Biomedical subjects

A Madhukar

Publications and source records attributed to A Madhukar.

11 recordsLinked to original sources

PubMed2001

Simulations of atomic level stresses in systems of buried Ge /Si islands.

Stress distribution in laterally ordered arrays of coherent Ge islands on Si(001) buried in Si cap layers is examined using atomistic simulations. The obtained hydrostatic stress dependence on the spacer layer thickness shows a nearly linear inverse dependence, unlike the commonly used inverse cubic dependence derived in the framework of an isolated embedded force dipole source model. Additionally, the hydrostatic stress on the spacer surface is found to scale more closely with the area of the island rather than its volume as implicit in the use of the force dipole model.

Journal Article↗

PubMed2000

Stress domains in Si(111)/a-Si3N4 nanopixel: ten-million-atom molecular dynamics simulations on parallel computers

Parallel molecular dynamics simulations are performed to determine atomic-level stresses in Si(111)/Si(3)N4(0001) and Si(111)/a-Si3N4 nanopixels. Compared to the crystalline case, the stresses in amorphous Si3N4 are highly inhomogeneous in the plane of the interface. In silicon below the interface, for a 25 nm square mesa stress domains with triangular symmetry are observed, whereas for a rectangular, 54 nmx33 nm, mesa tensile stress domains ( approximately 300 A) are separated by Y-shaped compressive domain wall. Maximum stresses in the domains and domain walls are -2 GPa and +2 GPa, respectively.

Journal Article↗

PubMed2000

Dislocation emission at the Silicon/Silicon nitride interface: A million atom molecular dynamics simulation on parallel computers

Mechanical behavior of the Si(111)/Si(3)N4(0001) interface is studied using million atom molecular dynamics simulations. At a critical value of applied strain parallel to the interface, a crack forms on the silicon nitride surface and moves toward the interface. The crack does not propagate into the silicon substrate; instead, dislocations are emitted when the crack reaches the interface. The dislocation loop propagates in the (1; 1;1) plane of the silicon substrate with a speed of 500 (+/-100) m/s. Time evolution of the dislocation emission and nature of defects is studied.

Journal Article↗

PubMed2000

Manipulation of gold nanoparticles in liquid environments using scanning force microscopy

Precise and controlled manipulation of individual gold nanoparticles (deposited on a Si/SiO2 surface) in liquid environments using the tip of a scanning force microscope is reported for the first time. Experiments were performed in deionized water and in ethanol as a prototype for an organic solvent. Analysis of the amplitude signal of the cantilever before and during manipulation reveals that the particles are pushed across the surface, similar to the manipulation of nanoparticles in air.

Journal Article↗

PubMed1995