40220140501005

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 1, January (2014), © IAEME

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IMPACT OF Sn CONCENTRATION AND HEAT TREATMENT ON STRUCTURAL AND MORPHOLOGICAL PROPERTIES OF THIN

Cd1-xSnxSe FILMS

M.F.A. Alias, Iqbal S. Naji, Hajir Abd Alsatar Alshamary

Physics Department, Science College, University of Baghdad

P.O.Box 47162, Jadiriyah,Baghdad / IRAQ ABSTRACT Cadmium tin selenide (Cd1-xSnxSe) alloy are prepared and thin Cd1-xSnxSe films are

deposited on a glass substrate at different Sn concentration (x=0.00, 0.25, 0.50, 0.75 and 1.00) by

using thermal evaporation technique. The prepared films annealed at temperature equal to 573K and

studied the effect of heat treatment on the structural and morphological properties of the prepared

films. X-ray diffraction pattern reveals a mix of cubic and hexagonal phases.Morphological test

shows the grain size which is almost spherical distributed over the entire surface of the substrate.

Keywords: Cd1-xSnxSe Alloys and Films, Heat Treatment, Structural and Morphological Properties.

I. INTRODUCTION

Cadmium selenide (CdSe) is a direct band gap material semiconductor with band gap

energy of 1.74 eV is a II–VI semiconductor compound material with potential applications in low

cost electronics and optoelectronics devices such as solar cells , photoconductors , thin film

transistors , light emitting diodes biomedical imaging devices , and laser diodes [1-4].Thin films

were prepared by various techniques [5-11]. Crystallize CdSe has either the wurtzite (hexagonal

structure) which exhibits high resistance against photo-corrosion, or the zinc blende (cubic structure).

The cubic structure is metastable and can be transformed to the hexagonal wurtzite structure

following an annealing process [12] or mechanically grinding CdSe samples[13].

SnSe is IV-VI a p-type semiconductor has a phase transition from the orthorhombic to the

cubic at 813 K [4].SnSe has excellent optical and optoelectronic properties, which is widely used as

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sensor and laser materials, thin films polarizer, thermoelectric cooling materials , photovoltaic cells ,

memory switching ,solar photovoltaic devices and infrared electronic devices[1,13]. Thin SnSe films

were deposited by different methods [14-16] .Thin films of Cd chalcogenides and their combination

with elements of groups III–VI have been identified as promising candidates particularly for

photoelectrochemical (PEC) applications [17].

Cadmium tin selenide CdSnSe is a promising material for thin film solar cells because of its

ability to absorb the visible light due to its graded energy gap [18]. Electrolytic deposition [13] and

vacuum evaporation [19] techniques have been employed for deposition of CdSnSe thin films.

In the present work, the Cd1-xSnxSe alloys prepared, then films are deposited on glass

substrate at different Sn concentration and annealed at 573K .The effect of Sn concentration and

annealing temperature on the structural and morphological properties of the prepared film are

investigated.

II.EXPERIMENTAL PROCEDURE

Cd1-xSnxSe compound was synthesized in a quartz tube by taking cadmium metal, tin powder,

and selenium powder in their respective stoichiometric ratios as(x=0.00, 0.25, 0.50, 0.75 and

1.00).The tube was evacuated then sealed. It was slowly heated in an electrical furnace at certain

temperture and kept it at this temperature for 3 hours. Vacuum thermal evaporation technique was

used to deposit Cd1-xSnxSe thin films at room temperature using an Edward coating unit onto cleaned

glass substrates at 10-5

mbar. The prepared thin films were annealed under vacuum at temperature

(Ta) equal to 573K.

X-ray diffraction (XRD)(6000 shimadza) using Cu radiation was used to measure XRD

patterns for prepared films. The inter planer distance (d) was calculated using Bragg,s law which is:

2d sin θ = mλ (1) where m is integer, θ is the Bragg angle and λ is wavelength. D is the grain size, in a polycrystalline

film is measured by Scherer's formula:

(2)

where ∆ (2θ) is the full width at half maximum (in radians) of the peak.

Morphological test was examined by atomic force microscopy (AFM) using scanning probe

microscope type (AA3000) to study the effect of annealing temperature on the morphological

properties.

III. RESULTS AND DISCUSSION

X-ray diffraction experiments have been carried out in order to study the structural properties

of the prepared Cd1-xSnxSe alloys and films, i.e, to investigate the crystallographic phase, the overall

crystalline quality, and the possible texture of those thin films.

