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d
n
1
y
4
n
g
|
3
.
Figure 2.3
Absorption and emission spectra of di
er
treatment with HF. Reprinted with permission from O. I. Micic, J.
Sprague, Z. Lu and A. J. Nozik,
Appl. Phys. Lett.
, 1996, 68, 3150.
Copyright 1996, AIP Publishing LLC.
erent-sized InP QDs a
Chapter 5.) This was resolved by Micic
et al.
, who described a simple etching
process of the InP QDs with either HF or NH
4
F, in which the
uoride ions
removed phosphorus vacancies (V
P
) and dangling bonds (as con
rmed by
electron paramagnetic resonance
37
) which are known electron traps. The
uoride ions replaced oxygen in the surface oxide layer,
38
although some
defects were known to still exist in the core of the particle.
39
This etching
process resulted in a blue shi
in the absorption spectra of the particles as
they became smaller, while the emission became entirely band edge, losing
the low trap emission feature as shown in Figure 2.3.
38
Importantly, the
emission quantum yields increased massively to 30% at 300 K. It was
reported that deep trap emission could be avoided if the InP particles were
prepared with an excess of phosphorus, although the band edge emission
was extremely weak, and the absorption spectra did not have an excitonic
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