ABSTRACT: In this work,the optical properties of chromic chloride(푪풓푪풍ퟑ )thin film prepared at different thickness has been measured. The relationship between transparency, absorbance and photon energy for the prepared samples has been studied. It has been found, the behavior of curves is the same for each samples.Moreover, it has been observed thatThe best fit of theexperimental curve to a band gap function was obtained for 푛 = 2 to direct bandgap energy values the obtained values are 1.531 eV, 1.533 eV,1.536 eV, and 1.539 eV for dip the rated of 퐶푙 (0.0 - 0.25 – 0.50 and 0.75 ) respectively.

1. Quest Journals
Journal of Research in Humanities and Social Science
Volume 5 ~ Issue 2 (2017) pp: 37-40
ISSN(Online) : 2321-9467
www.questjournals.org
*Corresponding Author: Ahmed Gadem Mohamed Ali 37 | Page
1
Department Of Chemistry, Faculty Of Education, Peace University, Sudan
Research Paper
A Study of Some Optical Properties of Chromic
Chloride(𝐂𝐫𝐂𝐥 𝟑 )Thin Film
Ahmed Gadem Mohamed Ali1, 3
,Montasir Salman Elfadel Tyfor2, 3
1
Department of Chemistry, Faculty of Education, Peace University, Sudan
2
Department of Physics Faculty ofEducation in (Al-Hasahisa), Gezira University Sudan
3
FacultyofScience &Arts Al-BAHA University KSA.
Received 07Feb. 2017; Accepted22Feb. 2017 © The author(s) 2017. Published with open access at
www.questjournals.org
ABSTRACT: In this work,the optical properties of chromic chloride(𝑪𝒓𝑪𝒍 𝟑 )thin film prepared at different
thickness has been measured. The relationship between transparency, absorbance and photon energy for the
prepared samples has been studied. It has been found, the behavior of curves is the same for each
samples.Moreover, it has been observed thatThe best fit of theexperimental curve to a band gap function was
obtained for 𝑛 = 2 to direct bandgap energy values the obtained values are 1.531 eV, 1.533 eV,1.536 eV, and
1.539 eV for dip the rated of 𝐶𝑙 (0.0 - 0.25 – 0.50 and 0.75 ) respectively.
Keywords:Film thickness, Energy band gap,(𝑪𝒓𝑪𝒍 𝟑 ) , Optical Properties.
I. INTRODUCTION
The physical properties plays important role in material science, it has been able to interpret many of
the phenomena related to materials, The changes in the physical properties of a system can be used to describe
its transformations or evolutions between its momentary states [1] Physical properties include appearance,
texture, color, odor, melting point, boiling point, density, solubility, polarity, and many others [2]. In this work
we study the Absorption coefficient derived from (𝐂𝐫𝐂𝐥 𝟑 )thin film with different thickness and Transmission
spectra for (𝐂𝐫𝐂𝐥 𝟑 )samples with different thin film thickness to describe the optical properties for(𝐂𝐫𝐂𝐥 𝟑 ),
many devices are used to study the optical properties of materials, but the problem is how to choose effective
devices for measurement of these properties. The optical measurements comprise measuring the absorbance and
transmittancewith range (350 - 900 nm), in the current study, by using (UV mini 1240 spectrophotometer.
II. CHROMIC CHLORIDE(𝐂𝐫𝐂𝐥 𝟑 ) STRUCTURE AND APPLICATIONS
Anhydrous chromium (III) chloride agrees the YCl3 structure, with 𝐶𝑟3 + occupying two thirds of
the octahedral interstices in alternating layers of a pseudo-cubic close packed lattice of 𝐶𝑙− ions. The absence of
cations in alternate layers leads to weak bonding between adjacent layers. For this reason, crystals of
CrCl3 cleave easily along the planes between layers, which results in the flaky (micaceous) appearance of
samples of chromium (III) chloride.[3][4], Chromium(III) chloride is used as the precursor to many organ
chromium compounds, for example chromium, Phosphine complexes derived from CrCl3 catalyze the
dimerization of ethylene to 1-hexene.[5][6], One niche use of CrCl3 in organic synthesis is for the in
situ preparation of chromium(II) chloride, a reagent for the reduction of alkyl halides and for the synthesis of
(E)-alkenyl halides. The reaction is usually performed using two moles of CrCl3 per mole of lithium aluminum
hydride, although if aqueous acidic conditions are appropriate zinc and hydrochloric acid may be sufficient,
Chromium(III) chloride also used as a Lewis acid in organic reactions, for example to catalyze the
nitroso Diels-Alder reaction.[7]

2. A Study Of Some Optical Properties Of Chromic Chloride(𝑪𝒓𝑪𝒍 𝟑 ) Thin Film…
*Corresponding Author: Ahmed Gadem Mohamed Ali 38 | Page
Fig (1) shows the relation between absorbance and photon energy
Fig (2) shows the relation between transparent and photon energy
Fig (3) shows the relation between reflection and photon energy
1.507 1.518 1.529 1.540 1.551 1.562 1.573 1.584 1.595
0.56
1.12
1.68
2.24
2.80
3.36
3.92
4.48
5.04
Absorpation(%)
h ( eV )
CrCl 0.00
CrCl 0.25
CrCl 0.50
CrCl 0.75
1.507 1.518 1.529 1.540 1.551 1.562 1.573 1.584 1.595
-4.27
-3.66
-3.05
-2.44
-1.83
-1.22
-0.61
0.00
0.61
Transimission(%)
h ( eV )
CrCl 0.00
CrCl 0.25
CrCl 0.50
CrCl 0.75
1.507 1.518 1.529 1.540 1.551 1.562 1.573 1.584 1.595
-3.08
-2.64
-2.20
-1.76
-1.32
-0.88
-0.44
0.00
0.44
Reflaction(%)
h ( eV )
CrCl 0.00
CrCl 0.25
CrCl 0.50
CrCl 0.75

