Physics of semiconductors and advanced crystals
The group aims to develop innovative processes for future semiconductor devices and other advanced materials using its expertise in structural and electrical characterization and modelling. The experimental activity is based on several laboratories at the DFA for processing, such as a Physical vapor deposition cluster (sputtering and e-beam), Direct Laser Writing, Rapid and Laser Thermal Processing, a chemical laboratory and several characterization techniques, such as Secondary ion mass spectrometry, High resolution X-ray diffraction, Van der Pauw - Hall also at cryogenic temperatures, AFM and related techniques (c-AFM, KPFM, SMM, etc), Raman spectroscopy, optical measurements. In addition to these, at the nearby National Laboratories of Legnaro, the group has access under an agreement between UNIPD-DFA and INFN-LNL to other facilities such as Rutherford Backscattering Spectrometry/Nuclear Reaction Analysis in a channeling configuration, a clean room and chemical laboratory, and additional sputtering equipment. In addition, the group has access to international synchrotron light facilities (ESRF, ELETTRA).
Staff
Full Professors: Marco Bazzan, Davide De Salvador, Andrea Gasparotto, Enrico Napolitani, Andrea Sanson
Assistant Professors: Enrico Di Russo, Valeria Milotti, Francesco Sgarbossa
Technical staff: Nicola Argiolas, Luca Bacci, Sara Carturan, Giorgio Delfitto, Gianluigi Maggioni, Carlo Scian
Post-doc
Stefano Bertoldo, Alessandro Venier
PhD students
Daniele Demeneghi, Daris Fontana, Zhouhe Li, Filippo Nicolasi, Giulia Maria Spataro, Alessandro Tonon, Davide Valzani
External collaborators
Chiara Carraro (INFN, Laboratori Nazionali di Legnaro), Walter Raniero (INFN, Laboratori Nazionali di Legnaro)
Research activities
Group IV semiconductor hyperdoping for information technology, photonics and energy
The activity is aimed at developing materials with novel properties, based on group IV semiconductors (Si, Ge, SiGe, GeSn...), to improve the performance of future devices in various fields such as nanoelectronics, photonics (detection, emission and modification of light in the infrared), photovoltaics, plasmonics, quantum information, sensing, etc.. To this end, we study processes based on irradiation with ultra-short (tens of nanoseconds) laser pulses in the UV, in combination with physical vapor deposition techniques, to incorporate dopants with nanoscale control beyond the limits imposed by equilibrium solid solubility physics (hyperdoping). The processes induce rapid phase transitions (liquid/solid, amorphous/crystalline) characterised by extremely interesting nanoscale physical phenomena.
Contacts: Enrico Napolitani, Enrico Di Russo, Davide De Salvador
Synthesis and processing of two-dimensional quantum semiconductors
In recent years, there has been a growing interest in two-dimensional quantum materials, and in particular in Transition Metal Dichalcogenides (TMD), such as MoS2, MoSe2, WS2, etc. Unlike the well-known graphene, they have an energy gap, a property that makes them extremely interesting as potential substitutes for silicon in future high-performance nanoelectronic devices. The group aims to study methodologies to synthetise TMD materials, modify their properties, and fabricate devices, combining UV-pulsed laser processes, physical vapor deposition techniques and microlithography. The activity is aimed at applications in various fields, such as nanoelectronics, photovoltaics, photocatalysis and quantum information.
Contacts: Enrico Napolitani, Enrico Di Russo
Development of High-Purity Germanium Detectors for Gamma Ray Detection
For several years, the group has been involved in developing Pulsed Laser Melting (PLM) technology, applied to the fabrication of high-purity germanium gamma detectors. These detectors are the preferred instruments for high-resolution nuclear spectroscopy, but they currently cannot be produced with radiation-resistant fine segmentation. More specifically, this means it is not currently possible to have detectors with isolated contacts that are sensitive to the position of gamma interaction and that can also be heated to repair radiation damage, which these detectors typically experience when used in nuclear physics experiments or space applications. In collaboration with the National Laboratories of Legnaro, the group has demonstrated that PLM technology overcomes this hurdle, producing and testing innovative prototypes based on this technology, and is investigating the transfer of this technology to the leading European industry, a world leader in the production of these types of devices.
