7 Applications Perspectives of Nanodispersed Chalcogenides of Transition. . .
105
in transistor technology, sun batteries, photocatalysis, and optoelectronics. Other 2D
TMDC are promising for tunnel field transistors, sun batteries with single transition,
light diodes, optoelectronic devices, and photoelectric cells. Molybdenum (IV)
sulfide had already been used in thin-layer transistors with ionic dielectric gel. They
had shown excellent zone transport with low-threshold voltage, high mobility, and
the ratio of the currents on and off.
Transistors on MoS 2 had demonstrated excellent high mechanic flexibility and
no deterioration of electrical characteristics in bending. Memory devices, based on
MoS 2 , have also been proposed. Ambipolar field transistors on thin layers of WS 2
with ionic liquid as dielectric have been presented too [18].
7.3 The Structure of Chalcogenides of Transition Metals
7.3.1 MoS 2
Molybdenum in sulfides exists only in the form of ions Mo (II), Mo (III), Mo (IV),
and Mo (V). Molybdenum sulfides are currently represented by MoS 2 , Mo 2 S 3 , and
a variety of Shevrelya phases enriched with sulfur containing fragments of Mo 6 S 8 ,
Mo 15 S 19 , and amorphous sulfides of MoS x with x ≥ 3.
MoS 2 as molybdenite was known to the ancient Romans, who confused it with
graphite and PbS [20]. Differences between molybdenite and graphite had been
found by Scheele in 1778. Later, molybdenite became the base of molybdenum
ore and came to be used as lubricant. After the discovery of fullerene and carbon
nanotubes, the focus was on so-called inorganic fullerenes, which also includes
closed structures of MoS 2 . After the discovery of graphene, the investigation of
single layers of MoS 2 began. This caused to the monolayer transistor producing on
their based.
Molybdenum (IV) sulfide in nature is found in two phases: molybdenite and
X-ray amorphous yordisite, both presented by soft minerals of lead-gray color
[19]. Molybdenum (IV) sulfide has a structure consisting of trigonal prisms
with molybdenum atoms in center, bonded with each other on the verge of
creating a densely packed layer. Only relatively weak forces (van der Waals) are
among layers, explaining the lubricating properties of MoS 2 , as well as graphite,
shown in Fig. 7.1a. The crystal structure and the lattice parameters of MoS 2 are
presented in Fig. 7.1b.
There are three crystal modification of MoS 2 : hexagonal 2H, rhombic 3R, and
tetragonal 1 T (sulfur polyhedron around molybdenum is formed not as prism, but
as a distorted octahedron [19, 24–26]. Noted modifications are presented in Fig. 7.2.
Besides, there are numerous poly-types that differ from each other by different
packing layers.
The presence of defects in the layers of MoS 2 leads to the dependence of their
chemical composition on temperature: at temperature of 750 ◦ ´ the composition
105
in transistor technology, sun batteries, photocatalysis, and optoelectronics. Other 2D
TMDC are promising for tunnel field transistors, sun batteries with single transition,
light diodes, optoelectronic devices, and photoelectric cells. Molybdenum (IV)
sulfide had already been used in thin-layer transistors with ionic dielectric gel. They
had shown excellent zone transport with low-threshold voltage, high mobility, and
the ratio of the currents on and off.
Transistors on MoS 2 had demonstrated excellent high mechanic flexibility and
no deterioration of electrical characteristics in bending. Memory devices, based on
MoS 2 , have also been proposed. Ambipolar field transistors on thin layers of WS 2
with ionic liquid as dielectric have been presented too [18].
7.3 The Structure of Chalcogenides of Transition Metals
7.3.1 MoS 2
Molybdenum in sulfides exists only in the form of ions Mo (II), Mo (III), Mo (IV),
and Mo (V). Molybdenum sulfides are currently represented by MoS 2 , Mo 2 S 3 , and
a variety of Shevrelya phases enriched with sulfur containing fragments of Mo 6 S 8 ,
Mo 15 S 19 , and amorphous sulfides of MoS x with x ≥ 3.
MoS 2 as molybdenite was known to the ancient Romans, who confused it with
graphite and PbS [20]. Differences between molybdenite and graphite had been
found by Scheele in 1778. Later, molybdenite became the base of molybdenum
ore and came to be used as lubricant. After the discovery of fullerene and carbon
nanotubes, the focus was on so-called inorganic fullerenes, which also includes
closed structures of MoS 2 . After the discovery of graphene, the investigation of
single layers of MoS 2 began. This caused to the monolayer transistor producing on
their based.
Molybdenum (IV) sulfide in nature is found in two phases: molybdenite and
X-ray amorphous yordisite, both presented by soft minerals of lead-gray color
[19]. Molybdenum (IV) sulfide has a structure consisting of trigonal prisms
with molybdenum atoms in center, bonded with each other on the verge of
creating a densely packed layer. Only relatively weak forces (van der Waals) are
among layers, explaining the lubricating properties of MoS 2 , as well as graphite,
shown in Fig. 7.1a. The crystal structure and the lattice parameters of MoS 2 are
presented in Fig. 7.1b.
There are three crystal modification of MoS 2 : hexagonal 2H, rhombic 3R, and
tetragonal 1 T (sulfur polyhedron around molybdenum is formed not as prism, but
as a distorted octahedron [19, 24–26]. Noted modifications are presented in Fig. 7.2.
Besides, there are numerous poly-types that differ from each other by different
packing layers.
The presence of defects in the layers of MoS 2 leads to the dependence of their
chemical composition on temperature: at temperature of 750 ◦ ´ the composition