PHYSICS AND TECHNOLOGY OF MATERIALS

Lectures and seminars in classroom

6 CFU (7h/CFU)

Should circumstances require the lectures to be given online on in a mixed manner, some variations to the mechanisms illustrated above may become necessary, aiming however at fulfilling the planned
course programme.

Properties and distinctive characteristics of materials (metals, ceramics, polymers, semiconductors, and composites). Bonding in solids: metallic, ionic, covalent, Van der Waals, and mixed. Semi-quantitative assessments of bond energy and relationships with compressibility. Crystal structures, packing factor. Relationships between microscopic structure and mechanical properties. Surface energy of solids: atomistic, thermodynamic, and mechanical descriptions. Layer-by-layer and island growth of deposited films. Grain boundary energy in a polycrystal; equilibrium shape of crystalline grains. Transmission electron microscope: operating principles and applications. Thermodynamics and phase diagrams. Review of thermodynamic state functions. Stable and metastable phases. Phase stability criteria. Single-component systems: PV diagram, critical temperature, two-phase coexistence, vapor pressure, triple point. Solidification curves, homogeneous and heterogeneous nucleation, influence of liquid-solid interface structure on growth rate, interface stability, and dendrite formation. Nucleation and grain growth in amorphous silicon. Ideal and real binary solutions: construction of phase diagrams, mixing energy, configurational entropy. Completely miscible systems. Ostwald ripening. Solidification curves. Constitutional supercooling. Cellular structures, segregation coefficient, normal freezing, solid purification processes. Diffusion in solids. Microscopic description of atomic diffusion and derivation of the diffusion coefficient. Steady state: diffusion equation for an ideal solution. Continuity equation and Fick's second law. Measurement of the diffusion coefficient and significance of activation energy. Method for measuring vacancy formation energy. Interstitial diffusion. Concentration profile of two elements after diffusion. Interdiffusion: effective diffusion coefficient. Mechanical properties of solids. Young's modulus, Poisson's ratio, shear and bulk moduli, stress-strain relationships, stress and strain tensors, elastic constants of a solid and their dependence on structural symmetry, plasticity of solids, yield stress, fracture. Point and line defects. Burgers vector of dislocations. Description of dislocation geometric properties; strain field and elastic energy of screw and edge dislocations; dislocation interactions. Metal impurity gettering in silicon single crystals. Thin-film deposition via evaporation. Nucleation; grain growth via ripening and coarsening. Mechanical characteristics of thin films; interaction with the substrate; strain field; thermal expansion and its influence on substrate bowing. Interdiffusion in thin films and compound formation. Metallization and interconnects in semiconductor devices. Preparation of single-crystal semiconductor layers via chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). Description of experimental setups for epitaxial growth. Homostructures and heterostructures; lattice mismatch and critical thicknesses in the Si-Ge system. Electrical and optical properties of semiconductor layers and their applications in optoelectronics and microelectronics.

‘Materials Science’ J.C.Anderson, K.D.Leaver, R.D.Rawlings, J.M.Alexander. Chapman and Hall.

‘Termodinamica Statistica’ C.Kittel, H.Kroemer. Boringhieri.

‘Electronic Thin Film Science: For Electrical Engineering and Materials Scientist’ King-Ning Tu,

J.W. Mayer, L. C. Feldman. Prentice Hall.

Verification of learning takes place through a final oral exam that can have as topics all those covered during the course. The purpose of the interview is to verify the overall level of knowledge and its ability to explain the topics studied in a clear and critical way. During the exam, the student may be asked to perform simple calculations to verify the ability to quickly deal with problems that require at least identifying the orders of magnitude of physical quantities.

Verification of learning can also be carried out electronically, should the conditions require it.

Differences between amorphous, polycrystalline and monocrystalline states of matter

Diffusion of atoms in solids and on the surface

Nucleation

Phase Transitions

Growths of epitaxial thin films