Strain dependence electrical resistance and cohesive strength of ITO thin films deposited on electroactive polymer

Abstract

Transparent, conducting, indium tin oxide (ITO) films have been deposited, by pulsed dc magnetron sputtering, on glass and electroactive polymer (poly (vinylidene fluoride)-PVDF) substrates. Samples have been prepared at room temperature by varying the oxygen partial pressure. Electrical resistivity around 8.4x10-4 Ω. cm has been obtained for films deposited on glass, while a resistivity of 1.7x10-3 Ω. cm has been attained in similar coatings on PVDF. Fragmentation tests were performed on PVDF substrates with thicknesses of 28 µm and 110 µm coated with 40 nm ITO layer. The coating´s fragmentation process was analyzed and the crack onset strain and cohesive strength of ITO layers were evaluated.

Indium tin oxide exhibiting high poly-crystallinity on oxygen plasma-treated polyethylene terephthalate surface

“…This is because an additional annealing treatment is needed to transform its structure from amorphous to poly-crystalline. Thus, it is difficult to apply ITO films onto flexible plastic substrates such as polyethylene terephthalate [PET], polyimide, polyethylene naphthalate, and polycarbonate because these polymer substrates have low glass transition temperatures [6]. In general, there are several disadvantages to fabricating ITO on plastic substrates as opposed to glass substrates, which can be fabricated with a relatively low treatment temperature.…”

Explicit relationship between electrical and topological degradation of polymer-supported metal films subjected to mechanical loading

“…The main driving force for this research area is rapid development of flexible electronics concepts and technologies [1,2]. The most straightforward way to characterize the evolution of mechanical damage is to use optical or scanning electron microscopy to track the structural changes at different stages of mechanical loading [3][4][5][6][7][8].…”

“…Additionally, one can record the electrical resistance of a film during mechanical test and correlate the changes in resistance signal to the structural changes within the film under test [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Significant structural degradation, such as cracking of a brittle film under monotonic loading, is indicated by a rapid growth of electric resistance [3][4][5].…”

“…Additionally, one can record the electrical resistance of a film during mechanical test and correlate the changes in resistance signal to the structural changes within the film under test [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Significant structural degradation, such as cracking of a brittle film under monotonic loading, is indicated by a rapid growth of electric resistance [3][4][5]. In the case of ductile films, such as copper, silver or gold, the resistance increases slowly with applied strain and a reference curve which represents the constant volume approximation [7][8][9][10][11] is usually used to estimate the induced mechanical damage.…”

“…This is explained by the increasing probability of random patterns where several cracks are merged together. Equation (3) has a symmetric form with respect to two variables (Cl, l0) and is considered to be the most appropriate for the characterization of real samples since the linear crack density is the typical experimental parameter used for the description of cracking in polymer-supported films [3][4][5][6][7]. However, since C l depends on l 0 , a more rigorous expression of resistance as a function of two independent variables would be…”