Elucidation of the growth mechanism of MoS2 during the CVD process

ABSTRACTChemical vapor deposition (CVD) growth of two-dimensional molybdenum disulfide (MoS2) using molybdenum trioxide (MoO3) and sulfur (S) powder often results in intermediate molybdenum oxy-sulfide (MoOS2) species along with MoS2 due to a lack of control over the vapor pressure required for the clean growth. Much effort has been devoted in understanding and controlling of these intermediate MoOS2 specifies. Here, we show that with a second step sulfurization at moderate temperatures, these MoOS2 crystals can be transformed to monolayer MoS2 crystals. Scanning electron microscopy, Raman and photoluminescence spectroscopy and atomic force microscopy characterization carried out before and after re-sulfurization confirm the monolayer MoS2 growth via this route. This study shows that MoOS2 formed at the intermediate state can be successfully recycled to MoS2.

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CVD Growth of Monolayer MoS2 on Sapphire Substrates by using MoO3 Thin Films as a Precursor for Co-Evaporation

MRS Advances ◽

10.1557/adv.2018.657 ◽

2018 ◽

Vol 4 (10) ◽

pp. 587-592 ◽

Cited By ~ 2

Author(s):

Sajeevi S Withanage ◽

Saiful I Khondaker

Keyword(s):

Thin Films ◽

Molybdenum Trioxide ◽

Chemical Vapor ◽

Optical Quality ◽

High Optical Quality ◽

Force Microscopy ◽

Sapphire Substrates ◽

Cvd Growth ◽

Scalable Synthesis ◽

Microscopy Characterization

ABSTRACTScalable synthesis of two-dimensional molybdenum disulfide (MoS2) via chemical vapor deposition (CVD) is of considerable interests for many applications in electronics and optoelectronics. Here, we investigate the CVD growth of MoS2 single crystals on sapphire substrates by using thermally evaporated molybdenum trioxide (MoO3) thin films as molybdenum (Mo) source instead of conventionally used MoO3 powder for co-evaporation synthesis. The MoO3 thin film source provides uniform Mo vapor pressure in the growth chamber resulting in clean and reproducible MoS2 triangles without any oxide or oxysulfide species. Scanning electron microscopy, Raman spectroscopy, photoluminescence spectroscopy and atomic force microscopy characterization were performed to characterize the growth results. Very high photoluminescence (PL) response was observed at 1.85 eV which is a good implication of high optical quality of these crystals directly grown on sapphire substrate.

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Application of Atomic Force Microscopy Characterization Technology in MgAl-CO32--LDH Exfoliation Behavior

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1094.122 ◽

2015 ◽

Vol 1094 ◽

pp. 122-126 ◽

Cited By ~ 2

Author(s):

Jie Zhang ◽

Xiang Li Xie ◽

Cun Jun Li ◽

Hai Wang ◽

Lin Jiang Wang

Keyword(s):

Atomic Force Microscopy ◽

Ultrasonic Treatment ◽

Colloidal Suspension ◽

Second Step ◽

Thickness Variation ◽

Force Microscopy ◽

Atomic Force ◽

Two Phases ◽

Microscopy Characterization ◽

Atomic Force Microscopy Characterization

MgAl-CO32--LDH was exfoliated via two-step ultrasonic treatment in formamide. Atomic force microscopy (AFM) was employed to characterize the thickness variation of MgAl-CO32--LDH during exfoliation. MgAl-CO32--LDH was dispersed in formamide with continuous ultrasonic treatment for 4 h, getting a non-transparent turbid liquid. The non-transparent turbid liquid was laid aside one day and separated into two phases, the upper semi-translucent colloidal suspension containing partial exfoliated MgAl-CO32--LDH was dispersed in formamide with continuous ultrasonic treatment again. The AFM results reveal that the thickness of pristine MgAl-CO32--LDH is 250 nm while the MgAl-CO32--LDH nanosheet obtained from the first-step ultrasonic treatment is 90 nm with obvious transverse sliding. The thickness of MgAl-CO32--LDH nanosheet obtained after the second-step ultrasonic treatment is about 7 nm, which is almost in agreement with the theoretical thickness of 10 monolayers of MgAl-CO32--LDH (0.76 nm).

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