Controlled Synthesis And Device Construction Of Two-Dimensional Hetero-Structures And Hetero-Phase Structures

Two-dimensional?2D?transition metal chalcogenides?TMCs?atomic crystals have emerged as promising building blocks for creating functional architectures and devices due to their diverse compositions and unique properties.2D heterostructures and hetero-phase structures composed of TMCs exhibit new physical phenomena and unique electrical properties,and therefore,have great potential for the applications in future nanoelectronics and optoelectronics.However,the studies on 2D heterostrccutres are still at the infant stage and there exist many challenges in electronic-grade 2D heteromaterials processing,such as precisely controlled synthesis of the heteromaterials at atomic scale,the structure-property relationship,the nondestructive construction of high-performance device and integrated circuits and so on.Here,we explored chemical methods for synthesizing 2D heterostructures and hetero-phase structures based on TMCs by the rational design of precursors.We investigated the relationship between composition,structure and properties in these 2D heterostructures and hetero-phase structures and explored possible approaches for tuning the band structure of these materials.We characterized the electrical properties of these 2D heterostructures and hetero-phase structures for fabricating high performance field effect devices.We proposed a nondestructive approach for constructing 2D electronic devices in which the 2D electronic components in the active layer are chemically synthesized and integrated simultaneously in a single step.The main contents are as the following three parts:1.Controlled synthesis and properties of 2D MoS₂/WS₂ heterostructuresThe major challenge in the growth of MoS₂/WS₂ heterostructures is the sequential supply of Moand W to avoid the formation of the alloys.To address this,we developd a novel approach for synthesizing MoS₂/WS₂ heterostructures via chemical vapor deposition?CVD?by using core-shell WO_3-x/MoO_3-xnanowires as growth precursor,which naturally ensures the sequential growth of MoS₂ and WS₂.We investigated the relationship between composition,structure and properties in these 2D heterostructures via various high-precision characterizations and measurements.The obtained heterostructures exhibited high crystallinity,strong interlayer interaction,and high mobility,suggesting their promising applications in nanoelectronics.2.Controlled patterned synthesis of 2D 1T'/2H MoTe₂hetero-phase structuresWe proposed a new method for preparing 2H/1T'MoTe₂ hetero-phase structures via CVD by tuning the defects densities in the productions.As the thin film precursors for the phase-selective growth of MoTe₂ can be patterned into desired architectures via standard lithographic processes,we achieved the simultaneous growth of 2H and 1T'MoTe₂ into predesigned patterns.The interface of the two phases was connected seamlessly with atomically sharp boundaries,suggesting that the two phases were connected via covalent bonds.The hetero-phase structures can potentially serve as semiconducting channels and metallic electrodes and interconnects to create functional devices.3.Construction and integration of all 2D devicesWe presented a nondestructive approach for constructing 2D electronic devices in which the 2D electronic components in the active layer are chemically synthesized and integrated simultaneously in a single step and each component is connected via covalent bonds instead of physical interfaces.As a proof of the concept,we synthesized FETs and arrays of logic devices with high performance through the phase-patterned growth of ultrathin atomic layers.We also explored the construction of FETs with ultrashort gate length,multilayered FETs with vertical interconnections and flexible devices with our approach.This approach makes the design and optimization of electronic devices based on 2D materials much more flexible and preserves the intrinsic performance of the materials to the largest extent and therefore,provides a new route for constructing nanoelectronic circuits.