Chapter 1
Introduction and Existing Information about
Transition Metal Chalcogenides
The use of crystals dates back as far as there are records of history itself. They were used in
Biblical times, throughout Ancient Egypt, Rome and date to all ancient cultures. Crystal in fact came
from the period in history when the earth was forming. The heating and cooling of the planet formed
the magnificent crystalline objects we have today. Over the years, uses of crystals have not really
changed and they are still being used in the same way as the ancients.
Chapter 1
1.1 INTRODUCTION
Crystals are the unacknowledged pillars of modern technology. Without
crystals, there would be no electronic industry, no photonic industry, no fiber optic
communications, which depend on materials/crystals such as semiconductors,
superconductors, polarizers, transducers, radiation detectors, ultrasonic amplifiers,
ferrites, magnetic garnets, solid state lasers, non-linear optics, piezo-electric, electrooptic, acousto-optic, photosensitive refractory of different grades, crystalline films for
microelectronics and computer industries. Crystal growth is an interdisciplinary
subject covering Physics, Chemistry, Material science, Chemical engineering,
Metallurgy, Crystallography, Mineralogy, etc. In the past few decades, there has been
a growing interest on crystal growth processes, particularly in view of the increasing
demand of materials for technological applications. Atomic arrays that are periodic in
three dimensions, with repeated distances are called single crystals. It is clearly more
difficult to prepare single crystal than poly-crystalline material and extra effort is
justified because of the outstanding advantages of single crystals. The reason for
growing single crystals is, many physical properties of solids are obscured or
complicated by the effect of grain boundaries. The chief advantages are the
anisotropy, uniformity of composition and the absence of boundaries between
individual grains, which are inevitably present in polycrystalline materials. The strong
influence of single crystals in the present day technology is evident from the recent
advancements in the above mentioned fields. Hence, in order to achieve high
performance from the device, good quality single crystals are needed. Growth of
single crystals and their characterization towards device fabrication have assumed
great impetus due to their importance for both academic as well as applied research.
Transition metal chalcogenides: oxides, sulfides, selenides and tellurides are
important technological materials. The potential is increasingly being recognized,
with recent advanced applications of transition metal chalcogenides including: solar
energy conversion, solar control coating, microelectronic devices, catalysts, sensors,
optical fiber and laser sources [1-4]. The family of the TMDCs forming TX2 is
composed of the transition metals (groups 3-12 of the periodic table) T like titanium
or zirconium and chalcogenides (group 16) X like selenium, sulphur or tellurium. The
most well-known TMDC is MoS2 which has found an application as solid lubricant
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 2
Chapter 1
and also promising for photovoltaic is e.g. zirconium disulfide (ZrS2) which is a
subject of active research in HU group EES [1]. The TMDCs typically grow in
layered crystals similar to graphite. Their electronic properties range from metals like
VSe2 to insulators like HfS2 [2].
It is common that the three heaviest elements of the sulfur sub-group, namely
selenium, tellurium, and polonium, be collectively referred to as the “chalcogens,”
and the term chalcogen be addressed only for these elements – in practice, only for the
chemically and technologically important selenium and tellurium; however, according
to the official guides to inorganic nomenclature, the term applies equally to all the
elements in group 16 of the periodic table, thus being proper also for oxygen and
sulfur. On the other hand, several textbooks imply that oxygen is excluded from the
chalcogens, this probably being the consequence of having discussed the chemistry of
oxygen [5].
The term “chalcogen” was proposed around 1930 by Werner Fischer [6], when
he worked in the group of Wilhelm Biltz at the University of Hannover, to denote the
elements of group 16. It was quickly accepted among German chemists, and it was
Heinrich Remy who recommended its official use in 1938 while being a member of
the Committee of the International Union of Chemistry (later IUPAC) for the Reform
of the Nomenclature of Inorganic Chemistry. Following this, it was internationally
accepted that the elements oxygen, sulfur, selenium, and tellurium will be called
chalcogens and their compounds chalcogenides. The term derives from the Greek
terms χαλκ´oς meaning copper and γενv´ω meaning giving birth, and it was meant in
the sense of “ore-forming element” (cf. “hydrogen” similarly originating from ´ υδωρ
meaning water; also “oxygen”, etc.).
The chemistry of soluble metal chalcogenide complexes, either containing
chalcogen–chalcogen bonds or only chalcogen–metal, has been studied extensively
primarily for sulfur, and after the mid-1970s for selenium and tellurium as well.
Metal–sulfur systems have a long chemical history in all aspects, but from the 1960s
the interest in the related complexes was renewed, owing to their significance in
bioinorganic chemistry and to hydrodesulphurization and other catalytic processes.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 3
Chapter 1
The early progress in the identification of the many possible coordination modes
available for sulfide ligands has been summarized neatly by Vahrenkamp [7]. A large
number of synthetic molecular transition metal complexes with either terminal or
bridging sulfide ligands have been reported and their catalytic activity has been
reviewed [8-9]. The coordination modes and structural types of soluble metal
selenides and tellurides, synthesized in solution or in the solid state, have been sorted
and described in the seminal review by Ansari and Ibers [10]. An excellent
introduction to the synthetic and structural coordination chemistry of inorganic
selenide and telluride ligands, covering all the facts up to 1993, can be found in Roof
and Kolis [11], with the emphasis on compounds of mostly molecular nature.
