Thickness Dependent Physical Properties of Thermally Evaporated Nanocrystalline CdSe Thin Films

doi:10.1007/s40195-015-0326-5

Abstract

Abstract:

This paper presents a study on thickness dependent physical properties of cadmium selenide thin films. The films of thickness 445, 631 and 810 nm were deposited employing thermal evaporation technique on glass and ITO-coated glass substrates followed by thermal annealing in air atmosphere at 200 °C. These films were subjected to X-ray diffractometer, UV-Vis spectrophotometer, scanning electron microscopy (SEM) and electrometer for structural, optical, surface morphological and electrical analysis respectively. The structural analysis reveals that the films are nanocrystalline in nature with cubic phase and preferred orientation (111). The crystallographic parameters such as lattice constant, inter-planar spacing, grain size, internal strain, dislocation density, number of crystallites per unit area and texture coefficient are calculated and discussed. The optical band gap is found in the range 1.75-1.92 eV and observed to increase with thickness. The SEM study shows that the annealed films are uniform, fully covered and well defined. The electrical analysis shows that the conductivity is varied with film thickness and found within the order of semiconductor behavior.

Key words: Thin films, X-ray diffraction, Optical properties, Electrical properties, Evaporation

Anuradha Purohit, Subhash Chander, Satya Pal Nehra, Mahendra Singh Dhaka. Thickness Dependent Physical Properties of Thermally Evaporated Nanocrystalline CdSe Thin Films[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(10): 1299-1304.

Figures/Tables 8

Fig. 1 XRD patterns of CdSe thin films

Table 1 Crystallographic parameters of CdSe thin films of different thickness

Thickness (nm)	2θ (°)	(hkl)	d (Å)		a (Å)	N × 10¹⁵ (m^-2)
Thickness (nm)	2θ (°)	(hkl)	Obs.	SD	a (Å)	N × 10¹⁵ (m^-2)
445	25.42	(111)	3.50	3.51	6.055	20.3
631	25.46	(111)	3.495	3.51	6.046	46.1
810	25.48	(111)	3.492	3.51	6.041	20.5

Fig. 2 Variation in grain size a, strain and dislocation density b with thickness of CdSe thin films

Fig. 3 Variation in texture coefficient with thickness of CdSe thin films

Fig. 4 Absorbance a and transmittance b optical spectra of CdSe thin films of different thickness

Fig. 5 Tauc plot (αhν)2 versus h ν a and extinction coefficient (k) b of CdSe thin films

Fig. 6 SEM images of CdSe thin films of different thickness: a 445 nm, b 631 nm, c 810 nm

Fig. 7 Current-voltage characteristics of CdSe thin films of different thickness

References 33

[1]	X. Zhang, S. Wang, D. Ding, X. Liu, J.H. Tan, J.K. Furdyna, Y.H. Zhang, D.J. Smith, J. Electron. Mater. 38, 1558(2009)
[2]	Y. Araki, K. Ohkuno, T. Furukawa, J. Saraie, J. Cryst. Growth 301-302, 809(2007)
[3]	W. Lee, W.C. Kwak, S.K. Min, J.C. Lee, W.S. Chae, Y.M. Sung, S.H. Han, Electrochem. Commun. 10, 1699(2008)
[4]	A. Kongkanand, K. Tvrdy, K. Takechi, M. Kuno, P.V. Kamat, J. Am. Chem. Soc. 130, 4007(2008)
[5]	J. Kaur, S.K. Tripathi, J. Alloys Compd. 622, 953(2015)
[6]	Y.M. Park, R. Andre, J. Kasprzak, L.S. Dang, E.B. Amalric, Appl. Surf. Sci. 253, 6946(2007)
[7]	C.M. Shen, X.G. Zhang, H.L. Li, Appl. Surf. Sci. 240, 34(2005)
[8]	S. Velumani, X. Mathew, P.J. Sebastian, S.K. Narayandass, D. Mangalaraj, Sol. Energy Mater. Sol. Cells 76, 347 (2003)
[9]	A. Purohit, S. Chander, A. Nehra, S.P. Nehra, C. Lal, M.S. Dhaka, AIP Conf. Proc. 1661, 050009(2015)
[10]	S. Erat, H. Metin, M. Ari, Mater. Chem. Phys. 111, 114(2008)
[11]	M.A.H. Perez, J.A. Hernandez, G.C. Puente, J.R.V. Garcia, E.R. Salinas, Phys. E 40, 2535 (2008)
[12]	R. Kumar, G. Kumar, A. Umar, J. Nanosci. Nanotechnol. 14, 1911 (2014)
[13]	A. Goswami, Thin film fundamentals (New Age International Publishers, New Delhi, 2014)
[14]	D.J. Miller, D. Hanemann, Sol. Energy Mater. 4, 223(1981)
[15]	R.A. Boudreau, R.D. Rauh, Sol. Energy Mater. 7, 385(1982)
[16]	M. Bouroushian, J.C. Got, Z. Loizos, N. Spyrellis, G. Maurin, Thin Solid Films 381, 39 (2001)
[17]	P.P. Hankare, A.D. Jadhav, V.M. Bhuse, A.S. Khomane, K.M. Garadkar, Mater. Chem. Phys. 80, 102(2003)
[18]	P. Gaur, B.P. Malik, A. Gaur, Phys. B 457, 332 (2015)
[19]	R.B. Kale, C.D. Lokhande, Appl. Surf. Sci. 223, 343(2004)
[20]	M.G.S.A. Basheer, K.S. Rajni, V.S. Vidhya, V. Swaminathan, A. Thayumanavan, K.R. Murali, M. Jayachandran, Cryst. Res. Technol. 46, 261(2011)
[21]	Y. Zhao, Z. Yan, J. Liu, A. Wei, Mater. Sci. Semicond. Process. 16, 1592(2013)
[22]	A. Purohit, S. Chander, A. Nehra, S.P. Nehra, C. Lal, M.S. Dhaka, AIP Conf. Proc. 1665, 080017(2015)
[23]	A. Purohit, S. Chander, S.P. Nehra, C. Lal, M.S. Dhaka, Opt. Mater. 47, 345(2015)
[24]	A. Purohit, S. Chander, S.P. Nehra, M.S. Dhaka, Phys. E 69, 342 (2015)
[25]	Powder Diffraction Data File, Joint Committee of Powder Diffraction Standard, International Center for Diffraction Data, USA, Card No.65-2891, 19-0191
[26]	R.S. Reddy, A. Sreedhar, A.S. Reddy, S. Uthanna, Adv. Mater. Lett. 3, 239(2012)
[27]	S. Chander, M.S. Dhaka, Mater. Sci. Semicond. Proc. 40, 708(2015)
[28]	S.P. Nehra, S. Chander, A. Sharma, M.S. Dhaka, Mater. Sci. Semicond. Proc. 40, 26(2015)
[29]	K. Alamgir, T. Pervaiz, S. Arif, Energy Source A 34, 297 (2012)
[30]	S.S. Shinde, P.S. Shinde, S.M. Pawar, A.V. Moholkar, C.H. Bhosale, K.Y. Rajpure, Solid State Sci. 10, 1209(2008)
[31]	M. Dhanam, R.R. Parbhu, P.K. Manoj, Mater. Chem. Phys. 107, 289(2008)
[32]	M.T.S. Nair, P.K. Nair, R.A. Zingaro, E.A. Meyers, J. Appl. Phys. 74, 1879(1993)
[33]	A. Purohit, S. Chander, A. Sharma, S.P. Nehra, M.S. Dhaka, Opt. Mater. 49, 51(2015)