We demonstrate that HfO2, a high-K dielectric, can be prepared on the top surface of 2D HfS2 through plasma oxidation, which results in a heterostructure composed of a 2D van der Waals semiconductor and its insulating native oxide.

In the rapidly progressing field of organometal halide perovskites, the dimensional reduction can open up new opportunities for device applications. Herein, taking the recently synthesized trimethylsulfonium lead triiodide (CH 3 ) 3 SPbI 3 perovskite as a representative example, first-principles calculations are carried out and the nanostructuring and device application of halide perovskite nanowires are studied. It is found that the 1D (CH 3 ) 3 SPbI 3 structure is structurally stable, and the electronic structures of higherdimensional forms are robustly determined at the 1D level. Remarkably, due to the face-sharing [PbI 6 ] octahedral atomic structure, the organic ligandremoved 1D PbI 3 frameworks are also found to be stable. Moreover, the PbI 3 columns avoid the Peierls distortion and assume a semimetallic character, contradicting the conventional assumption of semiconducting metal-halogen inorganic frameworks. Adopting the bundled nanowire junctions consisting of (CH 3 ) 3 SPbI 3 channels with sub-5 nm dimensions sandwiched between PbI 3 electrodes, high current densities and large room-temperature negative differential resistance (NDR) are finally obtained. It will be emphasized that the NDR originates from the combination of the near-Ohmic character of PbI 3 -(CH 3 ) 3 SPbI 3 contacts and a novel NDR mechanism that involves the quantum-mechanical hybridization between channel and electrode states. This work demonstrates the great potential of low-dimensional hybrid perovskites toward advanced electronic devices beyond actively pursued photonic applications.

Seeding promoters facilitate the nucleation and growth of transition metal dichalcogenides in chemical vapor deposition (CVD). However, sophisticated roles of seeding promoter remain unclear. Here, adopting triangular-shaped crystal violet (CV) consisting of nonpolar and polar parts as the seeding promoter, we study the role of seeding promoter for the growth of molybdenum disulfide (MoS2). We systematically control the geometrical configuration of CV on SiO2/Si substrate by changing the solvent polarity and find that it strongly affects the growth of monolayer or multilayer MoS2 domains via CVD. Monolayer MoS2 domains were predominantly grown on randomly lying-down CV configurations on SiO2/Si substrate, whereas multilayer MoS2 domains are synthesized at concentrated polar parts in CV micelle on the substrate. Density functional theory calculations reveal that the initial nucleation step for the MoS2 growth is the adsorption of S on CV and the most favourable S adsorption site is the polar part in CV. Furthermore, it is found that the CV adsorption to SiO2 is mediated by the polar CV part and additionally strengthened in the lying-down CV configuration. Enhancing the thermal stability as well as hindering the re-aggregation of CV at high temperature, the lying down CV configuration allows the predominant growth of monolayer MoS2. This work provides a general framework to understand the growth of MoS2 from aromatic seeding promoters.

In this letter we have studied an influence of surface morphology on the optical property of vertically aligned ZnO nanorods. At low temperature the near band edge excitonic emission shows a strong dependence on surface morphology. A prominent and well resolved near band edge photoluminescence (PL) peak was obtained for nanowires with decreasing diameter and thus assigned due to the contributions to the optical properties of individual nanorods. Depending on surface morphology, the difference in low temperature PL property is attributed to the tailing of the density of states due to the potential fluctuations in randomly distributed intrinsic defects.

In article number https://doi.org/10.1002/adfm.201807620, Yong‐Hoon Kim and co‐workers show that the PbI3 nanowire, the inorganic framework of trimethylsulfonium lead triiodide (TMSPbI3) perovskite, assumes a semi‐metallic character, and displays excellent negative differential resistance (NDR) characteristics emerging from the PbI3‐TMSPbI3‐PbI3 junctions through the novel quantum‐hybridization NDR mechanism.