Metal chalcogenides have played a major role in the field of low-dimensional
solids. It was the unraveling of the origin of the resistivity anomalies observed in
layered transition metal chalcogenides that stimulated the interest in low-dimensional
inorganic materials. Metal clustering and low-dimensional structures are frequently
found among transition metal chalcogenides, as a consequence of the fact that, in
contrast to the ionic 3D-type oxides, these compounds tend to form covalent
structures, so that the reduced relative charge on the metal favors metal–metal
bonding. In the metal-rich compounds (actually those containing M-M bonds)
preferred coordination polyhedra occur for the non-metal (chalcogen) atoms. The
linkage of these polyhedra takes place in such a way that they often end up with an
arrangement identical to that known from isolated metal clusters. However, clusters
are rarely isolated in the chalcogenide structures. They condense by sharing common
vertices, edges, or faces, or more unusually they may be connected via significant
chemical bonding between the vertices. They also form columns, in which the central
metal atoms interact to give chains running in the same direction. In layered
chalcogenides, which have enough d-electrons for significant M–M bonding in two
dimensions, the dimensionality of M–M interactions is increased. Further, in certain
cases, the cluster network is best regarded as a 3D metal framework, i.e., as a metal
packing arrangement. It may be emphasized in this connection that the occurrence of
M–M bonds in metal chalcogenide has substantiated the use of classification schemes
based on structural elements rather than oxidation numbers, rationalizing thus the
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 4
Chapter 1
coincidental integer values of the oxidation state of transition metals and consequently
the apparent stoichiometries [12].
The complexes in which metal clusters are coordinated by chalcogenide or
polychalcogenide ligands occupy a special position among the so-called inorganic or
high-valence clusters, the most characteristic being those of 4d- and 5d-metals of
groups V-VII. Currently, the chalcogenide cluster chemistry of the main group and dtransition metals is firmly established. The area has been the subject of several
reviews [13-14]. A recent survey of new and older results for the early transition
metal-chalcogenides has been given by Fedorov et al. [15]. Considerably less
developed is the cluster chemistry of the lanthanoids. Ionic lanthanides form
comparatively unstable compounds with S, Se, and Te, so that as-composed clusters
are rare [16].
From TMDC titanium dieseline (TiSe2), two compounds TiSxSe2−x and
TiTexSe2−x are derived, the later were chosen as TiS2 and TiTe2 which are also
members of the TMDC family having very similar crystal and electronic structures
but a bigger band gap for TiS and a band overlap for TiTe 2. TiSe2 is a very interesting
subject studying CDWs, as it is a semiconductor with a very small band gap [17]
allowing to investigate the necessity of a positive or negative band gap for the phase
transition by tuning the band gap size with band gap engineering. Additionally, its
crystal structure makes physisorption experiments possible, since it does not have
dangling bonds in the c direction - (001) surface which could react with the adsorbed
molecules. The electronic structures are very similar as well; the relative position of
the valence and conduction band is the main relevant difference here. While TiTe2 is a
semimetal with a band overlap also referenced as negative gap, TiSe 2 is a small-gap
semiconductor and TiS2 a semiconductor with a bigger gap. Similar to TiSe2, there
exists conflicting results about the nature of the band gap for TiS2. While theoretical
calculations are ranging from semi-metal [18] to a gap of 2 eV [19], experimental
results also indicate semi-metallic [20] or semiconducting behavior. In the work of
Th¨urmer [21], TiS2 is found to be a semiconductor, yet he did not determine the
exact size of the band gap. So the experimental value of 0.3 eV from Chen et al. [22]
will be used though this is considered as a lower bound. Some other TMDCs also
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 5
Chapter 1
show CDW phase transitions as their low dimensionality favors CDWs [23].
However, neither TiS2 nor TiTe2 which are important for the understanding of the
ternary compounds, show a CDW phase. In some high temperature superconductors
this phenomenon appears as well, sometimes in combination with spin density waves.
This close relation to superconductivity was even more emphasized by the discovery
of a competing superconducting state in TiSe2 induced by pressure [24] or Cu
intercalation [25].
Particularly, the layered transition metal dichalcogenides (TMDCs) have
received much attention of researchers which is going on accelerated because of vast
variety of their electronic and optical properties [26-36]. During past few decades
these materials have been widely studied from both theoretical as well as application
point of view. Following the energy crisis in the early 1970s, considerable efforts
were made in the investigation of new semiconductors for interfacial solar energy
conversion devices [31-35]. The semiconducting layered TMDCs form a major class
of materials that have been investigated for energy conversion in Photoelectrochemical (PEC) cell and solid state (p-n and schottky) solar cell. Many
compounds of this class are also investigated almost exclusively as dry and solid
lubricants in high vacuum devices, nuclear reactors, rotating anode X-ray etc. The
electronic configurations of d-bands are brought about by crystal structure (coordination) changes, non-stoichiometry and valency changes and large variations or
transitions in the electronic properties are observed [30].
