes in a H₂/Ar ambient, representing an order of magnitude reduction in the defect density compared to pre‐anneal data. Passivation of a boron‐diffused p⁺ surface (96 Ω/□) is also demonstrated, resulting in a J₀ of 52 fA cm^–2. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

On the interfacial capacitance of an electrolyte at a metallic electrode around zero surface charge

The behaviour of the capacitance of a planar double layer containing a restricted primitive model electrolyte (equi-sized rigid ions moving in a continuum dielectric) at and around zero surface charge is examined for a polarizable electrode with particular emphasis on a metallic surface. Capacitance results are reported for symmetric valency (1:1) salts encompassing a range of concentrations and temperatures covering both electrolyte solution and ionic liquid regimes. Although the modified Poisson–Boltzmann theory is principally employed, at higher concentrations the theoretical calculations have been supplemented by Monte Carlo simulations. Capacitance anomaly, that is, increase of capacitance with temperature at low temperatures, is seen to occur when the electrode is an insulator with a low dielectric constant or when it is unpolarized. No capacitance anomaly is, however, seen for a metallic electrode with an infinite dielectric constant and in this situation the capacitance increases (a) dramatically at low temperatures (strong coupling) at a given concentration, and (b) as concentration increases at a given temperature. These capacitance trends are consistent with earlier works in the presence or absence of surface polarization and, in particular, the results for a conducting electrode at ionic liquid concentrations are consistent with that recently reported by Loth et al. [Phys. Rev. E, 82, 056102 (2010)]. Overall the theoretical predictions are qualitative to semi-quantitative with the simulations.     

Formation of titanium oxide films on the surface of porous silicon carbide

The influence of rapid thermal annealing (RTA) on the properties of a titanium film on the surface of porous silicon carbide is considered. It is shown that an increase in the RTA temperature to 900°C stabilizes the phase composition of the forming titanium oxide over the film, which is identified as rutile. Due to the formation of titanium oxide nanoclusters under the action of RTA, an additional photoluminescence band arises near 2.5 eV. Based on Auger spectrometry data, a multilayer model to calculate the optical parameters of titanium oxide films covering porous silicon carbide is suggested.     

Hysteresis effect and surface energy of drops in silicon

We report here the observation of the hysteresis effect of the drop luminescence in silicon at the temperature of 6.6 K. Hysteresis ratios up to 2.1 have been registered. The surface energy σ of drops is deduced from the measurement of the energy shift of the drops luminescence at low pumping level. The results yield: σ = (125±60) × 10^?4ergcm^?2.     

Thermodynamics of nucleation in an internal oxide getter in silicon

Nucleation of precipitates of silicon dioxide is studied theoretically within the framework of the classical theory of nucleation. Elastic stresses, accompanying nucleation, are taken into account under the assumption that the nucleus and matrix are incoherent and the silicon is elastically isotropic. The results of a numerical calculation of the form and dimensions of the critical nucleus, the free energy of its formation, and the rate of nucleation as a function of the annealing temperature in the range 773–1473 K for oxygen concentrations in the starting single crystal of (0.4–1.4)·10¹⁸ cm^–3 are presented. It is shown that homogeneous nucleation of precipitates is, in principle, possible. The magnitude of the specific free energy of the interphase boundary is estimated based on the data obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 25–29, August, 1988.     

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.     

Formation of ultrasmall germanium nanoislands with a high density on an atomically clean surface of silicon oxide

The experimental results of an investigation into the initial stages of growth of a germanium film on an atomically clean oxidized silicon surface are reported. It is shown that the growth of the germanium film in this system occurs through the Volmer-Weber mechanism. Elastically strained nanoislands with a lateral size of less than 10 nm and a density of 2 × 10¹² cm^?2 are formed on the oxidized silicon surface. In germanium films with a thickness greater than 5 monolayers (ML), there also arise completely relaxed germanium nanoislands with a lateral size of up to 200 nm and a density of 1.5 × 10⁹ cm^?2.