# PHYSICAL TECHNOLOGIES FOR ENERGY AND ENVIRONMENT

## Learning outcomes of the course unit

Expected fornative results: On the basis of a scientific approach, the students will be introduced to some of the major global problems of the third millennium such as: Energy and Environment with particular emphasis on the economic, social and ethics consequences which could follow each particular solution suggested by the research progress- In particular, the fundamentals principles and models of the physics of electronics materials, basically used to develop devices for applications in energy and environment, are briefly introduced. Some relevant experimental techniques and technology process are illustrated in order to appreciate the opportunities given by modeling the electronic materials for particular applications and for understanding the behavior of simple semiconductor devices. In addition, the future exploit of the “green economy”, with its positive role in improving the work market, will be illustrated to the future young physicists.

## Prerequisites

Requirements: A good knowledge of the principles and laws of classical physics, mainly concerning thermodynamics electromagnetism and optics. A sufficient expertise in managing the differential calculus and the basic principles of statistical and quantum mechanics with particular regard to the use of the Schrödinger equation to solve the elementary quantum mechanics problems ( such as the energy levels of an electron confined in a potential box or bonded to the nucleus of an Hydrogen atom.

## Course contents summary

Motivations and contents: Physics provides the theoretical foundation for essentially all of the technologies and processes involved from resource exploration and extraction, conversion, transmission and distribution to provide the energy services demanded by our societies. Without thermodynamics there would be no heat engines that from the mainstay of the world’s current electricity generation or transportation systems; without the laws of classical mechanics, classical electro-magnetics or relativity theory, there would be no the development of nuclear fission, photovoltaics or fuel cells. In the past, the extensive use of energy technologies, especially when utilizing fossil energy resources, has also generated undesirable by-products, wastes and pollution greatly dangerous for the human health, climate and ecosystems. The fundamental laws of physics tell us that there is no technology without wastes, risks and interaction with the environment. Again, physics has been instrumental in our understanding of the adverse impacts of energy production and use ranging from climate change, the interaction of the atmosphere and the oceans to the abatement of pollutants in flue gases.

The lectures of this course re scheduled in three sections:

o I. Microelectronic technology: Basic physics properties of semiconductors.

o II.Vacuum technology: Production and measurements of Vacuum, to thin films and epitaxial layer deposition for industrial and research applications.

o III.Photovoltaic technology: Thermodynamic aspects of the photovoltaic conversion of solar energy. Physics of solar cells, state of art and future opportunities of photovoltaics.

## Course contents

I. The physics principles of semiconductor materials.

• Semiconductor materials for energy and environment.

• Lattice and crystalline structures. The Bravais lattice. Unit base and lattice vectors. Simple structure and symmetry properties. Diamond-like structure (SC, BCC, FCC). The reciprocal lattice. The Wigner Seitz cell in the direct and reciprocal space. The Brillouin zone.

• Analysis of the crystalline structures. Electromagnetic spectrum, interaction radiation-matter. Electrons, x.rays, neutrons. Hysterical review: the cathode rays, the Thpmson’s electron, the experiments of Davisson- Germer and M.V. Laue. The Bragg’s law. The neutrons of Fermi. The physic of X.rays. Wave diffraction by periodic structures. The elastic diffusion of X.-rays.

• Electronuc states and band structures. Valence and core electrons. Single electron approximation. The limit case of the free electron. The Bloch’s theorem. The Brillouin zone. The dispersion law. The boundary condition of Born-Von Karman. Density of states and Fermi Energy, The Bragg reflection at the boundaries of the Brillouin zone. The forbidden energy gap: insulators, metals, semiconductors. Introduction to band structure determination and 3D band structure properties of diamond like crystals.

• Electron and hole dynamics. The semi-classical approach. The tensor effective mass. The concept of hole. Doping of semiconductor with hydrogen-like impurities (shallow levels). Experimental methods.

• Statistic of the carrier at the thermodynamic equiliobrium.

