Review on robust laser light interaction with titania – Patterning, crystallisation and ablation processes

Abstract

Titanium dioxide is regarded as a very promising semiconducting material that is widely applied in many everyday-use products, devices, and processes. In general, those applications can be divided into energy or environmental categories, where a high conversion rate, and energy and power density are of particular interest. Therefore, many efforts are being put towards the elaboration of novel production routes, and improving the material's properties such as light absorption, and charge concentration, as well as development of the surface area to improve the efficiency of particular process. Typically, bulk doping and surface modifications can be distinguished, applying some sol-gel, chemical vapour deposition, and hydrothermal processes in the presence of dopant precursors. However, development of waste disposal and many up-scaling optimisation routes have to be performed to consider the proposed path worthy of wide scale, commercial use. In contrast to the wet-chemistry methods, laser technology offers unique material treatment by light of a particular wavelength, fluence, and pulse repetition rate. In consequence, the changes can affect the bulk structure or only its surface. Such an approach provides a wide range of possible modifications without the use of any chemical products, and therefore avoids the formation of any by-products. Moreover, knowing the facile scaling up of laser treatment towards a higher technology readiness level, we believe such an approach stands out from synthesis and/or modification carried out first in small flasks and using small amounts of substrates. In this review, we would like to emphasize the results of selected studies presenting possible laser beam and titania interactions ensuring changes in the surface zone or deeply in the internal structure. The works evoked here indicate that this powerful technique can, among other things, provide slight surface melting of titania nanotubes, their phase transition from an amorphous solid to anatase or, when the fluence exceeds a certain threshold, the ablation of material out of the titania target.