Nano-manipulation; 2D superlattices; Friction; Layered materials; Twisted graphene; Electrical transport; Generation of twisted bi-layer interface
Koren Elad Leven Itai Lörtscher Emanuel Knoll Armin Hod Oded Duerig Urs (2016), Coherent commensurate electronic states at the interface between misoriented graphene layers, in Nature Nanotechnology
Koren Elad Duerig Urs (2016), Moiré scaling of the sliding force in twisted bilayer graphene, in Phyisical Review B
, 94(Iss. 4 — 1), 045401-1-045401-11.
Koren Elad Duerig Urs (2016), Superlubricity in quasicrystalline twisted bilayer graphene, in Phyisical Review B
, 93(Iss. 20 — ), 201404.
Graphene, an ideal 2-dimensional electron gas (2DEG) system, is considered to be one of the most promising materials for future semiconductor electronic and quantum devices due to its superior electronic properties. It also exhibits rich physical properties depending on how it is stacked on top of another 2D crystal. For a non-commensurate stacking the interlayer interaction forms new class of 2D superlattices with electronic properties tailored by the rotation angle between the crystals orientations. When the two layers are made of the same material, an additional set of commensurate 2D superlattices will emerge at specific angles. Attributes such as large lattice parameters, various lattice symmetries, fictitious magnetic field, enhanced magnetic flux per unit cell and strong immunity to surface corrugation may results in superior physical properties. The presence of a rotational mismatch will also determine whether a perpendicular electric field will induced a bandgap in bilayer graphene systems; a prerequisite to build transistor-type devices for next generation computing. From a mechanical aspect, a rotational mismatch in 2D layered systems is known to strongly suppress friction and energy dissipation, an effect which is known as superlubricity.Despite of the rich physics, the challenge to accurately handle, orient and manipulate 2D materials in general and graphene in particular is the main inhibitor for the study of these nanoscale materials and for the realization of devices. In addition, the weak interlayer interaction giving rise to only minor energy difference between large varieties of co-existing stacking configurations is very often leading to controversial results and debates in the scientific community. Consequently, many fundamental questions remain open and therefore prevent full exploitation of the unique mechanical and electronic properties of such layered materials in all their forms. Here, I propose to exploit a new technological approach which I have recently developed at IBM. The technology allows unprecedented accurate and dynamic control over the stacking configuration of 2D layered materials. Combining the excellent nanopositioning accuracy of scanning probe microscopy and the unique mechanical actuation of layered materials solely driven by interface forces (adhesion), the technique enables both lateral and rotational control and manipulation whereas both the mechanical and electronic properties can be characterized for any desired configuration and under variable experimental conditions. Long standing questions such as electric field effect and interlayer charge transport will be addressed for different rotational configurations. In addition, we will explore new exotic 2D phases of layered materials which emerge in special rotational configurations and which were not accessible till date as rotational positioning accuracy better than 1° has to be established.