- Email: [email protected]
Copper selenide films via screen printing and sintering technique for semiconductor device applications: Synthesis and characterization
Journal Pre-proof Copper selenide films via screen printing and sintering technique for semiconductor device applications: synthesis and characterization Kapil Sharma, D.K. Sharma, Vipin Kumar
PII:
S0030-4026(20)30210-2
DOI:
https://doi.org/10.1016/j.ijleo.2020.164376
Reference:
IJLEO 164376
To appear in:
Optik
Received Date:
29 December 2019
Accepted Date:
8 February 2020
Please cite this article as: Sharma K, Sharma DK, Kumar V, Copper selenide films via screen printing and sintering technique for semiconductor device applications: synthesis and characterization, Optik (2020), doi: https://doi.org/10.1016/j.ijleo.2020.164376
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier.
Copper selenide films via screen printing and sintering technique for semiconductor device applications: synthesis and characterization Kapil Sharma, D. K. Sharma, Vipin Kumar* Department of Physics, KIET Group of Institutions, Ghaziabad, India
ABSTRACT
of
In present investigation polycrystalline copper selenide (CuSe) film was grown on glass substrate via economical & non vacuum based screen-printing and sintering technique. Optimum parameters
ro
to grow good quality films were found. Grown film was analyzed structurally, morphologically, optically and electrically. The film was uniform and had good adherence to substrate.
-p
Polycrystalline nature of film with hexagonal structure was confirmed through XRD analysis. Presence of copper (Cu) and selenium (Se) was exhibited by EDS spectrograph. Direct type of
re
optical band gap of 2.15 eV for the CuSe film was established by optical characterization. The temperature dependent electrical conductivity (DC) confirmed the semiconducting behavior of the
lP
film. Larger forward current at all voltages indicates the reasonably good conductivity of the film. Hall Effect measurement shows p-type of conduction for the film.
Jo
ur na
Keywords: CuSe, XRD; Band gap; Conductivity.
___________________________________________________________________________________________ *
Corresponding Author E-mail: [email protected] Fax: 91-1232-262060
1. Introduction Films of metal selenides (crystalline and amorphous both) are of high significance due to their technical importance. Out of all metal selenides, CuSe is one of the widely studied I-VI p-type semiconducting material because of its remarkable optical, electronic properties. It has inherent applications in the field of electro-optical devices, solar cell, photovoltaic devices, thermo electric converter and many more [1-2]. Copper selenide alloy exists in distinct stoichiometry like CuSe, Cu2Se, Cu3Se2 and Cu5Se4 along with non-stoichiometric Cu2-XSe [23]. Depending on growth process and stoichiometry, different crystalline phases of CuSe has
of
been described in literature such as cubic, hexagonal, tetragonal and orthorhombic [2]. CuSe films for using in wide range of applications can be grown by various vacuum based and
ro
non-vacuum based methods such as thermal evaporation [4], vacuum evaporation [5], chemical bath deposition [6], spray pyrolysis method [7] and solution growth technique [8] etc. Most of
-p
these methods need sophisticated technical equipments and high temperature in vacuum, which results into the increase in expenses of these methods.
Objective of present research is to grow CuSe film on well cleaned glass substrate by employing
re
inexpensive, adaptable, time saving, less polluting and non-vacuum based screen-printing and sintering technique. This technique is suitable for large area substrate deposition of any shape
lP
and size [9]. Recent literature indicates that this technique is productively used for growing the films of various metal selenides, metal sulphides and metal oxides [10]. In this context, present study proposes the growth of CuSe film via screen printing and sintering technique for the first
ur na
time. Grown film was investigated structurally, optically and electrically for semiconductor device applications.
Experimental Procedure
In order to grow CuSe film via screen –printing and sintering technique, stoichiometric amount
Jo
(1:1) of constituent elements Copper (Cu) and Selenium (Se) were alloyed in a mortar and pestle. For complete and homogeneous miscibility of copper and selenium nonstop vibrational shaking was done for 30 min. A Slurry having CuSe alloy, 10% weight of Copper chloride and a suitable amount of ethylene glycol were carefully mixed. Copper chloride and ethylene glycol was taken as an adhesive and binder respectively. The obtained paste was then used to grow CuSe film via screen printing technique on well cleaned glass substrate. Initial drying to avoid the cracks in the film was carried out at 120°C for 2 hours on a hot plate. Finally the dried film was sintered in a furnace at 200°C for 10 min to decompose the remaining organic substances.
