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OPTICAL AND SPECTROSCOPIC METHODS FOR THE STUDY OF MATERIALS

CODE 61864 2019/2020 6 credits during the 1st year of 9012 PHYSICS (LM-17) GENOVA 6 credits during the 1st year of 9017 Materials Science and Engineering (LM-53) GENOVA 6 credits during the 2nd year of 9017 Materials Science and Engineering (LM-53) GENOVA FIS/01 Italian GENOVA (PHYSICS) 2° Semester AULAWEB

OVERVIEW

It is a course on the optical properties of  materials and the basic experimental methods to study them. Empahsis is placed on the applications of spectroscopic ellipsometry. A basic knowledge of electromagnetism in dielectrics, wave, solid-state physics. The course is mainly aimed at students in condensed matter physics, materials science and chemistry.

AIMS AND CONTENT

TEACHING METHODS

Traditional lectures. Laboratory demonstrations. Laboratory experiences.

SYLLABUS/CONTENT

A. Classical Models

1. Introduction
Basic optical processes. Classification of materials with respect to their optical properties.
2. Classical propagation in homogeneous and isotropic dielectrics.
Lorentz resonances. Dielectric function and complex refractive index.  Many resonances.  Kramers- Kronig relations. Normal dispersion and interpolation formulas for the refractive index (Cauchy, Sellmeyer). Optical properties of glasses and other amorphous insulators. Dispersion consequences. Prisms. Group velocity dispersion
3. Classical models for metals
Drude model for free carriers. Dielectric function of simple metals. Low frequencies limit. Plasma frequency. Plasma oscillations of the free electron gas. The case of aluminum.
4. Inhomogeneous materials
Clausius - Mossotti equation. Heterogeneous dielectric media. Effective medium approximation: Maxwell-Garnett, Bruggeman, Lorentz-Lorenz. formulas

5. Anisotropic Dielectrics
Birefringence. Ordinary and extraordinary ray. Dielectric tensor.

B. Interfaces: reflection and refraction

6. Jones vectors and matrices
Fresnel coefficients. Principal angle. Critical angle. Jones representation of polarization states. Jones matrices. Matrix description of  main components for optical spectroscopy experiments (with laboratory demonstrations).
7. Reflectometry and ellipsometry
Reflectivity. Ellipsometry: Δ and Ψ. Fundamental relationship of ellipsometry. Reflectometry and ellipsometry from an isotropic, substrate + thin-film system. Instrumentation and measurement methods. Null ellipsometry  (with laboratory demonstration). Spectroscopic ellipsometry: main configurations (with laboratory demonstrations). Ellipsometer / sample system transfer function with Jones matrices.
Laboratory experience: spectroscopic ellipsometry and reflectometry from simple systems: Au surfaces and glass. Surface effects: roughness and contamination
Laboratory experience: spectroscopic ellipsometry of thin and ultrathin films. Measurement of thickness of an oxide layer on Si (transparency region)

C. Semi-classical models for the absorption
8. Interband transitions
Simplified  band structure of semiconductors. Direct Gap:  transition probability calculations near the absorption threshold. Indirect Gap: transitions assisted by phonons. Comparison with experimental data.   Full band structure.   Effects of parallelism between bands. Absorption threshold in amorphous oxides. Interband transitions in noble metals.
Laboratory experience: spectroscopic ellipsometry from Si wafers (absorption region)
Laboratory experience: spectroscopic ellipsometry from films of amorphous oxides. Determination of the optical gap.
9. Excitons. luminescence processes
Excitons in pure materials: experimental data. Strongly and weakly bound excitons. Simple models. Molecular semiconductors. Luminescence Processes and measurements. LED materials (heterostructures). Materials for photovoltaic applications.

D. Thin  ultra-thin and nanostructured films

10. Nanoparticles
Optical properties of metal particles. Absorption and scattering. Plasmonic resonances. Particle aggregates. nanogranular and nanoporous materials. 2D organized systems of metal nanoparticles. Plasmons in the visible and UV. Optical spectroscopic methods for the study of optical properties of semiconductor nanostructures for photonics (seminar).
11.  Ultra-thin Films
Langmuir-Blodgett films and self-assembled organic monolayers. New 2D materials: optical properties of graphene.
12. Thin Multilayers
Calculation of the reflection and transmission coefficient for the multilayers. Mirrors and optical  filters. "Perfect" Mirrors  for interferometers. Metamaterials. Photonic crystals . Natural Bragg reflectors. Ultra-thin magnetic films. Magneto-optical Kerr effect.
Laboratory experience: spectroscopic ellipsometry of multilayer amorphous oxides

13. Raman spectroscopy

Principles. Basic instrumentation. Surface enhanced Raman Spectroscopy

Textbook M. Fox, Optical properties of Solids, Oxford University press

Other texts available at the DIFI's library

H. Arwin, Thin Film Optics and Polarized Light

O. Stenzel The Physics of Thin Film Optical Spectra, Springer

H. Tompkins, W.A. Mc Gahan, Spectroscopic Ellipsometry and Reflectometry, Wiley,

TEACHERS AND EXAM BOARD

Exam Board

MAURIZIO CANEPA (President)

FRANCESCO BISIO

MICHELE MAGNOZZI

LORENZO MATTERA

LESSONS

TEACHING METHODS

Traditional lectures. Laboratory demonstrations. Laboratory experiences.

LESSONS START

March 2017,  first week

Class schedule

All class schedules are posted on the EasyAcademy portal.

EXAMS

EXAM DESCRIPTION

The final exam deals with a seminar of the student on a broad topic. The topics are assigned by the lecturer at least three weeks in advance to the exam.

ASSESSMENT METHODS

Frequent and active presence to the lectures and laboratory activities.  Evaluation of the seminar presented for the exam: coherence with course contents, validity and degree of analysis of presented contents. Ability of critical analysis  of treated arguments.

FURTHER INFORMATION

https://dida.fisica.unige.it/dida/