Low-temperature implantation of activator atoms into zinc sulfide under stimulation by atomic hydrogen

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 2, pp. 187–191, February, 1990.     

Computer calculation of positron diffusion and annihilation in atomic hydrogen

We have performed a computer-aided analysis of position behaviour in atomic hydrogen. Effect of electric, magnetic and temperature fields on the diffusion and annihilation of positrons has been studied. Electric field is varied over a wide range of 0–200 V cm⁻¹ amagat⁻¹, magnetic field over 0–30 kG while the temperature range considered is 300–10,000°K. The position decay rate decreases with electric and temperature fields but increases with magnetic fields. However, the effect of these fields is reversed on the diffusion coefficient.     

Low-temperature franz-keldysh oscillations in uniaxially stressed germanium

In this paper we report some typical results of high-field electroreflectance on single crystals of germanium, stressed uniaxially along the (001) direction. Measurements were made at 10°K near the fundamental direct edge. The electric field was applied by Schottky barrier. Franz-Keldysh oscillations exhibiting up to twenty peaks enabled us to determine the broadening parameter Γ = 1.4 meV and the ratio of the reduced masses μ₀₂/μ₀₁ = 0.97.     

Molecular dynamics simulation of atomic hydrogen diffusion in strained amorphous silica

Understanding hydrogen diffusion in amorphous SiO_2(a-SiO_2),especially under strain,is of prominent importance for improving the reliability of semiconducting devices,such as metal-oxide-semiconductor field effect transistors.In this work,the diffusion of hydrogen atom in a-SiO_2 under strain is simulated by using molecular dynamics(MD) with the ReaxFF force field.A defect-free a-SiO_2 atomic model,of which the local structure parameters accord well with the experimental results,is established.Strain is applied by using the uniaxial tensile method,and the values of maximum strain,ultimate strength,and Young's modulus of the a-SiO_2 model under different tensile rates are calculated.The diffusion of hydrogen atom is simulated by MD with the ReaxFF,and its pathway is identified to be a series of hops among local energy minima.Moreover,the calculated diffusivity and activation energy show their dependence on strain.The diffusivity is substantially enhanced by the tensile strain at a low temperature(below 500 K),but reduced at a high temperature(above500 K).The activation energy decreases as strain increases.Our research shows that the tensile strain can have an influence on hydrogen transportation in a-SiO_2,which may be utilized to improve the reliability of semiconducting devices.     

Energetics of atomic hydrogen diffusion on Si(100)

We present first principles calculations of the potential energy surface for the diffusion of a single hydrogen atom on Si(100)2 × 1. Surface relaxation is found to be very important for the energetics of diffusion. A strong anisotropy is predicted for hydrogen motion: H should diffuse mainly along dimer rows, where activation energies are ~ 1.3 eV, while the barrier for row-to-row hopping is ~ 0.5 eV higher. Our results indicate that diffusion can be considered a fast process compared to H₂ recombinative desorption.     

Low-temperature photoluminescence in germanium irradiated by fast neutrons

This study was carried out to investigate low-temperature (T=4.2 K) photoluminescence caused by interdopant recombination transitions in n-germanium irradiated by fast (epicadmium) reactor neutrons and subjected to “complete” annealing (+450°C, 24 h). It is shown that lines of interdopant radiative recombination observed in initial and in irradiated and annealed specimens are caused by both initial impurities and (mainly) dopants (As and Ga) implanted by transmutation as well as by defect sets stable at long-time high-temperature annealing that do not contain fine dopants. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 479–482, July–August, 1997.     

Low-temperature intracenter relaxation times of shallow donors in germanium

The relaxation times of localized states of antimony donors in unstrained and strained germanium uniaxially compressed along the [111] crystallographic direction are measured at cryogenic temperatures. The measurements are carried out in a single-wavelength pump–probe setup using radiation from the Novosibirsk free electron laser (NovoFEL). The relaxation times in unstrained crystals depend on the temperature and excitation photon energy. Measurements in strained crystals are carried out under stress bar S > 300, in which case the ground-state wavefunction is formed by states belonging to a single valley in the germanium conduction band. It is shown that the application of uniaxial strain leads to an increase in the relaxation time, which is explained by a decrease in the number of relaxation channels.     

