Since decades, 2-D semiconductors have been prepared by gas phase deposition techniques and incorporated in opto-electronic devices using lithography. More recently, 2-D quantum well layers have been molded into the honeycomb geometry by lithography and the use of nanostructured gates. Alternatively, nanostructured 2-D semiconductors have been prepared by nanocrystal self-assembly: With oriented attachment of nanocrystals, atomically coherent semiconductors can be prepared, with a superimposed square or honeycomb geometry.
The honeycomb geometry allows one to combine all good properties of a semiconductor (such as a 2 band gap) with valence and conduction bands that show a linear energy-wavevector dispersion relation, and thus massless carriers (as in graphene). It is thus of great interest to compare the properties of these new semiconductors with the conventional 2-D systems with parabolic bands. 2-D semiconductors with a honeycomb geometry show unseen properties; not only the Dirac-type bands, but due to spin-orbit coupling, also a quantum spin Hall edge effect and topological flat bands. This conference wishes to bring together researchers form the nanocrystal field, and of the classic and novel 2-D semiconductors to discuss the latest theoretical and experimental developments with a special focus to compare 2-D semiconductors with parabolic bands and a linear Dirac-type band structure.
- Synthesis of nanostructured semiconductors by nanocrystal assembly and oriented attachment Lithographic imprint of the honeycomb geometry in 2-D semiconductors
- Incorporation of self-assembled structures in opto-electronic devices
- Transport properties of nanostructured semiconductors
- Opto-electrical properties of Dirac systems vs. conventional parabolic semiconductors
- Topological electronic phases, such as the quantum spin Hall effect
Vanmaekelbergh's research started in the field of semiconductor electrochemistry in the 1980s; this later evolved into the electrochemical fabrication of macroporous semiconductors as the strongest light scatterers for visible light, and the study of electron transport in disordered (particulate) semiconductors. In the last decade, Vanmaekelbergh's interest shifted to the field of nanoscience: the synthesis of colloidal semiconductor quantum dots and self-assembled quantum-dot solids, the study of their opto-electronic properties with optical spectroscopy and UHV cryogenic Scanning Tunneling Microscopy and Spectroscopy, and electron transport in electrochemically-gated quantum-dot solids. Scanning tunnelling spectroscopy is also used to study the electronic states in graphene quantum dots. More recently, the focus of the research has shifted to 2-D nano structured semiconductors, e.g. honeycomb semiconductors with Dirac-type electronic bands.
Alexander AchtsteinAlexander W. Achtstein studied Physics at University of Augsburg and Ludwigs Maximilians University Munich (LMU). He recieved a PhD from Technical University of Berlin in 2013. After a postdoc period at TU Delft he returned to TU Berlin. His research concentrates on the linear and nonlinear optical as well as electronic properties of 2D semiconductors, with a focus on II-VI nanosheets and transition metal dichalcogenides.
I obtained my PhD degree in applied physics at Ghent University in 2009, studying near-infrared lead salt quantum dots. This was followed by a postdoc on quantum dot emission dynamics at Ghent University in collaboration with the IBM Zurich research lab. In 2012 I joined the Istituto Italiano di Tecnologia, where I led the Nanocrystal Photonics Lab in the Nanochemistry Department. In 2017 I returned to Ghent University as associate professor, focusing mostly on 2D and strained nanocrystals. The research in our group ranges from the synthesis of novel fluorescent nanocrystals to optical spectroscopy and photonic applications.
Laurens Siebbeles (1963) is leader of the Opto-Electronic Materials Section and deputy head of the Dept. of Chemical Engineering at the Delft University of Technology in The Netherlands. His research involves studies of the motion of electrons in novel nanostructured materials that have potential applications in e.g. solar cells, light-emitting diodes and nanoelectronics. Materials of interest include organic nanostructured materials, semiconductor quantum dots, nanorods and two-dimensional materials. Studies on charge and exciton dynamics are carried out using ultrafast time-resolved laser techniques and high-energy electron pulses in combination with quantum theoretical modeling.
Frank Wise