Fig.(1) shows the X-ray diffraction for thin Cd 1-xSnxSe alloys.The sharp peaks present in

XRD patterns indicate that the films are polycrystalline in nature and the preferred orientation is

along (111) for x=0.25, 0.5 and 0.75.This result is agreed with that observed by Shaban[18].At


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x=0.0, the preferred orientation is along (100) while for x=1 is (040).All the concentration confirm a

mix phase of hexagonal and orthorhombic structure.

Fig.(2) show the XRD pattern for thin Cd1-xSnxSe films at x=0.0 shows the preferred

orientation is along (002) and other weak peaks (100),(101) and (013)planes and the intensity

increased with the annealing and become more clear and sharp.All the peak were hexagonal phase.

Fig.(3) shows XRD pattern for thin Cd1-xSnxSe film for x=0.25, at room temperature and annealed at

573K. It shows hexagonal and orthorhombic phases of the film with preferred orientation along

(002).Another weak peaks are observed at plans orientation which are (100),(111),(040),(110) and

(112) planes. For the results obtained for thin film for x=0.00 and x=0.25 agreed with that shown by

Kissenger et al [5], Patil et al[9] and Vishwakarama et al [20].They found the preferred orientation

along (002) planes.

Fig.(4) show the XRD pattern for thin Cd1-xSnxSe film for x=0.50 deposited at room

temperature and annealed at 573K.It showed amorphous nature at room temperture and after the

annealing .The films has preferred orientation along (002) and (111) Another peaks are observed at

(100),(101),(040),(041),(110),(200) and(112).It shows mix phase of hexagonal and orthorhombic.

This results agreed with Vishwakarama et al [20], which found the preferred orientation along (002)

planes for CdSe, while Butt et al [14] have found preferred orientation along (111) for SnSe.

The Preferred orientation along (111) and (040) planes for thin Cd1-xSnxSe film for x=0.75 as

showed in Fig.(5). It shows orthorhombic phase for the thin film, before and after the annealing.

These results are agreed with Shaban et al [18] and Dhanasekaran et al [2].

Fig.(6) shows a XRD pattern for thin SnSe film, at room temperature and annealed at

temperture equal to 573K. It shows amorphous nature at room temperture and after the annealing

temperture the film showed prefertial orientation along (111) plane which confirm the orthorhombic

phase. These results are agreed with Mariappan et al [16] and Butt et al [14]. Tables (1) illustrate

the parameters of XRD investigation as affected by Sn concentration and annealing temperature on

thin Cd1-xSnxSe film. It is clear from this Table that all the concentration, the grain size and the

intensity of the peak increase with increasing the anealing temperture.

The topography of the film surfaces has been displayed in the AFM images. The images

confirm the formation of spherically shape. The grains size are small with uniform morphology and

well-defined grain boundaries are observed before the annealing and become too clear after the

annealing except for x=1 (SnSe) show amorphous surface with out well -defined grain boundaries

before the annealing and that change after the annealing process. This agreed with result obtained

from X-ray diffraction investigation. All the films reveal that the films have uniform distribution of

grain size over total coverge of the substrate with compact and fine grained morphology and

homogeneous, with out cracks or holes and well covered to the glass substrate. Fig.(6 )shows the

AFM images for preaperd thin Cd1-xSnxSe films with all concentration of Sn (x=0, 0.25,0.50, 0.75

and .01) which show the effect of annealing on the average crystallite. Table (2) show the effect of x

and annealing temperature on the average crystalline and average roughness.

It shows from the images and Table that for x=0.0, x=0.50, x=0.75 and x=1.0 the average

crystalline and roughness decrease after annealed, while increase for x=0.25.

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 ISSN 0976 – 6553(Online) Volume 5, Issue 1, January (2014), © IAEME

Fig.(1) X-ray diffraction for Cd

Fig.(2) X-ray diffraction for CdSe

Fig.(3) X-ray diffraction for

al Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 1, January (2014), © IAEME

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ray diffraction for Cd1-xSnxSe alloy at different Sn concentration

ray diffraction for CdSe thin films as deposited and annealed at 573K

ray diffraction for thin Cd1-xSnxSe film for x=0.2

al Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),

concentration

thin films as deposited and annealed at 573K

25.

