image: (a) Schematic of monolayer Sb2O3 with (111) plane. (b) Schematic illustration of growth modes and molecule behavior during the typical vdW epitaxy process. (c) Illustration of the proposed growth pathway of single-crystal Sb2O3 thin film. (d-g) Corresponding AFM images. Scale bar, 200 nm.
Credit: ©Science China Press
A groundbreaking study on van der Waals (vdW) epitaxy has introduced new possibilities in the production of wafer-scale, single-crystal molecular films, addressing a longstanding challenge in semiconductor technology.
To develop ultrathin materials for next-generation ultra-scaled devices, the fabrication of high-quality 2D materials is essential. While vdW epitaxy has been successfully applied to 2D atomic crystals, the weak vdW forces in all three dimensions within molecular crystals make it challenging to achieve the ordered molecular alignment required for high-quality thin films. This limitation further restricts their application in advanced devices.
In a new research article published in National Science Review, scientists at Huazhong University of Science and Technology and Hebei University have fine-tuned the nucleation process by controlling the interactions between the epitaxial layer and the substrate. Through careful design of lattice and symmetry matching, they achieved unidirectional nuclei formation, essential for forming uniform crystal structures. Additionally, the team tackled the Schwoebel-Ehrlich barrier, enabling layer-by-layer growth and controlled coalescence of nuclei. These advances have allowed for the growth of single-crystal Sb2O3 films with precise thickness control, which is crucial for scalable semiconductor applications.
The research team utilized the ultrathin, highly-oriented Sb2O3 films as gate dielectrics in MoS2-based field-effect transistors (FETs), yielding devices with superior performance. The improved dielectric quality of these Sb2O3 films enabled an exceptionally low leakage current (~10-14 A) and an ideal vdW interface with the channel material, which together led to superior switching characteristics. This configuration allowed the device to achieve a subthreshold swing close to the theoretical limit of 60 mV/dec, indicating highly efficient gate control. The success of this approach marks a significant leap forward in managing molecular alignment in vdW epitaxy, opening up pathways for the large-scale synthesis of 2D molecular crystals with high crystallinity, a key requirement for future electronic and optoelectronic devices. This work not only advances vdW epitaxy technology but also underscores the growing potential of molecular crystals in next-generation device applications, pointing towards new directions in the development of high-performance 2D materials.
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See the article:
Van der Waals epitaxial growth of single-crystal molecular film
https://doi.org/10.1093/nsr/nwae358
Journal
National Science Review