Intrinsic carrier density and Fermi-Dirac distribution. The Boltzmann approximation as asymptotic classical behavior. Acceptor and donor levels in semiconductors. Density of carriers and temperature dependence of the Fermi level Semi-insulating semiconductors and compensation effects.

• Introduction to electronic transport in semiconductors. Bloch’s oscillations and collisions. The time relaxation approximation. The Boltzmann’s equation. Electrical conductivity and Ohm’s law. Introduction to magnetotransport properties. Electric charges in a magnetic field and cyclotron resonance. The Limit of the classical approach. Hall effect and magnetoresistance. Experimental methods.

• Introduction to the optical properties. Optical constants and macroscopic model. Transmission, absorption and reflection of light. Multiple reflections from thin layers. Fundamental absorption and absorption coefficient for direct and indirect optical transitions. Elements of optical spectroscopy. Experimental methods.

• Excess carriers. Level of excess carrier injection. Charge neutrality equation. Generation- Recombination mechanism. Lifetime of carriers. Diffusion processes amd carrier diffusion length. Einstein’s rule. Ambipolar diffusion equation. Applications of the continuity equation: the case of uniform and lateral injection. Experiment of Haynes and Shockley.

• The p/n Jubction. The ideal case: static behavior of the p/n junction. Forward and reverse bias, currents through the junction. Capacitance of the junction. Non ideal behavior. Generation-recombination currents. Breakdown of the junction.

• Heterojunctions. Isotype and hetero-type junctions. Epitaxial growth technologies and bang gap engineering. Elements of semiconductor nanostructures physics and technology. Definition of quantum structures (quantum wells, quantum wires, quantum dots).

II. Ther vacuum technologies.

• Review of thermodynamic fundamentals: thermo logy, calorimetry and kinetic theory of the gas.

• Production and measurements of the vacuum:

• Materials for vacuum technology ( metal. glass, elastomers, adhesive, ceramic cement)

• Thin film deposition techniques: thermal evaporation, sputtering, electron gun). Epitaxial techniques: MBE, MOVPE.

III. Photovoltaic technologies.

• Thermodynamics and photovoltaic conversion of solar light..

• The physics of a solar cells.

• The market of the solar cells.

• Innovative photo

## Recommended readings

All the students regularly registered can have a lock to the slides of the lectures at the course web site:

http://fisicatriennale.unipr.it/cgibin/campusnet/corsi.pl/Show?_id=ad61;...

However, some basic textbooks are suggested:

M. Guzzi: “ Principi di Fisica dei semiconduttori” Ed. Hoepli, Milano 2008

B. Ferrario: " Introduzione alla Tecnologia del Vuoto" edizione riveduta da A. Calcatelli, Patron Editore – Bologna 1999.

## Teaching methods

Teaching: The course is based on frontal lectures and presentations of some special topics. These talks will be followed by interviews to researchers expert in applications of electronic materials for energy, health or environment. The participation of the students to the general discussions is highly expected and for that particularly stimulated. Finally, optional visits to laboratories, located in the area of Parma, active in the preparation af advanced materials, could be also provided to the interested students.

Considering the undergraduate character of the course, the mathematical formalism is limited to a basic level in order to avoid possible difficulties to students which have not yet a compressive knowledge of the modern physics . For this purpose the attention will be focused on a phenomenological approach to the fundamental properties and application of electronic materials and related technologies.

## Assessment methods and criteria

Method of evaluation: Grades will consist of homework and a final exam. In order to reduce the weight of the final exam, optional class credit will be assessed by monitoring the presence to the lectures and considering the active participation to ihe class work. . Therefore the final grade is formed by:

15% based on an active presence and class work participation

35% from graded homework

50 % from the final exam.

At the end of the lectures and seminars each student , regularly registered for the final exam, will receive by electronic mail , at least 10-15 days before of the exam, a list of possible topics for the preparation of its homework which the student must submit and discuss and comment at the in presence of the examination committee.