Dottorato di Ricerca in Fisica

Università di Modena e Reggio Emilia

Dottorato di Ricerca in Fisica e Nanoscienze, XXI ciclo
colloquia doctoralia
15 Dicembre 2008

ore 14, aula C

Dipartimento di Fisica

Via Campi 213/a, Modena
Programma

Dottorato di Ricerca in Fisica

14:00 Andrea Benassi

14:30 Enrico Gualtieri

15:00 Fabrizio Moro

15:30 Lorenzo Pardini

Dottorato di Ricerca in Nanoscienze e Nanotecnologie

16.00 Luca Gragnaniello

16:30 Vijajaharan Venogopal
The Graduate School in Nano- and Physical Sciences has been established in Modena in 2005 by the University (www.unimore.it), in close collaboration with the National Research Center S3 ("nanoStructures and bioSystems at Surfaces", www.s3.infm.it) of INFM-CNR. The focus of the School is on development and application of advanced experimental and theoretical/ computational methods for the study of matter and systems at the micro- and nano-scale.The faculty and the program have strongly interdisciplinary character, from physics to chemistry, biology and engineering. The students will take advantage of a lively international environment, with access to state-of-the-art experimental/computational facilities and participation in major international projects and collaborations. The School is structured in two 3-year PhD curricula:

(a)PhD in Physics. This course is devoted to advanced research in the physics of condensed matter and materials science and electronics, through experimental and theoretical techniques. Examples of specific subjects include: surface science; electronic, optical and ionic spectroscopies and microscopies; quantum many-body theory; physics of high correlated and magnetic systems, electronic transport in materials and devices, etc.

(b)PhD in Nanosciences and Nanotechnology. This is a strongly multidisciplinary course which is open to students with different background (physics, chemistry biology, engineering, etc.). Students will learn about fundamental phenomena that are relevant at the nanoscale, approaches to the fabrication and the analysis of nanostructures, as well as advanced nanotechnology applications.

Both curricula emphasize fundamental science as well as applications within information technologies (nanoelectronics, nanomagnetism, nanomechanics, nanotribology, etc) and within life sciences (biotechnology, medicine, diagnostics and drug design).

The Director of the PhD School is Prof. Stefano Ossicini. The Director of the PhD Course in Physics is Prof. Stefano Frabboni and the Director of the PhD Course in Nanoscience and Nanotechnology is Prof. Marco Affronte.
PhD Course in Physics
Andrea Benassi
Role of the vacuum fluctuation forces in microscopic systems

Tutor: prof. Carlo Calandra.

Dispersion forces (van der Waals and Casimir forces) arising from zero point oscillations of the electromagnetic field are currently investigated for their possible role in a variety of phenomena, ranging from surface and device physics to particle physics and cosmology. In particular they have been considered responsible of processes occuring during thin film deposition or in the design and operation of micro- and nano-devices. Because both the sign and the intensity of these forces depend upon the boundary conditions of the electromagnetic fields, they can be tailored to meet different physical conditions. The present thesis reports on the results of studies concerning the role of dispersion forces in the interactions of thin metal films. In particular the following topics have been investigated (i) the stability of deposited metal films; (ii) the size effects in the Casimir interaction between ultrathin films; (iii) the first principles calculation of the force between ultrathin silicon films; (iv) the influence of metal insulator transition in device actuated by the electro-magnetic vacuum force.
2003 First Degree in Physics at the Universita' di Modena e Reggio Emilia Thesis:"A study on vibrational properties of simple molecules by an ab-initio molecular dynamic parallel code" 2005 Master Level Degree in Physics at the Universita' di Modena e Reggio Emilia Thesis:"Analysis of the Casimir effect at nanoscales for planar geometries" Teaching:

