Layered Chalcogenide Materials Synthesis, Energy and Emerging Anisotropic Applications

Dear Colleagues,

Two-dimensional (2D) chalcogenides are a class of materials composed of transition metals or post-transition metals bonded with chalcogen elements (S, Se, or Te). These materials exhibit unique electronic, optical, and mechanical properties, making them highly attractive for applications in nanoelectronics, optoelectronics, energy storage, and catalysis. This low-symmetry anisotropic material has recently been revitalized due to its high intrinsic mobility and in-plane anisotropic properties, which are useful in anisotropic electronic and optoelectronic devices. Anisotropic optoelectronics based on low-symmetry materials hold immense potential for enabling multidimensional visual perception with improved miniaturization and integration capabilities. The low symmetries of these novel materials give rise to inhomogeneous materials’ properties (such as electron, thermal, valley, and spin transport as well as optical responses), as well as entirely new properties such as ferroelasticity, ferroelectricity, spin-wave phenomena, large nonlinear optical response, and superconductivity. Novel electronic topological properties, nonlinear elastic properties, and structural phase transformations also take place due to low crystal symmetry. Since these unique intrinsic angle-dependent properties of low-symmetry materials cannot be easily realized in highly symmetric materials, the emergence of in-plane anisotropic properties can provide another new degree of freedom to tune previously unexplored properties and offer a tremendous opportunity for designing new devices with emerging technology, including quantum applications.

The anisotropic materials possess merits comparable to those of the most studied isotropic graphene and 2D transition metal dichalcogenides (TMDs), but also exhibit unique in-plane electrical, optical, and thermal anisotropy due to their asymmetrical crystalline structure. The anisotropic properties provide researchers one more degree of freedom to design and fabricate high-performance and even novel devices. However, there are still many problems to resolve to attain a comprehensive understanding of the properties of low symmetry anisotropic materials and realize their full potential in multifunctional applied fields. Despite the wide study of the optical anisotropy of low-symmetry materials, the quantitative measurement of this key parameter is still a major hurdle. Obtaining low-symmetry materials at a large scale calls for further investigations to be performed. Although many researchers have deeply investigated the properties of heterostructures based on low-symmetry materials, the isotropic/anisotropic and anisotropic/anisotropic 2D stacked heterostructures require more in-depth study to elucidate the unique properties, including via quantum science and upgrading the device performance. Since the anisotropic ratio of these materials is focused, exploring new materials and techniques to enhance the in-plane anisotropy is essential and promising for future anisotropic devices including quantum technological applications. Moreover, integrating anisotropic materials with photonic structures, providing a versatile platform for light–matter interactions, further enhances the field of integrated photonics with anisotropic materials. In this perspective, the goal of this Special Issue is to focus on the synthesis, emerging application of anisotropic 2D chalcogen materials, and heterostructures for photonic and optoelectronic devices including emerging quantum applications.

The boom of new low-symmetry layered materials with high anisotropy could open up considerable possibilities for next-generation anisotropic multifunctional devices. This Special Topic is intended to bring together researchers working on cutting-edge research in this field, including, but not limited to, the following:

1. Mechanism and technology for growth and fabrication.
2. In-plane anisotropy: electrical transport, magneto-transport, optoelectronic, thermoelectric, ferroelectric, and piezoelectric properties.
3. Low-symmetry 2D materials.
4. Optoelectronic properties of anisotropic materials.
5. Optoelectronic devices and sensors.
6. Theoretical analysis of anisotropic materials with low symmetry: modeling and simulation.
7. Anisotropic/isotropic and isotropic/anisotropic heterostructures.
8. Spintronics and quantum applications.

Dr. Abdus Salam Sarkar
Dr. Subhashis Das
Guest Editors

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• two-dimensional (2D) chalcogenide materials
• synthesis
• in-plane anisotropy
• photodetectors
• solar cells
• phototransistors
• sensors and devices
• anisotropic quantum and spintronics