The HD-PIT project aims to understand and engineer the processes inducing a phase transition from the diamond cubic (dc) into the hexagonal diamond (hd) phase by nanoindentation of SiGe layers epitaxially grown on Si wafers. The final goal is to realize… Read more hd SiGe pits in the films, which could be subsequently used as a template for the realization of hd SiGe epitaxial dots. Silicon technology drives phenomenal advances in nano-electronics, but the indirect nature of Si bandgap hinders exploitation for photonic integrated circuits. Interestingly, theoretical studies have shown that the hd phase of SiGe, with a relatively high Ge content, turns the alloy into a direct bandgap material. Recently, SiGe with the hd structure has been obtained by epitaxial growth on III-V nanowires. Confirming the predictions, a direct bandgap has been demonstrated. Despite the high potential of these polytypes for photonics, the present synthesis approaches are not fully compatible with Si technology. Another approach based on pressure-induced phase transition has been exploited, obtaining occasionally the Si and Ge hd phase by nanoindentation. However, a clear control of the hd phase appearance in this context is still lacking neither it is verified for SiGe alloys. The project will explore the possibility to realize a controlled and extended transition to the hd phase by nanoindentation of Ge-rich SiGe films, being an optimal solution to obtain desired electronic properties in a system fully integrated into the Si platform. A synergic approach leveraging multiscale atomistic simulations, micro-Raman and electron microscopy experiments, will be used for a rational design of the nanoindentation experiments. In fact, it will allow for an efficient search through the large parameter space that includes a wide range of nanoindentation conditions and many different characteristics of the SiGe films. Because of the high Ge content of the SiGe films, they will be grown under strong out-of-equilibrium conditions on Si substrate by low-energy plasma-enhanced chemical vapour deposition (LEPECVD). While Raman micro-spectroscopy and transmission electron microscopy will be used to assess the formation of the hd phase, the multiscale atomistic simulations will guide the experiments. They will involve first-principle calculations of the electronic, structural, and thermodynamic properties of the hd compounds at the atomic scale, but also larger-scale classical molecular dynamics simulations of the whole indentation process, exploiting state-of-the-art interatomic potential based on machine learning approaches. The project will provide fundamental knowledge to boost the monolith integration of hd group IV compounds for on-chip optical components, such as nano-laser and optical amplifiers, thus enabling optical network-on-chip and being breakthroughs for quantum computing, high performance and green ICT.

Few-metal atoms aggregates deposited on solid supports, usually oxides, are close to the optimal limit of size/activity ratio in heterogenous catalysis. Downsizing to the sub-nano dimension allows to save precious material and maximise the ratio of active metal atoms in the aggregates. The… Read more aim of the present project is to study the growth, aggregation, chemical nature and reactivity of sub-nanometric metal clusters at the surfaces of ultrathin oxide films. The motivation for using ultrathin films rather than bulk surfaces is that they allow for additional degrees of freedom, permitting a fine tuning of the cluster properties. Indeed, for thicknesses of few monolayers the properties of the clusters' atoms may be influenced, e.g., by the strain in the oxide film due to the lattice mismatch with the metal support and by charge transfer occurring via electron tunnelling from the metal support through the ultrathin film. The presence of oxygen at the metal/oxide interface may also play a role in determining the oxidation state, the morphology and the stability of the metal clusters at the oxide surfaces. We propose to investigate aggregates of different metal atoms (Ni and Pd) deposited on the surface of MgO films supported on Ag(100). The clusters will be characterised with state-of-the-art experimental surface science techniques such as scanning probe microscopies (STM and AFM) and electron based spectroscopies (XPS, STS, HREELS). Experimental results will be supported by first-principles DFT based calculations (acronyms defined in the main text). The catalytic activity will be investigated for three reactions: CO2 methanation, methane oxidation to methanol, and steam reforming. These reactions are of paramount relevance to green chemistry and fine synthesis, since they deal with the usage of harmful greenhouse gases (CO2, CH4) and with the prototypical activation of very stable C-O and C-H bonds. We aim at exploring the reactivity of Ni and Pd clusters both toward reduction (CO2 methanation) and oxidation (methane oxidation and steam reforming) reactions, based on the different affinity to Ministero dell'Università e della Ricerca MUR - BANDO 2022 oxygen displayed by Ni and Pd and aiming at performing different processes on the same, well-defined catalytic system. In some selected cases, we plan to study, within this project, also the morphology, stability and reactivity of bimetallic NiPd clusters. The strength of the SUMCAR project relies on the possibility to define the active particles at the atomic level by combining microscopy, spectroscopy and atomistic simulations, and to follow the evolution of the adsorbed reactant molecules through the reactions. The project benefits of previous consolidated common works carried out by the team to characterise the spontaneous oxidation of Ni nanoclusters on MgO/Ag(100). Preliminary promising results display the tendency of these aggregates to strongly activate CO molecules under relatively mild thermal conditions.

The pandemic crisis, the numerous public demonstrations in support of climate and ecological justice, and the recent energetic crisis have pointed out the actual importance of reaching a rapid and complete ecological transition towards technological sustainability and energetic independence. Even… Read more if it is well known that the quality of life of the global population is strictly related with the degree of accessibility to energy sources, this simple assumption hides behind itself several issues and criticalities, one above all the correlation existing between the remarkable ecological implications caused by traditional fossil fuels extraction, motions and consumption (with emission of greenhouse gasses, GHG, in the atmosphere) for providing energy, and the increment in soils, water, and air pollution at the basis of the serious climate change that is affecting our planet. The National Recovery and Resilience Plan (NRRP), part of the Next Generation EU financial program, aims at accomplishing relevant scientific and technological advancements in the direction of the green revolution and ecological transition. In this context, photo(electro)chemistry is a very promising and appealing technology able to accomplish the conversion of renewable sources into fuels for energy applications in a greener way. Hence, photo(electro)catalyzed processes involving the CO2 (the major GHG from air pollution) reduction into valuable C2+ products (CO2RR), and hydrogen evolution (HER) from water splitting are among the major promising chemical routes for energy production, alternatives to the traditional fossil fuels. The possibility of exploiting these routes to produce energy at large scale is still strongly affected by the selection of both promising catalysts and suitable process parameters, thus fundamental research is needed to fully understand the driving factors that allow these technologies to be fully exploitable. The PERFECT project aims at investigating in depth the photo(electro)-induced catalytic activities of Cu-containing compounds in CO2RR and HER, by monitoring how changes at the catalyst and process parameters level might enhance the yield of conversion and selectivity of the final products. This approach requires a preliminary survey of the different catalysts (Milestone 1), a deep investigation of possible morphological effects (Milestone 2), and the investigation of possible effects induced by process parameters (Milestone 3). This way, important technological guidelines useful for addressing the still unsolved technological demands in terms of the efficient design of both catalyst and process will be provided. Hence, to realize the project aims, we set up a relatively young and multidisciplinary consortium made up of scientists with expertise in the synthesis of catalytic materials (Project PI, R. Nisticò, UNIMIB), their application in photo(electro)catalysis (M.V. Dozzi, UNIMI), and advanced characterizations (L. Mino, UNITO).