ABSTRACT
The ever-increasing space exploration enterprise calls for novel and high-quality radiation-resistant materials, among which nonlinear optical materials and devices are particularly scarce. Two-dimensional (2D) materials have shown promising potential, but the radiation effects on their nonlinear optical properties remain largely elusive. We previously fabricated 2D bismuthene for mode-locking sub-ns laser; herein, their space adaption was evaluated under a simulated space radiation environment. The as-synthesized thin layers of bismuthene exhibited strong third-order nonlinear optical responses extending into the near-infrared region. Remarkably, when exposed to 60Co γ-rays and electron irradiation, the bismuthene showed only slight degradation in saturable absorption behaviors that were critical for mode-locking in space. Ultrafast spectroscopy was applied to address the radiation effects and damage mechanisms that are difficult to understand by routine techniques. This work offers a new bottom-up approach for preparing 2D bismuthene, and the elucidation of its fundamental excited-state dynamics after radiation also provides a guideline to optimize the material for eventual space applications.
ABSTRACT
Ultrasmall metallic nanogaps are of great significance for wide applications in various nanodevices. However, it is challenging to fabricate ultrasmall metallic nanogaps by using common lithographic methods due to the limited resolution. In this work, we establish an effective approach for successful formation of ultrasmall metallic nanogaps based on the spontaneous nanoscale dewetting effect during metal deposition. By varying the initial opening size of the exposed resist template, the influence of dewetting behavior could be adjusted and tiny metallic nanogaps can be obtained. We demonstrate that this method is effective to fabricate diverse sub-10 nm gaps in silver nanostructures. Based on this fabrication concept, even sub-5 nm metallic gaps were obtained. SERS measurements were performed to show the molecular detection capability of the fabricated Ag nanogaps. This approach is a promising candidate for sub-10 nm metallic gaps fabrication, thus possessing potential applications in nanoelectronics, nanoplasmonics, and nano-optoelectronics.
ABSTRACT
A graphene oxide paper (GOP) was irradiated with 500 keV proton for total fluence of 2 × 1013 cm-2 to 2 × 1015 cm-2 in a ground-based irradiation simulator. The spacing of layer, surface chemical composition, structural defects, thermal conductivity and electrical property of the GOP before and after irradiation was measured. The results indicated that the spacing of layer decreased after irradiation. The ratio of total carbon atom and total oxygen atom increased from 2.40 to 4.31 as well as the sp2 hybridized carbons obviously increased after 2 × 1015 cm-2 irradiation. The XPS analysis suggested the occurrence of reduction, and the Raman spectra indicated that the defects were produced after proton irradiation. Furthermore, the thermal conductivity of GOP decreased, and then increased smoothly as the irradiation fluences were increased, and the electrical property showed the similar trend. The change in the thermal and electrical properties for GOP could be attributed to the defects and the removal of oxygen-containing functional groups, which lead to the phonon conduct path and scattering centers changed under proton irradiation. This study could promote the application of GOP in future space expeditions.