1.2 OCCURRENCE AND SYNTHESIS
Since none of the ZrSTe, TiSTe and TiSeTe (amorphous or single crystal) is
known to occur naturally, all of them are required to be synthesized in the laboratory
for characterization. For the growth of compound single crystals, various growth
techniques are available at present. These include both, growth from the melt as well
as growth from the vapor. The well-known method over the years for the growth of
transition metal chalcogenides includes Bridgeman and vapor transport techniques.
We have successfully employed the chemical vapor transport technique for the
growth of the single crystals of ZrSTe, TiSTe, and TiSeTe. Table 1.1 summarizes the
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 6
Chapter 1
information and physical properties of constituent elements of ZrSTe, TiSTe, and
TiSeTe compounds.
Table 1.1 The elemental information.
Elements
Zirconium Titanium
Sulphur
Tellurium
Selenium
Properties
(Zr)
(Ti)
(S)
(Te)
(Se)
Atomic Number
40
22
16
52
34
( g·mol−1)
91.22
47.86
32.06
127.6
78.96
Electron
[Kr] 4d2
[ Ar ]
[Ne] 3s2
[ Kr ]
[Ar] 4s2
configuration
5s2
3d1 4s2
3p4
4d10 5s25p4
3d10 4p4
Electrons per shell
2,8,18,10,2
2,8,10,2
2, 8, 6
2,8,18,18,6
2, 8, 18, 6
Phase
solid
Solid
solid
solid
solid
Atomic weight
Density
(near room
temperature)
(g·cm−3)
Melting point (K)
6.51
4.54
2.07
6.24
4.39
2125
1933
388.36
722.8
494
Boiling point (K)
4650
3560
717.8
1261
958
20.9
15.45
1.727
17.49
6.69
581.6
429
45
50.6
95.48
4
4
6, 4, 2, 1, 2
(strongly
acidic
oxide)
±2,4,6
6, 4, 2, 1, 2
(strongly
acidic
oxide)
1.33
1.54
2.58
2.1
2.55
1st : 6.84
1st: 6.82
1st : 999.6
1st : 9.009
1st : 941.0
2nd : 13.13
2nd: 13.58
2nd : 2252
2nd : 18.6
2nd : 2045
3rd : 22.99
3rd: 7.491
3rd : 3357
3rd : 27.96
3rd :2973.7
Heat of fusion
(J·mol−1) × 103
Heat of
vaporization
(J·mol−1) × 103
Oxidation states
Electronegativity
(Pauling scale)
Ionization energies
-1
(J·mol ) × 10
3
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 7
Chapter 1
Atomic radius
(cm) × 10-8
Covalent radius
(cm) × 10-8
2.16
2
100
1.42
115
1.45
1.32
102
1.36
116
N/A
N/A
180
206
190
43.3×10-6
40×10-6
>1023×10-6
104×10-6
10-6
227
219
205
235
519
van der Waals
radius
(cm) × 10-10
Electrical
resistivity
(293 K) ( Ω·cm)
Thermal
conductivity
(300 K)
( W·cm−1·K−1) ×
10-3
1.3 CRYSTAL STRUCTURE
Binary metal chalcogenides of great variety occur, since with a given
chalcogen many metals and metalloids form several compounds and sometimes long
series of compounds. Although complex structures are not unusual, for a large part the
binary compounds belong or relate to the very basic structural types and may be
approached easily in a descriptive manner. “Three-dimensional” structures,
commonly the cubic NaCl (rock salt; RS) and zinc blende (ZB), or the hexagonal
NiAs and wurtzite (W) types, as well as “2D” layer-lattice varieties related to the CdI2
type, are the major structure types observed.
Most transition elements react with chalcogen atoms to give dichalcogenides
MX2 with a precise 1:2 stoichiometry, crystallizing in either 2D or 3D structures, as
originating from the competition between cationic d levels and anionic sp levels. The
“2D” layered structures, which can be formulated as MIV+(XII–)2, consist of
sandwiched sheets of the X–M–X form, separated by a “van der Waals” gap between
the X layers of adjacent sheets. Inside the sheets, the coordination of the metal ions is
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 8
Chapter 1
sixfold, either octahedral (as in the 1T polytype, which is more commonly denoted as
the CdI2 structure) or a body-centered trigonal prism (2H polytype).
Two-thirds of the about 60 MX2 compounds assume layered structures, found
in particular for all the early transition metals of groups IV-VII (with the exception of
manganese). The non-layered MX2 compounds assume a quite different structure
motif and occur exclusively in group VIII and beyond. Most of these materials are
composed of infinite “3D” networks of metal atoms and discrete X 2 units with an X-X
distance almost equal to that expected for an X-X single bond.
The layered transition metal dichalcogenides, although comprising of
structurally and chemically well-defined family, display a number of remarkable
characteristics, such as broad homogeneity ranges, order–disorder transitions, strong
d–p covalent mixing, and fast ionic diffusion. They cover actually a wide spectrum of
electrical properties ranging from insulators like HfS2, through semiconductors like
MoS2 and semi-metals like WTe2 and TcS2, to true metals like NbS2 and VSe2; they
exhibit also intriguing magnetic and metal–insulator transitions, unusually high
melting points, or superconductivity at high temperatures. In effect, this class of
compounds has been most important in pioneering investigations on unusual
electronic phenomena such as superconductivity, quantum size effects, and charge
density waves (i.e., coupled fluctuations of electronic density and atomic positions
along a conducting chain or layer). Moreover, their 2D nature is associated with very
rich intercalation chemistry with many potential applications. For an extensive
description of the various arrangements and polytypes in the layered MX 2 phases, the
reader should refer the reviews of Whittingham [37] and Rouxel [38]. Noteworthy
also is the extensive compilation of early data on layered MX 2 given by Wilson and
Yoffe [39], who worked out a group-by-group correlation of transmission spectra of
the compounds to available electrical and structural data and produced band models in
accord with a molecular orbital approach.
