RESUMEN
As demand for higher integration density and smaller devices grows, silicon-based complementary metal-oxide-semiconductor (CMOS) devices will soon reach their ultimate limits. 2D transition metal dichalcogenides (TMDs) semiconductors, known for excellent electrical performance and stable atomic structure, are seen as promising materials for future integrated circuits. However, controlled and reliable doping of 2D TMDs, a key step for creating homogeneous CMOS logic components, remains a challenge. In this study, a continuous electrical polarity modulation of monolayer WS2 from intrinsic n-type to ambipolar, then to p-type, and ultimately to a quasi-metallic state is achieved simply by introducing controllable amounts of vanadium (V) atoms into the WS2 lattice as p-type dopants during chemical vapor deposition (CVD). The achievement of purely p-type field-effect transistors (FETs) is particularly noteworthy based on the 4.7 at% V-doped monolayer WS2, demonstrating a remarkable on/off current ratio of 105. Expanding on this triumph, the first initial prototype of ultrathin homogeneous CMOS inverters based on monolayer WS2 is being constructed. These outcomes validate the feasibility of constructing homogeneous CMOS devices through the atomic doping process of 2D materials, marking a significant milestone for the future development of integrated circuits.
RESUMEN
Vertical graphene nanowalls (VGNs) with excellent heat-transfer properties are promising to be applied in the thermal management of electronic devices. However, high growth temperature makes VGNs unable to be directly prepared on semiconductors and polymers, which limits the practical application of VGNs. In this work, the near room-temperature growth of VGNs was realized by utilizing the hot filament chemical vapor deposition method. Catalytic tantalum (Ta) filaments promote the decomposition of acetylene at â¼1600 °C. Density functional theory calculations proved that C2H* was the main active carbon cluster during VGN growth. The restricted diffusion of C2H* clusters induced the vertical growth of graphene nanoflakes on various substrates below 150 °C. The direct growth of VGNs successfully realized the excellent interfacial contact, and the thermal contact resistance could reach 3.39 × 10-9 m2·K·W-1. The temperature of electronic chips had a 6.7 °C reduction by utilizing directly prepared VGNs instead of thermal conductive tape as thermal-interface materials, indicating the great potential of VGNs to be directly prepared on electronic devices for thermal management.
RESUMEN
The controllable synthesis of large-area and uniform hexagonal boron nitride (h-BN) films has been recently achieved on metal-boron alloy catalysts with the use of N2 feedstock, representing important progress in an economic and environmentally friendly process. However, the systematic investigation of the growth mechanism is still lacking, which impedes the further development of this method. In this work, on the basis of density functional theory (DFT) calculations and experiments, we reveal the vacancy-assisted growth mechanism of h-BN on Fe2B substrate. It is found that B vacancies created by the formation of BN dimers play important roles in the migration of B and N atoms near the catalyst surface. The diffusions of B and N atoms in the Fe2B substrate need to overcome energy barriers of only less than 1.5 eV, which enables abundant dissolution of N atoms near the catalytic surface. Moreover, we found the critical barrier for h-BN growth is in the nucleation stage, which is â¼2 eV. These advantages enable the synthesis of h-BN at a low temperature of 700 K in our experiments. This vacancy-assisted growth of h-BN films on Fe2B substrates is beneficial to the wafer-scale fabrication of multilayer materials, paving the way to potential applications in two-dimensional electronic and optoelectronic devices.