Hot spot dynamics in carbon nanotube array devices

Large-Scale Thin CsPbBr3 Single-Crystal Film Grown on Sapphire via Chemical Vapor Deposition: Toward Laser Array Application

Single-crystal perovskites with excellent photophysical properties are considered to be ideal materials for optoelectronic devices, such as lasers, light-emitting diodes and photodetectors. However, the growth of large-scale perovskite single-crystal films (SCFs) with high optical gain by vapor-phase epitaxy remains challenging. Herein, we demonstrated a facile method to fabricate large-scale thin CsPbBr₃ SCFs (∼300 nm) on the c-plane sapphire substrate. High temperature is found to be the key parameter to control low reactant concentration and sufficient surface diffusion length for the growth of continuous CsPbBr₃ SCFs. Through the comprehensive study of the carrier dynamics, we clarify that the trapped-related exciton recombination has the main effect under low carrier density, while the recombination of excitons and free carriers coexist until free carriers plays the dominate role with increasing carrier density. Furthermore, an extremely low-threshold (∼8 μJ cm^-2) amplified spontaneous emission was achieved at room temperature due to the high optical gain up to 1255 cm^-1 at a pump power of 20 times threshold (∼20 P_th). A microdisk array was prepared using a focused ion beam etching method, and a single-mode laser was achieved on a 3 μm diameter disk with the threshold of 1.6 μJ cm^-2. Our experimental results not only present a versatile method to fabricate large-scale SCFs of CsPbBr₃ but also supply an arena to boost the optoelectronic applications of CsPbBr₃ with high performance.

Graphene-enabled and directed nanomaterial placement from solution for large-scale device integration

Directed placement of solution-based nanomaterials at predefined locations with nanoscale precision limits bottom-up integration in semiconductor process technology. We report a method for electric-field-assisted placement of nanomaterials from solution by means of large-scale graphene layers featuring nanoscale deposition sites. The structured graphene layers are prepared via either transfer or synthesis on standard substrates, and then are removed once nanomaterial deposition is completed, yielding material assemblies with nanoscale resolution that cover surface areas >1 mm². In order to demonstrate the broad applicability, we have assembled representative zero-dimensional, one-dimensional, and two-dimensional semiconductors at predefined substrate locations and integrated them into nanoelectronic devices. Ultimately, this method opens a route to bottom-up integration of nanomaterials for industry-scale applications.

The placement of nanomaterials at predefined locations is a key requirement for their integration in nanoelectronic devices. Here, the authors devise a method allowing placement of solution-based nanomaterials by using structured graphene layers as deposition sites with the aid of an electric field.