Ultrathin two-dimensional (2D) semiconducting layered materials offer a great potential to extend the Moore's Law (1). One key challenge for 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. The insulating van der Waals layer, hexagonal boron nitride (hBN), is an excellent interface dielectric to 2D semiconductors, efficiently reducing charge scatterings (2, 3). Recent studies have shown the growth of single-crystal hBN films on molten Au surfaces (4) or bulk Cu foils (5). However, using molten Au is not favored in industry due to high cost, cross-contamination, and potential issues of process control and scalability. Cu foils may be suitable for roll-to-roll processes, but unlikely to be compatible with advanced microelectronic fabrication on Si wafers. Thus, only a reliable approach to grow single-crystal hBN on wafers can help realize the broad adoption of 2D layered materials in industry. Previous efforts on growing hBN triangular monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when they merge as films (6,7). Growing singlecrystal hBN on such a high-symmetry surface planes (5,8) is commonly believed to be impossible even in theory. In stark contrast, we have successfully realized the epitaxial growth of single-crystal hBN monolayers on a Cu ( 111) thin film across a 2-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxy to the underlying Cu lattice is enhanced by the lateral docking to Cu (111) steps, to ensure the mono-orientation of hBN monolayers. The obtained singlecrystal hBN, incorporated as an interface layer between MoS2 and HfO2 in a bottom-gate configuration, has enhanced the electrical performance of transistors based on monolayer MoS2. This reliable approach of producing wafer-scale single-crystal hBN truly paves the way for developing futuristic 2D electronics.First, a single-crystal Cu (111) thin film on a wafer is needed. Single-crystal Cu in thick foils can be achieved through recrystallization induced by implanted seeds (5,9). However, for the formation of Cu (111) thin film on a wafer, the crystallinity strongly relies on the underlying substrate lattices. Here we used a c-plane sapphire as the substrate, on which a 500-nm-thick polycrystalline Cu film was sputtered followed by extensive thermal annealing to achieve singlecrystal Cu (111) films (10). One challenge is that Cu (111) tends to form twin grains separated by twin grain boundaries, through kinetic growth processes. Fig. 1a illustrates the atomic arrangements for the typical twinned Cu (111) structure. We find that the post-annealing at a high temperature (1,040 -1,070 °C) in the presence of hydrogen is the key to removing the twin grains, consistent with recent reports (10,11). Figures 1b and 1c show the optical micrographs (OMs) and electron backscatter diffraction (EBSD) patterns for the Cu (111) thin films after annealing at 1,000 °...

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Advanced data encryption requires the use of true random number generators (TRNGs) to produce unpredictable sequences of bits. TRNG circuits with high degree of randomness and low power consumption may be fabricated by using the random telegraph noise (RTN) current signals produced by polarized metal/insulator/metal (MIM) devices as entropy source. However, the RTN signals produced by MIM devices made of traditional insulators, i.e., transition metal oxides like HfO2 and Al2O3, are not stable enough due to the formation and lateral expansion of defect clusters, resulting in undesired current fluctuations and the disappearance of the RTN effect. Here, the fabrication of highly stable TRNG circuits with low power consumption, high degree of randomness (even for a long string of 224 − 1 bits), and high throughput of 1 Mbit s−1 by using MIM devices made of multilayer hexagonal boron nitride (h‐BN) is shown. Their application is also demonstrated to produce one‐time passwords, which is ideal for the internet‐of‐everything. The superior stability of the h‐BN‐based TRNG is related to the presence of few‐atoms‐wide defects embedded within the layered and crystalline structure of the h‐BN stack, which produces a confinement effect that avoids their lateral expansion and results in stable operation.

Thin dielectric films are essential components of most micro-and nanoelectronic devices, and they have played a key role in the huge development that the semiconductor industry has experienced during the last 50 years. Guaranteeing the reliability of thin dielectric films has become more challenging, in light of strong demand from the market for improved performance in electronic devices. The degradation and breakdown of thin dielectrics under normal device operation has an enormous technological importance and thus it is widely investigated in traditional dielectrics (e.g., SiO 2 , HfO 2 , and Al 2 O 3 ), and it should be further investigated in novel dielectric materials that might be used in future devices (e.g., layered dielectrics). Understanding not only the physical phenomena behind dielectric breakdown but also its statistics is crucial to ensure the reliability of modern and future electronic devices, and it can also be cleverly used for other applications, such as the fabrication of new-concept resistive switching devices (e.g., nonvolatile memories and electronic synapses). Here, the fundamentals of the dielectric breakdown phenomenon in traditional and future thin dielectrics are revised. The physical phenomena that trigger the onset, structural damage, breakdown statistics, device reliability, technological implications, and perspectives are described.