Ultrathin MoO2 nanosheets with good thermal stability and high conductivity

Abstract

Exploration and development of new two-dimensional (2D) materials with good stability and remarkable physical properties have become the research hotspots. We report for the first time the monodispersity of ultrathin MoO2 nanosheets have been synthesized through an improved chemical vapor deposition (CVD) method using only molybdenum trioxide as precursor. The grown MoO2 nanosheets have an average thickness of ∼ 5 to 10 nm and exhibit good crystal-quality. Temperature-dependent Raman spectra show that the ultrathin MoO2 nanosheets have high thermal stability up to 503 K. In addition, the first order temperature coefficients of the MoO2 characteristic Raman modes O1–Mo and O2–Mo were firstly found to be -1.91×10-2 and -3.94×10-2 cm−1/K, respectively. Two-probe electrical measurements show that the as-fabricated ultrathin MoO2 nanosheets devices preserve a high electrical conductivity in ambient conditions, reaching up to 200 - 475 S/cm. The exceptionally high conductivity of individual MoO2 nanosheet is ascribed to the unique crystal structure. Our results demonstrate that the ultrathin MoO2 nanosheets show great potential applications in constructing new integrated electronic devices and systems.

Laser Fluence Dependence of the Electrical Properties of MoO2 Formed by High Repetition Femtosecond Laser Pulses

“…The highest resistivity corresponds to the lowest per pulse laser fluence, while the lowest resistivity corresponds to the highest per pulse laser fluence. These measurements agree well with recently reported highly conductive MoO 2 nanosheets, with conductivity values in the range of 200–475 S cm −1 (resistivity in the order of 2–5 × 10 −3 Ω cm); and resistivity values for MoO 2 thin films in the order of 7 × 10 −4 Ω cm . We must point out that in our case at low per pulse laser fluence a very thin MoO 2 layer, only a few nanometers thick, must form; however, at higher per pulse laser fluences a thicker, several hundreds of nanometers, layer of MoO 2 should form.…”

“…While MoO 2 thin films are usually fabricated by deposition methods like pulsed laser deposition (PLD), pulsed injection‐metal organic chemical vapor deposition, electrodeposition, sputtering and chemical reduction . More demanding forms of MoO 2 like ultrathin nanosheets have been prepared by thermal evaporation in a controlled atmosphere …”

Comparative Studies on Two-Dimensional (2D) Rectangular and Hexagonal Molybdenum Dioxide Nanosheets with Different Thickness

“…The identification details of Raman peaks for thin/thick hexagonal and rectangular nanosheets are given in Fig. S3 in supplementary file; the results are well agreed with the reported results of monoclinic MoO 2 thin film fabricated by different CVD synthesis routes [54,55]: thickness and peaks shifting depend on growth's conditions [56,57]. In the present work, for the first time, we report 13 vibrational peaks for orange color, while 11 peaks for blue-colored regular hexagonal and rectangular MoO 2 nanosheets, confirming the existence of mixed structures in MoO 2 nanosheets.…”

From MoO2@MoS2 Core–Shell Nanorods to MoS2 Nanobelts

“…The inserted EDS spectrum from the position marked by red circle shows that only two elements have been detected, corresponding to oxygen (O) and molybdenum (Mo), respectively. The HRTEM image shown in Figure b reveals the superior crystallization of these nanorods, exhibiting the interplanar spacing value of 0.293 and 0.249 nm, in agreement with MoO 2 and MoO 2 (020) . The SAED pattern in Figure c displays a two‐fold‐symmetric diffraction pattern, indicating the two‐fold‐symmetry of the MoO 2 nanorod.…”