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					                             IPASJ International Journal of Electrical Engineering (IIJEE)
                                                                         Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
A Publisher for Research Motivation........                                        Email: editoriijee@ipasj.org
Volume 1, Issue 6, December 2013                                                                 ISSN 2321-600X



       Electrical Properties of Copper Selenide Thin
                            Film
                                     Ezenwa I. A., Okereke N. A. and Okoli L. N.
                                      Anambra State University, Uli, Anambra State, Nigeria




                                                         ABSTRACT
Copper selenide (CuSe) thin films was grown by Chemical Bath method on glass substrate at room temperature. The electrical
properties of the deposited thin films were investigated using standard four point probe technique. Our result shows variation of
the sheet resistance of the deposited films from                           , the sheet resistivity was found to vary from
                                              , while the electrical conductivity varies from                                  to
                         . Our values of the resistivity of the films shows that CuSe are semiconducting films.
Keywords: Thin films, Chemical Bath, Electrical Properties.

    1. INTRODUCTION
Copper selenide belongs to I–VI compound semiconductor materials. It usually exists as copper (I) selenide (Cu2Se or
Cu2–xSe) or copper (II) selenide (CuSe or Cu3Se2). Cu3Se2 is often reported as an impurity phase along CuSe. Copper (I)
selenide exists in the cubic, tetragonal, orthorhombic or monoclinic forms. Copper (I) selenide exists in cubic,
tetragonal or orthorhombic or monoclinic forms. Orthorhombic copper (I) selenide can be converted to its cubic phase
by heating the material or by electrochemical polarization. This phase transition is also possible at room temperature,
by controlling the selenium concentration [1] The monoclinic/ orthorhombic form of b-Cu2–xSe might be used as a p-
type window material for solar cells and the cubic form (a-Cu2–xSe) is a high temperature phase [2]. Copper selenide is
a semiconductor with p-type conductivity, it is found to have low resistivity, resistivity of about                       ,
Conductivity of                           and Sheet resistance between                 was obtained by [3]. property useful
in the solar cell production. Cu2-xSe is reported to possess a direct band gap of 2.2 eV and an indirect band gap of 1.4
eV for x = 0.2 [4]. The indirect band gap being near the optimum value for solar cell applications [5], the material
could offer a high efficiency of conversion. The interest for copper selenide semiconducting thin film is motivated by
its application in solar cell technology [6]. The use of these films to form a junction with n-type semiconductors either
as absorber in heterojunction with CdS or as window material in heterojunction with n-Si has been demonstrated [7].
Copper selenide can also be used as an ideal solar control coating [8].

    2. MATERIALS AND METHOD
Copper selenide (CuSe) thin films were deposited on glass substrate by chemical bath deposition method. The
deposition      of    CuSe      thin      film    by    CBD       was     based     on     the    reaction     between
                                                         which served as the source of copper ion,         and sodium
selenosulphate                   which served as the source of anion,        EDTA solution was used as a complexing
agent. Five slides were grown, the concentration of Copper (II) chloride dehydrate, sodium selenosulphate, ammonia
solution, temperature (300K) and deposition time were kept constant, while the concentration of EDTA was altered.
The                solution used in this experiment was prepared by mixing 5g selenium powder (99 % purity) with 25g
anhydrous sodium sulphite in 250 ml of distilled water. The mixture was refluxed at a temperature of                for
2hours, 30 minutes before being used in the experiments. The                 so prepared was used immediately because
of instability of the                compound. Ammonium solution was used to maintain the pH of the bath in an
alkaline medium suitable for the deposition. The pH of the baths were obtained at values between              .
The electrical properties of the deposited copper selenide films were studied using a standard four point probe
technique. The arrangement was made in such a way that the voltage across the transverse distance of the films was
measured using silver paste on top of the coated slide to ensure good ohmic contact to the film. The four point probes

Volume 1, Issue 6, December 2013                                                                                        Page 1
                            IPASJ International Journal of Electrical Engineering (IIJEE)
                                                                       Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
A Publisher for Research Motivation........                                      Email: editoriijee@ipasj.org
Volume 1, Issue 6, December 2013                                                               ISSN 2321-600X

were arranged such that the two outer probes were connected to current supply and the two inner probes to a voltage
supply. As current flows between the two outer probes, voltage drop across the inner probes was measured. The sheet
resistivity of the thin film depends on the current, voltage and thickness values of prepared thin film. Equations:




Were used to calculate the sheet resistivity, sheet resistance and electrical conductivity of the grown thin film.