A thickness of 2 µm for the film was obtained by Taylor Hobson instrument. Structural features of film was analyzed with a Philips x-ray diffractometer model PW 11450/09 with Cu-Kα radiation (λ=1.5405A0) source. The surface morphology and compositional analysis of the film was done by using scanning electron microscopy and EDS spectroscopy respectively. The optical feature (Reflection spectra) of the film was measured in the (100-900) nm wavelength range by using a Hitachi U-3400 Spectrophotometer. Evaluation of band gap for the film was done using Tauc plot. Current-voltage measurement for the film was made on a (Keithley 6514) source meter. Typical two probe method was employed for the measurement of DC electrical conductivity in dark. Hall Effect evaluations for the film were made at room temperature by
ro
of
ECOPIA (HMS-500) Hall Effect set up.
2. Results and discussion
-p
3.1. X-ray diffraction analysis
X-ray spectroscopy (XRD) is a nondestructive and valuable technique to explore the structure of
re
atoms. This technique can be explored to study the structure, crystallinity, phase composition and the grain size of the material under investigation. Fig. 1 depicts XRD plot of CuSe screen-printed
lP
and sintered film. The CuSe film was scanned in the 2θ range 30°- 75°. Materialization of well crystallized CuSe film was showed by strong and sharp diffraction peaks [11]. XRD plot shows that CuSe film is oriented along different planes displaying a polycrystalline nature. These planes
ur na
are (103), (110), (114), (108) and (116). These peaks were in fine agreement with the standard JCPDS data which confirms the growth of single phase hexagonal structure of CuSe. It can be clearly seen that the major peak (114) is strongly overshadow the other peaks indicating the preferred orientation of crystallites along (114) plane. The grain size (average) of the CuSe film
Jo
was analyzed using the popular Debye-Scherer formula [12]. D
0.94 . cos
Where λ depicts the x-ray wavelength (in nanometer), θ is the Bragg’s diffraction angle (in radian), and β is the FWHM of the xrd peak appearing at the diffraction angle θ. The grain size (average) as analyzed from X-ray line broadening peak and above formula were found to be about 92 nm. The cell constants ‘a’ and ‘c’ for hexagonal phase of CuSe film was found to be 3.954 A0 and 17.113 A0; which are well consistent with the reported cell constants for CuSe [1]
3.2. Surface morphology and compositional analysis The image of scanning electron micrograph (SEM) of CuSe screen-printed and sintered film is revealed in Fig.2. The micrograph shows the uniform distribution of grains on entire surface. Some cracks were also visible in the micrograph. The grains having well-defined boundaries with small size are observed. Energy dispersive spectrograph (EDS) showing the presence of copper and selenium in the screen printed sintered CuSe film is given in Fig 3. The average percentage of copper and selenium as estimated from EDS were 53.6 and 46.4% respectively and shows that film is nearly
ro
3.3. Optical analysis
of
stoichiometric with the initial amount of copper and selenium.
Optical features are very important as far as applications of any material in any type of device
-p
fabrication [13]. In this study optical reflection spectra were recorded to evaluate the optical band gap value of CuSe screen-printed and sintered film. Fig.4 shows that the reflection spectra
re
of CuSe screen printed and sintered film. A sudden fall in this spectrum at a particular wavelength confirms the presence of optical band gap in the film. As described by Tauc [14] ‘α’
lP
the absorption coefficient for a semiconductor having direct band gap can be articulated as αhν = C (hν - Eg)1/2 where C is a constant and hν and Eg represents the photon energy and optical band gap respectively. For evaluating the optical band gap from reflection spectra a graph between
ur na
(h) 2 (on y-axis) versus hv (on x-axis) is plotted [10-11]. Here is proportional to Ln [(RmaxRmin) / (R- Rmin)] where reflectance falls from Rmax (maximum reflectance) to Rmin (minimum reflectance) due to the absorption by the material of the film, R shows the reflectance for a given photon energy. So here is expressed in terms of reflectance as Ln [(Rmax - Rmin) / (R - Rmin)] and the optical band gap of the film material is evaluated. A plot of (h)2 or [ hν Ln [(Rmax -
Jo
Rmin) / (R- Rmin)]2 versus hv for screen –printed and sintered CuSe film is demonstrated in Fig. 5. Direct type of optical band gap was confirmed from the linear part of this plot. The extrapolation of straight line part of this plot to energy axis i.e x-axis gives the value of optical band gap of film material. In this study the direct type of band gap of CuSe screen-printed sintered film was observed to be 2.15 eV. The obtained value of optical band gap is in good accord with the earlier published reports on this material [1, 15].
