Już 8 października 2026 roku o godz. 12:30 w Audytorium Aleksandra Jabłońskiego prof. Olivier Pagès (Université de Lorraine, Francja) wygłosi wykład pt. "Lattice dynamics of semiconductor mixed crystals".
Streszczenie:
Due to their simple (cubic) structure and constituents (atoms), the pseudo-binary A1‑xBxC disordered semiconductor alloys (SCA) with zincblende (zb) structure set a benchmark to explore how physical properties are impacted by disorder. In particular, through its diversity, the lattice dynamics offers a unique playground to assign the relevant length scales at which operate various kinds of disorders induced by alloying. With two (cation + anion) atoms per primitive cell, the zb-A1‑xBxC SCA do not only exhibit acoustic modes, due to in-phase cationic and anionic motions, bearing a “cumulative” (bond-collective, multi-bond:1-mode) message about the alloy disorder, but also optical modes, due to out-of-phase cationic and anionic displacements, reflecting effective cation-anion A-C and B-C bond-stretchings. The optical modes are interesting because they offer a bond-specific (A-C- or B-C) insight into the alloy disorder in the spirit of a 1-bond®1-mode paradigm, beyond the bond-collective (A-C and B-C) insight provided by the acoustic modes. A longstanding controversy was whether, beyond bond species, the optical phonons see the local fluctuations in composition inherent to alloying around a given bond, or are just blind to these. Over the past two decades we developed through an international partnership (presently formalized as the ViSA-IRP / Vibrations of Semiconductor Alloys - International Research Partnership) a so-called percolation scheme [1] supporting a view that the optical modes are actually sensitive to the local bond environment, distinguishing "same" (homo) from "alien" (hetero) environments of a given bond in the spirit of a 1-bond®2-mode paradigm. In this talk I will review the key milestones in setting this percolation scheme, supported by inelastic light (Raman) / neutron scattering experiments and ab initio phonon calculations.
[1] T. Alhaddad et al. Taxonomy of high pressure vibration spectra of zincblende semiconductor alloys based on the percolation model, Sci. Rep. 15, 1212 (2025).
Organizatorem Kolokwium Czwartkowego jest Instytut Fizyki UMK w Toruniu.