Solid solutions are very common among structurally related compounds. Just
as metallic elements of similar structure and atomic properties form alloys, certain
chemical compounds can be combined to produce derivative solid solutions, which
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 9
Chapter 1
may permit realization of properties not found in either of the precursors. The
combinations of binary compounds with common “anion” or common “cation”
element, such as the “isovalent alloys” of IV–VI, III–V, II–VI, or I–VII members, are
of considerable scientific and technological interest as their solid-state properties
(e.g., electric and optical such as type of conductivity, current carrier density, band
gap) modulate regularly over a wide range through variations in composition. A
general descriptive scheme for such alloys is as follows [40].
Structurally group V transition metal dichalcogenides can be regarded as
strongly bonded X-M-X layers or sandwiches which are loosely coupled to one
another by weak van der Waals type force. Within a single X-M-X sandwich, the M
and X atoms form two dimensional hexagonal arrays. Depending on the relative
alignment of the two X atom sheets within a single X-M-X sandwich two distinct
two-dimensional structures can be obtained. In one, the metal atoms are octahedrally
coordinated by six neighboring X atoms whereas in the other, the coordination of the
metal atoms is trigonal prismatic variations in the stacking sequence and the registry
of successive X-M-X symmetries respectively [41]. Low dimensional crystals are of
great interest because of their particular properties related to the crystalline anisotropy
[42].
The 2D layered structures of Group IV-VI transition metal dichalcogenides
MX2 (M = Ti, Zr, Hf, Nb, Ta, Mo, W) as well as of the ternary alkali metal/3d-metal
systems AMX2 (A = alkali metal; M = Ti, V, Cr, Mn, Fe, Co, Ni) are capable of
intercalating various guest species. The most well investigated is the intercalation of
alkali metals (A) to dichalcogenide hosts, resulting in the formation of AxMX2 phases
(0 < x ≤ 1; M = Ti, Zr, Hf, V, Nb, Ta, Mo,W; X = mainly S, Se), which, in effect,
have served for fundamental studies of the intercalation-induced structural changes
and charge transfer. Transition metal derivatives of layered sulfides and selenides are
also known, forming intercalates of the type M xMX2 (M = 3d transition metal, M =
Nb, Ta; X = S, Se). Interestingly, ditellurides form metal-rich layer compounds rather
than intercalation phases, such as MM Te2 (M = Fe, Co, Ni; M = Nb, Ta), stabilized by
strong bonding interactions between early and late transition metals. Intercalation
processes regard also 3D lattices, i.e., the Chevrel phases MxMo6X8, Nb3X4 (X = S,
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 10
Chapter 1
Se), AxTi3S4, TlxV3S4 (intercalation into tunnels), as well as 1D structures, i.e., MX3
(M = Ti, Zr, Hf; X = S, Se), AFeS2 (A = Na to Cs), AMo3X3 (A = alkali metal; X = S,
Se) [43-45].
Of special interest to intercalation studies are complex non-stoichiometric
systems, such as the so-called “misfit” layer chalcogenides that were first synthesized
in the 1960s [46]. Typically, the “misfit compounds” present an asymmetry along the
c-axis, evidencing an inclination of the unit cell in this direction, due to lattice
mismatch in, say, the b-axis; therefore these solids prefer to fold and/or adopt a
hollow fiber structure, crystallizing in either platelet form or as hollow whiskers. One
of the first studied examples of such a misfit compound has been the kaolinite
mineral.
The early transition metals (Groups IV and V) form a wide variety of binary
chalcogenides, which frequently differ in both stoichiometry and structure from the
respective oxides. All the Group 4 dichalcogenides, MX2, occur in layered CdI2-type
structures (1T stacking polytype). TiS2, TiSe2, TiTe2, ZrTe2, and HfTe2 compounds
may be roughly classified as metallic materials due to an overlap of the chalcogenide
s and p states with the metal d states, whereas ZrS2, ZrSe2, HfS2, and HfSe2 are more
ionic in nature [47].
Titanium monosulfide, TiS, assumes two forms, both of which are of the NiAs
type. In Ti3S4, the packing of sulfur is of the ABAC type, with alternate layers of
metal sites being fully occupied but the intermediate sites half filled. A series of
intermediate phases Ti2+xS4 (0.2 < x < 1) also occurs. The trisulfide TiS3 is best
represented as TiS2–(S2)2–. The trichalcogenides of Group IVA elements are typified
by ZrSe3, which exhibits a monoclinic structure consisting of chains of trigonal
prismatic [ZrSe6] units sharing opposite faces and has semiconducting properties.
