[seminar] Podsjetnik na DANAŠNJI seminar na IF-u u 15:00h

[Niksa Krstulovic]

Poštovani, ispričavam se na prošloj obavijesti bez naslova današnjeg predavanja. 
Obavijest s naslovom šaljem u nastavku. Hvala na razumijevanju. 









Institut za fiziku, Bijenička cesta 46, 



predavaonica u zgradi Mladen Paić 

četvrtak, 22. svibnja 2014., u 15:00 sati 







PHOTOPHYSICS OF SEMICONDUCTING TWO-DIMENSIONAL 

TRANSITION METAL DICHALCOGENIDES 





Christoph Gadermaier 







Department of Complex Matter and International Postgraduate School 

Jozef Stefan Institute 

Jamova 39, 1000 Ljubljana, Slovenia 

E-mail: christoph.gadermaier at ijs.si 





Recent progress in the exfoliation of layered materials and the nanofabrication of functional structures has revived the interest in two-dimensional materials with properties complementary to graphene, in particular transition metal dichalcogenides (TMDs) such as MoS2. Depending on the coordination and oxidation state of the metal atoms, TMDs can be metallic, semimetallic, or semiconducting. In addition, superconductivity and charge-density wave effects have been observed in some TMDs. A transistor and a logical circuit device based on a monolayer of MoS2 have recently been demonstrated. 

The functional properties of any material are determined by its response to external stimuli, which drive it out of equilibrium. Hence, fundamental understanding is gained from studying relaxation processes. A salient question in semiconducting TMDs is the electronic nature of photoexcited states, which determines their optoelectronic and energy harvesting functionalities. On the one hand, there are imperative indications for excitons as the primary photoexcitations, with a binding energy that strongly increases with decreasing number of layers, reaching 0.5 – 1 eV for the monolayer. On the other hand, efficient photovoltaics and highly sensitive photodetectors based on monolayer MoS2 transistors have been demonstrated, which both require mobile carriers created by the absorption of light. 

Here we use femtosecond optical spectroscopy to show that a significant fraction of the photoexcited excitons in MoS2 dissociates within a few ps. We discuss the implications of the excitation wavelength and layer number dependence for the possible dissociation mechanism and present preliminary results on the electron dynamics in heterostructures with an increased charge separation efficiency. 







Voditelji seminara IF-a: Nikša Krstulović i Osor Bari šić 


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Nikša Krstulović, PhD 
Research associate 

Institute of Physics 
Bijenicka 46 
HR-10000 Zagreb, Croatia 

Phone: 00385 1 4698 872 
00385 1 4698 851 
Fax: 00385 1 4698 889 

http://www.ifs.hr/ 
http://spectra.ifs.hr/ 
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