Showing papers on "Silicon published in 1983"

7 × 7 Reconstruction on Si(111) Resolved in Real Space

Abstract: The 7× 7 reconstruction on Si(111) was observed in real space by scanning tunneling microscopy. The experiment strongly favors a modified adatom model with 12 adatoms per unit cell and an inhomogeneously relaxed underlying top layer.

Transition metals in silicon

Abstract: A review is given on the diffusion, solubility and electrical activity of 3d transition metals in silicon. Transition elements (especially, Cr, Mn, Fe, Co, Ni, and Cu) diffuse interstitially and stay in the interstitial site in thermal equilibrium at the diffusion temperature. The parameters of the liquidus curves are identical for the Si:Ti — Si:Ni melts, indicating comparable silicon-metal interaction for all these elements. Only Cr, Mn, and Fe could be identified in undisturbed interstitial sites after quenching, the others precipitated or formed complexes. The 3d elements can be divided into two groups according to the respective enthalpy of formation of the solid solution. The distinction can arise from different charge states of these impurities at the diffusion temperature. For the interstitial 3d atoms remaining after quenching, reliable energy levels are established from the literature and compared with recent calculations.

Modeling of carrier mobility against carrier concentration in arsenic-, phosphorus-, and boron-doped silicon

Abstract: New carrier mobility data for both arsenic- and boron-doped silicon are presented in the high doping range. The data definitely show that the electron mobility in As-doped silicon is significantly lower than in P-doped silicon for carrier concentrations higher than 1019cm-3. By integrating these data with those previously published, empirical relationships able to model the carrier mobility against carrier concentration in the whole experimental range examined to date (about eight decades in concentration) for As-, P-, and B-doped silicon are derived. Different parameters in the expression for the n-type dopants provide differentiation between the electron mobility in As-and in P-doped silicon. Finally, it is shown that these new expressions, once implemented in the SUPREM II process simulator, lead to reduced errors in the simulation of the sheet resistance values.

Thin Film Solar Cells

Abstract: Why Thin Film Solar Cells?- Basic Physical Processes in Solar Cell Materials- Photovoltaic Behavior of Junctions- Photovoltaic Measurements, Junction Analysis, and Material Characterization- Thin Film Deposition Techniques- Properties of Thin Films for Solar Cells- Cu2S Based Solar Cells- Polycrystalline Thin Film Silicon Solar Cells- Emerging Solar Cells- Amorphous Silicon Solar Cells- Photoelectrochemical Cells- Novel Concepts in Design of High-Efficiency Solar Cells

1.54‐μm luminescence of erbium‐implanted III‐V semiconductors and silicon

Abstract: Well‐resolved sharply structured luminescence spectra at 1.54 μm were observed in erbium‐implanted GaP, GaAs, InP, and Si. The optical transitions occur between the weakly crystal field split spin‐orbit levels, 4I13/2→4I15/2, of Er3+(4f11). Typical spectral linewidths in GaAs are 2 cm−1(0.25 meV) at 6 K and 11 cm−1(1.36 meV) at room temperature.

Time-Resolved Reflectivity Measurements of Femtosecond-Optical-Pulse-Induced Phase Transitions in Silicon

Abstract: The reflectivity of silicon has been measured following excitation with intense 90-fsec optical pulses. These measurements for the first time clearly resolve in time the process of energy transfer to the crystal lattice and the dynamics of the phase transition to the melted state.

rf‐plasma deposited amorphous hydrogenated hard carbon thin films: Preparation, properties, and applications

Abstract: The deposition of amorphous hydrogenated hard carbon (a–C:H) thin films from benzene vapor in a rf plasma is described. a–C:H was deposited on glass, quartz, Si, Ge, and GaAs. Negative self‐bias VB and gas pressure P are shown to be the two significant parameters for an accurate control of the deposition process. The dependence of growth rate and deposition temperature on VB and P was determined; this gives an empirical relation for the average energy E of the ions forming the thin films. Refractive index (1.85–2.20 in the IR), optical gap (0.8–1.8 eV) and density (1.5–1.8 g/cm3) of a–C:H was measured. The optical gap varies linearly with the content of bonded hydrogen in the films. The density of a–C:H is proportional to the average ion energy E. We demonstrate the application of a–C:H as antireflective coating on Ge for 10.6 μm (reflection <0.2% at 10.6 μm) and as terminating layer of an optical multilayer stack.

