-
The luminescence of
nanocrystalline ZnO particles:
the
mechanism of the ultraviolet and visible emission
氧化锌纳米晶体粒子的发光：紫外发光与可见发光机理
Abstract
(
摘要
)
Results
of
steady-state
luminescence
measurements
performed
on
suspensions
of
nanocrystalline
ZnO
particles
of
different
sizes
are
presented.
(<
/p>
本文提供了对不同粒径大小的氧化锌纳米晶体粒子悬浮液的稳态发光测量结
果。
)
In all cases two emission
bands are observed.(
在所有的例子中，观测
is
an
exciton
emission
band
in
the
UV
and
the
到两个发光带。
)
One
second
an
intense
and
broad
emission
band
in
the
visible,
shifted
by
approximately 1.5 eV with
respect to the absorption onset. (
第一个是存
在于
紫外区的激子发光带；
第二个是存在于可见光区的强烈且宽
的发光带，
这个发光带的吸收起
始点以约
1.5eV
进行变换。
)
As the size of the particles increases,
the intensity
of
the
visible
emission
decreases,
while
that
of
the
exciton
emission
increases. (
随着粒子大小的增加，可见区发光的
强度减弱，而激子发光强度增加。
)
In
accordance
with
previous
results,
a
model
is
presented
in
which
the
visible
emission is assigned to the radiative
recombination of an electron
from a
level close to the conduction band edge and a
deeply trapped hole
in the bulk
(
Vo**
) of the ZnO particle.
(
根据之前的结果，
提出了一个模型，
可见发
光是接近导带边缘水平的电子与氧化锌粒子本体（
V
o**
）的深陷阱空穴的辐射再结合。
)
The size dependence of the
intensity ratio of the visible to exciton
luminescence
and
the
kinetics
are
explained
by
a
model
in
which
the
photogenerated hole is
transferred from the valence band to a
V
o*
level in
the bulk of the
particle in a two-step process. (
可见发光和激
子发光之强度比的
尺寸依赖性及动力学原理可由这样一个模型解释：
在这个模型中，
光致空穴通过一个两步的
过程从低能满价带
迁移到粒子本体的
V
o*
水平。
)
The first step of
this process is an
efficient surface-
trapping, probably at an
O
2-
site.
(
这个过程的第一步，是极可
能在
O
2-
处的有效
表面俘获。
)
Keywords:
Semiconductors; Nanoparticles; Quantum size
effects; ZnO
(
关键词：
半导体；
纳米粒子；
量子尺寸效应；
氧化锌
)
1.
Introduction
(
引言
)
ZnO
has
been
known
as
a
luminescent
material
for
a
century
and
nowadays it is used for
various applications such as vacuum fluorescent
displays (VFD's). (
氧化锌作为一种发光
材料，已经在一个世纪前为人们所知悉。如今，
它有着广泛应用，
如真空荧光显示器
（
VFD
’
s
）
。
)
However, despite numerous studies,
the
mechanism
behind
the
visible
luminescence
has
still
not
been
established.
(
尽管有着大量的研究，
但其在可见光区的发光机理仍未确立。
)
Much of
the
research
on
the
luminescence
of
ZnO
is
performed
on
single
crystalline powders or single
crystals.
(
大量氧化锌发光的研究是基于单结晶粉
末或者单晶体。
)
Two emission bands are usually
found.
(
人们通常可以观测
到
两个发光带。
)
A relatively weak and narrow UV
emission band is observed
around 380 nm
(3.25 eV), just below the onset of absorption. (
一个是在波长
为
380nm
（
3.25eV
）附近的较弱和较窄的紫外发光带，仅
在吸收起始点之下。
)
This
band is due
to the radiative annihilation of excitons. (
这个发光带是由激子的辐
射湮灭所产生。
)
The lifetime of this exciton emission is
very short, of the
order of several
tens to hundreds of picoseconds [1].
(
激子发光的寿命是非常
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