At present, the main objective of developing new materials for TCO films is to achieve lower resistivity and higher transmittance in the visible range spectrum. Recently, a combination of dielectrics, semiconductors and metals were used to fabricate transparent conducting oxides offering highly opto-electric performances, combined with excellent environmental stability, reproducibility, and good surface morphology [1, 2]. These structures were influenced by many factors that can effectively improve the opto-electrical performance, such as the nature and the percentage of dopant used [3, 4]. Some research mentioned that doping ZnO with Al at 0.5% produce layers possess good opto-electric performances [5, 6].

The present paper study the influence of the low Al doping (0.5%) on opto-electric performances in two ZnO/Al/ZnO structures with thickness (25nm/5nm/25nm) and (50nm/10nm/50nm), respectively. Thin AZO (ZnO doped with Al at 0.5%) and Al films were deposited on non-ferrous glass (10cm ´10cm) as (AZO/Al/AZO) multilayer structure using magnetron sputtering in DC mode. The layers were deposited successively on glass substrate at room temperature by rotating the substrate holder without breaking the vacuum. The XRD patterns show that the peaks of the spectra correspond to ZnO wurtzite structure. Both films are polycrystalline and have a preferred crystallographic orientation in the (002) plane along the c-axis perpendicular to the substrate surface. In order to show the effects of Al doping in the multilayer structure, the resistivity and optical transmittance are characterized and discussed.

It is found that the low Al doping (0.5%) of the ZnO layers in AZO/Al/AZO tri-layer film present higher opto-electric performances compared at ZnO/Al/ZnO multilayer films. The maximum figure of merit value achieved of AZO/Al/AZO structure is 11.87í—10^-4W^-1 corresponding at the thicknesses (50/10/50 nm), much higher than that obtained with the same thickness of the ZnO/Al/ZnO (3.92´10^-4W^-1).

References

[1] S. Calnan, A. N. Tiwari, Thin Solid Films 518 (2010) 1839.

[2] B. G. Lewis, D. C. Paine, MRS Bulletin 25 (2000) 22.

[3] J. L. Vossen, Physics of Thin Films, Vol 9, Academic Press, New York (1977) 35.

[4] E. Fortunato, L. Raniero, L. Silva, A. Goní§alves, A. Pimentel, P. Barquinha, H. Aguas, L. Pereira, G. Goní§alves, I. Ferreira, E. Elangovan, R . Martins, Sol Engy Mat Sol Cells 92 (2008) 1605.

[5] P. Sagar, M. Kumar, R.M. Mehra, Materials Science- Poland 23 (2005) 3.

[6] S. Tewari, A. Bhattacharjee, PRAMANA- Journal of physics 76 (2011) 153.