Chemistry Reference
In-Depth Information
Fig. 10.15
STM images of (
a
)2MLand(
b
) 8ML nanodots. (
c
) PL spectra of the nanodots with
average base lengths
L
of 17, 21, 31, 54 nm. The
inset
shows the size dependence of the PL peak
positions (
open circles
) and a theoretical curve plotted using (
10.2
)(
solid line
)
using
E
bulk
76 eV at 4.2 K (the energy of the optical transition between the
GaSb conduction band and the acceptor),
=
0
.
the
nanodot height), as shown by the solid line in the inset of Fig.
10.15
c. We neglected
the strain effect on the energy band gap because, from Raman spectroscopy results,
all the present nanodots were found to have similarly small strains. The inset in
Fig.
10.15
c shows the results of the experiment were consistent with the theoretical
curve, indicating that the nanodot size dependence of the PL peak position was due
to the quantum confinement effect.
μ
=
0
.
036
m
0
[
54
], and
r
=
L
/
2(
≈
10.3.7 Application to Growth of GaSb Thin Films
The GaSb nanodots on ultrathin SiO
2
films have bulk lattice constant as described
in Sect.
3.6
, indicating that the lattice mismatch strains are almost relaxed in the
nanodots due to the small contact areas on Si substrates. This implies that the GaSb
nanodots can be used as seeding crystals for the growth of GaSb thin films on Si
substrates. Figure
10.16
a shows an STM image of the GaSb nanodots grown at the
substrate temperature of 200
◦
C with the size of
10
12
cm
−
2
.
∼
8 nm and density of
∼
23 nm thickness were subsequently codeposited at 200
◦
Con
Gallium and Sb with
∼
