Chemistry Reference
In-Depth Information
structure and diffusion of adatoms between domains. The density of macrosteps
depends on the initial distance between monatomic steps, the substrate temperature,
the superstructural transition rate, and it is controlled by kinetic limitations associ-
ated with the necessity of significant mass transfer over the surface [
46
].
Control of germanium monolayer formation on the step silicon (111) surface
makes it possible to provide conditions for the growth of regular lateral superlat-
tices, in which germanium strips along the monatomic steps of the surface alternate
with silicon surface strips [
35
]. A major factor complicating lateral superlattice for-
mation during germanium submonolayer deposition onto the silicon surface is the
clustering of monatomic steps of the substrate during polycentric nucleation of the
reconstructed domains induced by germanium [
8
].
To optimize the technological processes of the oxidation of a nanostructured
object, the initial stages of the interaction of oxygen with the silicon (111) surface
in the temperature range of 500-900
◦
C were studied [
47
]. Intensity oscillations of
the electron beam specularly reflected from the silicon surface were detected in the
case of implementation of the two-dimensional-island mechanism of thermal etch-
ing of silicon in a molecular oxygen flow. The activation energy of surface diffusion
of vacancies initiated by the interaction of oxygen with silicon was estimated as
1
15 eV [
48
].
To improve the silicon substrate morphology, the structure and reconstruction of
the silicon (001) surface, i.e., the most commonly used substrate in silicon micro-
and nanoelectronics, were studied [
49
]. It was shown in [
45
] how the electric cur-
rent heating of the crystal affects the surface reconstruction processes on the silicon
(001) face. Based on quantitative data obtained by analyzing the step motion kinetics
and diffusion of an array of adatoms and vacancies on the silicon (001) surface, step
bunch formation was detected [
16
]. Possible models of the effect of electromigration
on step-bunching processes are discussed in [
50
].
Another example of self-assembly is the formation of regular chains of gold clus-
ters along monatomic step bunches [
51
]. It was shown that there were preferential
displacements of three-dimensional gold islands adsorbed on the silicon (111) sur-
face toward an overlying terrace [
52
]. This phenomenon led to the accumulation
and coalescence of gold islands near the upper edge of step bunches. Thus, the
mechanism of self-assembly of gold clusters is implemented due to preliminary
self-assembly in the system of monatomic steps.
The above data on atomic processes on the silicon surface allowed not only opti-
mization of the conditions for obtaining low-dimensional structures on the basis of
conventional silicon technologies, but also created prerequisites for nanostructure
formation based on the detected effects of self-assembly on the silicon surface. It
seems that such complex multistage processes of bottom-up self-assembly on the
size scale will become fundamental in the controlled formation of semiconductor
nanostructures for the next-generation nanoelectronic elements and sensorics on a
silicon surface. The presented data on atomic processes on the silicon surface lay
the groundwork for nanotechnologies for controlled synthesis of silicon nanostruc-
tures with tailored configurations and the required electrical, mechanical, and other
properties.
.
35
+
0
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