3.4. Electrical analysis Copper selenide has gained wide popularity in last decade because of its strong applications in semiconductor industry. For any semiconductor device applications the value of dark electrical conductivity is considered as a very vital electrical parameter. In this context the dark electrical conductivity measurement of the CuSe screen-printed film was carried out in the range of temperature 300-500 K by a typical two probe set up. The plot of inverse of temperature (1000/T) with log of conductivity (log σDC) is depicted in Fig. 6. The increase in conductivity with rising temperature is an indication of semiconducting behavior of grown CuSe film. The conductivity of CuSe film was observed to be of the order of 10-3 (Ohm cm)-1, which is well
with temperature is expressed as:
ro
σ dc = σ0 exp [ -Ea / kT]
of
matched with the previously reported value [1]. The usual relation for variation of conductivity
where all symbols has their usual meaning. For the evaluation of activation energy, it is
-p
customary to use the slope of log σDC against 1000/ T plot. The activation energy is found to be 0.32 eV for screen-printed CuSe film, which is consistent with the earlier reported value [7].
re
To further assess the nature of screen-printed CuSe film the I-V response characteristics were analyzed. Fig.7 presents I-V characteristics (Forward bias) of copper CuSe screen-printed
lP
sintered film. It can be clearly seen from fig.7 that current increases with voltage i.e. current is free to flow through the device. Large value of current (forward) at all values of voltage symbolizes the good conductivity of CuSe film [16]. This remarkable behavior of increase in
ur na
current with increasing voltage is of great interest to improve the efficiency of photovoltaic cell and solar cell.
Study of Hall Effect was explored to examine the material properties of CuSe film. The values of Hall mobility and carrier concentration for CuSe film (sintered at 200°C) were 24.5 cm2/Vs and 24 x 1013/cm3. The positive polarity of Hall coefficient confirmed the p-type conductivity for the
Jo
sintered CuSe film; which is in well confirmation with typically reported for this semiconductor [17].
4. Conclusions We have productively grown CuSe film on well cleaned glass substrate using screen-printing and sintering technique. Grown films were investigated structurally, morphologically, optically and electrically. XRD analysis established the polycrystalline nature of CuSe with hexagonal crystal structure. Result of SEM analysis showed the uniform surface morphology with presence of some cracks on entire film. The Optical study revealed that CuSe screen-printed and sintered film has direct type of band gap at 2.15 eV. The dark electrical conductivity study of the CuSe film supports the semiconducting behavior. The I-V characterization of grown CuSe film was also reported. As confirmed from Hall coefficient sign in this investigation, the CuSe sintered
-p
Declaration of interests
ro
strongly recommends the use of these films in semiconductor devices.
of
film exhibit p-type conductivity. These features of CuSe screen-printed and sintered film
Jo
ur na
lP
re
The authors declare that they have no known competing finanl interests or personal relationships that could have appeared to influence the work reported in this paper.
References [1] P. P. Hankare, A. S. Khomane, P. A. Chate, K.C. Rathod, K. M. Gardakar, Preparation of copper selenide thin films by simple chemical route at low temperature and their characterization, J. Alloys Compd. 469 (2009) 478-482. [2] S. Thirumvalavan, K. Mani, S. Sagadevan, Investigation of the structural, optical and electrical properties of copper selenide thin films, Mater. Res. 18 (2015) 1000-1007. [3] M. Petrovic, M. Gilic, J. Cirkovic, M. Romcevic, N. Romcevic, J. Trajic, I. Yahia, Optical
of
properties of CuSe thin films-Band gap determination, Sci. Sinter. 49 (2017) 167-174.
ro
[4] Y. Yakuphanoglu, C. Viswanathan, Electrical conductivity and single oscillator model
properties of amorphous CuSe semiconductor thin film, J. Non-Cryst. Solids 353 (2007)
-p
2934-2937.
