Black Arsenic-Phosphorus: Layered Anisotropic Infrared Semiconductors with Highly Tunable Compositions and Properties

Abstract: Two-dimensional (2D) layered materials with diverse properties have attracted significant interest in the past decade. The layered materials discovered so far have covered a wide, yet discontinuous electromagnetic spectral range from semimetallic graphene, insulating boron nitride, to semiconductors with bandgaps from middle infrared to visible light. Here, we introduce new layered semiconductors, black arsenic-phosphorus (b-AsP), with highly tunable chemical compositions and electronic and optical properties. Transport and infrared absorption studies demonstrate the semiconducting nature of b-AsP with tunable bandgaps, ranging from 0.3 to 0.15 eV. These bandgaps fall into long-wavelength infrared (LWIR) regime and cannot be readily reached by other layered materials. Moreover, polarization-resolved infrared absorption and Raman studies reveal in-plane anisotropic properties of b-AsP. This family of layered b-AsP materials extend the electromagnetic spectra covered by 2D layered materials to the LWIR regime, and may find unique applications for future all 2D layered material based devices.

• The paper introduces a novel mineralizer-assisted chemical transport method to achieve tunable band gaps ranging from 0.15 eV to 0.3 eV.
• The study combines polarization-resolved infrared absorption, Raman spectroscopy, and DFT calculations to reveal marked in-plane anisotropy in b-AsP materials.
• The research highlights the potential of b-AsP for LWIR photodetection and electronics, paving the way for innovative 2D semiconductor technologies.

Overview of Black Arsenic-Phosphorus: Layered Anisotropic Infrared Semiconductors with Tunable Compositions and Properties

The paper presents a thorough investigation into black arsenic-phosphorus (b-AsP), a new family of layered semiconducting materials characterized by anisotropic properties and significant tunability in their electronic and optical attributes. Through innovative synthesis techniques grounded in a mineralizer-assisted chemical transport reaction, the authors effectively manipulate the arsenic and phosphorus composition to generate materials possessing highly customizable properties. This pioneering effort marks a considerable advancement in the field of two-dimensional (2D) materials, particularly in their potential application to the long-wavelength infrared (LWIR) regime.

Highlights and Results

A principal achievement of this study is the successful synthesis and characterization of b-AsP materials with varying arsenic phosphorus ratios. Employing a mineralizer-assisted short way chemical transport method allows precise control over composition, ranging from pure black phosphorus (b-P) to compositions significantly rich in arsenic. The resultant materials exhibit tunable band gaps from 0.3 eV to 0.15 eV, effectively extending into the LWIR range and addressing gaps that other 2D materials like graphene and TMDCs fail to cover. Notably, this tunability is a direct consequence of altering the arsenic content, which influences the electronic structure and interlayer interactions.

The authors conducted extensive polarization-resolved infrared absorption studies and Raman spectroscopy to evaluate the anisotropic properties of these materials. The b-AsP materials demonstrated significant polarization-dependent behavior, reflecting distinct in-plane anisotropic characteristics. These findings were complemented by density functional theory (DFT) calculations, providing theoretical underpinning and validation for the experimental observations.

In terms of electronic transport properties, the construction of back-gate field-effect transistors (FETs) using these materials reinforced their semiconducting nature. Notably, the ambipolar transport behavior and distinctive on/off current ratios further corroborate the potential of b-AsP in electronic applications.

Implications and Future Prospects

The successful characterization of b-AsP opens avenues for its integration into devices operating within the LWIR spectrum. This novel material thus offers significant promise for optoelectronic applications, including infrared photodetection and optical imaging, within a spectral range that holds strategic and commercial importance.

The anisotropic electronic and vibrational properties of b-AsP invite further exploration into tailoring these characteristics for specific applications. The research holds potential for influencing future developments in the synthesis of 2D materials with tunable properties. Additionally, understanding interlayer interactions within these materials could assist in refining methods for material manipulation and application.

Conclusion

By shaping the composition of black arsenic-phosphorus, the authors have unlocked a new toolkit for the design of 2D semiconductors through controlled synthesis. This research contributes a significant piece to the puzzle of expanding the functional utility of layered materials in regions of the electromagnetic spectrum previously beyond reach. As research progresses, black arsenic-phosphorus may serve as a foundation for innovative solutions in electronics and optoelectronics, particularly in domains requiring specific infrared characteristics. The groundwork laid by this study promises advancements that could reshape our approach to material science in semiconductor technology.