Since February 2007 Lecturer at Physics Department, Universita' degli Studi di Modena e Reggio Emilia. Exercise classes on basic quantum mechanics. Schools, Courses and Workshop: June 2008: 60 Years of Casimir's effect, Brasilia (Brazil) May 2008: V Nanoquanta Young researchers meeting, Modena (Italy) November 2007: DEISA training, Bologba (Italy) May 2007: IV Nanoquanta Young researchers meeting, San Sebastian (Spain) January 2007: 13th International Workshop on Computational Physics and Material Science: Total energy and Forces Methods, Trieste (Italy) October 2006: 2nd Specialistic School on Parallel Computation, Bologna (Italy) September 2006: 11th Nanoquanta Workshop on Electronic Excitations, Houffalize (Belgium) July 2006: 15th Summer School on Parallel Computation, Bologna (Italy) May 2006: From C to C++ and object oriented programming, Bologna (Italy) May 2006: C language for scientific programming, Bologna (Italy) 2003: C.I.N.E.C.A.: course on MPI parallel computation and course on Unix like operative systems, Bologna (Italy)
Enrico Gualtieri
Improving tribological properties of steels by surface texturing and coating

Tutor: Prof. Sergio Valeri

Nowadays, tribology represents a pivotal frontier to be explored in basic and applied Physics at all scales where mating surfaces are involved, and the minimization of friction and wear losses is required. Surface Engineering deals with the modification of solid surface phase in order to optimize its performances during the interaction with the surrounding systems, and is meant to be considered an attractive approach for tribological challenges. Within this context, the thesis work is aimed to give a contribution to the development of strategies for the improvement of tribological properties of steel surfaces. Applications of innovative “tribo-coatings” were characterized by an intensive use of Dual Beam Machine that has proved to be a powerful instrument allowing to correlate tribological behaviours to sub-surface microstructure. Laser Surface Texturing (LST) involves topographical modifications via regular distributions of ablated micro-dimples, which presence can significantly affect sliding behaviours reducing friction, damping wear, and improving lubrication mechanisms. These tribological benefits were quantified through pin/ball-on-disk experiments performed under different lubrication configurations. Indeed, laser-steel interaction was investigated in order to detect and explain “collateral effects” due to LST in terms of locally confined morpho-structural modifications induced by laser heating (i.e. grain-size modification, hardening).
Degree in Physics cum laude at the University of Modena & Reggio Emilia (2005). Thesis: “Caratterizzazione chimica, strutturale e morfologica di nanostrutture di Fe preparate su substrati di ossidi metallici”; supervisor: prof. S. Valeri.

Teaching assistant of Mechanical Engineering students (Laboratory of General Physics “A” in 2007, 2008).

School: INSA-LaMCoS PhD Summer School on Tribology, 2007, Lyon (France). Conferences: 5^th AITC-AIT international conference on tribology, 2006, Parma (Italy): proceeding; NANOTRIBOLOGY Final Meeting, 2006, Modena (Italy): poster; 34^th Leeds-Lyon Symposium On Tribology, 2007, Lyon (France): oral; 32^th AIM National Meeting, 2008, Ferrara (Italy): oral.

8 publication in national and international journals.

Fabrizio Moro
Structural, electronic and magnetic properties of Molecular Nanomagnets on surfaces