[5] P. Peranantham, Y. L. Jeyachandaran, C. Viswanathan, N. N. Parveena, P.C. Chitra, D.
re
Mangalraj, Sa.K. Narayandass, The effect of annealing on vacuum-evaporated copper selenide
lP
and indium telluride thin films, Mater. Charact. 58 (2007) 756-764. [6] R. H. Bari, V. Ganesan, S. Potadar, L.A. Patil, Structural, optical and electrical properties of chemically deposited copper selenide films, Bull. Mater. Sci. 32 (2009) 37-42.
ur na
[7] A.A. Yadav, Nanocrystalline copper selenide thin films by chemical spray pyrolysis, J. Mater Sci. Mater. Electron. 25 (2014) 1251-1257. [8] S. R. Gosavi, N.G. Deshpande, Y. G. Gudage, R. Sharma, Physical, optical and electrical properties of copper selenide (CuSe) thin films deposited by solution growth technique at room
Jo
temperature, J. Alloys Compd. 448 (2008) 344-348.
[9] K. Sharma, D. K. Sharma, V. Kumar, Synthesis and characterization of screen-coated nickel selenide films for semiconductor device application, Optik 182 (2019) 519-523.
[10] V. Kumar, S. Agarwal, D. K. Dwivedi, Study on optical investigations and DC conduction mechanism in polycrystalline chalcogenide (Cd, Zn) semiconductor films grown by screenprinting method, J. Mater. Sci. Mater. Electron. 28 (2017) 1715-1719.
[11] V. Kumar, K. Sharma, D. K. Sharma, V. G. Masih, Study on mechanically alloyed tin telluride screen-printed films for optoelectronic device applications, Opt. Quant. Electron. 51 (2019) 129. [12] T.C. Tasdemirci, Study of the physical properties of CuS thin films grown by SILAR method, Opt. Quant. Electron.51 (2019) 245. [13] R. A. Zargar, A. H. Shah, M. Arora, F. A. Mir, Crystallographic, spectroscopic and electrical study of ZnO:CdO nanocomposite-coated thin films for photovoltaic
of
applications, Arab. J. Sci. Eng. 44 (2019) 6631-6636.
ro
[14] J. Tauc (Ed). Amorphous and liquid semiconductors, Plenum press, New York, (1974).
[15] K. Ramesh, S. Thanikaikarasan, B. Bharrathi, Structural, morphological and optical
-p
properties of copper selenide thin films, Int. J. Chem. Tech. Res. 6 (2014) 5408-5411.
re
[16] G. Govindasamy, K. Pal, M. Abd Elkodous, G. S. El-Sayyad, K. Gautam, P. Murugasan, Growth dynamics of CBD-assisted nanostructured thin film: optical,
30 (2019) 16463-16477.
lP
dielectric and novel switchable device applications, J. Mater. Sci. Mater. Electron.
ur na
[17] L. N. Maskaeva, E. A. Fedorova, V. F. Markov, M. V. Kuznetsov, O. A. Lipina, A. V. Pozdin, Copper (I) selenide thin films: composition, morphology, structure and
Jo
optical properties, Semiconductors 52 (2018) 1334-1340.
Figure Captions: Fig. 1: X-ray diffraction pattern of screen-printed and sintered CuSe film. Fig. 2: SEM (top view micrograph) image of screen-printed sintered CuSe film. Fig. 3: EDS spectra of screen-printed sintered CuSe film. Fig. 4: Reflection spectra of screen-printed sintered CuSe film. Fig. 5: Energy Band gap determination of screen- printed sintered CuSe film from reflection spectra.
of
Fig. 6: Plot of logσ dc versus 1000/T of CuSe screen-printed sintered film.
