Transcript Document

A crucial role of surface electrons in closing oxidation
channels at initial stage of oxide growth on Si(001)
Han Han and J. G. Che
Department of Physics, Fudan University
Our first principles simulations for a single oxygen atom barrierless adsorbing on Si(001) show that in contrast to the conventional
silicon oxidation, only a few oxidation channels exist. The fact that most channels surrounding the up and down atoms of the Si-dimers
are closed for the oxidation indicates that this oxidation control may be attributed to electrons on the Si-dimers. We reveal at the
atomic level that if the narrow regions of the channels can be occupied by pre-growth such as depositing one monolayer of Sr on the
Si(001), the oxidation channels can be closed and the high-quality interface between oxides and silicon can be realized.
I. Background:
Sharp oxides and Si interface is useful, but
have challenge in preventing silicon oxidation.
Some SrTiO3(001)/Si(001) interfaces are listed
in the left figure in different years.
Until recent years, SrTiO3/(100) interface
without silicon oxide was grown successfully.
The right figure site from Science 324, 17
(2009): written and imaged on a 6 ML
SrTiO3/Si sample by PFM.
II. Oxidation process in
such experiment
conditions: barrierless
III. The oxidation channels in
the process:
IV. The role of Sr and the
surface electrons on Si(001):
2 1
Previous calculations: O do not break
backbond (BB) on Si(001) surface
directly (oxidation), but can diffuse
from DB to BB with a barrier of 0.5eV.
Cited from Phys. Rev. Lett. 80, 2000
(1998)
Previous calculations: the BB oxidation
channels are around the backbond on Si(001)
surface: the PES( potential energy surface)
for atomic oxygen on Si(001) surface. Cited
form J. Phys.Chem. B. 109, 17649 (2005).
Sr atoms (2e- per atom) occupy the
center of the oxidation channels and
provide electrons to saturate the
dangling bonds of Si(001) surface:
structure of 0ML, 0.5ML and 1ML Sr
absorbed on Si(001).
clean Si(001)
situation
with Ga (blue
atom) doped
Our findings: O can barrierless adsorb
on the BB. Four stable configurations are
found. Figures are structures for Si-dimer
of clean Si(001) (a) and for O adsorption
on DB (b), TD (c), BB (d), and BD (e).
(short for dangling bond, top of dimer,
backbond and bridge of two dimers,
respectively)
with As (green
atom) doped
Our findings: fully relaxed results show most
channels surrounding the up and down atoms of
the Si-dimers are closed: topview of the startsites for O adsorption to BB (black squares), TD
(red circles) and BD (blue triangles), respectively.
The rest blank area belongs to DB.
The role of surface electrons checked
by doping Ga (hole) and As (electron)
on Si(001) surface: Holes increase the
oxidation area and electrons reduce it.