On the deactivation of the dopant and electronic structure in reactively sputtered transparent Al-doped ZnO thin films

Horwat, David; Jullien, Maud; Capon, Fabien; Pierson, J.F.; Andersson, Joakim; Endrino, José L.

doi:10.1088/0022-3727/43/13/132003

Cited by 35 publications

(35 citation statements)

References 21 publications

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“…In the sol-gel method, a colloidal solution of polymer particles (the "sol") is prepared from precursors [68, pp. [2][3][4][5][6][7][8]. This sol can be transferred to the substrate by techniques such as dip coating or spin coating.…”

Section: Chemical Solution Based Methodsmentioning

confidence: 99%

“…This is also the case for organic polymer substrates that are used for flexible devices [7, p. 5]. Additionally, the properties of the films can degrade due to the bombardment with negative oxygen ions during the film growth [8,9].…”

Section: Les Films Déposés à Des Températures De Substrat De 200mentioning

confidence: 99%

“…This means that out-of-equilibrium growth techniques are needed for the deposition of AZO films, as secondary phases such as ZnAl 2 O 4 or Al 2 O 3 can be formed [20]. Additionally, the formation of a homologous Al 2 O 3 (ZnO) m phase has been deduced from X-ray absorption near edge structure (XANES) measurements [8,63]. These secondary phases cause a deactivation of the dopant atoms and therefore a degradation of the electrical properties.…”

Section: Properties Of Zinc Oxidementioning

confidence: 99%

“…The formation of secondary phases, such as the homologous Al 2 O 3 (ZnO) m phase, can also be induced by the oxygen ion bombardment. Using XANES, Horwat et al [8] deduced a stronger presence of that phase at substrate positions in front of the target axis in AZO films, that were reactively sputtered at room temperature. Vinnichenko et al [63] found that the formation of the homologous phase occurs independently of the substrate temperature, but the volume fraction of the homologous phase increases above an optimum deposition temperature.…”

Section: Sputter Deposition Of Azo Thin Filmsmentioning

confidence: 99%

“…The bombardment of the growing film with negative oxygen ions is believed to cause the deactivation of charge carriers due to the formation of insulating secondary phases [8,9,63]. The formation of secondary phases has been reported to increase at high substrate temperatures due to the preferential desorption of Zn [63].…”

Section: Paper 2: Restoring the Properties Of Transparent Al-doped Znmentioning

confidence: 99%

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Deposition of Al-doped ZnO films by high power impulse magnetron sputtering

Mickan¹

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Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle.In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N 2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600• C. This improvement can be mostly explained by the increase I in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films. II Populärvetenskaplig sammanfattningFör många viktiga tillämpningar i vårt moderna liv, såsom skärmar till mobiltelefoner eller solceller, är det nödvändigt att ha ett transparent material som har en elektrisk ledningsförmåga. Att både vara transparent och vara elektriskt ledande är en ovanlig materialegenskap. Material som är elektriskt ledande, såsom metaller, är vanligtvis inte transp...

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