Low-temperature diffusion of phosphorus in silicon

Nontrivial mechanisms of low-temperature diffusion of impurities in solids have been discovered recently. We studied accelerated diffusion of phosphorus in a single crystal of silicon, which takes place during decomposition of an over-saturated inhomogeneous solid solution. A thin (1.5–2 m) doped layer was formed by low-temperature diffusion from the gas phase. The distribution profile, which was determined by the method of differential conductivity, shows that heat treatment at 550°C leads to a decrease in the donor concentration in the subsurface region and to the impurity movement into the bulk of the sample. The diffusion coefficient has been calculated on the computer using experimental data, and in the range between 400°C and 700°C has been represented by the Arrhenius equation. The value of the frequency term is equal to 3.7·10^–6 cm²/sec, and the value of the activation energy is 1.81 eV. The presented results have been analyzed, as well as the data obtained from the measurements on carrier mobility (using the Hall effect) and the parameters of the crystal lattice (using the method of asymmetric double crystal x-ray spectrometer). A physical model for the dissociation diffusion is proposed, which is controlled by the decay, and analytical expressions are obtained which describe the main characteristics of the process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 56–60, September, 1988.     

Intervalley diffusion of hot electrons in germanium

In many-valley semiconductors for certain specific orientations of the applied electric field E, the different drift velocities of electrons in different valleys should give rise to an additional diffusion called intervalley diffusion. Experimental evidence of this effect is presented. This was obtained by measuring the longitudinal diffusion coefficient of electrons in Ge, at 77 and 190 K, for E parallel to the 〈100〉 and 〈111〉 directions. The interpretation of the effect has been confirmed by Monte Carlo calculations.     

Low-temperature thermal conductivity of highly enriched and natural germanium

Experimental data on the thermal conductivity K(T) of crystals of natural and highly enriched germanium (99.99%) ⁷⁰Ge with lapped and polished surfaces are analyzed in the temperature range ∼1.5–8 K. In all the samples in the temperature range ∼1.5–4 K the standard boundary mechanism of scattering dominates. As the temperature is raised, an isotopic scattering mechanism is observed in the natural samples. In the highly enriched samples the theoretical values of K(T) turn out to be much smaller than the experimental ones. It is conjectured that a Poiseuille viscous flow regime of the phonon gas emerges in this case. Zh. éksp. Teor. Fiz. 114, 1757–1764 (November 1998)     

Impact ionization of deep acceptor gold in germanium

We observed the dependence of conductivity on an applied high electric field in compensated gold-doped germanium between 77 and 300K. A slight decrease in conductivity, mainly due to the field-dependent carrier mobility, is followed by a relatively large increase in conductivity. The magnitude of this increase depends on the lattice temperature, being larger at low temperatures, and on the compensation ratio. The increase in conductivity is supposed to be due to impact ionization of the frozen-out neutral acceptor gold in the strong electric field. This interpretation is supported by the temperature dependence of the hole concentration in the gold-doped germanium.     

Low-temperature diffusion bonding of pure aluminum

1 keV argon ion beam was employed to remove the oxide film of pure aluminum before diffusion bonding. A sound joint of pure aluminum was obtained by ion activation-assisted diffusion bonding at the low temperature of 350 ° C $350~{}^{\circ}\mathrm{C}$ , while the high-quality joining of pure aluminum was infeasible by conventional diffusion bonding at the temperature lower than 500 ° C $500~{}^{\circ}\mathrm{C}$ . The residual oxide film ratios of joints decreased with the increase of ion cleaning time. When the specimens were cleaned for 120 min, the joint with the maximum tensile strength of 62.3 MPa and the elongation of 14.1 % was obtained. The argon ion beam etching surface treatment provides a new route for the low-temperature diffusion bonding. The reliable diffusion bonded joint of pure aluminum indicates that low-temperature diffusion bonding is feasible for bulk materials, especially for materials with the outstanding plasticity.     

