The high performance of alloy materials can be maintained with compositional “plainification”

Vertical three-dimensional integration of two-dimensional (2D) semiconductors holds great promise, as it offers the possibility to scale up logic layers in the z axis^1–3. Indeed, vertical complementary field-effect transistors (CFETs) built with such mixed-dimensional heterostructures^4,5, as well as hetero-2D layers with different carrier types^6–8, have been demonstrated recently. However, so far, the lack of a controllable doping scheme (especially p-doped WSe₂ (refs. ^9–17) and MoS₂ (refs. ^11,18–28)) in 2D semiconductors, preferably in a stable and non-destructive manner, has greatly impeded the bottom-up scaling of complementary logic circuitries. Here we show that, by bringing transition metal dichalcogenides, such as MoS₂, atop a van der Waals (vdW) antiferromagnetic insulator chromium oxychloride (CrOCl), the carrier polarity in MoS₂ can be readily reconfigured from n- to p-type via strong vdW interfacial coupling. The consequential band alignment yields transistors with room-temperature hole mobilities up to approximately 425 cm² V⁻¹ s⁻¹, on/off ratios reaching 10⁶ and air-stable performance for over one year. Based on this approach, vertically constructed complementary logic, including inverters with 6 vdW layers, NANDs with 14 vdW layers and SRAMs with 14 vdW layers, are further demonstrated. Our findings of polarity-engineered p- and n-type 2D semiconductor channels with and without vdW intercalation are robust and universal to various materials and thus may throw light on future three-dimensional vertically integrated circuits based on 2D logic gates.

The greatly increased grain boundary (GB) mobility in nanograined metals under mechanical loading is distinguished from that in their coarse-grained counterparts. The feature leads to softening of nanograined materials and deviation of strength from the classical Hall-Petch relationship. In this Letter, grain size dependences of GB migration in nanograined Ag, Cu, and Ni under tension were investigated quantitatively in a wide size range. As grain size decreases from submicron, GB migration intensifies and then diminishes below a critical grain size. The GB migration peaks at about 80, 75, and 38 nm in Ag, Cu, and Ni, respectively. The suppression of GB migration below a critical size can be attributed to GB relaxation during sample processing or by postthermal annealing. With relaxed GBs the governing deformation mechanism of nanograins shifts from GB migration to formation of through-grain twins or stacking faults. GB relaxation, analogous to GB segregation, offers a novel approach to stabilizing nanograined materials under mechanical loading.

A prototype Schwarz crystal (SC) structure of dividing–space minimal grain boundaries (GBs) constrained by coherent twin boundaries (CTBs) was recently discovered in extremely fine-grained polycrystalline Cu. In this Letter, constraining effects of $3D$ CTB network on the formation and thermostability of SC are addressed via atomistic simulations. GB migration and evolution of CTB network trigger formation of SC diamond. CTB constraints are critical to generate GBs of zero mean curvature underlying vanishing capillary pressure, and to counterbalance the elastic driving forces of lattice. GB motion can be suppressed at temperatures close to the melting point with GB aperture down to 3 nm.

Ductile polycrystals are usually metals with high-symmetry structures that provide multiple slip systems to coordinate the synergetic deformation of adjacent grains. However, while exceptional plasticity was recently discovered in a series of low-symmetry semiconductors, their deformation mechanism remains mysterious. Here, taking monoclinic Ag ₄ SSe as a case study, we show that the inherent high-symmetry anion sublattice with a quasi–body-centered cubic (bcc) structure is embedded in the monoclinic matrix. This, coupled with the highly diffuse cations, results in multiple slip systems and is responsible for the superior plasticity as normally unexpected in low-symmetry structures. We observe typical slip systems conforming with those of the bcc structure by experiment. This finding clarifies the deformation mechanism of Ag ₂ S-based low-symmetry semiconductors and sheds light on future exploration of ductile inorganic semiconductors.