Periodic Reporting for period 3 - Strained2DMaterials (Unlocking new physics in controllably strained two-dimensional materials)
Reporting period: 2018-11-01 to 2020-04-30
We developed an approach to chemically modify 2D materials and to investigate strain and doping that results from such modification. We showed that defects in 2D materials are chemically active. We demonstrated approaches to study the properties of such defects and to modify them in situ.
Together with the group of Saikat Ghosh (IIT Kanpur), we investigated 2D material membranes towards applications in NEMS (nanoelectromechanical systems). Specifically, we studied graphene resonators deposited on a much larger and heavier SiNx membrane. We demonstrated widely tunable, broad bandwidth, and high gain all-mechanical motion amplifiers based on graphene/silicon nitride (SiNx) hybrids. In these devices, a tiny motion of a large-area SiNx membrane is transduced to a much larger motion in a graphene drum resonator coupled to SiNx. We obtain a displacement power gain of 38 dB and demonstrate 4.7 dB of squeezing, resulting in a detection sensitivity of 3.8 fm/Hz^0.5 close to the thermal noise limit of SiNx. Furthermore, we discovered that strong coupling to mechanically non-linear graphene induces large non-linearity in normally mechanically linear SiNx. The induced non-linearity in SiNx allows us to observe a range of behavior previously unseen in SiN resonators including frequency comb generation and Arnold tongues.
1) Discovery of a non-linear Hooke's law in crumpled graphene
2) Experimental discovery of exciton/trion funneling in non-uniformly strained TMDCs and single quantum emitters in non-uniformly strained hBN
3) Development of NEMS devices based on coupled SiNx/graphene hybrids: ultrasensitive mechanical amplifiers and devices with tunable nonlinearities
4) Development of approaches to non-uniform strain engineering
5) Development of approaches to chemically engineer 2D materials
Until the end of the project, we plan to achieve the following main goals:
1) Demonstration of strain-controlled 2D ""phononic crystals""
2) Demonstration of tunable pseudomagnetic fields in TMDC and graphene. Exploration of the emergent physical phenomena related to these fields.
3) Development of techniques to probe surface contamination of 2D materials, towards the creation of devices with well-characterized mechanical properties."