General synthesis of 2D rare-earth oxide single crystals with tailorable facets

Atomic engineering of two-dimensional materials via liquid metals

Two-dimensional (2D) materials, known for their distinctive electronic, mechanical, and thermal properties, have attracted considerable attention. The precise atomic-scale synthesis of 2D materials opens up new frontiers in nanotechnology, presenting novel opportunities for material design and property control but remains challenging due to the high expense of single-crystal solid metal catalysts. Liquid metals, with their fluidity, ductility, dynamic surface, and isotropy, have significantly enhanced the catalytic processes crucial for synthesizing 2D materials, including decomposition, diffusion, and nucleation, thus presenting an unprecedented precise control over material structures and properties. Besides, the emergence of liquid alloy makes the creation of diverse heterostructures possible, offering a new dimension for atomic engineering. Significant achievements have been made in this field encompassing defect-free preparation, large-area self-aligned array, phase engineering, heterostructures, etc. This review systematically summarizes these contributions from the aspects of fundamental synthesis methods, liquid catalyst selection, resulting 2D materials, and atomic engineering. Moreover, the review sheds light on the outlook and challenges in this evolving field, providing a valuable resource for deeply understanding this field. The emergence of liquid metals has undoubtedly revolutionized the traditional nanotechnology for preparing 2D materials on solid metal catalysts, offering flexible possibilities for the advancement of next-generation electronics.

Boronization: A General Strategy for Rare Earth Oxides with Enhanced High-κ Gate Dielectric Performance

Rare earth oxides (REOs) can be used as high-κ gate dielectrics that are at the core of electronic devices. However, a bottleneck remains with regard to obtaining high-performance REO dielectrics due to the serious hygroscopic issue and high defect states. Here, a general boronization strategy is reported to enhance the high-κ REO gate dielectric performance. Complementary characterization reveals that boronization is capable of reducing oxygen vacancies/hydroxyl defects in REOs and suppressing moisture absorption, leading to the improvement of leakage current, breakdown strength (up to 9 MV/cm), and capacitance-frequency stability. Furthermore, oxide transistors based on boronized REO dielectrics demonstrate state-of-the-art device characteristics with a high mobility of 40 cm2/V s, a current on/off ratio of 108, a subthreshold swing of 82 mV/dec, a hysteresis of 0.05 V, and superior bias stress stability.

Facet engineering of ultrathin two-dimensional materials

Ultrathin two-dimensional (2D) materials exhibit broad application prospects in many fields due to the enhanced specific surface area to volume ratio and quantum confinement effect. Because of the atomic thickness and various orientations, ultrathin 2D materials exposing specific facets have drawn great attention for various applications in catalysis, batteries, optoelectronics, magnetism, epitaxial template for material growth, etc. Though maintaining the atomic thickness of 2D materials while controlling crystal facets is an enormous challenge, breakthroughs are being made. This review provides a comprehensive overview of the recent advances in the facet engineering of 2D materials, ranging from a basic understanding of facets and the corresponding approaches and the significance of facet engineering. We also propose current challenges and forecast future development directions including the establishment of a facet database, the fabrication of new 2D materials, the design of specific substrates, and the introduction of theoretical calculations and in situ characterization techniques. This review can guide researchers to design ultrathin 2D materials with unique and distinct facets and provide an insight into the applications of energy, magnetism, optics, biomedicine, and other fields.