Tutor: Prof. Umberto del Pennino

Molecular NanoMagnets (MNM’s) are mesoscopic objects recently proposed as the smallest possible data-storage devices as well as qubits for the quantum computation. Up to date the key point for their application as nano-devices is the assembling on surfaces of MNM’s retaining the bulk properties. In this thesis work, suitable protocols for the deposition from solution of new MNM families on the Au(111) surface and for their structural, electronic and magnetic characterization are established. Self-assembled submonolayers of several derivatives of Mn-based and Cr₇Ni MNM’s have been characterized by imaging (STM) and X-ray photoemission spectroscopy techniques. The electronic and magnetic properties of the MNM’s have been investigated by X-ray Absorption Spectroscopy and X-ray Magnetic Circular Dichroism at the ESRF in Grenoble. Mn-based MNM submonolayers show that their properties change dramatically with respect to the bulk compounds due to the high chemical instability of the Mn cluster. On the contrary, the Cr₇Ni rings preserve the local symmetries and the oxidation states of the metallic ions while the Cr-Cr and Cr-Ni super-exchange couplings result reduced due to a structural distortion of the ring. The deposition of different sulphur-functionalized Cr₇Ni derivatives proves that, in principle, we can control the interplay between the structure of the ring and the super-exchange couplings, because they strongly depend on the choice of the functionalization mediating the interaction with the gold surface. Finally, Cr₇Ni derivatives that satisfy the main requirements for their exploitation as qubit even after their adsorption on surface are proposed.
Degree in Physics at the University of Lecce, Thesis “Laser-induced breakdown spectroscopy for compositional analysis of multielemental thin films” Supervisors Prof.^ssaE. D’Anna (July 2005). 4 papers published in international journals, 1 like first author. Teaching assistant of Physics I (2006, 2007). Schools: ARS2 - Trieste (April 2007); SCEN 06 - Pisa (June 2006). Conferences/Workshops: Poster presentation 11th ICMM - Florence (Sept. 2008). Poster presentation JEMS - Dublin (Ireland) (Sept. 2008). Oral presentation MAGMANet Workshop - Huesca (Spain) (Sept. 2008). QUEMOLNA Workshop - Modena (Apr. 2008). Conference on PAFT XIII edition - Vietri sul Mare (Italy) (March 2007). Seminars: MPI fϋr Metallforschung – Stuttgart (Germany) (Feb. 2007). Stages: IPMCS - Strasbourg (France) (Jan. 2008).
Lorenzo Pardini.
Ab initio calculation of dichroic spectra

Tutors: prof. Franca Manghi & Dr. Valerio Bellini

X-ray magnetic circular dichroism (XMCD), together with X-ray absorption spectra (XAS), is one of the most effective tools for investigating the magnetic properties of matter, since it presents several capabilities not afforded by traditional techniques, such as the possibility to discriminate orbital and spin contribution to the total magnetic moment. This task can be afforded exploiting two sum rules, whose validity and range of applicability are not well established, especially to condensed matter systems with hybridized multiband structures. The main task of my PhD work has been the development of a program package to calculate dichroic spectra within an ab-initio all electron scheme. Through a careful analysis of the results obtained for 3d transition metals, I have verified on one side the accuracy of the numerical method adopted and, on the other side, the applicability of the orbital and spin sum rules, checking in particular the effect of the energy cut-off on the inferred momenta. Many body effects have also been included in the calculated spectra via the three body scattering theory, showing an improvement in the agreement between theoretical and experimental spectra. Last, XMCD and X-ray absorption spectra have been calculated at the L edge of selected chromium-based molecular magnets and the results have been successfully compared to the experiments: I have found that molecular magnets spectra exhibit common features determined by the local chromium symmetry.

Degree in Physics at the University of Pisa; Title of the thesis: “Studio sperimentale di plasmi prodotti con la tecnica LIBS a doppio impulso”; supervisors: Dr. Gabriele Cristoforetti, Prof. Danilo Giulietti.

Teaching assistant for the course "Termodinamica e fluidodinamica", (2006/2007 - 2007/2008).

Schools: Parallel Calculation – CINECA, Bologna, 2006; Correlated materials, Les Houches, 2006.

Conferences and workshops: FOPS06, 2006, Munich; XIII Total Energy and Force Method, Trieste, 2007; XV VUV, Berlin, 2007; XV Wien2k Workshop, Vienna, 2008 (oral); V Nanoquanta YRM, Modena, 2008 (oral); XX EPS-CMD, Roma, 2008 (oral).
PhD Course in Nanoscience and Nanotechnology