Oxygen-bonding environments in glow-discharge-deposited amorphous silicon-hydrogen alloy films

Abstract: This paper presents the results of a systematic study of oxygen incorporation in $a\ensuremath{-}\mathrm{Si}:\mathrm{H}$ alloys produced by the glow-discharge decomposition of Si${\mathrm{H}}_{4}$, ${\mathrm{H}}_{2}$, and ${\mathrm{O}}_{2}$. We identify four oxygen-related absorption bands, at 2090, 980, 780, 500 ${\mathrm{cm}}^{\ensuremath{-}1}$, and show that the absorption strength in each band scales linearly with the oxygen concentration. We demonstrate that oxygen can increase the solubility of hydrogen in $a\ensuremath{-}\mathrm{Si}$ in the monohydride bonding geometry. The features identified above are shown to be characteristic of a bonding site in which the oxygen and hydrogen atoms are bonded to the same silicon atom. We find no features in the infrared absorption that are associated with bonding configurations having OH groups. In films containing both oxygen and polysilane bonding, as evidenced by the doublet absorption at 845 and 890 ${\mathrm{cm}}^{\ensuremath{-}1}$, we find no evidence for bonding sites in which a substantial fraction of the silicon atoms have one oxygen and two hydrogen neighbors.

Silicon-29 NMR study of dehydrated/rehydrated silica gel using cross polarization and magic-angle spinning

Abstract: A /sup 29/Si NMR study was carried out on silica gel, using cross polarization and magic-angle spinning (CP/MAS). Spectra were examined on silica samples prepared at various stages of dehydration. It was found that the spectral changes observed in these experiments could not be accounted for by a single structural model of the types that have been advanced previously for silica surfaces. However, these /sup 29/Si spectral features are consistent with a heterogeneous silica surface consisting of separate regions resembling the 100 face and 111 face of ..beta..-cristobalite.

Neutralization of Shallow Acceptor Levels in Silicon by Atomic Hydrogen

Abstract: Most of the shallow acceptor levels due to boron in single-crystal silicon can be neutralized by atomic hydrogen at temperatures between 65 and 300\ifmmode^\circ\else\textdegree\fi{}C. This treatment can result in a sixfold increase in resistivity.

Synthesis of continuous silicon carbide fibre

Abstract: Polycarbosilanes which were synthesized by three methods were melt-spun and cured by heating at low temperatures in air The curing mechanism and the structure of these cured fibres were studied and the relationship between the structure and the pyrolysis process is discussed The structure of the cured fibre is represented by means of five structural elements and the rate of oxidation of the methyl group The pyrolysis process of the cured fibre is discussed in five stages, and the effect of oxygen introduced into polycarbosilane fibre by curing on the pyrolysis process is clarified The structure of the fibre obtained during the pyrolysis process strongly depends on the molecular weight of polycarbosilane

Charge trapping instabilities in amorphous silicon‐silicon nitride thin‐film transistors

Abstract: The most important instability mechanism in amorphous silicon‐silicon nitride thin‐film transistors is charge trapping in the silicon nitride layer, which leads to a threshold voltage shift (ΔVT). We have measured the time, temperature, and gate voltage dependence of ΔVT and conclude that the rate limiting process, in the charge transfer from semiconductor to insulator, is the conduction in the nitride by variable‐range hopping. The threshold shift (under positive bias) is temperature dependent with an activation energy of 0.3 eV. This activation energy is identified with the mean hop energy required to inject charge deep into the silicon nitride at the low applied fields appropriate to transistor operation.

Heat of crystallization and melting point of amorphous silicon

Abstract: Thin layers of amorphous silicon (a‐Si) were produced by noble gas ion implantation of (100) substrates held at 77 K. Rutherford backscattering and channeling, and differential scanning calorimetry were used to measure the heat of crystallization, ΔHac, to be 11.9±0.7 kJ/mol, substantially less than the value predicted by scaling ΔHac of a‐Ge. The crystal growth velocity is found to have the form v=v0 exp(−2.24 eV/kT). We obtain a new estimate, 1420 K, for the melting temperature of a‐Si.

