RESUMEN
Emerging two-dimensional semiconductor materials possess a giant second order nonlinear response due to excitonic effects while the monolayer thickness of such active materials limits their use in practical nonlinear devices. Here, we report 3300 times optomechanical enhancement of second harmonic generation from a MoS2 monolayer in a doubly resonant on-chip optical cavity. We achieve this by engineering the nonlinear light-matter interaction in a microelectro-mechanical system enabled optical frequency doubling device based on an electrostatically tunable Fabry-Perot microresonator. Our versatile optomechanical approach will pave the way for next generation efficient on-chip tunable light sources, sensors, and systems based on molecularly thin materials.
RESUMEN
We report that the size dependence of electronic properties at nanosized metal-semiconducting oxide interfaces is significantly affected by the interface atomic structure. The properties of interfaces with two orientations are compared over size range of 20-200 nm. The difference in interface atomic structure leads to electronic structure differences that alter electron transfer paths. Specifically, interfaces with a higher concentration of undercoordinated Ti result in enhanced tunneling due to the presence of defect states or locally reduced tunnel barrier widths. This effect is superimposed on the mechanisms of size dependent properties at such small scales.
RESUMEN
Here we demonstrate the effects of tip loading force on the contact quality and local current-voltage character between conductive AFM tips and individual noble metal nanoparticle-strontium titanate (NP-STO) interfaces. These results show that though contact quality may improve with increased loading force, nanoparticle deformation remains negligible for loading forces in the nN-µN range. Maintaining a moderate loading force in the tens to hundreds of nN therefore enables size-dependent transport of individual NP-STO interfaces to be determined.