3. A Study Of Some Optical Properties Of Chromic Chloride(𝑪𝒓𝑪𝒍 𝟑 ) Thin Film…
*Corresponding Author: Ahmed Gadem Mohamed Ali 39 | Page
Fig (4) show the relation between absorption coefficient and photon energy
(5) show the relation between extinction coefficient and photon energy
Fig (6) the optical energy gap (Eg) value of Cr Cl
1.507 1.518 1.529 1.540 1.551 1.562 1.573 1.584 1.595
2.40x106
3.60x106
4.80x106
6.00x106
7.20x106
8.40x106
9.60x106
1.08x107
1.20x107
AbsorpationCoefficient(cm-1
)
h ( eV )
CrCl 0.00
CrCl 0.25
CrCl 0.50
CrCl 0.75
1.316 1.344 1.372 1.400 1.428 1.456 1.484 1.512 1.540
0.00
3.60x1013
7.20x1013
1.08x1014
1.44x1014
1.80x1014
2.16x1014
2.52x1014
2.88x1014
3.24x1014
(h)2
(eV.cm-1
)2
h ( eV )
Eg
CrCl 0.00 = 1.531 eV
Eg
CrCl 0.25 = 1.533 eV
Eg
CrCl 0.50 =1.536 eV
Eg
CrCl 0.75 = 1.539 eV
1.507 1.518 1.529 1.540 1.551 1.562 1.573 1.584 1.595
0.78
1.56
2.34
3.12
3.90
4.68
5.46
6.24
7.02
ExtincetionCoefficient(k)
h ( eV )
CrCl 0.00
CrCl 0.25
CrCl 0.50
CrCl 0.75

4. A Study Of Some Optical Properties Of Chromic Chloride(𝑪𝒓𝑪𝒍 𝟑 ) Thin Film…
*Corresponding Author: Ahmed Gadem Mohamed Ali 40 | Page
III. RESULTS AND DISSECTIONS
Fig (1) shows the relation between absorbance and photon energy, we found the behavior of curves is
the same for each curves. The rapid increase of an absorption in the low energy and sudden increase in special
energy, this is refer to electronic transition, and this increase is continuous with the increase of photon energy,
absorbance value increased with rated of 𝐶𝑙 increase.
Fig (2) shows the relation between transparent and photon energy, we had been found rapid decrease in low
energies and sudden decrease in special energies and it continuous with decrease in high energy, rated of
𝐶𝑙increase refers to the decrease in transparent value.
The reflection were calculated depended energy safe law using the relation
R + T+ A = 1 ………………………………. (1)
When: R- Reflection, T- TransmitionFig (3) shows the relation between reflection and photon energy.
we had been found rapidly increase in reflection value .until to arrive to peak, then it reduce from high energy
because of less absorption in low energies from energy gap Transmition decreasing due to reflection increasing
using the relation (1) .At high energies from energy gap, the a absorbance is increasing, this cause the reduce in
reflection, and the upper corresponding energy gap value (1.55-1.6)eV. Increasing threated of 𝐶𝑙 due to minor
change in to peak curves, it is shifted low energies.
The absorption coefficient 𝛼 was calculated using
𝛼 =
2.303 𝑥𝐴
𝐿
(2)
Where α is absorption coefficient L optical axes length on the sample
Fig (4) shows the plot of absorption coefficient as a function of photon energy. It could be seen from
the graphthat 𝐶𝑟 𝐶𝑙 had maximum absorptions between 1.54 and1.56 eV
In depended on conclusion absorption value in relation (1), extinction coefficient was measured by using
relation
𝑘 =
𝛼𝜆
4𝜋
(3)
Were K is Extinctioncoefficient,λ is Wave length
And the fig (5) show the relation between extinction coefficient and photon energy. It was found that
the decreasing at extinction coefficient value with increase the rated of 𝐶𝑙 because of decreasing absorption
coefficient value with increase of the rated of 𝐶𝑙 like relation (2)
The optical energy gab was calculated using the well-knownTauc’s relation:
𝛼 = 𝐴 (ℎ𝜐 − 𝐸𝑔) 𝑛ℎῡ(4)
Where𝐴 is a constant, ℎ𝜐 is the photon energy, and 𝛼 isthe absorption coefficient, while 𝑛 depends on
the nature ofthe transition. For direct transitions 𝑛 = 1/2 or 2/3, whilefor indirect ones 𝑛 = 2 or 3, depending on
whether theyare allowed or forbidden, respectively. The best fit of theexperimental curve to a band gap function
was obtained for 𝑛 = 2 to direct bandgap energy values the obtained values are 1.531 eV, 1.533 eV,1.536 eV,
and 1.539 eV for dip the rated of 𝐶𝑙 (0.0 - 0.25 – 0.50 and 0.75 ) respectively Fig (6). There is a slight increasein
band gap as the dip times increases.
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