[institut] среда 7.11, 14:30h, Семинар Центра за физику чврстог стања : Local Electronic Confinement in Graphene - From Raman Response of Covalent Derivatives to Optics with Electrons``

[Đorđe Jovanović]

Поштоване колегинице и колеге,

Са задовољством вас позивам на семинар Центра за физику чврстог стања и 
нових материјала под насловом:

Local Electronic Confinement in Graphene: From Raman Response of 
Covalent Derivatives to Optics with Electrons

који ће одржати проф. др Војислав Крстић, из Department of Physics, 
Friedrich-Alexander-Universität(FAU), Erlangen, Germany.

Семинар ће се одржати у среду 7. новембра 2018. године са почетком у 
14:30 часова у Институту за физику у Београду у читаоници „Др Драган 
Поповић“ у приземљу.

Добро дошли

др Ђорђе Јовановић

Сажетак:

Local electronic confinement is a key-ingredient for the successful 
control of electronic and optoelectronic properties of any material. In 
graphene however, due to its specific hexagonal lattice structure (two 
triangular sublattices) and the circumstance to be made of carbon atoms, 
electronic confinement can have many different flavours than just the 
localisation of electrons. Here we address two manifestations of 
electronic confinement, one mainly chemistry driven, the other driven by 
physical interactions:
Covalent functionalization of graphene is a continuously progressing 
field of research.
However, in virtually all optical responses, an unresolved enhancement 
in peak intensity with increase of sp3 carbon content is observed. To 
elucidate this general phenomenon we present a phenomenological model 
[1] which takes into account the circumstance that upon covalent 
functionalization confined π-conjugated domains (photoluminescent) 
surrounded by sp3 carbon regions in graphene monolayers are formed.[2,3] 
Our model, underpinned by combined Raman measurements and an in-situ dry 
electrostatic doping technique, incorporates the modulation of the Raman 
intensities through the photoluminescence active domains, and correlates 
the individual D- and G-mode intensities to the degree of 
functionalization. Through this, evaluations of Raman spectra using our 
model circumvent the ambiguities and information loss encountered when 
using the ratio of D- and G-mode intensities.
Physical confinement involves the use of potential barriers and wells in 
contrast to altering chemical bonds. However, the use of electrostatic 
potentials for confinement of the relativistic electrons in graphene is 
not efficient due to the Klein paradox. Nevertheless, the introduction 
of local electrostatic potentials is theoretically predicted to have a 
confining action in form of a caustic motion of electrons within the 
potential [4]. We will show that this effectively results in a guiding 
of electrons through scattering, which is the electronic analogue of the 
well-known Mie scattering [5].


References

1.  P. Vecera, S. Eigler, M. Koleśnik-Gray, V. Krstić, A. Vierck, J. 
Maultzsch, R. A. Schäfer, F. Hauke, A. Hirsch, Scientific Reports 7, 
45165, DOI: 10.1038/srep45165 (2017)
2.  J. Robertson, E.P. O’Reilly, Phys. Rev. B 35, 2946-2957 (1987).
3.  F. Demichelis, S. Schreiter, A. Tagliaferro, Phys. Rev. B 51, 
2143-2147 (1995).
4.	R.L. Heinisch, F.X. Bronold, H. Fehske, Phys. Rev. B 87, 155409 
(2013).
5.  J.M. Caridad, S. Connaughton, C. Ott, H.B. Weber, V. Krstić, Nature 
Communications 7, 12894, DOI: 10.1038/NCOMMS12894 (2016)