Transition metal trichalcogenides MX3 (M = Zr, Ti, Hf, Nb, Ta and X = S, Se
& Te) that crystallize in the shape of parallel fiber constitute a diversified family
ranging from superconductors to wide band gap semiconductor [48]. Different
physical properties originate from small variation of the X-X and M-M legend lengths
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 11
Chapter 1
resulting in structures possessing three different types of trigonal prismatic chains.
Their basic structural units are formed as MX6 trigonal prisms that share trigonal
faces and consisting of chains parallel to the monoclinic b axis. Each chain shifted
with respect to two neighboring ones by half the lattice parameter along the b
direction. The chains are linked by metal-chalcogen bonds and form layers bound by
much weaker van der Waals forces. Their structure makes them useful for battery
cathode intercalation and photochemical cell applications [49].
The MX3 layered compounds (ZrSe3 and ZrS3) crystallize monoclinically
(space group P21/m) in fibrous strands or filamentary ribbon-shaped platelets. A
linear chain of metal atoms is parallel to the b axis (the growth axis), and six
chalcogen (X) atoms surround each metal atom forming distorted trigonal prisms as
shown in figure 1.1. The layer-type lattice has the metal ions in the center of the
distorted trigonal prisms which share trigonal faces thus forming isolated columns
shown in figure 1.1.
Figure 1.1 Three dimensional crystal structure of ZrSe3
In the titanium–selenium system, various stoichiometries such as Ti2Se, Ti3Se,
TiSe0.95, TiSe1.05, Ti0.9Se, Ti3Se4, Ti0.7Se, Ti5 Se8, TiSe2 and TiSe3 have been
identified. A variety of phases are known also for the titanium–tellurium system,
including the compounds Ti5Te4, Ti3 Te4, Ti2Te3, Ti5Te8 and TiTe2 [50].
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 12
Chapter 1
The elements Zr and Hf are generally more similar in their chemistry than any
other pair of congeneric elements as having nearly identical atomic or ionic radii,
electronegativities, and elemental structures (actually, the similarities of Nb and Ta
are nearly as close); however, their metal-rich chemistry is often surprising in its
structural and physical aspects with fairly sharp distinctions emerging between the
two elements [51].
1.4 PROPERTIES OF SOME TRANSITION METAL CHALCOGENIDES
Guest-host interactions of low-dimensional transition metal chalcogenides
have been extensively studied because of such compounds exhibit unusual physical
properties, interesting structural chemistry, and many applications [52-56].
Recently, much attention has been focused on the chemistry of ternary
transition metal tellurides and, in particular, investigation of ternary layered group V
M′-Te (M′=3d transition metals) systems have lately produced many interesting
materials. [57]. A large number of layered transition metal chalcogenide compounds
exhibiting a very large spectrum of electrical and optical properties are known today.
1.4.1 Electrical properties
Most of the technological, electronic and optoelectronic applications utilize
semiconductor material in crystalline forms [58]. Transition metal dichalcogenides
(TMDCs) form a class of compounds known for their layered structure, where the
term “layered” refers to the existence of parallel planes where bonds are much weaker
than inside the region that the limit. Such feature makes these materials highly
anisotropic and in extreme cases two dimensional.
A large variety of properties arise from this peculiarity, rendering TMDCs
interesting not only from the theoretical point of view (e.g. charge density waves [5962], superconductivity [63-65]), but also for various practical applications. Due to
their low shear resistance TMDCs are used as solid state lubricants [66-71]. Titanium
Sulfides are nonstoichiometric compounds that have commercial applications in dry
lubrication, semiconductors, and energy batteries [72].
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 13
Chapter 1
Solid material that reveals some physical properties nearly invariant over a
substantial temperature range can be very useful for the applications [73]. Electrical
resistivity is a physical property of enormous importance, both for the understanding
of the solids and their actual applications. The electrical resistivity of solids, apart
from the possibility of superconductivity, can vary in the order of 1032 which may be
the widest of any common physical properties of solids [74]. Moreover, the
temperature dependence of the electrical resistivity behaves quite irregular, since
various different mechanisms, including the phonon scattering, impurity and defect
scattering, mutual scattering of electrons, and so forth, are involved in the electrical
transport in different temperature ranges [74-75].
1.4.2 Optical properties
Optical properties of any semiconducting material play an important role for
their device applications. The optical band gap E g of materials is one of the crucial
optical parameters for this purpose. It has been found [76] that for maximum solar
energy conversion, Eg of any single crystal solar cells should be within 1.0 eV to 1.4
eV. The semiconducting materials having band gap value near to this optimum value
are therefore considered to be a most suitable for photovoltaic applications. So, the
study of optical band gap determination is desirable for all the semiconducting
materials. The optical properties of the IVA trichalcogenides [77-79] are in contrast to
the VB compounds. Preliminary optical absorption measurements on ZrS 3 were taken
by Schairer and Schafer [80].
The class of compounds known as transition metal dichalcogenides (TMDCs)
consists of about 60 compounds of the general formula MX 2, where X is a chalcogen
(S, Se, Te), and M is Re, Pt, Sn, Pb, or a transition metal of the groups IVb, Vb, VIb.
Some comprehensive reviews describe their structural, electronic, and optical
properties [81-83]. The optical properties of TMDCs were first explained in terms of
their electronic bands by Wilson and Joffe [81] in a model, which has been improved
by theoretical calculations and experimental data, but so far has not been contradicted
[83].
