Search

Two-dimensional (2D) van der Waals heterojunctions have many unique properties, and energy band modulation is central to applying these properties to electronic devices. Taking the 2D graphene/MoS2 heterojunction as a model system, we demonstrate that the band structure can be finely tuned by changing the graphene structure of the 2D heterojunction via ultraviolet/ozone (UV/O3). With increasing UV/O3 exposure time, graphene in the heterojunction has more defect structures. The varied defect levels in graphene modulate the interfacial charge transfer, accordingly the band structure of the heterojunction. And the corresponding performance change of the graphene/MoS2 field effect transistor indicates the shift of the Schottky barrier height after UV/O3 treatment. The result further proves the effective band structure modulation of the graphene/MoS2 heterojunction by UV/O3. This work will be beneficial to both fundamental research and practical applications of 2D van der Waals heterojunction in electronic devices. [ABSTRACT FROM AUTHOR]

The Au/SiO2 nanocomposite grating coupler with a period of 600 nm was fabricated by implantation of 140 keV Au ions at a fluence of 6 × 1016 ions·cm−2 in combination with subsequent electron-beam lithography and ion beam etching. The thermal evolution of Au nanoparticles and its influence on the vertical coupling efficiency of the prepared grating coupler has been investigated in detail. The results clearly show that the coupling efficiency of the nanocomposite grating coupler could be affected by the thermal evolution of Au nanoparticles, which increases in the annealing temperature range up to 800 °C, and then decreases at 900 °C and above. Theoretical calculation demonstrates that the change of the coupling efficiency should be closely related to the synergistic effect of the scattering effect and the variation in the volume fraction of Au nanoparticles due to the thermal growth. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) van der Waals heterojunctions have many unique properties, and energy band modulation is central to applying these properties to electronic devices. Taking the 2D graphene/MoS2 heterojunction as a model system, we demonstrate that the band structure can be finely tuned by changing the graphene structure of the 2D heterojunction via ultraviolet/ozone (UV/O3). With increasing UV/O3 exposure time, graphene in the heterojunction has more defect structures. The varied defect levels in graphene modulate the interfacial charge transfer, accordingly the band structure of the heterojunction. And the corresponding performance change of the graphene/MoS2 field effect transistor indicates the shift of the Schottky barrier height after UV/O3 treatment. The result further proves the effective band structure modulation of the graphene/MoS2 heterojunction by UV/O3. This work will be beneficial to both fundamental research and practical applications of 2D van der Waals heterojunction in electronic devices. [ABSTRACT FROM AUTHOR]

TiO 2 in nanoscale exhibits unique physicochemical and optoelectronic properties and has attracted much more interest of the researchers. In this work, TiO 2 nanostructures are synthesized in amorphous SiO 2 slices by implanting Ti ions, or sequentially implanting Ti and Cu ions combined with annealing at high temperature. The morphology, structure, spatial distribution and optical properties of the formed nanostructures have been investigated in detail. Our results clearly show that the thermal growth of TiO 2 nanostructures in SiO 2 substrate is significantly enhanced by presence of post Cu ion implantation, which depends strongly on the applied Cu ion fluence, as well as the annealing atmosphere. Due to the formation of Cu 2 O in the substrate, rutile TiO 2 nanorods of large size have been well fabricated in the Ti and Cu sequentially implanted SiO 2 after annealing in N 2 atmosphere, in which Cu 2 O plays a role as a catalyst. Moreover, the sample with well-fabricated TiO 2 nanorods exhibits a narrowed band gap, an enhanced optical absorption in visible region, and catalase-/peroxidase-like catalytic characteristics. Our findings provide an effective route to fabricate functional TiO 2 nanorods in SiO 2 via ion implantation.