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The equilibrium structure of [100] oriented steps on the (100) surface of a simple cubic crystal has been examined by Monte Carlo simulation methods. The structures of four surfaces (20,1,0), (10,1,0), (5,1,0) and (100), were simulated and the results combined to determine the properties of an isolated step. The step edge (ledge) energy/length first increases with temperature and then decreases continuously until, at a temperature TR, it vanishes. This temperature, TR, corresponds to the critical temperature for surface roughening, at which the structural and thermodynamic properties of the stepless surface exhibit singularities. These results indicate that TR may be regarded as the temperature above which surface steps may form without increasing the surface free energy. Alternatively, these results show that TR also corresponds to the temperature above which the cusp in a polar plot of surface free energy disappears and the surface becomes nonsingular. e/kTR as determined in this simulation is ∼ 1.57, where e is the strength of the first neighbor bond.

A pair approximation method is described for the interface kinetics of a simple cubic (100) surface with no surface migration. Condensation and evaporation are considered explicitly in a system of master equations applied to a pair of sites; and the effect of the neighboring sites is treated with a set of parameters which are determined self-consistently. Runge Kutta numerical integration of the equations yields the time evolution of the surface. The results for a high entropy of transformation indicate a region of metastable states (zero growth rate) for small driving force, and the instantaneous growth rate is a periodic function of time for larger driving force. The period of the variations is the time required to grow a monolayer, and the amplitude is less than that obtained by Temkin using the mean field approximation. The variations appear as artifacts of most approcimation methods which treat a limited number of sites. The average growth rate is less than the limiting Wilson-Frenkel law for all growth conditions studied. This results since the surface becomes quite rough in the presence of a large condensation rate, and therefore its evaporation rate is greater than the evaporation rate of an equilibrium surface assumed in the Frenkel model. The metastable region is absent at low entropies of transformation and here the growth rate is nearly linear in the driving force. Agreement with Monte Carlo data is excellent for a low entropy of transformation and for all materials at high growth rates.

Laser annealing of silicon in the pulsed, high energy density mode results in melting and rapid epitaxial resolidification. The incorporation of dopant atoms in the resultant crystals in excess of the retrograde solubility maximum provides firm evidence for the occurence of nonequilibrium, impurity trapping processes at the solid-liquid interface during crystal growth.

The structure of the (110) crystal-vapor or crystal-melt interface of an fcc crystal has been calculated in zeroth order approximation. The results indicate that structural roughening of the interface occurs in the range 0.03 kT / L kT / L . Here L is the enthalpy of vaporization or melting and T is the absolute temperature. The relative population of surface energy levels has also been computed. For kT / L > 0.3, the surface approximates an ideally rough configuration. The surface self diffusion coefficient has been computed from the theoretical distribution of atoms at the interface. The results indicate a positive departure from Arrhenius behavior in the temperature interval where roughening occurs. In the L / kT range encountered in metal-vapor systems the theoretically obtained log ( D s versus L / kT relationship is linear. The departure from linearity commonly observed in fcc metal-vapor system is therefore not predicted to be the result of structural roughening of the (110) orientation surface.