Deactivation of the boron acceptor in silicon by hydrogen

Abstract: Two new experiments are presented which suggest that the ‘‘bulk‐compensating donor’’ phenomenon observed in p‐Si is probably a deactivation process of the boron acceptor by hydrogen with the formation of a B−H+ pair. The two experiments are (i) avalanche hole injection in Al‐gate metal‐oxide‐silicon capacitor from boron‐diffused n‐Si substrate and (ii) 5‐keV electron irradiation of Al/p‐Si Schottky diodes. Atomic hydrogen may be released by the avalanche injected energetic electrons or holes or keV electrons from the Al–H, AlO–H, Si–H, and SiO–H sites in the Al gate and the SiO2 film as well as at the Al/SiO2 and SiO2/Si interfaces, which may then migrate to the boron acceptor sites to form the B−H+ pair. Observed hydrogen bond breaking rate by holes is as much as two orders of magnitude larger than by electrons, which is consistent with the thermal hole capture and energetic electron impact bond‐breaking models.

Femtosecond-Time-Resolved Surface Structural Dynamics of Optically Excited Silicon

Abstract: The dynamics of the structural changes that take place on a silicon surface following excitation with an intense optical pulse are observed with 90-fs time resolution. The threefold rotational symmetry of the silicon $〈111〉$ surface becomes rotationally isotropic within a picosecond after excitation consistent with a transition from the crystalline to the liquid molten state.

Minority carrier recombination in heavily-doped silicon

Abstract: A review of our present understanding about the minority carrier recombination in silicon with dopant concentration in the range of 1018–1020 cm−3 is presented. After providing a short phenomenological description of carrier recombination processes and lifetime, the main theories of carrier recombination in a semiconductor are briefly reviewed and their expected contributions to carrier recombination in silicon at heavy doping are indicated. The various methods used for measuring the minority carrier lifetime in heavily doped silicon are described and critically examined. Four different mechanisms are examined to explain the available lifetime data. Two of these involve SRH-type phononic recombination (i) via deep level traps generated by dopant introduced defects and (ii) through shallow donor/acceptor states. The other two non-phononic mechanisms are: (iii) Band to band Auger recombination and (iv) trap assisted Auger recombination. Mechanism (i) can not explain the observed insensitivity of lifetime to processing conditions and the dopant atoms, and contribution of (ii) remains insignificant up to the heaviest doping. Phonon assisted band to band Auger recombination appears to explain the measured lifetimes satisfactorily in p-type silicon. However, for n-type silicon this mechanism predicts considerably higher values of lifetime than the measured results and it is likely that mechanism (iv) (and probably (i) also) competes with this process. Calculations indicate that the rate of trap-assisted Auger recombination through the dopant generated acceptor states in p-type silicon and through donor states in n-type silicon becomes large enough to compete with the band to band Auger process at heavy doping. In n-type silicon Auger recombination through crystal defects like vacancies may also become important. Perhaps all these processes contribute to the carrier recombination at heavy doping but which of these controls the lifetime in n-type silicon is not known.

High-resolution silicon-29 nuclear magnetic resonance spectroscopic study of rock-forming silicates

Abstract: High-resolution silicon-29 magic-angle sample-spinning NMR spectroscopic studies of a wide range of natural and synthetic silicates indicate (l) considerable overlap among the ranges of isotropic chemical shifts for crystals of different polymer types. This expands upon the work of Lippmaa et a/. (1980), who found well-separated ranges; (2) a wide range of chemical shift anisotropies (CSA) and asymmetry parameters (q) that are related to symmetry and structure; (3) a relatively poor correlation between isotropic chemical shift and average Si-O bond length; (4) a better correlation between isotropic chemical shift and total cation-oxygen bond strength for the four oxygens ofeach silicon tetrahedron;,and (5) discrepancies between the NMR results and crystal structure refinements for kyanite and wollastonite. These results indicate that both the Si-O bond length-chemical shift and bond strength-chemical shift relationships are useful tools for investigating the structures of crystalline silicates and, perhaps more importantly, silicate glasses, clays, and zeolites that cannot be examined by single crystal X-ray or neutron diffraction methods.

