Hydrogenation-induced atomic stripes on the2H−MoS2surface

Abstract

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...

Stable and scalable 1T MoS2 with low temperature-coefficient of resistance

“…The visible stripe-like patterns in Fig. 1(e) is due to the rearrangement of Mo and S atoms during the transformation 28 . A possible atomic arrangement is shown in the inset to Fig.…”

Electron beam-formed ferromagnetic defects on MoS2 surface along 1 T phase transition

“…The inset of Fig. 2a shows the fast Fourier transform (FFT) image, where the inner and outer hexagons correspond to the (100) and (110) planes3940. The two defects lead to having two (yellow and cyan) hexagons with a twist angle 24° at each plane, respectively.…”

“…The electrical conductivity, carrier density, and the Hall mobility were measured as a function of temperature from 100 K to 350 K with a fixed magnetic field of 0.5 T using a Hall measurement system with Au contacts (HMS 5000). HRTEM (JEM-2100F) images for the exfoliated samples by sonication in methanol were taken at an energy of electron beam (200 keV)40. The electron irradiation-induced defects are supposed to be hardly influenced by the TEM measurements.…”

Defect Passivation of Perovskite Films for Highly Efficient and Stable Solar Cells

“…The posttreatment of perovskite films with MACl has been widely investigated to improve the perovskite surface properties. [138,142,143] Recently, Hwang et al [144] used this method for reducing the surface defects in band-tail states of a perovskite film to improve the photovoltaic parameters of PSCs. However, the low degree of chloride incorporation in the perovskite structure still remains a major challenge to using MACl extensively.…”