Jo
ur na
lP
re
-p
ro
Fig. 7: I-V characteristics of screen-printed sintered CuSe film.
of
ro
-p
re
lP
ur na
Jo Fig.1
of
ro
-p
re
lP
ur na
Jo Fig.2
of
ro
-p
re
lP
ur na
Jo Fig.3
of
ro
-p
re
lP
ur na
Jo Fig.4
of
ro
-p
re
lP
ur na
Jo
Fig.5
of
ro
-p
re
lP
ur na
Jo Fig.6
of
ro
-p
re
lP
ur na
Jo Fig.7
PII:
S0030-4026(20)30210-2
DOI:
https://doi.org/10.1016/j.ijleo.2020.164376
Reference:
IJLEO 164376
To appear in:
Optik
Received Date:
29 December 2019
Accepted Date:
8 February 2020
Please cite this article as: Sharma K, Sharma DK, Kumar V, Copper selenide films via screen printing and sintering technique for semiconductor device applications: synthesis and characterization, Optik (2020), doi: https://doi.org/10.1016/j.ijleo.2020.164376
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier.
Copper selenide films via screen printing and sintering technique for semiconductor device applications: synthesis and characterization Kapil Sharma, D. K. Sharma, Vipin Kumar* Department of Physics, KIET Group of Institutions, Ghaziabad, India
ABSTRACT
of
In present investigation polycrystalline copper selenide (CuSe) film was grown on glass substrate via economical & non vacuum based screen-printing and sintering technique. Optimum parameters
ro
to grow good quality films were found. Grown film was analyzed structurally, morphologically, optically and electrically. The film was uniform and had good adherence to substrate.
-p
Polycrystalline nature of film with hexagonal structure was confirmed through XRD analysis. Presence of copper (Cu) and selenium (Se) was exhibited by EDS spectrograph. Direct type of
re
optical band gap of 2.15 eV for the CuSe film was established by optical characterization. The temperature dependent electrical conductivity (DC) confirmed the semiconducting behavior of the
lP
film. Larger forward current at all voltages indicates the reasonably good conductivity of the film. Hall Effect measurement shows p-type of conduction for the film.
Jo
ur na
Keywords: CuSe, XRD; Band gap; Conductivity.
___________________________________________________________________________________________ *
Corresponding Author E-mail: [email protected] Fax: 91-1232-262060
1. Introduction Films of metal selenides (crystalline and amorphous both) are of high significance due to their technical importance. Out of all metal selenides, CuSe is one of the widely studied I-VI p-type semiconducting material because of its remarkable optical, electronic properties. It has inherent applications in the field of electro-optical devices, solar cell, photovoltaic devices, thermo electric converter and many more [1-2]. Copper selenide alloy exists in distinct stoichiometry like CuSe, Cu2Se, Cu3Se2 and Cu5Se4 along with non-stoichiometric Cu2-XSe [23]. Depending on growth process and stoichiometry, different crystalline phases of CuSe has
of
been described in literature such as cubic, hexagonal, tetragonal and orthorhombic [2]. CuSe films for using in wide range of applications can be grown by various vacuum based and
ro
non-vacuum based methods such as thermal evaporation [4], vacuum evaporation [5], chemical bath deposition [6], spray pyrolysis method [7] and solution growth technique [8] etc. Most of
-p
these methods need sophisticated technical equipments and high temperature in vacuum, which results into the increase in expenses of these methods.
Objective of present research is to grow CuSe film on well cleaned glass substrate by employing
re
inexpensive, adaptable, time saving, less polluting and non-vacuum based screen-printing and sintering technique. This technique is suitable for large area substrate deposition of any shape
lP
and size [9]. Recent literature indicates that this technique is productively used for growing the films of various metal selenides, metal sulphides and metal oxides [10]. In this context, present study proposes the growth of CuSe film via screen printing and sintering technique for the first
ur na
time. Grown film was investigated structurally, optically and electrically for semiconductor device applications.
Experimental Procedure
In order to grow CuSe film via screen –printing and sintering technique, stoichiometric amount
Jo
(1:1) of constituent elements Copper (Cu) and Selenium (Se) were alloyed in a mortar and pestle. For complete and homogeneous miscibility of copper and selenium nonstop vibrational shaking was done for 30 min. A Slurry having CuSe alloy, 10% weight of Copper chloride and a suitable amount of ethylene glycol were carefully mixed. Copper chloride and ethylene glycol was taken as an adhesive and binder respectively. The obtained paste was then used to grow CuSe film via screen printing technique on well cleaned glass substrate. Initial drying to avoid the cracks in the film was carried out at 120°C for 2 hours on a hot plate. Finally the dried film was sintered in a furnace at 200°C for 10 min to decompose the remaining organic substances.
