6,323 research outputs found
Atomically straight steps on vicinal Si (111) surfaces prepared by step-parallel current in the kink-up direction
We demonstrate that annealing of a vicinal Si(111) surface at about 800 C
with a direct current in the direction that ascends the kinks enhances the
formation of atomically straight step edges over micrometer lengths, while
annealing with a current in the opposite direction does not. Every straight
step edge has the same atomic configuration U(2,0), which is useful as a
template for the formation of a variety of nanostructures. A phenomenological
model based on electromigration of charged mobile atoms explains the observed
current-polarity dependent behavior.Comment: Accepted for publication in Appl. Phys. Lett. Numbers of pages and
figures are 12 and 4, respectivel
Self-assembly of parallel atomic wires and periodic clusters of silicon on a vicinal Si(111) surface
Silicon self-assembly at step edges in the initial stage of homoepitaxial
growth on a vicinal Si(111) surface is studied by scanning tunneling microscopy
(STM). The resulting atomic structures change dramatically from a parallel
array of 0.7 nm wide wires to one dimensionally aligned periodic clusters of
the diameter ~ 2 nm and periodicity 2.7 nm in the very narrow range of growth
temperatures between 400 and 300 C. These nanostructures are expected to play
an important role in future development of silicon quantum computers.
Mechanisms leading to such distinct structures are discussed.Comment: Accepted for publication in Phys. Rev. Lett. Numbers of pages and
figures are 13 and 3, respectivel
Algebraic structure of the Feynman propagator and a new correspondence for canonical transformations
We investigate the algebraic structure of the Feynman propagator with a
general time-dependent quadratic Hamiltonian system. Using the Lie-algebraic
technique we obtain a normal-ordered form of the time-evolution operator, and
then the propagator is easily derived by a simple ``Integration Within Ordered
Product" (IWOP) technique.It is found that this propagator contains a classical
generating function which demonstrates a new correspondence between classical
and quantum mechanics
Three-nucleon interactions: dynamics
A discussion is presented of the dynamics underlying three-body nuclear
forces, with emphasis on changes which occurred over several decades.Comment: Talk given at the FM50 symposium, Tokyo, October 200
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