Contacts: Davide De Salvador.
Crystals for Channeling Experiments
The expertise gained in crystal processing and characterization has laid the groundwork for developing an intriguing research area that concerns the coherent interaction of accelerated beams with crystalline materials. Crystals with appropriately modulated curvature, achieved through various techniques (mechanical holders, lithographic films, stress-inducing films produced by PLM, etc.), can be used to deflect even ultra-relativistic accelerated beams. This opens up innovative applications for accelerator technologies, radiation production, and detectors for ultra-relativistic particles. In collaboration with the National Laboratories of Legnaro, the group constructs and tests crystalline devices, mainly made of germanium, and conducts experiments at LNL, the University of Mainz (MAMI), and CERN, as part of INFN national and international collaborations and projects.
Contacts: Davide De Salvador, Francesco Sgarbossa
Semiconductor alloys for light-emitting devices, power electronics and photovoltaics
Compound semiconductors, mainly from elements of groups III-V, III-N (nitrides), II-VI and other alloys containing metals such as Cu and Zn, are strategic materials: due to their properties they are used to make devices in various fields, such as LED and Laser visible light emitters (Nitrides), devices for power electronics (nitrides, gallium oxide, SiC), solar cells for applications in photovoltaics (II-VI). For all these materials, the areas of research are varied, and they address the various steps necessary to realize devices with higher efficiencies, lower costs and greater environmental sustainability. By way of example we mention some of the problems addressed: introduction, activation and stability of dopants through processes of diffusion, ion implantation, laser processing, heat treatments (e.g., Mg and C in nitride alloys GaN, AlGaN, InGaN, selenium and copper in II-VI alloys); deposition, mixing and doping of multilayer structures of semiconductor alloys for high-efficiency thin-film photovoltaic devices (CIGS, CdTe, CZTS, antimonides); implementation of new dopants (Si, Ge) and study of activation processes in oxides of gallium used for power electronic devices.
Contacts: Andrea Gasparotto, Enrico Napolitani
Controlling the thermal expansion of materials
Thermal expansion of materials is a problem in many technological applications requiring thermal stability. Indeed, when different materials are in contact, they can expand differently, causing issues such as material failure. Therefore, controlling thermal expansion is crucial in the design of new materials. In the past two decades, after the discovery of unconventional materials with negative thermal expansion (NTE) properties over a wide temperature range, the goal of controlling thermal expansion has become feasible and the number of studies on this topic has grown rapidly. This research activity studies the physical phenomena related to NTE and explores possible methods for controlling thermal expansion. As part of this activity, the group regularly participates in experiments at important international synchrotron radiation laboratories, including ESRF (Grenoble) and ELETTRA (Trieste).Selected publications:
- Nature Comm. 14, 4439 (2023).
- J. Am. Chem. Soc. 142, 6935 (2020).
- Nature Comm. 8, 14441 (2017).
Contacts: Andrea Sanson
Materials for Energy
This research line investigates materials of functional interest for energy-related applications, with a particular focus on thermoelectric and ferroelectric materials, including relaxors. The research activity focuses on the analysis of the relationship between the local structure and dynamics of these materials and their functional properties, with the aim of improving their performance and efficiency.
In the context of this research activity, the group also participates in experiments at international synchrotron radiation facilities (ESRF, Elettra).
Selected publications:
- J. Am. Chem. Soc. 146, 3498 (2024).
- Adv. Energy Mater. 11, 2100661 (2021).
Contacts: Andrea Sanson
Charge transport in ferroelectric oxides
Compared to other materials of technological interest, our understanding of the mechanisms of photogeneration and charge transport in ferroelectric oxides is still limited, and at the same time of extreme importance for many important applications ranging from nonlinear optics to the exploitation of solar energy. The research activity in this area is aimed at the theoretical and experimental study of the self-localization and motion of charge carriers (polarons), mainly in Lithium Niobate, through the preparation of dedicated samples, analysis with optical and electrical techniques and theoretical modeling of the results.
Contacts: Marco Bazzan, Davide De Salvador
