Annealing characteristics of highly doped ion implanted phosphorus layers in silicon

A combination of sheet resistance, stripping and Hall effect measurements have been made on phosphorus layers implanted into silicon at 40 and 100 keV with doses between 1 × 10¹⁵ and 5 × 10¹⁶ atoms/cm². The implants were made at room temperature and 450°C. After annealing at 650°C, the profile of electrically active phosphorus following a high dose room temperature implant, was found to be flat topped with a concentration of approximately 5 × 10²⁰/cm³. Very little diffusion occurred when annealing to 850°C where the free electron concentration increased to approximately 1.5 × 10²¹/cm³. Highly doped channeled tails were found when implanting at 450°C along the 〈110〉 direction and damage was being continuously annealed out preventing the formation of an amorphous phase. The rapid diffusion of the profile into the bulk found when annealing between 650°C and 850°C was speculated to be due to the presence of a dense dislocation entanglement in these layers following a hot implant.     

Uniform persistence and net functions

We obtain uniform persistence for a class of retarded functional differential equations as a consequence of a general result involving certain multiple Lyapunov-like functions which we call net functions. Applications include population dynamics models of Kolmogorov type with time delays.     

Synthesis,structure and stability of phases in the system Li2OPdO2

Li₂PdO₂ and Li₂PdO₃ have been synthesized. Powder X-ray data are reported for both phases. Li₂PdO₂ is body-centered orthorhombic, Immm, a = 3.74₀, b = 2.97₅, c = 9.35₄ Å. It is isostructural with Li₂CuO₂, with which it forms a complete series of solid solutions. The crystal structure of Li₂PdO₂ has been determined. it comprises sheets of tetrahedrally coordinated lithium and oxygen atoms, parallel to (001), held together by ribbons of (PdO₂)_∞ in which each palladium atom is coordinated by four oxygen atoms in a rectangular-planar arrangement.     

Derivatives of trifluorovinylsulfur pentafluoride (SF5CFCF2) II

Trifluorovinylsulfur pentafluoride (SF₅CFCF₂) and carbonyl fluoride will add, in the presence of cesium fluoride and acetonitrile, to form SF₅CF(CF₃)C(O)F. This new acid fluoride serves as a source for preparing derivatives containing the SF₅CF(CF₃) - grouping. The following new compounds have been prepared and characterized: SF₅CF(CF₃)X where X = C(O)F, C(O)CH₃, C(O)OH, C(O)NH₂, CN. The dimer, (SF₅CFCF₂)₂, has also been prepared. Infrared, mass, and nmr spectra are presented in order to support their proposed structure.     

Fragmentation of highly excited small neutral carbon clusters

We present a combined experimental and theoretical study of fragmentation of small Cn clusters (n = 5,7,9) produced in charge transfer collisions of fast (nu = 2.6 a.u.) singly charged Cn+ clusters with He. Branching ratios for all possible fragmentation channels have been measured. Comparison with microcanonical Metropolis Monte Carlo simulations based on quantum chemistry calculations allows us to determine the energy distribution of the excited clusters just after the collision.     

Rate of decay for solutions of stochastic differential equations

A theorem is given which demonstrates that solutions of a stochastic differential equation decay to zero at least as fast as a function ψ(t) provided $\text{L[}\text{ln}\text{V] ?}\text{(d}\text{dt)}\text{(}\text{ln}\text{ψ)}$, where V is a Liapunov-like function and L is the operator associated with the stochastic equation. The result is an extension of a recent result of A. Friedman and M. Pinsky. A further generalization is discussed.     

Site directed synthesis of mono and disubstituted SF5-polyfluoroalkyl benzenes

A novel method for the preparation of o-, m-, p-SF₅CF₂CFYC₆H₄X (Y = Br, F and X = m-Br, p-Br, Cl, CH₃, CF₃, NO₂, o-NO₂, F, CF₃, CH(CH₃)₂) derivatives was devised by a two-step reaction: SF₅Br-addition to o-, m-, p-CF₂CFC₆H₄X followed by reaction of AgBF₄ with the o-, m-, p-SF₅CF₂CFBrC₆H₄X adducts. Additional studies have been carried out with several derivatives and includes the preparation of SF₅CF₂C(O)C₆H₅, p-CF₃CFBrC₆H₄NO₂, SF₅CF₂CF₂C₆H₃(NO₂)₂, SF₅CF₂CF₂C₆H₃(NH₂)₂, and an SF₅CF₂CF₂-containing polyimide and dye. The complete characterization (IR, NMR, and MS) of these compounds is given.     

Electronegativities from core-ionization energies: electronegativities of SF5 and CF3

Core-ionization energies have been measured for SF(6) (S 2p), SF(5)SF(5) (S 2p), SF(5)Br (S 2p and Br 3d), and SF(5)CF(3) (S 2p and C 1s). These results, together with others that establish correlations between core-ionization energies and Pauling electronegativities, make it possible to assign group electronegativities to SF(5) and CF(3). This method gives electronegativities for these groups comparable to that of bromine, whereas analysis of the effect of these groups on acidity indicates electronegativities comparable to that of fluorine. Other methods of estimating electronegativity fall between these extremes. These disparities can be understood in part as reflecting the effects of polarizibility of the substituent, which tends to lower both the core-ionization energy and the deprotonation energy, making the electronegativity appear to be less in one case and more in the other. In addition, and possibly more important, the core-ionization energies presented here reflect the effect of the group on an adjacent atom, whereas the acidity reflects the effect on a remote atom. It appears that fluorine has a large effect on an adjacent atom but a relatively small effect on a remote atom. By contrast SF(5) and CF(3) have a relatively small effect on an adjacent atom, but this effect falls off only slowly with distance from the substituent. Thus, the effective electronegativities of CF(3) and SF(5) relative to those of the halogens depend on the site at which the molecule is probed as well as on the process that is under consideration.