Materials Literature
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We propose a model for porous silicon, an irregular structure obtained by removing some silicon atoms randomly from a perfect silicon crystal. It is shown by using two-dimensional clusters with a tight-binding model that this model exhibits the energy-gap widening and the nonexponential decay of the photoluminescence…
Classical trajectory calculations were employed to study diamond (100) surface reconstructions. Atomic forces were computed from two types of potential-energy functions. A quantum mechanical potential based on the semiempirical PM3 (parametric method number three) Hamiltonian was used to describe the central core of t…
Using a micro-Raman setup, in-plane Raman scattering was performed on short-period (001)-Si/Ge superlattices, and the complete phonon spectrum (longitudinal and transverse, optical and acoustic modes) could be studied. In the relevant wave-vector range, the in-plane dispersion was found to affect the frequencies of fo…
Single crystals of barium zirconium sulfide, Ba 3 Zr 2 S 7 , were prepared from BaS, Zr and S at 1323 K by using a BaCl 2 flux. The compound belongs to the Ruddlesden-Popper (A n+1 B n X 3n+1 ) family with A=Ba, B=Zr, X=S and n=2. It is isostructural to Sr 3 Ti 2 O 7 and crystallizes in alternately stacked double pero…
Electronic structures in metallic and insulating phases of the Li, Cu, and Ba complexes of 2,5-R1,R2-DCNQI [R1=R2=Br (abbreviated as DBr) or R1=R2=CH3 (abbreviated as DMe); DCNQI=N,N′-dicyanoquinonediimine; 2,5- is usually omitted] have been studied by observing temperature dependencies of their infrared absorption ba…
The optical behavior of polycrystalline SILSO silicon wafers with a mechanically V-grooved surface has been studied between 300 and 1500 nm. The texturization was carried out by a conventional dicing saw using beveled blades. For a 35° V-grooved surface and a nonmetallized backside the optical path length in the weakl…
We present theoretical studies of various hydrocarbon radicals and molecules on the (100) surface of diamond. We use molecular dynamics and a dynamical quenching algorithm to calculate the energetics of different adsorption configurations, allowing for full relaxation of the underlying lattice. We use a parametrized m…
Radial properties of starburst polymers are calculated by renormalization group techniques starting from the Edwards model of the chain. The calculations are carried out for a polymer in good solvents grown out to an arbitrary number of generations g and having an arbitrary branch functionality f. Excluded volume effe…
Several porous silicon, siloxene (Si6H6O3), heat-treated siloxene, and layered polysilane (Si6H6) samples have been studied with K- and L-edge x-ray photoabsorption, photoemission, and powder x-ray diffraction. The x-ray absorption of layered polysilane and porous-Si are found to be remarkably similar. In particular,…
Micromagnetic numerical computations are used to simulate the equilibrium magnetization distribution within (periodic) stripe patterns in thin films with a canted easy axis and intermediate quality factor. Two thicknesses are considered, either close to the critical thickness for domain nucleation in zero field or in…
Grafted polymer layer composed of a binary mixture of incompatible chains under good solvent condition is simulated using the bond-fluctuation model. The equilibrium structures of the partially phase separated states are investigated as a function of the incompatibility and relative fraction by monitoring the monomer…
We present detailed calculations using the total-energy pseudopotential method in the local-density approximation of the relative stability and pressure-induced behavior of complex tetrahedrally bonded structures formed metastably in silicon and germanium by depressurization from their metallic phases. The correspondi…
The frequency dependence of the absorption constant \ensuremath{\alpha}(\ensuremath{\omega}) and the enhancement of the refractive index n(\ensuremath{\omega}) in the region of interband transitions between confined quasi-two-dimensional states of the valence and conduction bands of PbTe/${\mathrm{Pb}}_{1\mathrm{\ensu…
Effect of ion implantation on the conductivity of zinc oxide was examined by using highly resistive zinc oxide thin films deposited by rf magnetron sputtering at room temperature to reduce the effect of oxygen vacancies. With the doping by 1×1017 atoms/cm2 gallium the conductivity is 1.0×103/Ω cm for as-implanted film…
The result of a combined study of the absorption and photoluminescence (PL) from high-optical-quality free-standing porous Si films is presented. These films, which have a scattering loss less than 10%, allow unambiguous, detailed study of the system's absorption edge and, in addition enable us to correlate the absorp…
Several theoretical studies of the stability of (111)-terminated ionic crystals with the NaCl structure have predicted that the crystal Madelung energy can be stabilized by a simple surface reconstruction. However, previous attempts to grow (111)-terminated crystals have resulted in either unreconstructed or faceted s…
Low pressure sputter atom deposition is a commonly used method for coating and trench filling in semiconductor chip manufacturing. In this paper we present a selfconsistent simulation of this process in which both the sputtered atoms and the background gas are computed by means of the Direct Simulation Monte Carlo (DS…
The two-dimensional melting transition of charged polystyrene spheres in aqueous colloidal suspension has been studied by molecular dynamics simulation of a screened Coulomb system. Some central predictions of the Kosterlitz–Thouless–Halperin–Nelson–Young theory of defect-mediated melting are confirmed, such as an app…
We have employed reflection high energy electron diffraction (RHEED) and high resolution transmission electron microscopy (HREM) to study Cu films grown on hydrogen terminated Si(100) and Si(111) substrates by molecular beam epitaxy. X-ray diffraction and RHEED studies indicate 〈100〉Cu growth on Si(100) and 〈111〉Cu gr…
The conformational and thermodynamic behavior of chain molecules tethered to a planar surface are studied for a variety of solvent qualities with a recently developed single-chain mean-field theory. The lateral pressure isotherms calculated from the theory for chains of n=50 segments show very good quantitative agreem…