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Nam
of
researcher The Subject
No. of
The 28 Days
Compressive
Amer
M.AL-Mahdawi
Strength of Portland
Cement
1-8
Suhad M.AL-Taee
in Iraqi
And
International
Standards
F.A.Ismhil
Optical properties of Mn203
N.F.Habubi
Thin
Films Using Chemical
9-15
Spray Pyrolysis Technique
Mohammed Baqir Twaij
.The Moral
Lesson of
16-22
Gorboduc
Convenient Synthesis ·or 3,5
Najat J.AI-Obaydia
diamino
Substituted
1,2,4
Mahmoud N.AI-Jibouri
Thiadiazoles by oxidative
23-28
Mohammad G.Abid
Dimerization
of Thioureas
Substituted
A
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AL-fath Journal, No.l5,2003
lsmhi, F.A
Habucation, N.F
Optical properties
of
Mn
2
0
3
Thin Films Using
Chemical
Spray
Pyrolysis Technique
F.A. Ismhil N.F. Habubi
Department of
Physics-
College of
Education
I
AL-Mustansiriya University
Abstract
Thin film
of
Mn203 have been prepared using
spray
pyrolysis
technique . The effect on optical properties were studied ,
these
includes the absorbency • optical energy gap for direct
allowed
and forbidden band to band transition , our study on
Mn
2
0
3
lead
us to know
that
Mn
2
0
3
is a direct semiconductor;-
Introduction
Recently there has been considerable inferable interest in
the development of new types
of
low cost solar absorption coatings
ｵ pyrolysis technique , this method has been proved to
be
of
great interest in many applications , selective
surfaces for solar energy conversion , anti reflecting coatings
and
electro luminescent devices can take advantage from this simple
,
cheap and convenient technique , This method is greatly used
nowadays for
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found
to
be in good agreement with those
of
ASTM
card
for
polycrystalline y-Mn203.
The absorption and transmission
spectra
of these films were
recorded
using Pye-Uincom SP/8800 in the
range
of (300-900) nm
and all measurements
were carried at
room temperature , the
measurements were repeated using a large
number
of films and
reproducible
results
were
obtained , a simple
computer
program
were used to calculate the optical parameters .
Results and
Discusssion
The
absorption coefficient is calculated from the relation
(10]:
ｾ
a ........... (1)
.
.
where
ｾ is the difference in
the absorption
at each
wavelength of two thin. films of different thickness .
The
phonon energy dependence
of
the optical absorption coefficient of
Mn203 is shown in fig(2) , it can be seen that the-absorption
edge
is
not
so sharp , this may be related to the polycrystalline
structure
of
the
coatings . _
As expected
direct
transition occur in the region of high
absorption a.> 10
3
cm-
1
, and indirect transition occur in the low
absorption
region a.> 10
3
cm-
1
, so Mn
2
0
3
is a direct transition
material, using the assumption that
the
transition probability
becomes constant near the absorption edge,the variation
of
the
absorption
coefficient with photon energy for
direct
allowed band
to
band
transition
is
of
the
form [7]:
2 2 2
(
=
(hf-Eg)
=
(LnT1-2) .. .. . (2)
where ｾ is aconstant
depending on the
probabability of
transition .
Ln
T
t-2
is the transmission of the first
and
the second
film respectively .
The
absorption coefficient
is
calculated from
the absorption
andtransmission
spectrum
and the result are the result
are
almost
ident ical , Fig (3) shows a plot of (Ln T
1
_
2
)
2
versus hf, the plot
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shows
straight
line
when
extended to
(Ln
T
1
_
2
)
2
=0 giving
the value
of Eg
=2.25
±
0.05 eV
for direct
allowed.band to band
transition.
The
energy gap
in the
direct forbidden transition (kt=O)
is
calculated
from
the
relation [11]:
(aht)
213
.= a
0
(hf-Eg)
........
(3)
A satisfactory fit was
obtained
from
(a
ht)
213
as a function
of
photon
energy
as
shown in fig (
4)
extrapolation
of the straight
line
to
(a
ht)
213
=0
gives the
band
gap
of the direct forbidden
transition
Eg=1.85
±
0.05 eV. The
variation
of
the absorption
cofficient
with photon
energy for
direct transition
is given by
[11]:
Where n=2
for
allowed
indirect transition
and n=3
for
.
forbidden indirect transition
,
E
g is
the
·
indirect band gap and
Ep
the absorbed
(+) or emitted (-)
photon
,it
can
be clearly
seen
from
fig (5) and
(6),
the plots of
(a ht)
112
and (a ht)
113
versus
hf
, does
not
indicate
any
straight
line
portion
intercepting
the hf
axis suggesting the absence of
indirect
allowed
transition
.
Mn203
was prepared for
the
first
time using
spray
pyrolysis
technique
, and
for our
knowledge
there
is no publication
have
been
reported in
this
matter
except
for Mn
2
0
3
films [7].
The
value
of the direct transition were
calculated
and
found to be 2.81 eV.
Conclusion
The
absorption
coefficient is high and is of
order
10
5
cm-
1
,
we finally conclude
that Mn
2
0
3
is a
direct semiconductor,
since
of indirect transition were found
.
References
1. A.K.Abass , Z.A.Ahmed
and
R.E.
Tahir,
Phys.Sta.Sol.
(a)
97 234(1986).
2.
N.F.Habubi
,
M.M.Radi, W.Z.Manookain,
J.Math .Phys.
,13,(2) ,(1992) .
12
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3. NF.Habubi , K.A. Mishjal , A.A. Hesen ,
J.of
Education
College, No. 1, (1994).
4. A.K.Abass , N.H. Ahmed ,J .Phys. Chern
.Solids,
47 ,143
(1985).
5. R.H. Misho , W.A. Murad ,G.H.
Fattahalla
,
Thin
Solid
Films , 5, 169 (1988) .
6. G.W.
Pratt
and
Roland
Coelhs,
Phys
.Rev.
16,281 (1951).
7. Z.A. Ahmed, W.A. Taha, A.J. Buggaly, J.Math .Phys ., 13
,1
(1992).
8. O.P. Agnihotri , M.I. Mohamed , A.K. Abass and K.I.
Arshak,
Solid Sate
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AL-fath Journal No.15 2003
.sz
Fig(J) XRD (Intensity versus 26).
l
I
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j
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_,
I
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- _
Absorption Coefticient versus Photon Energy
.
--
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I
I
I
I
ｾ
14
Ismhi F.A
Habucation
, N.F
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AL-fath Journal No.l5 2003
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--
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Fig(4)
(n
versus Photon Energy.
--,.---,--- .:
-
Fig(5) (a hf) versus Photon Energy.
I
/
/
J
--;---. , . ----
Fig(6) (a hf)' J versus Photon Energy.
15
lsmhi
F.A
_ Habucation N.F
·'
