Few-layer
MoS2 films stay at the forefront of current
research of two-dimensional materials. At present, continuous MoS2 films are prepared by chemical vapor deposition (CVD) techniques.
Herein, we present a cost-effective fabrication of the large-area
spatially uniform films of few-layer MoS2 flakes using
a modified Langmuir–Schaefer technique. The compression of
the liquid-phase exfoliated MoS2 flakes on the water subphase
was used to form a continuous layer, which was subsequently transferred
onto a submerged substrate by removing the subphase. After vacuum
annealing, the electrical sheet resistance dropped to a level of 10
kΩ/sq, being highly competitive with that of CVD-deposited MoS2 nanosheet films. In addition, a consistent fabrication protocol
of the large-area conductive MoS2 films was established.
The morphology and electrical properties predetermine these films
to advanced detecting, sensing, and catalytic applications. A large
number of experimental techniques were used to characterize the exfoliated
few-layer MoS2 flakes and to elucidate the formation of
the few-layer MoS2 Langmuir film.
A 13.56 MHz RF discharge in hydrogen was studied within the pressure range of 1-10 Pa, and at power range of 400 -1000 W. The electron energy distribution function and electron density were measured by a Langmuir probe. The gas temperature was determined by the Fulcher-α system in pure H2, and by the second positive system of nitrogen using N2 as the probing gas. The gas temperature was constant and equal to 450 ± 50 K in the Capacitively Coupled Plasma mode (CCP), and it was increasing with pressure and power in the Inductively Coupled Plasma mode (ICP). Also the vibrational temperature of ground state of hydrogen molecules was determined to be around 3100 and 2000 ± 500 K in ICP and CCP mode, respectively. The concentration of atomic hydrogen was determined by means of actinometry, either by using Ar (5 %) as the probing gas, or by using H2 as the actinometer in pure hydrogen (Q1 rotational line of Fulcher-α system) The concentration of hydrogen density was increasing with pressure in both modes, but with a dissociation degree slightly higher in the ICP mode (a factor 2).
Submitted to Physica Scripta
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