Spreading Dynamics of Polymer Nanodroplets

The spreading of polymer droplets is studied using molecular dynamics simulations. To study the dynamics of both the precursor foot and the bulk droplet, large drops of ~200,000 monomers are simulated using a bead-spring model for polymers of chain length 10, 20, and 40 monomers per chain. We compare spreading on flat and atomistic surfaces, chain length effects, and different applications of the Langevin and dissipative particle dynamics thermostats. We find diffusive behavior for the precursor foot and good agreement with the molecular kinetic model of droplet spreading using both flat and atomistic surfaces. Despite the large system size and long simulation time relative to previous simulations, we find no evidence of hydrodynamic behavior in the spreading droplet.Comment: Physical Review E 11 pages 10 figure

GROWTH KINETICS, CRYSTAL STRUCTURE, AND MORPHOLOGY OF OMVPE-GROWN HOMOEPITAXIAL CdTe

The growth rate, crystal structure, morphology, and electronic properties of homoepitaxial CdTe grown by OMVPE in an impinging jet reactor were investigated. Under operating conditions where surface reactions controlled the rate, the deposition rate depended on the diethyltelluride partial pressure to the .8 power and on the dimethylcadmium partial pressure to the .2 power, approximately. Cadmium was easily adsorbed and was ubiquitous on the surface during deposition ; tellurium was relatively scarce on the surface. Deposition on three of the four low-index orientations proceeded at the same rate ; CdTe grew on the (111)Te, however, at twice this rate. Hillocks were removed completely by deposition on a (100) surface misoriented three degrees toward the (111)Te. Modeling of the fluid dynamics and mass transport in the reactor confirmed the high mass transfer rates obtainable with the impinging jet reactor ; the mass transfer limited deposition, however, was nonuniform under the jet