A thickness of 2 µm for the film was obtained by Taylor Hobson instrument. Structural features of film was analyzed with a Philips x-ray diffractometer model PW 11450/09 with Cu-Kα radiation (λ=1.5405A0) source. The surface morphology and compositional analysis of the film was done by using scanning electron microscopy and EDS spectroscopy respectively. The optical feature (Reflection spectra) of the film was measured in the (100-900) nm wavelength range by using a Hitachi U-3400 Spectrophotometer. Evaluation of band gap for the film was done using Tauc plot. Current-voltage measurement for the film was made on a (Keithley 6514) source meter. Typical two probe method was employed for the measurement of DC electrical conductivity in dark. Hall Effect evaluations for the film were made at room temperature by
ro
of
ECOPIA (HMS-500) Hall Effect set up.
2. Results and discussion
-p
3.1. X-ray diffraction analysis
X-ray spectroscopy (XRD) is a nondestructive and valuable technique to explore the structure of
re
atoms. This technique can be explored to study the structure, crystallinity, phase composition and the grain size of the material under investigation. Fig. 1 depicts XRD plot of CuSe screen-printed
lP
and sintered film. The CuSe film was scanned in the 2θ range 30°- 75°. Materialization of well crystallized CuSe film was showed by strong and sharp diffraction peaks [11]. XRD plot shows that CuSe film is oriented along different planes displaying a polycrystalline nature. These planes
ur na
are (103), (110), (114), (108) and (116). These peaks were in fine agreement with the standard JCPDS data which confirms the growth of single phase hexagonal structure of CuSe. It can be clearly seen that the major peak (114) is strongly overshadow the other peaks indicating the preferred orientation of crystallites along (114) plane. The grain size (average) of the CuSe film
Jo
was analyzed using the popular Debye-Scherer formula [12]. D
0.94 . cos
Where λ depicts the x-ray wavelength (in nanometer), θ is the Bragg’s diffraction angle (in radian), and β is the FWHM of the xrd peak appearing at the diffraction angle θ. The grain size (average) as analyzed from X-ray line broadening peak and above formula were found to be about 92 nm. The cell constants ‘a’ and ‘c’ for hexagonal phase of CuSe film was found to be 3.954 A0 and 17.113 A0; which are well consistent with the reported cell constants for CuSe [1]
3.2. Surface morphology and compositional analysis The image of scanning electron micrograph (SEM) of CuSe screen-printed and sintered film is revealed in Fig.2. The micrograph shows the uniform distribution of grains on entire surface. Some cracks were also visible in the micrograph. The grains having well-defined boundaries with small size are observed. Energy dispersive spectrograph (EDS) showing the presence of copper and selenium in the screen printed sintered CuSe film is given in Fig 3. The average percentage of copper and selenium as estimated from EDS were 53.6 and 46.4% respectively and shows that film is nearly
ro
3.3. Optical analysis
of
stoichiometric with the initial amount of copper and selenium.
Optical features are very important as far as applications of any material in any type of device
-p
fabrication [13]. In this study optical reflection spectra were recorded to evaluate the optical band gap value of CuSe screen-printed and sintered film. Fig.4 shows that the reflection spectra
re
of CuSe screen printed and sintered film. A sudden fall in this spectrum at a particular wavelength confirms the presence of optical band gap in the film. As described by Tauc [14] ‘α’
lP
the absorption coefficient for a semiconductor having direct band gap can be articulated as αhν = C (hν - Eg)1/2 where C is a constant and hν and Eg represents the photon energy and optical band gap respectively. For evaluating the optical band gap from reflection spectra a graph between
ur na
(h) 2 (on y-axis) versus hv (on x-axis) is plotted [10-11]. Here is proportional to Ln [(RmaxRmin) / (R- Rmin)] where reflectance falls from Rmax (maximum reflectance) to Rmin (minimum reflectance) due to the absorption by the material of the film, R shows the reflectance for a given photon energy. So here is expressed in terms of reflectance as Ln [(Rmax - Rmin) / (R - Rmin)] and the optical band gap of the film material is evaluated. A plot of (h)2 or [ hν Ln [(Rmax -
Jo
Rmin) / (R- Rmin)]2 versus hv for screen –printed and sintered CuSe film is demonstrated in Fig. 5. Direct type of optical band gap was confirmed from the linear part of this plot. The extrapolation of straight line part of this plot to energy axis i.e x-axis gives the value of optical band gap of film material. In this study the direct type of band gap of CuSe screen-printed sintered film was observed to be 2.15 eV. The obtained value of optical band gap is in good accord with the earlier published reports on this material [1, 15].
