Achieving facile control of the wavelength of light emitters is of great significance for many key applications in optoelectronics and photonics, including on-chip interconnection, super-resolution imaging, and optical communication. The Joule heating effect caused by electric current is widely applied in modulating the refractive index of silicon-based waveguides for reconfigurable nanophotonic circuits. Here, by utilizing localized Joule heating in the biased graphene device, we demonstrate electrically controlled wavelength-tunable photoluminescence (PL) from vertical van der Waals heterostructures combined by graphene and two-dimensional transition metal dichalcogenides (2D-TMDCs). By applying a moderate electric field of 6.5 kV·cm–1 to the graphene substrate, the PL wavelength of 2D-TMDCs exhibits a continuous tuning from 662 to 690 nm, corresponding to a bandgap reduction of 76 meV. The electric control is highly reversible during sweeping the bias back and forth. The temperature dependence of Raman and PL spectroscopy reveals that the current-induced local Joule heating effect plays a leading role in reducing the optical direct bandgap of TMDCs. The bias-dependent optical reflectivity and time-resolved photoluminescence measurements show a consistent reduction of the optical band gap of 2D-TMDCs and increased PL lifetimes with the electric field over the heterostructures. Moreover, we demonstrate the consistent device operation from 2D materials grown by chemical vapor deposition, showing great advantages for the scalability.

Atomically thin graphene bubbles can form on a flat substrate due to trapped substances between graphene and the substrate, providing an impressive case to study the intriguing properties of graphene with a nanoscale curvature. The energy balance between the van der Waals interaction of graphene to the substrate and the elastic energy required to deform graphene determines the shape, size, and internal pressure of the graphene bubble. In this work, light interference-induced Newton rings were clearly resolved not only in optical microscopy images but also in Raman spectroscopy maps of the graphene bubble, which originated from the optical standing waves formed in the graphene/SiO 2 /Si microcavity. Importantly, for the first time, such optical standing waves were directly visualized by imaging the spatial temperature distribution of laser-irradiated graphene bubbles through Raman scan mapping. Raman spectra oscillations can be explained by the laser-induced local heating effect and nonuniform temperature on the surface of the graphene bubble. Furthermore, with a higher laser power of illumination, a direct light propulsion of the bubble was observed on a macroscopic scale. The trajectory of the graphene bubble movement can be effectively manipulated by controlling the position and travel direction of the laser beam. These results offer an exciting opportunity to tune the optoelectronic properties of graphene and other twodimensional materials at nanoscale confinement and to achieve the direct light manipulation of matter.

Graphene has outstanding electrical properties such as high carrier mobility and large operation current density due to it’s unique two-dimensional carbon honeycomb lattice structure. However, the carrier mobility and on/off ratio in current of traditional silicon-integrated graphene devices are largely limited due to the substrate-induced scattering effect. Exploring new device structure to prepare graphene devices is an important way to improve their performance. In this work, we propose a new fabricate technique for suspended Graphene/hBN van der Waals heterostructure device with high vield. Combined with improved transfer technology, it greatly improves the probability of successful suspending graphene devices, and we found that the Dirac point of the suspended graphene device is located in nearly zero gate voltage, which reduced the doping in graphene effectively, and further proved the advantages of our device structure in fabricating suspended devices.