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 14
Chapter 1
1.5 USES
Information about the physical properties of compound semiconductor would
enable us to use them in various applications like detector, photoelectrode in solar cell
etc. The main physical properties may include electrical properties, magnetic
properties, density, structural properties etc. TMTCs have attracted many research
workers on account of the interesting properties of the compounds of this family.
Layered transition metal trichalcogenides MX3 (M = metal; X= chalcogen)
may be considered as an ideal model system for the investigation of fundamental
aspects of semiconductor metal interaction. The ZrS 3 seems to be a suitable electrode
for solar energy conversion due to its ability to obtain relatively large photocurrents in
aqueous electrode [84]. Transition metal trichalcogenides have been used as cathode
in the lithium electrochemical cell [85]. n type ZrS3 can be used with p type WSe2 to
form a heterojunction rectifier device [86]. These properties [87-88] suggest its stable
and efficient application in the fabrication of photoelectrochemical solar cell.
With reference to these existing information about the technological
importance of zirconium and titanium based chalcogenides, author has put efforts for
the growth of ZrSTe, TiSTe and TiSeTe which is discussed in the next chapter.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 15
Chapter 1
REFERENCES
1.
A. Paulheim. Photoemission am tern¨aren Schichthalbleitersystem ZrS xSe2-x.
Diploma thesis, Humboldt Universit¨at zu Berlin, 01 (2010).
2.
JA Wilson and AD Yoffe. The transition metal dichalcogenides discussion
and interpretation of the observed optical, electrical and structural properties.
Advances in Physics, 18(73) (1969) 193.
3.
J. Rasch, T. Stemmler, and R. Manzke. Electronic properties of the
semiconductor TiSe2. Journal of Alloys and Compounds, 15th International
Conference on Solid Compounds of Transition Elements, Cracow, Poland,
442(1-2) (2007) 262–264.
4.
Ali Hussain Reshak and S. Auluck. Electronic and optical properties of the
1T phases of TiS2, TiSe2, and TiTe2 . Phys. Rev. B, 68(24) (2003) 245113.
5.
Jensen WB, A note on the term “Chalcogen”. J Chem Educ 74 (1997) 1063–
1064.
6.
Fischer W, A second note on the term “Chalcogen”. J Chem Educ 78 (2001)
1333.
7.
Vahrenkamp H, Sulfur atoms as ligands in metal complexes. Angew Chem
Int Ed Engl 14 (1975) 322–329.
8.
Draganjac M, Rauchfuss TB, Transition metal polysulfides: Coordination
compounds with purely inorganic chelate ligands. Angew Chem Int Ed Engl
24 (1985) 742–757.
9.
DuBois MR, Catalytic applications of transition metal complexes. Chem Rev
89 (1989) l–9.
10.
Ansari MA, Ibers JA, Soluble selenides and tellurides. Coord Chem Rev 100
(1990) 223–266.
11.
Roof LC, Kolis JW, New developments in the coordination chemistry of
inorganic selenide and telluride ligands. Chem Rev 93 (1993) 1037-1080.
12.
Simon A, Condensed metal clusters. Angew Chem Int Ed Engl 20 (1981) 121.
13.
Sokolov MN, Fedin VP, Sykes AG, Chalcogenide-containing metal clusters.
In:McCleverty JA, Meyer TJ (ed) The Comprehensive Coordination
Chemistry II, 2nd edn., 4 (2003) 761–823.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 16
Chapter 1
14.
Socolov MN, Metal Chalcogenides: Clusters, layers, nanotubes. In
Devillanova FA (ed) Handbook of chalcogen chemistry: New perspectives in
sulfur, selenium and tellurium, Royal Society of Chemistry: Cambridge, UK
(2007).
15.
Fedorov VE, Mironov YV, Naumov NG, Sokolov MN, Fedin VP,
Chalcogenide clusters of group 5–7 metals. Rus Chem Rev 76 (2007) 529–
552.
16.
Kornienko A, Emge TJ, Kumar GA, Riman RE, Brennan JG, Lanthanide
clusters with internal Ln ions: Highly emissive molecules with solid-state
cores. J Am Chem Soc 127 (2005) 3501–3505.
17.
J. Rasch, T. Stemmler, and R. Manzke. Electronic properties of the
semiconductor TiSe2. Journal of Alloys and Compounds, 15th International
Conference on Solid Compounds of Transition Elements, Cracow, Poland,
442(1-2) (2007) 262–264.
18.
Ali Hussain Reshak and S. Auluck. Electronic and optical properties of the
1T phases of TiS2, TiSe2, and TiTe2 . Phys. Rev. B, 68(24) (2003) 245113.
19.
D. R. Allan, A. A. Kelsey, S. J. Clark, R. J. Angel, and G. J. Ackland. Highpressure semiconductor-semimetal transition in TiS2. Phys. Rev. B, 57(9)
(1998) 5106–5110.
20.
F. R. Shepherd and P. M. Williams. Photoemission studies of the band
structures of transition metal dichalcogenides. I. Groups IVA and IVB.
Journal of Physics C: Solid State Physics, 7(23) (1974) 4416.
21.
