Crystalline Orientation‐Tunable Growth of Hexagonal and Tetragonal 2H─PtSe₂ Single‐Crystal Flakes

Abstract

Due to the narrow bandgap, environment stability, and Pt vacancy‐induced magnetism, PtSe2 has been considered a promising candidate for future broadband photodetection and electronics. However, the growth of single‐crystal PtSe2 is still a challenge. Herein, the synthesis of hexagonal and tetragonal 2H─PtSe2 single‐crystal flakes by precisely tailoring the growth temperature is reported. Through atomic structure analysis, hexagonal and tetragonal flakes are proven c‐axis and a‐axis orientations of 2H─PtSe2, indicating the preferred nucleation orientations are along the basal plane and vertically basal plane, respectively. The crystalline orientation‐dependent properties are studied including high‐pressure and polarized in situ‐Raman, electrical transport. The out‐of‐basal plane vibration (A1g) is sensitive to pressure showing 2.744 and 3.282 cm−1 GPa−1 corresponding to c‐2H─PtSe2 and a‐2H─PtSe2, respectively. The conductivity of c‐2H─PtSe2 is 57 times higher than that of a‐2H─PtSe2. Furthermore, by studying magnetic transport at low temperatures, both c‐2H─PtSe2 and a‐2H─PtSe2 exhibit butterfly‐shaped magnetoresistance hysteresis suggesting their ferromagnetic property. The c‐2H─PtSe2 has a higher |MR| ratio and higher coercive field compared with a‐2H─PtSe2, indicating that across multilayer carrier regulation for c‐2H─PtSe2 is more difficult than intra‐layer carrier regulation for a‐2H─PtSe2. This study opens the way to grow different crystalline orientations of 2D materials and will bring more abundant properties.

Sm and Gd Contacts in 2D Semiconductors for High-Performance Electronics and Spintronics

“…Two-dimensional (2D) semiconductor-based transistors are the highest potential candidates in the post-Moore age due to the atomically thin thickness, tunable band gap, and excellent immunity to the short-channel effect. − However, the energy barrier located at the metal electrode and 2D semiconductor interface is easily formed due to the significant difference of their density of states (DOS). − Moreover, the surface defect spontaneously formed on the 2D semiconductor facilitates the formation of the metal chalcogenide bonds, resulting in the Fermi pinning effect and consequently hindering the formation of the carrier accumulation region. − Therefore, the contact resistance between the metal electrode and 2D semiconductor becomes the dominant resistance and reaches even higher than that of the channel region. ,− Thus, reducing this energy barrier and optimizing the contacts are important strategies to improve the performance of 2D semiconductor-based electronics.…”

Cutting Edge High‐Throughput Synthesis and Characterization Techniques in Combinatorial Materials Science

“…[13] In 1995, Xiang and Schultz used mask-assisting deposition to parallelly manufacture a spatially addressable superconducting materials library, which pioneered the combinatorial approach in materials research. [14] After then, the combinatorial approach was applied to research on magnetoresistance, [15,16] luminescent, [17][18][19][20][21][22] superconducting, [13,[23][24][25] semiconductor, [26] catalysis, [27][28][29] metallic alloys, [30][31][32] hydrogels and polymers [33][34][35] and gradually formed a new discipline called as combinatorial materials science. [36][37][38][39] It is noted that the HT concept can run through the entire developing process of materials including computation, synthesis, characterization, and data mining.…”