Method of producing titanium nitride MOS device gate electrode

Abstract: An MOS device having a gate electrode and interconnect of titanium nitride and especially titanium nitride which is formed by low pressure chemical vapor deposition In a more specific embodiment the titanium nitride gate electrode and interconnect have a silicon layer thereover to improve oxidation protection

Energy Levels of Silicon, Si I through Si XIV

Abstract: Energy level data are given for the atom and all positive ions of silicon (Z=14) These data have been critically compiled, mainly from published material on measurements and analyses of the optical spectra We have derived or recalculated the levels for a number of the ions In addition to the level value in cm−1 and the parity, the J value and the configuration and term assignments are listed if known Leading percentages from the calculated eigenvectors are tabulated or quoted wherever available Ionization energies are given for all spectra Key words: atomic energy levels; atomic ions; atomic spectra; electron configurations; ionization potentials; silicon

Density of gap states of silicon grain boundaries determined by optical absorption

Abstract: The results of optical absorption measurements on fine‐grain polycrystalline‐silicon thin films indicate that the singly occupied dangling silicon bond lies 0.65±0.15 eV below the conduction‐band minimum in the grain boundary. The grain boundary band gap is ∼1.0 eV and there is evidence for exponential tailing of the band edges. The optical absorption was determined by photothermal deflection spectroscopy. The dangling silicon bond density has been measured on polycrystalline‐silicon thin films as a function of hydrogen passivation of the grain boundaries and on silicon‐on‐saphhire films. The optical absorption exhibits a defect shoulder which varies as the dangling bond density.

Magic‐Angle‐Spinning NMR (MAS‐NMR) Spectroscopy and the Structure of Zeolites

Abstract: After outlining the chemical features and properties which make zeolites such an important group of catalysts and sorbents, the article explains how high-resolution solid-state NMR with magic-angle spinning reveals numerous new insights into their structure. 29Si-MAS-NMR readily and quantitatively identifies five distinct Si(OAl)n(OSi)4-n structural groups in zeolitic frameworks (n = 0, 1,….4), corresponding to the first tetrahedral coordination shell of a silicon atom. Many catalytic and other chemical properties of zeolites are governed by the short-range Si, Al order, the nature of which is greatly clarified by 29Si-MAS-NMR. It is shown that, as expected from Pauling's electroneutrality principle and Loewenstein's rule, both in zeolite X and in zeolite A (with Si/Al = 1.00) there are no AlOAl linkages. In zeolite A and zeolite X with Si/Al = 1.00 there is strict alternation of Si and Al on the tetrahedral sites. Ordering models for Si/Al ratios up to 5.00 (in zeolite Y) may also be evaluated by a combination of MAS-NMR experiments and computational procedures. 29Si-MAS-NMR spectra reveal the presence of numerous crystallographically distinct Si(OSi)4 sites in silicalite/ZSM-5, suggesting that the correct space group for these related porosilicates is not Pnma. 27Al-MAS-NMR clearly distinguishes tetrahedrally and octahedrally coordinated aluminum, proving that, contrary to earlier claims, Al in silicalite is tetrahedrally substituted within the framework. In combination, 29Si- and 27Al-MAS-NMR is a powerful tool for monitoring the course of solid-state processes (such as ultrastabilization of synthetic faujasites) and of gas-solid reactions (dealumination of zeolites with silicon tetrachloride vapor at elevated temperatures). They also permit the quantitative determination of framework Si/Al ratios in the region 1.00 < Si/Al < 10 000. Since most elements in the periodic table may be accommodated within zeolite structures, either as part of the exchangeable cations or as building units of the anionic framework, there is immense scope for investigation by MAS-NMR and its variants (cross-polarization, multiple pulse and variable-angle spinning) of bulk, surface and chemical properties. Some of the directions in which future research in zeolite science may proceed are adumbrated.

Polycrystalline Silicon Micromechanical Beams

Abstract: Using the conventional MOS planar process, miniature cantilever and doubly supported mechanical beams are fabricated from polycrystalline silicon. Poly‐Si micromechanical beams having thicknesses of 230 nm to 2.3 μm and separated by 550 nm to 3.5μm from the substrate are made in a wide range of lengths and widths. Two static mechanical properties are investigated: the dependences of maximum free‐standing length and beam deflection on the thickness of the beam. By annealing the poly‐Si prior to beam formation, both of these properties are improved. Nonuniform internal stress in the poly‐Si is apparently responsible for the beam deflection.