Effect Of Zinc Oxide RF Sputtering Pressure on the Structural and Optical Properties of ZnO/PEDOT:PSS Inorganic/Organic Heterojunction

Document Type : Articles


Department of Electrical Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran


Zinc oxide nanostructures are deposited on glass substrates in the presence
of oxygen reactive gas at room temperature using the radio frequency magnetron
sputtering technique. In this research, the effects of zinc oxide sputtering pressure on the
nanostructure properties of the deposited layer are investigated. The deposition pressure
varies from 7.5 to 20.5 mTorr. AFM results show that with an increase in the deposition
pressure, the grain size increases and the surface roughness decreases. The energy gap
measured for the zinc oxide layers deposited at the pressures of 7.5, 14 and 20.5 mTorr
was 3.26, 3.18, and 3.19 eV, respectively. In order to investigate the junction between
zinc oxide and poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS),
a polymeric layer of thickness of 50 nm is deposited on a 300 nm zinc oxide layer by
spin coating technique. The dark I-V characteristics indicate that the reverse saturation
current density is 1.82 10-6, 1.96 10-7 and 7.58 10-8 A/cm2 for the deposition
pressures of 7.5, 14, and 20.5 mTorr, respectively. By increasing the deposition pressure
the ideality factor of the resulting Schottky barrier dropped from 3.4 to 1.7. The
effective Schottky barrier height of 0.73, 0.78, and 0.81 eV was obtained for the same
order of deposition pressures. It was found that the highest optical response could be
obtained for the samples deposited at the deposition pressure of 14 mTorr..


