Abstract

Abstract

TiO2 is a semiconductor oxide with many applications due to its properties. To increase the electron transport of the material, it is usually doped with transition metal ions so as not to alter its chemical and mechanical stability and thus be able to use this material for the manufacture of solar cells. In this work, the effect of the incorporation of the Mn dopant on the optical and electrical structures of the TiO2 fims grown by chemical methods under different conditions and deposited by the spin coating technique on glass substrates. Using optical spectroscopy, the influence of the starting precursor, thickness of the fims and the concentration of the dopant was mainly observed with respect to transmittance.

Abstract

Graphene deposited on planar surfaces often exhibits sharp and localized folds delimiting seemingly planar regions, as a result of compressive stresses transmitted by the substrate. Such folds alter the electronic and chemical properties of graphene, and therefore, it is important to understand their emergence, to either suppress them or control their morphology. Here, we study the emergence of out-of-plane deformations in supported and laterally strained graphene with high-fidelity simulations and a simpler theoretical model. We characterize the onset of buckling and the nonlinear behavior after the instability in terms of the adhesion and frictional material parameters of the graphene-substrate interface. We find that localized folds evolve from a distributed wrinkling linear instability due to the nonlinearity in the van der Waals graphene-substrate interactions. We identify friction as a selection mechanism for the separation between folds, as the formation of far apart folds is penalized by the work of friction. Our systematic analysis is a first step towards strain engineering of supported graphene, and is applicable to other compressed thin elastic films weakly coupled to a substrate.