Polytypism in semiconductors

Recent advances in the fabrication and characterization of polytypes semiconductor nanostructures have made crystal phase engineering a well-established tool to tailor material properties. This interdisciplinary symposium aims to identify challenges in the synthesis and characterization of new polytype semiconductors.

Scope:

Semiconductors constitute the building blocks of the current  microelectronic and optoelectronic industry. The standard (low energy) crystal phases of most semiconductors have already revealed all their potential and limitations in the development of advanced devices. On the other hand, polytypes of most semiconductors possess very different and peculiar physical characteristics with respect to their lowest energy structures. Main scope of this symposium is to promote the progress in the fundamental understanding (in the broad sense of theory combined with experiments) of the role of crystal phase engineering in materials’ design. Specific topics and issues that will be carefully considered are:

Synthesis: The synthesis (pressure, indentation, epitaxy…) of polytype single crystals or heterostructures in a controlled manner represents a great challenge for a long time. The growth of nanowires has initiated a new impetus to this effort. Besides, new paradigms such as selective area growth or remote epitaxy open plenty of rooms to explore for original phase synthesis.

Experimental characterization: It is expected that a novel phase may alter remarkably the properties of the nanostructures (such as band gap, effective mass, phonon and electron scattering processes and excitonic properties) due to the presence of distinct crystal symmetry or of a significant interface between two phases. This stimulates the development and application of advanced experimental methods.

Theoretical modelling: Experimental investigation of novel phases in nanostructures requires deep quantitative understanding of condensed matter at nanoscale. Indeed, a significant uncertainty prevails in discerning the fundamental effect of crystal phase-dependent factors, from other factors (size, shape, composition, local strain, interface states…) that affect the main physical and chemical properties. This is the  role of theory, modeling and simulations in the description of semiconductors polytypes.

Hot topics to be covered by the symposium:

• Phase transformation under extreme conditions or indentation
• Appropriate growth strategies of new crystal phases (VLS growth, Van der Walls epitaxy, …) and synthesis of polytypic heterostructures
• Modeling of critical processes during the synthesis of polytypes nanostructures in order to reach controlled composition, structure, geometry
• Experimental methods for investigating the properties of polytypic structures
• Theoretical methods for the description of electronic, optical and transport properties of novel polytypes
• Devices for the exploitation of the properties of polytypic structures

Confirmed invited speakers:

• Riccarco Rurali - Spain - rrurali@icmab.es
• Anna Fontcuberta y Morral - Switzerland - anna.fontcuberta-morral@epfl.ch
• Val Zwiller - Sweden - zwiller@kth.se
• Xavier Cartoixa - Spain - xavier.Cartoixa@uab.es
• Claes Thelander -  Sweden - claes.thelander@ftf.lth.se
• Vladimir Dubrovski – Russia - dubrovskii@mail.ioffe.ru
• Yann le Godec – France - yann.le_godec@sorbonne-universite.fr
• Heinz Schmid - Germany - sih@zurich.ibm.com
• Sebastien Lehmann - sebastian.lehmann@ftf.lth.se
• Claudia Rodhl – Germany - claudia.roedl@uni-jena.de
• Federico Panceira – France - federico.panciera@c2n.upsaclay.fr
• Jonas Lahnemann (Germany) jonas@pdi-berlin.de
• Lincoln Lauhon (USA) lauhon@northwestern.edu

Scientific committee:

• Gilles Patriarche C2N/CNRS/UPSaclay - France - gilles.patriarche@c2n.upsaclay.fr
• Kimberly Dick-Thelander Lund University - Sweden - kimberly.dick_thelander@chem.lu.se
• F. Bechstedt, Friedrich-Schiller Universität Jena - Germany - bechsted@ifto.physik.uni-jena.de