3.4. Electrical analysis Copper selenide has gained wide popularity in last decade because of its strong applications in semiconductor industry. For any semiconductor device applications the value of dark electrical conductivity is considered as a very vital electrical parameter. In this context the dark electrical conductivity measurement of the CuSe screen-printed film was carried out in the range of temperature 300-500 K by a typical two probe set up. The plot of inverse of temperature (1000/T) with log of conductivity (log σDC) is depicted in Fig. 6. The increase in conductivity with rising temperature is an indication of semiconducting behavior of grown CuSe film. The conductivity of CuSe film was observed to be of the order of 10-3 (Ohm cm)-1, which is well
with temperature is expressed as:
ro
σ dc = σ0 exp [ -Ea / kT]
of
matched with the previously reported value [1]. The usual relation for variation of conductivity
where all symbols has their usual meaning. For the evaluation of activation energy, it is
-p
customary to use the slope of log σDC against 1000/ T plot. The activation energy is found to be 0.32 eV for screen-printed CuSe film, which is consistent with the earlier reported value [7].
re
To further assess the nature of screen-printed CuSe film the I-V response characteristics were analyzed. Fig.7 presents I-V characteristics (Forward bias) of copper CuSe screen-printed
lP
sintered film. It can be clearly seen from fig.7 that current increases with voltage i.e. current is free to flow through the device. Large value of current (forward) at all values of voltage symbolizes the good conductivity of CuSe film [16]. This remarkable behavior of increase in
ur na
current with increasing voltage is of great interest to improve the efficiency of photovoltaic cell and solar cell.
Study of Hall Effect was explored to examine the material properties of CuSe film. The values of Hall mobility and carrier concentration for CuSe film (sintered at 200°C) were 24.5 cm2/Vs and 24 x 1013/cm3. The positive polarity of Hall coefficient confirmed the p-type conductivity for the
Jo
sintered CuSe film; which is in well confirmation with typically reported for this semiconductor [17].
4. Conclusions We have productively grown CuSe film on well cleaned glass substrate using screen-printing and sintering technique. Grown films were investigated structurally, morphologically, optically and electrically. XRD analysis established the polycrystalline nature of CuSe with hexagonal crystal structure. Result of SEM analysis showed the uniform surface morphology with presence of some cracks on entire film. The Optical study revealed that CuSe screen-printed and sintered film has direct type of band gap at 2.15 eV. The dark electrical conductivity study of the CuSe film supports the semiconducting behavior. The I-V characterization of grown CuSe film was also reported. As confirmed from Hall coefficient sign in this investigation, the CuSe sintered
-p
Declaration of interests
ro
strongly recommends the use of these films in semiconductor devices.
of
film exhibit p-type conductivity. These features of CuSe screen-printed and sintered film
Jo
ur na
lP
re
The authors declare that they have no known competing finanl interests or personal relationships that could have appeared to influence the work reported in this paper.
References [1] P. P. Hankare, A. S. Khomane, P. A. Chate, K.C. Rathod, K. M. Gardakar, Preparation of copper selenide thin films by simple chemical route at low temperature and their characterization, J. Alloys Compd. 469 (2009) 478-482. [2] S. Thirumvalavan, K. Mani, S. Sagadevan, Investigation of the structural, optical and electrical properties of copper selenide thin films, Mater. Res. 18 (2015) 1000-1007. [3] M. Petrovic, M. Gilic, J. Cirkovic, M. Romcevic, N. Romcevic, J. Trajic, I. Yahia, Optical
of
properties of CuSe thin films-Band gap determination, Sci. Sinter. 49 (2017) 167-174.
ro
[4] Y. Yakuphanoglu, C. Viswanathan, Electrical conductivity and single oscillator model
properties of amorphous CuSe semiconductor thin film, J. Non-Cryst. Solids 353 (2007)
-p
2934-2937.