S. Th¨urmer. Der Einfluss von Wasseradsorption auf die elektronische
Struktur der Titan-Dichalkogenide. Diploma thesis, Humboldt Universit¨at
zu Berlin, 7 (2009).
22.
C. H. Chen, W. Fabian, F. C. Brown, K. C. Woo, B. Davies, B. DeLong, and
A. H. Thompson. Angle-resolved photoemission studies of the band structure
of TiSe2 and TiS2. Phys. Rev. B, 21(2) (1980) 615–624.
23.
JA Wilson, FJ Disalvo, and S Mahajan. Charge-DensityWaves And
Superlattices In Metallic Layered Transition-Metal Dichalcogenides.
Advances In Physics, 24 (1975) 117– 201.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 17
Chapter 1
24.
AF Kusmartseva, B Sipos, H Berger, L Forro, and E Tutis. Pressure Induced
Superconductivity in Pristine 1T-TiSe2. Phys. Rev. Lett., 103 (2009)
236401.
25.
E Morosan, HW Zandbergen, BS Dennis, JWG Bos, Y Onose, T Klimczuk,
AP Ramirez, NP Ong, and RJ Cava. Superconductivity in CuxTiSe2. Nat.
Phys., 2(8) (2006) 544.
26.
J.A. Wilson and A.D. Yoffe, Advances in Physics, 18 (1969) 193-335.
27.
F.Levy (ed.), Preparation and crystal growth of materials with layered
structures, D Reidel Publishing Company, Dordrecht-Holland/Boston-USA
(1976).
28.
R.H. Friend and A.D. Yoffe, Advances in Physics, 36(1) (1987) 1-94.
29.
P.A. Lee, Optical and Electrical Properties of Layered Semiconductors, D
Reidel Publishing Company, Dordrecht-Holland/Boston-USA (1976).
30.
A. Aruchamy, Photoelectrochemistry and Photovoltaics of Layered
Semiconductors, Kluwer Academic Publishers, Netherlands (1992) 319-347.
31.
Yu. V Pleskov, Solar Energy Conversion: A Photoelectrochemical
Approach, Springer Verlag, Berlin-Heidenberg (1990).
32.
A. Heller, Semiconductor Liquid Junction Solar Cells, The Electrochemical
Society, Princenton, New Jersey (1977).
33.
K. L. Chopra and S. R. Das, Thin film Solar Cells, Plenum Press, New York
(1983).
34.
H. J. Hovel, Semiconductors and Semimetals, Academic Press, New York
(1975).
35.
M Sitting, Solar Cells for Photovoltaic generation of Electricity: Materials
devices and Applications, Energy Technology Review No. 48, Noyes Data
Corp., Park Ridge, New Jersey (1979).
36.
M. S. Whittingham, Progress in Solid State Chem., 12 (1978) 41-99.
37.
Whittingham MS, Chemistry of intercalation compounds. Prog Solid State
Chem 12 (1978) 41–99.
38.
Jobic S, Brec R, Rouxel J, Occurrence and characterization of anionic
bondings in transition metal dichalcogenides. J Alloy Compd 178 (1992)
253–283.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 18
Chapter 1
39.
Wilson JA, Yoffe AD, The transition metal dichalcogenides. Discussion and
interpretation of the observed optical, electrical and structural properties.
Adv Phys 18(73) (1969) 193–335.
40.
Madelung O, Semiconductors – Other than Group IV Elements and II-V
Compounds. In: Poerscke R (ed) Data in Science and Technology, SpringerVerlag, Berlin, Heidelberg, (1992).
41.
L.F. Mattheiss, Physical Review B, 8 (1973) 3719.
42.
Furuseth S, Brattas L and Kjekshus A ,Acta Chem. Scand Ser. A, 29 (1975)
623.
43.
Bruce PG, Irvine JTS, Insertion Compounds. In Encyclopedia of Materials:
Scienceand Technology, Elsevier Science Ltd : Oxford ISBN: 0-08-0431526,
(2001) 4115–4121.
44.
Schöllhorn R, Reversible topotactic redox reactions of solids by electron/ion
transfer. Angew Chem Int Ed Engl 19 (1980) 983–1003.
45.
Schöllhorn R, Electron/ion-transfer reactions of solids with different lattice
dimensionality. Pure Appl Chem 56 (1984) 1739–1752.
46.
Wiegers GA, Misfit Layer Compounds: Structures and Physical Properties.
Prog Solid State Chem 24 (1996) 1–13946.
47.
Lucovsky G, White RM, Benda JA, Revelli JF, Infrared-reflectance spectra
of layered Group-IV and Group-VI transition-metal dichalcogenides. Phys
Rev B 7 (1973) 3859–3870.
48.
Grimmeiss H G, Rabenau A, Hann H and Neiss P ,Z. Electrochem., 65
(1961) 776.
49.
Srivastava S K and Avansthi B N ,J. Mater. Sci., 27 (1992) 3693.
50.
Cordes H, Schmid-Fetzer R, Phase equilibria in the Ti-Te system. J Alloy
Compd 216 (1994) 197–206
51.
Hughbanks T, Exploring the metal-rich chemistry of the early transition
elements. J Alloy Compd 229 (1995) 40–53.
52.
Hulliger, F. Structural Chemistry of Layer-type Phases; Reidel: Dordrecht,
The Netherlands, 5 (1976).
