Percolation effect in structures with amorphous and crystalline silicon nanoclustersстатья
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Дата последнего поиска статьи во внешних источниках: 9 ноября 2017 г.
Аннотация:In this paper the correlations between optical, electrical
and structural properties of ensembles of amorphous and
crystalline silicon nanoclusters in silicon oxide matrix are
explained in terms of percolation theory. SiOx (1 ≤ x < 2)
thin films were deposited on silicon or quartz substrates
by reactive evaporation of SiO powder and were subsequently
thermally annealed at temperatures in the range
from 450 to 1200 oC. Five sets of samples with different
stoichiometry parameters x = 1.0, 1.1, 1.29, 1.56, 1.68 of
initial SiOx were fabricated. The volume fraction of total
excess silicon as well as the volume fraction of silicon
nanocrystals in high temperature annealed structures are
calculated for each sample set. It is found that samples
with excess Si volume fraction of more than 16 % (which
is critical value in percolation theory) demonstrate a local
maximum at about 500-600 oC in the dependence of integrated
photoluminescence intensity on annealing temperature,
which is attributed to the first percolation
threshold in the system of amorphous Si nanoclusters. In
turn, the second percolation threshold is detected in the
system of crystalline Si nanoclusters, when their volume
fraction exceeds 16 %. Such effect, resulted in dramatic
increase of the electrical conductance of SiOx film, was
registered experimentally for the set of samples with
x = 1.0.