Now, researchers at Shanghai Jiao Tong University, in collaboration with other institutions, have joined forces to announce an innovative new approach. This scalable, green method produces high yields of high-quality black phosphorus nanoribbons (BPNRs). This is a major step towards increasing our ability to produce BPNRs with uniform dimensions and sharp boundaries. It of course reduces defects too, and that is especially important for electronic applications. This unique approach applies strain to pump up the performance of electronic devices. It provides a consistent supply of high-performance materials.
Under the direction of Professor Changxin Chen, the research team has been engaged in a concentrated effort. They are working toward a reproducible process to synthesize narrow BPNRs with smooth edges and good orientation. They recently published those findings in the journal Nature Materials. Their approach has astounding implications to change the way materials are applied in the fabrication of electronics.
This new fabrication technique enables the uniform production of nanoribbons with an average width of 32 nanometers. Remarkably, some of these ribbons are only 1.5 nanometers wide. This is an important breakthrough, as the previous BPNRs with smallest widths ever reported are only 1.5 nm wide. This approach provides an efficient strategy for researchers to prepare large-area, few-layer, two-dimensional black phosphorus (BP). This development opens up the possibility for producing more efficient electronic components.
Enhanced Properties of BPNRs
Unlike traditional alternatives such as carbon nanotubes and graphene nanoribbons, BPNRs have notable benefits. One distinguishing attribute is their fully semiconducting nature compared to carbon nanotubes which can exist as either semiconducting or metallic. Professor Chen highlighted this distinction, stating, “BPNRs offer advantages as channel materials over other candidates such as carbon nanotubes, graphene nanoribbons, and two-dimensional (2D) black phosphorus (BP). For example, BPNRs are entirely semiconducting.”
Moreover, BPNRs have better mobility/bandgap trade-off than graphene nanoribbons. To that end, Professor Chen pointed out numerous benefits of BPNRs. They remove the requirement to synthesize large-area, few-layer 2D BP and offer large, widely tunable bandgaps. This unique combination of properties makes BPNRs a compelling and attractive alternative in the advancement of high-performance electronic devices.
With their new method of fabrication, Chen and his team were able to realize this exciting technology with a remarkable yield of 95%. This maximizes their ability to create a large, consistent output of high-quality nanoribbons, quickly and efficiently. This high yield is especially important for commercial applications, where scalability can be a major barrier.
Superior Performance in Photodetection
The recently developed narrow BPNRs have shown excellent performance as near-infrared photodetectors. These lead to responsivity measures as high as 11.2 A/W, and specific detectivity greater than 1.1×10^11 cm Hz^1/2 W^-1. These remarkable metrics place these nanoribbons well beyond most current generation near-infrared detectors fabricated from one-dimensional and two-dimensional nanomaterials, as well as other hybrid systems.
Professor Chen noted the significance of these findings in the context of field-effect transistor (FET) applications: “With the prepared BPNRs, the field-effect transistor performance with an on/off ratio of 1.7×10^6 and mobility of 1,506 cm² V⁻¹ s⁻¹ represents the highest comprehensive performance among the FETs based on BPNRs or 2D BP reported so far.” Such compelling performance metrics are a testament to the unique and transformative role that BPNRs may occupy in the next generation of e-devices.
The research team was able to succeed through unorthodox means. They used a pulsed thermal evaporation method to synthesize bulk BP crystals with an enlarged lattice parameter along the armchair direction. “We first used a short-way transport reaction to synthesize bulk BP crystals with a slightly enlarged lattice parameter along the armchair direction,” explained Chen.
Future Directions for Research
“We’re working on improving our collection and research processes,” says Professor Chen. Specifically, they pursue even more extreme control over the production of BPNRs. “As part of our future research, we will develop controlled strategies to produce high-quality BPNRs with unidirectional alignment and uniform widths,” he stated.
These developments are significant for addressing current issues with scalability and structural variability. Without them, imparting BPNRs into practical large-scale electronic circuits may be under considerable constraints. Meeting these goals is critical not just to maximize the usefulness of BPNRs, but to spur innovation in semiconductor technology.