    3. Results and discussion

                                   Table 1 Electrical Properties of CuSe Thin Film




                 Average           Average                           Sheet            Sheet              Electrical
                 Voltage           Current         Thickness         Resistivity      Resistance         Conductivity
 Sample          (V)               (A)             (μm)              (Ω –m)           (Ω)                (Ω-1 – m-1)
 CuSe1                2.15x10-4        8.75x10-6       0.0462          5.14x10-6           24.57             19.4x104
 CuSe2                1.93x10-4        8.32x10-6        0.320          33.6x10-6           23.20             2.97x104
 CuSe3                1.86x10-4        6.98x10-6        0.486          58.7x10-6           26.65             1.70x104
 CuSe4                1.64x10-4        5.83x10-6        0.517          65.9x10-6           28.13             1.51x104
 CuSe5                1.57x10-4        3.48x10-6        0.777          159x10-6            45.12            0.629x104




                    Fig. 1 Variation of Sheet Resistance (Ω) with Thickness (µm) of CuSe the films




Volume 1, Issue 6, December 2013                                                                                     Page 2
                           IPASJ International Journal of Electrical Engineering (IIJEE)
                                                                      Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
A Publisher for Research Motivation........                                     Email: editoriijee@ipasj.org
Volume 1, Issue 6, December 2013                                                              ISSN 2321-600X




                   Fig. 2 Variation of Sheet Resistivity (Ωm) with Thickness (µm) of CuSe the films




                       Fig.3 Variation of Electrical Conductivity (Ω-1m-1) with Thickness (µm)


Figures 1, 2 and 3 show the variations of sheet resistance, sheet resistivity and electrical Conductivity. The sheet
resistance   of   the   films    varies    from                    ,    the     sheet    resistivity  varies   from
                                        , while the electrical conductivity varies from                           to
                          . These values are within the range of values obtained by (Lakshmi, 2001). The sheet resistance
and sheet resistivity of the films increase as the thickness increases while the electrical conductivity decreases as the
thickness increase. These show that as the concentration of complexing agent increases, the sheet resistance and sheet
resistivity of the films increase respectively while the conductivity decreases. The values of the resistivity of the films
show that CuSe are semiconducting films.


Volume 1, Issue 6, December 2013                                                                                  Page 3
                            IPASJ International Journal of Electrical Engineering (IIJEE)
                                                                       Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm
A Publisher for Research Motivation........                                      Email: editoriijee@ipasj.org
Volume 1, Issue 6, December 2013                                                               ISSN 2321-600X

    4. Conclusion
We have demonstrated using chemical bath deposition technique, the synthesis and electrical characterization of CuSe
thin film. The sheet resistance of the films were found to varies from                 , the sheet resistivity were found to
vary from                                                  , while the electrical conductivity shows variation
from                             to                        . Our values of the resistivity of the films show that CuSe are
semiconducting films.

References
[1] Haram S K and Santhanam K S V, (1994), Thin Solid Films, 238 21.
[2] Bickulova N N, Biskulova V T and Yugafarva Z A (1995) 10th Int. conf. solid state ionics, ABSV SSI-10
     (Singapore: North Holland Pub.)
[3] Hermann A.M and Fabick L., (1983)J. Crystal Growth, 61, 658-666.
[4] Loferski J. J., J. Appl. Phys. 27, 777 (1956).
[5] Chen W S, Stewark J M and Mickelson R A (1985), Appl. Phys.Lett., 46, 1095, 1695.
[6] Okimura H., Matsumae T., and Makabe R., (1980), Thin Solid Films, 71, 53.
[7] García V.M., Guerrero L.,. Nair M.T.S and Nair P.K., (1999), Effect of Thermal Processing on Optical and
     Electrical Properties of Copper Selenide Thin Films, Superficies y Vacío 9, 213-218.
[8] Lakshimi M., Bindu K., Bini S., Vijay Kumer K.P., Kartha C.S, Abe T. and Kashiuraba Y. (2000), Thin Solid
     Films, 370, 89 – 92.




Volume 1, Issue 6, December 2013                                                                                   Page 4

				
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Description: IPASJ International Journal of Electrical Engineering (IIJEE) Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm A Publisher for Research Motivation........ Email: editoriijee@ipasj.org Volume 1, Issue 6, December 2013 ISSN 2321-600X