International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 ISSN 0976 – 6553(Online) Volume 5, Issue 1, January (2014), © IAEME

Fig.(4) X-ray diffraction

Fig.(5) X-ray diffraction for thin Cd

Fig.(6) X-ray diffraction for thin Cd

al Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 1, January (2014), © IAEME

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ray diffraction for thin Cd1-xSnxSe film at x=0.50

ray diffraction for thin Cd1-xSnxSe film at x=0.75.

ray diffraction for thin Cd1-xSnxSe film at x=1.

al Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),


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Table.1: The effect of Sn concentration and heat treatment on XRD parameters for thin

Cd1-xSnxSe film x T

(K) 2θexp

(Deg.) 2θth

(Deg.) FWHM

dhkl Exp

(Å) D

(Å) dhkl Std

(Å) hkl phase

23.977 23.901 0.462 3.708 165 3.7226 (100) Hex-CdSe

R.T 25.272 25.354 0.324 3.521 237 3.5076 (002) Hex-CdSe

27.029 27.080 0.462 3.296 166 3.2883 (101) Hex-CdSe 0.00 45.803 0.740 1.979 110 1.9801 (013) Hex-CdSe

23.918 23.901

0.339 3.717 226 3.7226 (100) Hex-CdSe

573 25.417 25.354 0.193 3.501 397 3.5076 (002) Hex-CdSe

27.110 27.080 0.435 3.287 177 3.2883 (101) Hex-CdSe

46.022 0.580 1.971 140 1.9801 (013) Hex-CdSe

24.095 23.901 0.449 3.690 171 3.7226 (100) Hex-CdSe

25.666 25.354 0.561 3.468 137 3.5076 (002) Hex-CdSe

R.T 30.379 30.283 0.505 2.940 154 2.9527 (111) Orth-SnSe

31.108 30.644 0.393 2.873 198 2.8925 (040) Orth-SnSe

42.328 0.505 2.134 159 2.1493 (110) Hex-CdSe

44.572 44.073

0.729 2.031 111 2.0540 (150) Orth-SnSe 0.25 23.792 23.901 0.409 3.737 187 3.7226 (100) Hex-CdSe

25.272 25.354 0.462 3.521 166 3.5076 (002) Hex-CdSe

30.358 30.283 0.324 2.942 240 2.9527 (111) Orth-SnSe

573 30.775 30.644 0.356 2.903 218 2.8925 (040) Orth-SnSe

37.757 0.416 2.381 190 2.3804 (041) Orth-SnSe

42.012 0.509 2.149 158 2.1493 (110) Hex-CdSe

49.595 49.699 0.601 1.837 137 1.8326 (112) Hex-CdSe

R.T - - - - - - -

24.116 23.901 0.462 3.687 165 3.7226 (100) Hex-CdSe

25.364 25.354 0.555 3.509 138 3.5076 (002) Hex-CdSe

29.526 27.080 0.370 3.023 209 3.0538 (101) Orth-SnSe 0.50 30.451 30.283 0.462 2.933 168 2.9527 (111) Orth-SnSe

573 30.913 30.644 0.324 2.890 240 2.8925 (040) Orth-SnSe

37.803 0.509 2.378 156 2.3804 (041) Orth-SnSe

41.965 41.968 0.647 2.151 124 2.1493 (110) Hex-CdSe

47.699 48.845 0.462 1.905 177 1.8613 (200) Hex-CdSe

49.780 49.699 0.925 1.830 89 1.8326 (112) Hex-CdSe

R.T 29.930 30.283 0.912 2.983 85 2.9527 (111) Orth-SnSe 0.75 573 30.497 30.283 0.277 2.929 280 2.9527 (111) Orth-SnSe

31.006 30.644 0.555 2.882 140 2.8925 (040) Orth-SnSe 1.00 R.T - - - - - - -

573 30.491 30.283 0.842 2.929 92 2.9527 (111) Orth-SnSe


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R.T

Ta=375K

(a)

R.T

R.T

R.T Ta=573K

(b)

Ta=573K R.T

(c)


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Fig.(7) AFM images for thin Cd1-xSnxSe films at R.T, 573K and different Sn concentration (a) x=0.0 (b) x=0.25 (c) x=0.50 (d) x=0.75 (e) x=1.0

Table.2: The effect of heat treatment on average crystalline and roughness

for thin Cd1-xSnxSe films Average roughness Average crystallite(nm) x Ta (K)

1.73 100.83 0.00 R.T

0.477 86.86 0.25

0.501 72.51 0.50

0.453 80.12 0.75

0.904 109.89 1.00

0.186 92.46 0.00 573

1.51 103.28 0.25

0.244 72.60 0.50

0.421 80.94 0.75

0.735 75.17 1.00

R.T

R.T

(d)

R.T Ta=573 K

R.T Ta=573K

(e)


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IV. CONCLUSIONS

Thin Cd1-xSnxSe films are prepared from prepared alloys at various Sn concentration and heat

treatment. In general the structure for all prepared films at different Sn concentration has a mix phase

of hexagonal and orthorhombic structure. The grains size are small within nano scale and uniform

morphology and well-defined grain boundaries are observed before the annealing and become too

clear after the annealing except for x=1.

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Engineering & Technology (IJARET), Volume 4, Issue 4, 2013, pp. 38 - 49, ISSN Print:

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