53.
Rouxel, J.; Brec, R. Annu. ReV. Mater. Sci. 16 (1986) 137-162.
54.
Rouxel, J. Crystal Chemistry and Properties of Materials with Quasionedimensional Structures; D. Reidel: Dordrecht, Holland, (1986).
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 19
Chapter 1
55.
Scho¨llhorn, R. Materials and Models: Faces of Intercalation Chemistry;
Scho¨llhorn, R., Ed.; Kluwer: Dordrecht, The Netherlands, 17 (1994) 1-82.
56.
Whittingham, M. S.; Ebert, L. B. Applications of Intercalation Compounds;
Eds.; D. Reidel: Dordrecht, Holland, (1979) 533-562.
57.
Chwanchin Wang, Cahit Eylem, and Timothy Hughbanks Inorg. Chem. 37
(1998) 390-397.
58.
A.A. Al-Ghamdi, A.T.Nagat, et al., JKAU: Sci., 21 (1) (2009) 3.
59.
J.A. Wilson, F.J. DiSalvo, and S. Mahajan, Adv. Phys. 24 (1975) 117.
60.
J.A. Wilson, F.J. Di Salvo, and S. Mahajan, Phys. Rev. Lett. 32 (1974) 882.
61.
J.K. Burdett, J. Phys. Chem. 100 (1996) 13263.
62.
V. Vescoli, L. Degiorgi, H. Berger, and L. Forro, Phys. Rev. Lett. 81 (1998)
453.
63.
Y. Nishio, M. Shirai, N. Suzuki, and K. Motizuki, J. Phys. Soc. Jpn. 63
(1994) 156.
64.
K. Motizuki, Y. Nishio, M. Shirai, and N. Suzuki, J. Phys. Chem. Solids 57
(1996) 1091.
65.
S.H. Cai and C.W. Liu, Theochem 362 (1996) 379.
66.
M.C. Zonneville, R. Hoffmann, and S. Harris, Surf. Sci. 199 (1988) 320.
67.
Y. Golan, C. Drummond, M. Homyonfer, Y. Feldman, R. Tenne, and J.
Israelachvili, Advanced Materials 11 (1999) 934.
68.
S.R. Cohen, Y. Feldman, H. Cohen, and R. Tenne, Appl. Surf. Sci. 145
(1999) 603.
69.
S.R. Cohen, L. Rapoport, E.A. Ponomarev, H. Cohen, T. Tsirlina, R. Tenne,
and C. Levy-Clement, Thin Solid Films 324 (1998) 190.
70.
R. Tenne, L. Margulis, and G. Hodes, Advanced Materials 5 (1993) 386.
71.
L. Rapoport, Y. Bilik, Y. Feldman, M. Homyonfer, S.R. Cohen, and R.
Tenne, Nature 387 (1997) 791.
72.
Bonneau, P. R.; Jarris, R. R., Jr.; Kaner, P. B. Nature, 349 (1991) 510.
73.
Ailing Ji, Chaorong Li and Zexian Cao, Applied Physics Letters 89 (2006)
252120.
74.
C. Kittle, Introduction to Solid State Physics, 8 th ed., Wiley, New York,
(2004) 199.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 20
Chapter 1
75.
N. W. Ashcroft and N. D. Mermin, Solid State Physics, Thomson Learning,
Orlando, (1976) 512.
76.
Bucher,
in
“Photoelectrochemistry
and
Photovoltaic
of
Layered
Semiconductor”, Kluwer Academic Publishers, Dordrecht (1992) 1-81.
77.
Grisel A, Levy F and Wieting T J, Physics B+C, 99 (1980) 365.
78.
Jandl S, Deville Cavellin C and Harbec J Y, Solid State Commun., 31 (1979)
351.
79.
Zwick A and Renucei M A, Phys. Status Solidi (B), 96 (1979) 757.
80.
Schairer W and Schafer M W, Status Solidi A, 17 (1973) 181.
81.
J.A. Wilson and A.D. Yoffe, Adv. Phys. 18 (1969) 193.
82.
W. Jaegermann, in Photoelectrochemistry and Photovoltaics of Layered
Semiconductors (A. Aruchamy, ed.), Kluwer Academic Publishers,
Dordrecht, (1992).
83.
V. Grasso (ed.), Electronic Structure and Electronic Transitions in Layered
Materials, D. Reidel, Dordrecht, (1986).
84.
Onuki Y, Inada R, Tanuma S, Yamanaka S and Kamimura H ,Solid state
Ionic, 11 (1983) 195.
85.
Spah R, Lux-Steiner M, Bucher E and Wagner S ,Appl. Phys. Lett., 45(7)
(1984) 744.
86.
Gorochov O, Ketty A, Nagard N L, Clemetn C L, Redon A and Tributsch H
J. Electpchem. Soc. 130(6) (1983) 1301.
87.
Sieber K, Fotouhi and Gorochov O ,Mat. Res. Bull., 18 (1983) 1477.
88.
Kikiwa S, Ogawa N, Koizumi M and Onuki Y ,J. Solid State Chem., 41
(1982) 315.
Abhay K. Dasadia/Ph.D. thesis/Department of Physics/S. P. University/Vallabh Vidyanagar/May 2013
Page 21