The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

We report the effective methods to induce weak ferromagnetism in pristine MoS2 persisting up to room temperature with the improved transport property, which would lead to new spintronics devices. The hydrogenation of MoS2 by heating at 300 °C for 1 h leads to the easy axis out of plane, while the irradiation of proton with a dose of 1 × 10(13) P/cm(2) leads to the easy axis in plane. The theoretical modeling supports such magnetic easy axes.

We investigate the strain-induced electronic and magnetic properties of single-layer (1L) MoS 2 with vacancy defects using the density functional theory calculation. When the tensile strain is applied, 1L-MoS 2 with vacancy becomes ferromagnetic and metallic. We elucidate that, from the electronic band structure of vacancy-defect-doped 1L-MoS 2 , the impurity bands inside the gap play a role of seed to drive novel magnetic and electronic properties as the strain increases. In particular, we also find that 1L-MoS 2 with two-sulfur vacancy (V 2S ) shows the largest magnetic moment at ∼14% strain among various vacancy types and undergoes a spin reorientation transition from out-of-plane to in-plane magnetization at ∼13% strain. This implies that the strain-manipulated 1L-MoS 2 with V 2S can be a promising candidate for new spintronic applications.

We investigate the electronic band structure of the MoS 2 /Bi(111) heterostructure, for which the supercell calculation is performed due to the lattice mismatch between two structures but the effective primitive cell is recovered by using the band unfolding technique. It is found that the strong molybdenum-bismuth band hybridization together with a generation of the interfacial dipole field induces the giant Rashba-type splitting accompanying the proper spin topology in molybdenum-driven bands at the point. Similar splittings are also found in the heterostructure with other transition-metal dichalcogenides, i.e., with MoSe 2 , WS 2 , and WSe 2 .

We report that the hydrogenation of a single crystal 2H -MoS 2 induces a novel-intermediate phase between 2H and 1T phases on its surface, i.e., the large-area, uniform, robust, and surface array of atomic stripes through the intralayer atomic-plane gliding. The total energy calculations confirm that the hydrogenation-induced atomic stripes are energetically most stable on the MoS 2 surface between the semiconducting 2H and metallic 1T phase. Furthermore, the electronic states associated with the hydrogen ions, which is bonded to sulfur anions on both sides of the MoS 2 surface layer, appear in the vicinity of the Fermi level (E F ) and reduces the band gap. This is promising in developing the monolayer-based field-effect transistor or vanishing the Schottky barrier for practical applications. Thickness-dependent indirect-to-direct band-gap transition of molybdenum disulfide (MoS 2 ) [1,2] and a successful realization of the field-effect transistor (FET) using a singlelayer (1L-) MoS 2 [3] have renewed interests of transition-metal dichalcogenides. This has also boosted the development of two-dimensional (2D) materials for the high performance flexible electronic and optoelectronic devices [4,5]. For a preparation of 1L-MoS 2 , the top-down exfoliation methods such as mechanical exfoliation [1][2][3]6], liquid exfoliation by sonication in a good solvent [7], and chemical exfoliation through lithium (Li) intercalation [8,9] are conventionally used. Among several exfoliation methods, the Li intercalation makes MoS 2 nanosheets only in the nanometer-sized metallic 1T phase [10,11], while other methods usually in the semiconducting 2H phase [1][2][3]. Moreover, without intercalating Li, the 1T phase can be intentionally introduced in the 2H matrix by using a high dose of incident electron beam during heating 1L-MoS 2 , which accompanies intermediate phases as precursors [12]. This 2H/1T phase transition can be realized by gliding sulfur (S) and/or molybdenum (Mo) atomic planes with a change of the d-electron counts [13]. A miniaturization of 2D devices [14] plus a local induction of the metallic 1T phase [11][12][13] controlled (i.e., stripe-patterned) hydrogenation on the MoS 2 monolayer has been theoretically shown to be metallic [19].In this Rapid Communication, we find a novel-intermediate phase between 2H and 1T phases, which consists of a highlyregular surface array of atomic stripes on the MoS 2 surface, and determine its materialization condition in the hydrogenation of a single crystal MoS 2 . This finding motivates one to investigate the interaction between hydrogen and the MoS 2 surface based on a combination of the transmission electron microscopy (TEM), scanning photoelectron microscopy (SPEM), angleresolved photoelectron spectroscopy (ARPES), and firstprinciples calculation. Further, we indicate that the electronic states associated with the emerging phase appear near the Fermi level (E F ) and reduce the band gap, promising in vanishing the Schottky barrier.For the hydrogenation, natural single cryst...

Searching for novel two-dimensional (2D) semiconducting materials is a challenging issue. We investigate novel 2D semiconductors ZrNCl and HfNCl which would be isolated to single layers from van der Waals layered bulk materials, i.e., ternary transition-metal nitride halides. Their isolations are unquestionably supported through an investigation of their cleavage energies as well as their thermodynamic stability based on the ab initio molecular dynamics and phonon dispersion calculations. Strain engineering is found to be available for both single-layer (1L) ZrNCl and 1L-HfNCl, where a transition from an indirect to direct band gap is attained under a tensile strain. It is also found that 1L-ZrNCl has an excellent electron mobility of about 1.2 × 103 cm2 V−1 s−1, which is significantly higher than that of 1L-MoS2. Lastly, it is indicated that these systems have good thermoelectric properties, i.e., high Seebeck coefficient and high power factor. With these findings, 1L-ZrNCl and 1L-HfNCl would be novel promising 2D materials for a wide range of optoelectronic and thermoelectric applications.

We carry out first-principles calculations of the quasi-particle band structure and optical absorption spectra of H-passivated armchair MoS2 nanoribbons (AMoS2NRs) by employing the approach combining the Green’s function perturbation theory (GW) and the Bethe-Salpeter equation (BSE), i.e., GW+BSE. Optical absorption spectra of AMoS2NRs show the exciton multibands (their binding energies are close to or less than 1 eV) which are much stronger than a single layer of MoS2. However, they are absent in the spectra by the approach of GW and the random phase approximation (RPA), i.e., GW+RPA. This signifies that the excitonic correlation effects are strongly enhanced in the reduced dimensional structure of MoS2. We also calculate the exciton wave functions for the few lowest energy excitons, which are found to have non-Frenkel character.

We survey the thermodynamic stabilities and properties, electronic transports, and thermoelectric possibilities of two-dimensional (2D) ZnPS 3 and ZnPSe 3 , belonging to transition-metal phosphorus trichalcogenides, by employing the first-principles electronic structure calculation. Our first-principles calculation accompanying ab initio molecular dynamics and phonon calculation predicts that a single-layer (1L-) ZnPSe 3 would be thermodynamically stable; in addition, electron and hole mobilities of 1L-ZnPSe 3 amount to ∼440 and ∼400 cm 2 V −1 s −1 , respectively, which are comparable to 1L-MoS 2 . More interestingly, the lattice thermal conductivity of 1L-ZnPSe 3 is found to be lower than any other 2D material, which could reach the lowest, i.e., ∼0.13 W m −1 K −1 at room temperature. In contrast, the thermoelectric figure of merit of the pristine 1L-ZnPSe 3 is just ∼0.8 under optimal condition. Nevertheless, this is a very promising indication for a thermoelectric application of 1L-ZnPSe 3 because other elements to determine the thermoelectric figure of merit could be possibly engineered through a manipulation of underlying electronic structures. With this finding, 1L-ZnPSe 3 would be added as a novel promising candidate to a list of 2D thermoelectric materials.