Among all transition metal oxides, titanium dioxide (TiO₂) is one of the most intensively investigated materials due to its large range of applications, both in the amorphous and crystalline forms. We have produced amorphous TiO₂ thin films by means of room temperature ion-plasma assisted e-beam deposition, and we have heat-treated the samples to study the onset of crystallization. Herein, we have detailed the earliest stage and the evolution of crystallization, as a function of both the annealing temperature, in the range 250–1000 °C, and the TiO₂ thickness, varying between 5 and 200 nm. We have explored the structural and morphological properties of the as grown and heat-treated samples with Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometry, and Raman spectroscopy. We have observed an increasing crystallization onset temperature as the film thickness is reduced, as well as remarkable differences in the crystallization evolution, depending on the film thickness. Moreover, we have shown a strong cross-talking among the complementary techniques used displaying that also surface imaging can provide distinctive information on material crystallization. Finally, we have also explored the phonon lifetime as a function of the TiO₂ thickness and annealing temperature, both ultimately affecting the degree of crystallinity.

This is the “mobile” era, characterized by a growing demand of flexible substrates for novel products such as curved screens, folding smartphones, and wearable devices. In this framework, plastic electronics represents a suitable technology to replace silicon-based electronics. However, up to now, little attention has been devoted to rendering this technology more environmentally sustainable. It is thus necessary to develop new eco-designed devices that allow recycling of all the components and recovering the valuable materials through sustainable methods. For the first time, we report the fabrication of organic light emitting diodes made on an as-cast biopolymeric flexible substrate. Sodium alginate is a natural biodegradable polymer derived from brown algae; it is water-soluble and easy to manipulate for the realization of flat and transparent foils using an environmentally friendly process. Thus, the active stack can be directly deposited on the biopolymer substrate in a bottom-up architecture with no need for a pretreatment or a buffer layer. In addition, the devices can be disassembled and all of the valuable materials almost entirely recovered. This result opens up new and exciting opportunities for the fabrication of electronic and optoelectronic devices with a green platform for an ambient sustainable circular economy.