Luca Gragnaniello

Growth and Supra-Organization of Transition Metal Nanoclusters

Tutor: prof. Sergio Valeri

Ordered arrays of metal nanoclusters are promising materials for next generation microelectronics, ultra-high-density recording and nanocatalysis. However, whereas a lot of works have dealt the growth of nanoclusters on metals and on semiconductors, the production of ordered arrays of nanoclusters with identical size on oxide substrates is still a daunting challenge, although these systems would be very important for future applications. In this work it has been studied the growth and organization of transition metal nanoclusters on rocksalt oxides. The applicability of the self-assembling technique to create ordered arrays of nanoclusters on thick oxide substrates has been tested on one- and two-dimensional patterned oxides. For this purpose two prototype oxides have been chosen as substrates: MgO, that acts as an inert support, and CoO, that on the contrary is reactive and antiferromagnetic. In order to drive the self-assembly of metal nanostructures, templates have been prepared on these oxide surfaces. Bulk MgO has been used for the preparation of vicinal surfaces, exhibiting a quite regular array of steps which can represent a one-dimensional template. In order to characterize at the nanoscale the morphology of MgO surface, Noncontact–AFM has been studied and then used. CoO has been prepared as thin film on Ag(001) in order to form a two-dimensional surface pattern exploiting the formation of a network of interfacial dislocations. The growth and the organization of Fe and Ni clusters respectively on stepped MgO and patterned CoO has been deeply investigated.
Degree in physics cum laude at the University of Napoli, Title of thesis: “A study of the ultrashort laser ablation process”, supervisors: Prof. Riccardo Bruzzese, Dr. Salvatore Amoruso. Teaching assistant for the courses of Physics for Biotechnology Course (2007) and of Applied Physics for Biology Course (2008). Conferences, Schools and other Experiences: Madrid (Spain) September 2008: 11th International Conference on Non-contact Atomic Force Microscopy: NCAFM-2008; Osnabruck (Germany) - August 2007: Guest in the NanoScience Group of Prof. Michael Reichling for a Training on Noncontact Atomic Force Microscopy; London (England) - March 2007: COST WG4 Meeting; Pisa (Italy) - July 2006: Summer School on Metal Clusters and Surfaces; Napoli (Italy) - July 2006: Societ Italiana Luce Sincrotrone (SILS) Conference
Vijayaharan A Venugopal

Development of new materials for nano structured non volatile memory device

Tutor : Prof Giampiero Ottaviani
The demand of memory devices with increased speed, density and high performance keeping the production costs low have become a major challenge in the semiconductor industry. As the conventional devices are reaching its geometrical limits, the industry is looking for new technologies which could solve the above issues. Phase change memory based on reversible switching between amorphous and crystalline phases, proposed by S. Ovshinsky in 1968, due its exceptional features like long life cycles, low programming energy, large dynamic range, fast time response, long data retention and excellent scaling characteristics is considered to be one of the promising candidate for the next generation memory devices. Though this device is under study for about a decade now, it still has got some potential problems regarding their contact electrodes. In this work, The interaction properties and characterization of contact electrode material has been studied. Ti and TiN has been proposed to be as the top electrode element and TiSiN as the bottom electrode. The interaction between top electrode element and the Ge₂Sb₂Te₅ has been investigated. Whereas characterization of bottom electrode has been performed to study the properties of the material to verify their compatibility with the device.
Vijayaharan A Venugopal was born in Nagercoil, India. He graduated in Electronics and Communication Engineering from the Bharathiar University, India in 2004. He received the masters degree in microelectronics from the university of Newcastle upon tyne, United Kingdom in the year 2005. In 2006, he joined the university of Modena and Reggio Emilia, Italy, where he is now pursuing his doctorate degree in nano science and nanotechnology. Currently he is working on a project in collaboration with Numonyx, Agrate brianza, Italy titled “Development of new materials for nano structured non volatile memory device”. He has presented 2 posters in international summer school organised by University of Hamburg, Germany and Polytechnique of Grenoble, France. A paper has been submitted to Journal of Electronic Materials titled “Thermal Stability of Ge₂Sb₂Te₅ in contact with Ti and TiN “ and a patent is under evaluation. He is also a member of the Institution of Engineering and Technology, UK. His research interests include phase change memories, characterization of chalcogenide materials and electrical characterization of thin films.