(Invited) Wrinkling Graphene with Bacteria and Functionalization of MoS2 for Electronic Applications

The presentation with have two parts: (a) Wrinkle formation of 2D nanomaterials via bacteria and (b) MoS₂ functionalization for electronic applications. (A) Wrinkle-formation via thin-sheet compression is a phenomenon readily exhibited by two-dimensional (2D) nanomaterials (like graphene). In graphene, these wrinkles can modify the band structure and local electronic states. Here, we show that bacterial cells can be employed as sacrificial scaffolds to induced controlled wrinkles on attached graphene. The wrinkles orient longitudinally on cylindrical bacterial cells and their attributes (wavelength and amplitude) can be controlled with high precision (in nanometer scale) and obey the modified Herringbone model. A circumferential Young’s modulus of 39 MPa suggests a wrinkle-wavelength of 27.3 nm, consistent with our measurements (33 nm in FESEM and 36.7 nm in AFM images). (B) Ultrathin two dimensional metal dichalogenides (MoS₂, WS₂, so forth) exhibit confinement of carriers, evolution of band structure, high on/off rectification, and high thermal absorption. However their incorporation into other systems requires controlled functionalization and/or interaction with other nanoscale entities.  Here we enhance the stable sulfur/nobel metal functionalization via both diffusion limited aggregation and instantaneous reaction arresting (using microwaves).  These gold nanoparticles are incorporated selectively on MoS₂ crystallographic edges (with 60^o displacement). The Raman, electrical and thermal studies indicate a remarkably capacitive interaction between gold and thin MoS₂ sheet (CAu-MoS₂ = 2.17 mF/cm2), a low Schottky barrier (14.52 meV), a vastly reduced carrier-transport thermal-barrier (253 to 44.18 meV after gold functionalization), and increased thermal conductivity (from 15 W/mK to 23 W/mK post gold deposition). This process provides a route to affiliate MoS₂ with potential electronic application, such as electrodes attachment to hetero-structures of graphene and MoS₂, where a gold film could be grown to act as an electron-tunneling gate-electrode connected to MoS₂.