[1] F. J. Klupfel, F.-L. Schein, M. Lorenz, H. Frenzel, H. von Wenckstern and M. Grundmann. Comparison of ZnO-Based JFET, MESFET, and MISFET. IEEE Trans. Electron Devices 60 (2013, June) 1828–1833.
Available: https://ieeexplore.ieee.org/document/6515349
[2] M. Nakano, T. Makino, A. Tsukazaki, K. Ueno, A. Ohtomo, T. Fukumura,
H. Yuji, S. Akasaka, K. Tamura, K. Nakahara, T. Tanabe, A. Kamisawa,
and M. Kawasaki. Transparent polymer schottky contacts for a high performance visible-blind ultraviolet photodiode based on ZnO. Appl. Phys. Lett. 93 (2008, Sep) 1-3.
Available: https://aip.scitation.org/doi/10.1063/1.2989125
[3] M. Shafiei, J. Yu, R. Arsat, K. Kalantar-zadeh, E. Comini, M. Ferroni, G. Sberveglieri and W. Wlodarski. Reversed bias Pt/nanostructured ZnO Schottky diode with enhanced electric field for hydrogen sensing. Sens. Actuators, B: Chem 146 (2010, Apr) 512-507.
Available: https://www.sciencedirect.com/science/article/pii/S0925400509009642
[4] N. Hernandez-Como, et al. Ultraviolet photodetectors based on low temperature processed ZnO/PEDOT:PSS Schottky barrier diode. Materials Science in Semiconductor Processing 37 (2015, Sep) 14-18.
Available: https://www.sciencedirect.com/science/article/pii/S1369800114007550
[5] L.J. Brillson, Y. Lu. ZnO Schottky barriers and Ohmic contacts. Applied Physics Letters 109 (2011, Jun) 1-33.
Available: https://aip.scitation.org/doi/10.1063/1.3581173
[6] S. Vempati, S. Chirakkara, J. Mitra, P. Dawson, K.K. Nanda and S.B. Krupanidhi. Unusual photoresponse of indium doped ZnO/organic thin film heterojunction. Appl. Phys. Lett 100 (2012, Mar) 1-4.
Available: https://aip.scitation.org/doi/10.1063/1.4704655
[7] D.-H. Lee, D.-H. Park, S. Kim and S. Y. Lee. Half wave rectification of inorganic/organic heterojunction diode at the frequency of 1 kHz. Thin Solid Films 519 (2011, Jun) 5658-5661.
Available: https://www.sciencedirect.com/science/article/pii/S0040609011006675
[8] S. J. Mousavi. First–Principle Calculation of the Electronic and Optical Properties of Nanolayered ZnO Polymorphs by PBE and mBJ Density Functionals. Journal of Optoelectronical Nanostructures 2 (2017, Dec) 1-18.
Available: http://jopn.miau.ac.ir/article_2570.html
[9] S. Inguva, R. K.Vijayaraghavan, E. McGlynn and J. P. Mosnier. High quality interconnected core/shell ZnO nanorod architectures grown by pulsed laser deposition on ZnO-seeded Si substrates. Superlattices and Microstructures 101 (2017, Jan) 8-14.
Available: https://www.sciencedirect.com/science/article/pii/S0749603616304669
[10] T. Yan, C.-Y. J. Lu, R. Schuber, L. Chang, D. M. Schaadt, M. M. C. Chou, K. H. Ploog and C.-M. Chiang. Growth of c-plane ZnO on γ-LiAlO2 (1 0 0) substrate with a GaN buffer layer by plasma assisted molecular beam epitaxy. Applied Surface Science 351 (2015, Oct) 824-830.
Available: https://www.sciencedirect.com/science/article/pii/S0169433215013446
[11] Y. Zhao, Ch. Li, M. Chen, X. Yu, Y. Chang, A. Chen, H. Zhu and Z. Tang. Growth of aligned ZnO nanowires via modified atmospheric pressure chemical vapor deposition. Physics Letters A 380 (2016, Dec) 3993-3997.
Available: https://www.sciencedirect.com/science/article/abs/pii/S0375960116303528
[12] M. Borhani Zarandi, H. Amrollahi Bioki. Effects of Cobalt Doping on Optical Properties of ZnO Thin Films Deposited by Sol–Gel Spin Coating Technique. Journal of Optoelectronical Nanostructures 2 (2017, Dec) 33-44.
Available: http://jopn.miau.ac.ir/article_2572.html
[13] R. Nandi and S . S. Major. The mechanism of growth of ZnO nanorods by reactive sputtering. Applied Surface Science 399 (2017, Dec) 305-312.
Available: https://www.sciencedirect.com/science/article/pii/S0169433216328148
[14] J. Ganji. Concept of round non-flat thin film solar cells and their power conversion efficiency alculation. Renewable Energy 136 (2019, Jun) 664-670.
Available: https://www.sciencedirect.com/science/article/pii/S0960148119300333
[15] J. H. Huang, C. Y. Wang, C. P. Liu, W. H. Chu and Y.J. Chang. Large-area growth of vertically aligned ZnO pillars by radio-frequency magnetron sputtering. Applied Physics A 87 (2007, Jun) 749-753.
Available: https://link.springer.com/article/10.1007/s00339-007-3893-0
[16] Z. Dehghani Tafti, M. Borhani Zarandi, H. Amrollahi Bioki. Thermal Annealing Influence over Optical Properties of Thermally Evaporated SnS/CdS Bilayer Thin Films. Journal of Optoelectronical Nanostructures 4 (2019, Mar) 87-98.
Available: http://jopn.miau.ac.ir/article_3387.html
[17] S. Manouchehri, J. Zahmatkesh, M. Hassan Yousefi. Substrate Effects on the Structural Properties of Thin Films of Lead Sulfide. Journal of Optoelectronical Nanostructures 3 (2018, Jun) 1-18.
Available: http://jopn.miau.ac.ir/article_2860.html
[18] M. Mahdavi Matin, M. Hakimi, M. Mazloum-Ardakani. The effect of preparation method and presence of impurity on structural properties and
morphology of iron oxide. Journal of Optoelectronical Nanostructures 2 (2017, Mar) 1-8.
Available: http://jopn.miau.ac.ir/article_2195.html
[19] H.-W. Ra, R. Khan, J. T. Kim, B. R. Kang, K. H. Bai and Y. H. Im. Effects of surface modification of the individual ZnO nanowire with oxygen plasma treatment. Materials Letters 63 (2009, Nov) 2516-2519.
Available: https://www.sciencedirect.com/science/article/abs/pii/S0167577X09006612
[20] B. Angadi, H. C. Park, H. W. Choi, J. W. Choi and W. K. Choi. Oxygen plasma treated epitaxial ZnO thin films for Schottky ultraviolet detection. Journal of Physics D: Applied Physics 40 (2007, Feb) 1422-1425.
Available: https://iopscience.iop.org/article/10.1088/0022-3727/40/5/016/meta
[21] J. Husna, M. Mannir Aliyu, M. Aminul Islam, P. Chelvanathan, N. Radhwa Hamzah, M. Sharafat Hossain, M. R. Karim, N. Amin. Influence of Annealing Temperature on the Properties of ZnO Thin Films Grown by Sputtering. Energy Procedia 25 (2012, Jun) 55-61.
Available: https://www.sciencedirect.com/science/article/pii/S1876610212011708
[22] B. K. Sharma, N. Khare and Sh. Ahmad. A ZnO/PEDOT:PSS based inorganic/organic heterojunction. Solid State Communications 149 (2009, Mar) 771-774.
Available: https://www.sciencedirect.com/science/article/pii/S0038109809001203
[23] S. M. Sze and Kwok K. Ng, Physics of Semiconductor Devices, 3rd ed. New York, Wiley Interscience (2007).