LU CFI Zinātniskais seminārs (05-07.11.2012)

Pirmdien, 5. novembrī 15:00 Lecture 1. Intrinsic and extrinsic electronic excitations (EE) in binary dielectrics Introductory remarks: three types of solids, vibronic and electronic excitations, luminescence phenomenon, quasi-particles. Impurity EE: absorption and emission spectra of impurity centres; Frank-Condon approximation; thermal and optical quenching. zero-phonon lines, hot luminescence. Intrinsic EE: band structure of dielectrics; currentless mobile EE – excitons; relaxation, migration and self-trapping of excitons, electrons and holes; peculiarities of EE at the surface of solids; spectra of optical constants. Types of luminescence in dielectrics : intraband luminescence, recombination and tunnel luminescence, cross luminescence.   Otrdien, 6. novembrī 13:00 Lecture 2. Multiplication of electronic excitations (MEE) Mechanism of MEE in semiconductors; electron-hole and excitonic mechanisms of MEE in dielectrics; solid state analogue of the Frank-Hertz effect; spectral transformers with the quantum yield of emission above unity for lighting and plasma display panels; electric breakdown and electron avalanche.   Otrdien, 6. novembrī 15:00 Lecture 3. Radiation physics of wide-gap materials Defect classification: intrinsic point defects, solid solutions of impurity ions in crystals; linear (dislocations) and two-dimensional (surface) defects, elementary radiation defects. Mechanisms of radiation damage in solids: knock-out (impact) creation mechanisms of interstitials and vacancies in metals; decay of electronic excitations with the creation of Frenkel defects in wide-gap materials; creation spectra of Frenkel defects by synchrotron radiation; the decisive factors of radiation resistance of materials.   Trešdien, 7. novembrī 12:30 Lecture 4 - Seminar Talk. Electronic excitations and nonimpact mechanisms of radiation damage in binary and complex metal oxides under conditions of low or superhigh excitation density Role of excitons and electron-hole pairs in the excitation of luminescence and creation of Frenkel defects and their associations in binary wide-gap crystals. The criteria of radiation resistance against nonimpact mechanisms of stable defect creation in two classes of wide-gap materials (WGM) with E_FD < E_g or E_FD > E_g. Hot e-h recombination and solid-state analogue of the Franck-Hertz effect. Peculiarities of intrinsic electronic excitations in WGM with many atoms of different masses per unit cell (self-trapping and hopping diffusion of carriers, etc). Comparison of radiation effects in pure and heavy-ion-doped WGM under conditions of low or superhigh excitation density. Possible experimental manifestations of 3D defects created via the collapse of discrete solitons in complex WGMs irradiated with with heavy ions (~2 GeV, ¹⁹⁸Au, ²³⁸U).