ELECTRODEPOSITION, CHARACTERIZATION AND MODELING OF TECHNOLOGICALLY INTERESTING FILMS

The thesis presents the summary of the work of the three years of Ph.D. concerning the study of several electrodeposition processes spanning from aluminization to the characterization of systems obtained by means of the electrochemical atomic layer deposition (E-ALD) technique. However, the thesis focus mainly on the growth and characterization of sulphides materials and devices grown by meand of E-ALD. This research is grounded on the necessity to overcome the limitations found for the micro and nano-electronics industry. For instance a small portion of the elements table is exploited for the photovoltaics, computation unit and LED production. These process are mainly based on the top-down approach, which participated to the success of the silicon-based micro and nano-electronics industry but limiting the exploitation of the chemical elements to Si and a few other dopants. The adoption of a bottom-up approach to the manufacturing process of the micro and nano-electronics devices could enable the exploitation of a wide range of chemical elements. In principle, the bottom-up approach allows also to directly grow nanosctructures and devices. It should be noticed that, in this field, the quality of the products is usually lower with respect to the top-down approach in terms of crystallinity and chemical purity. Hence, a compelling question is if the bottom-up approach can deliver materials and devices at the necessary level to be exploited by the modern micro and nano-electronics industry. From its infancy, E-ALD is considered as very promising candidate to be answer positively to this question. For long time the E-ALD has been considered to be able to grow only binary compound semiconductors. This opinion is based also on a very simple description of the mechanism underlying the process. Recent results on relatively new ternary and binary compound semiconductors (mainly sulphides) revealed that this description is probably too simple. The lack of thorough characterization of the features of these new materials impaired a more than vague intuition of the actual mechanism of the E-ALD growth. Still, the possibilities of E-ALD for depositing more complex systems than just the binary compound semiconductors are opened. The thesis presents a wide range of operando synchrotron data to study the growth mechanism and the final structure of the E-ALD’s outcomes in order to have a better insight on the growth process. The result is a thorough structural, morphological and spectroscopic characterization of Ag(111)/Cu 2 S, Ag(111)/Cu x Zn y S and Ag(111)/Cu x Zn y S/CdS during their growth or at the end of it. Chemical speciation models has been implemented to study the complex results of the Cu x Zn y S characterization, enabling also the interpretation of its complex morphology and unexpected stoichiometry. The study suggests that the E-ALD process is a complex of three different factors (electrochemistry of the bulk phases, electrochemistry of the surfaces and the accumulation of stress) probably changing their relative importance according to the different stages of the growth. Eventually, the synthesis and characterization of the Ag(111)/CdS/Cu 2 S n-p junction is presented as a proof of concept that, although the outcome of the E-ALD process is quite complex, this doesn’t impair it from being able to grow nanoelectronic devices with a quality comparable to the bottom-up approach but with wider chemical variability.