[5] P. Peranantham, Y. L. Jeyachandaran, C. Viswanathan, N. N. Parveena, P.C. Chitra, D.
re
Mangalraj, Sa.K. Narayandass, The effect of annealing on vacuum-evaporated copper selenide
lP
and indium telluride thin films, Mater. Charact. 58 (2007) 756-764. [6] R. H. Bari, V. Ganesan, S. Potadar, L.A. Patil, Structural, optical and electrical properties of chemically deposited copper selenide films, Bull. Mater. Sci. 32 (2009) 37-42.
ur na
[7] A.A. Yadav, Nanocrystalline copper selenide thin films by chemical spray pyrolysis, J. Mater Sci. Mater. Electron. 25 (2014) 1251-1257. [8] S. R. Gosavi, N.G. Deshpande, Y. G. Gudage, R. Sharma, Physical, optical and electrical properties of copper selenide (CuSe) thin films deposited by solution growth technique at room
Jo
temperature, J. Alloys Compd. 448 (2008) 344-348.
[9] K. Sharma, D. K. Sharma, V. Kumar, Synthesis and characterization of screen-coated nickel selenide films for semiconductor device application, Optik 182 (2019) 519-523.
[10] V. Kumar, S. Agarwal, D. K. Dwivedi, Study on optical investigations and DC conduction mechanism in polycrystalline chalcogenide (Cd, Zn) semiconductor films grown by screenprinting method, J. Mater. Sci. Mater. Electron. 28 (2017) 1715-1719.
[11] V. Kumar, K. Sharma, D. K. Sharma, V. G. Masih, Study on mechanically alloyed tin telluride screen-printed films for optoelectronic device applications, Opt. Quant. Electron. 51 (2019) 129. [12] T.C. Tasdemirci, Study of the physical properties of CuS thin films grown by SILAR method, Opt. Quant. Electron.51 (2019) 245. [13] R. A. Zargar, A. H. Shah, M. Arora, F. A. Mir, Crystallographic, spectroscopic and electrical study of ZnO:CdO nanocomposite-coated thin films for photovoltaic
of
applications, Arab. J. Sci. Eng. 44 (2019) 6631-6636.
ro
[14] J. Tauc (Ed). Amorphous and liquid semiconductors, Plenum press, New York, (1974).
[15] K. Ramesh, S. Thanikaikarasan, B. Bharrathi, Structural, morphological and optical
-p
properties of copper selenide thin films, Int. J. Chem. Tech. Res. 6 (2014) 5408-5411.
re
[16] G. Govindasamy, K. Pal, M. Abd Elkodous, G. S. El-Sayyad, K. Gautam, P. Murugasan, Growth dynamics of CBD-assisted nanostructured thin film: optical,
30 (2019) 16463-16477.
lP
dielectric and novel switchable device applications, J. Mater. Sci. Mater. Electron.
ur na
[17] L. N. Maskaeva, E. A. Fedorova, V. F. Markov, M. V. Kuznetsov, O. A. Lipina, A. V. Pozdin, Copper (I) selenide thin films: composition, morphology, structure and
Jo
optical properties, Semiconductors 52 (2018) 1334-1340.
Figure Captions: Fig. 1: X-ray diffraction pattern of screen-printed and sintered CuSe film. Fig. 2: SEM (top view micrograph) image of screen-printed sintered CuSe film. Fig. 3: EDS spectra of screen-printed sintered CuSe film. Fig. 4: Reflection spectra of screen-printed sintered CuSe film. Fig. 5: Energy Band gap determination of screen- printed sintered CuSe film from reflection spectra.
of
Fig. 6: Plot of logσ dc versus 1000/T of CuSe screen-printed sintered film.
Jo
ur na
lP
re
-p
ro
Fig. 7: I-V characteristics of screen-printed sintered CuSe film.
of
ro
-p
re
lP
ur na
Jo Fig.1
of
ro
-p
re
lP
ur na
Jo Fig.2
of
ro
-p
re
lP
ur na
Jo Fig.3
of
ro
-p
re
lP
ur na
Jo Fig.4
of
ro
-p
re
lP
ur na
Jo
Fig.5
of
ro
-p
re
lP
ur na
Jo Fig.6
of
ro
-p
re
lP
ur na
Jo Fig.7