Low-temperature hypersensitization of phosphosilicate waveguides in hydrogen

Conventional hydrogen loading of phosphosilicate optical fibers at relatively low temperatures (80 degrees C) is sufficient to enhance the fiber's photosensitivity after hydrogen outdiffusion, allowing permanent Bragg grating structures to be produced. Thermal sensitization is proposed to be a major contributor to stable index change.     

The influence of hydrogen impurities on the atomic and electronic structures of carbyne crystals

An ab initio DFT study of atomic and electronic structure of carbyne crystals was carried out. The influence of hydrogen impurities on carbyne structure was investigated. Calculations with atomic relaxations showed that carbon chains in the carbyne crystal structure are bow-like curved; free-energy calculations showed that the most probable lengths of those chains are four and six atoms, which is in a good agreement with experiments. Carbyne-crystal electronic-structure analysis showed that there is a small gap of 0.09 eV near the Fermi level in four-atomic carbyne, while there is no such gap in six-atomic carbyne. In studying of the hydrogen impurity influence on the atomic and electronic structure of carbyne crystals, hydrogen atoms were embedded in two directions: across and along carbon chains in the crystal. As a result we found that the crystal structure is not distorted in the case of hydrogen embedded across the chains, while the type of bonding between carbon atoms in carbon chains in the carbyne crystal structure depended on the impurity concentration. The crystal structure was distorted when hydrogen was embedded along the chains. The concentration of impurities influences the conductivity of a carbyne crystal.     

Velocity of water diffusion through germanium oxide

The diffusion of water through an oxide film on germanium was investigated by measurement of the surface conductivity, and a relation was found between the coefficient of diffusion and the humidity of the ambient medium.     

Local vibrational modes of isolated hydrogen in germanium

Two distinct isolated hydrogen defects are observed in crystalline Ge by in situ infrared absorption spectroscopy. Implantation of protons into Ge at cryogenic temperatures gives rise to two intense absorption lines at 745 and 1794 cm(-1). The lines originate from distinct defects, each of which contains one H atom located on a <111> axis. The 1794-cm(-1) line is assigned to bond center H in the positive charge state, whereas the 745-cm(-1) line is ascribed to negatively charged H located on a <111> axis close to the tetrahedral site.     

Low-temperature diffusion of lithium in silicon-germanium solid solutions

The influence of germanium content on lithium diffusion in Si_1?x Ge_x solid solutions is investigated at temperatures from 300 to 500°C. It is found that the diffusion coefficient and the solubility of lithium abruptly decrease with a decrease in the temperature and an increase in the germanium content. As the diffusion temperature increases, the decrease in the lithium diffusion coefficient slows down with a change in the solid solution composition due to the effect of lattice elastic strains induced by germanium isovalent impurities.     

The influence of external uniaxial stretching on the electromigration and diffusion of hydrogen in iron

Electromigration and diffusion of hydrogen in iron, depending on unit elongation, were investigated. The resistivity method was applied in the investigations. It was found that the obtained experimental results cannot be described by means of a single flux of hydrogen, which diffuses in the electric field. In order to explain the obtained results, we assumed the existence of the following two fluxes of hydrogen in the stretched metal: migration, according to the interstitial mechanism, and migration according to the interstitial-defective mechanism. The dependence of effective valences and diffusion coefficients for both mechanisms were determined.     

Low-temperature diffusion of silicon atoms in the nickel-nickel silicide-silicon system

The diffusion of Si atoms from a silicon substrate through a layer of nickel monosilicide into a Ni film is investigated in the temperature interval 470–670°K by the method of radioactive isotopes. The distribution profile of Si in NiSi and Ni is derived. The GB-diffusion parameters of Si in NiSi are determined. It is shown that when T>570°K there is an increase in the thickness of the initial NiSi layer, and a kink appears on the in D=f(1/T) curve. The associated change in the activation energy of diffusion from 0.43 (470–570°K) to 0.72 eV (570–670°K) is explained by the formation of Ni-Si and Si-O type complexes. The diffusion of silicon atoms accompanied by complex-formation processes determines the evolution of the resistivity of the Ni-NiSi-Si contact.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 78–83, March, 1985.