Synthesis and spectroscopic characterization of alkali-metal intercalated ZrSe2

Article abstract of DOI:10.1039/c7dt03756b

We report on the synthesis and spectroscopic characterization of alkali metal intercalated ZrSe₂ single crystals. ZrSe₂ is produced by chemical vapour transport and then Li is intercalated. Intercalation is performed from the liquid phase (via butyllithium) and from the vapour phase. Raman spectroscopy of intercalated ZrSe₂ reveals phonon energy shifts of the Raman active A_1g and E_g phonon modes, the disappearance of two-phonon modes and new low wavenumber Raman modes. Angle-resolved photoemission spectroscopy is used to perform a mapping of the Fermi surface revealing an electron concentration of 4.7 × 10¹⁴ cm^-2. We also perform vapour phase intercalation of K and Cs into ZrSe₂ and observe similar changes in the Raman modes as for the Li case.

Full text of DOI:10.1039/c7dt03756b

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Efficient extraction of sulfate from water using
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Synthesis and spectroscopic characterization of
alkali-metal intercalated ZrSe2
Konstantin Nikonov,∗a Niels Ehlen,a, Boris Senkovskiya, Nihit Saigala, Alexander
Fedorova, Alexei Nefedovb, Christof Wöllb, Giovanni di Santoc, Luca Petacciac and
Alexander Grüneis∗a
We report on the synthesis and spectroscopic characterization of alkali metal intercalated ZrSe2
single crystals. ZrSe2 is produced by chemical vapour transport and then Li is intercalated. Inter-
calation is performed from the liquid phase (via butyllithium) and from the vapour phase. Raman
spectroscopy of intercalated ZrSe2 reveals phonon energy shifts of the Raman active A1g and
Eg phonon modes, the disappearance of two-phonon modes and new low wavenumber Raman
modes. Angle-resolved photoemission spectroscopy is used to perform a mapping of the Fermi
surface revealing an electron concentration of 4.7 × 1014 cm−2. We also perform vapour phase
intercalation of K and Cs into ZrSe2 and observe similar changes in the Raman modes as for the
Li case.
1 Introduction
Intercalation chemistry between a wide range of host materials
and intercalant species allows one to engineer the physical prop-
erties of layered materials. Perhaps the best-studied example of
this kind are the graphite intercalation compounds1. For alkali
and alkali-earth metal intercalants, the intercalant atom acts as
a charge dopant and graphite becomes superconducting2–4. In-
tercalation of related layered materials such as boron nitride5,
transition metal dichalcogenides (TMDCs)6,7 and black phospho-
rous8,9 has also been performed. The largest number of possi-
ble combinations between host and intercalant exists for TMDCs
which come in the largest variety of host structures10. Some of
the TMDCs like ZrSe2 are interesting materials for thermoelectric
application. In particular, it has been shown that doping can be
used to engineer the optimal Seebeck coefficient for a given tem-
perature11. Our experiments have also revealed that the struc-
tural quality of ZrSe2 remains intact after intercalation of various
alkali metals which allows performing a comparative study.
Regarding the intercalation, we have to distinguish 1) vapour
and liquid phase phase intercalation, 2) electrochemical interca-
lation and 3) liquid ammonia assisted intercalation. Vapour phase
intercalation can be performed in an ampoule or by evaporating
the alkali metal onto the surface of the host crystal. The latter
is especially used in surface science experiments such as photoe-
mission. The butyl-alkali intercalation method is based on inter-
Fig. 1 A) Schematics of the growth of ZrSe2 single crystals by chemical
vapour transport (CVT) reaction. B) butyllithium intercalation. C) Vapour-
phase intercalation: photograph and sketch (Me stands for alkali metal).
a
II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln,
Germany. Fax: ++49 221 470 5178; Tel: ++49 221 4703461; E-mail:
grueneis@ph2.uni-koeln.de; nikonov@ph2.uni-koeln.de;
b
Institut für Funktionelle Grenzflächen, Karlsruher Institut für Technologie, Hermann-
von-Helmholtz-Platz 1, 76344,Eggenstein-Leopoldshafen, Germany
c
Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
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action between butyl-alkali, typically butyllithium solution and
2 Synthesis
ZrSe2 crystals immersed into it. At first an electron is transferred
to ZrSe2 from Bu−, forming ZrSe−2 , and Li+ ion diffuse into lay-
ered structure of ZrSe2 to compensate negative charge. Then two
butyl radicals combine and form octane, which readily evaporates
from the solution.
2.1 Synthesis of pristine ZrSe2
Large crystals of ZrSe2 were grown from pure substances by
chemical transport reaction method in vapour phase (CVT)19
.
Figure 1A depicts a sketch of the growth procedure. Stoichio-
metric amounts of metallic Zr (Sigma-Aldrich) and granular Se
were sealed in evacuated quartz tube along with a Pyrex cap-
illary containing 0.05g of crystallised iodine as a transporting
agent. Sealed ampoule was placed in a two-zone tubular fur-
nace with temperature gradient of 115◦C between cold (810◦C)
and hot (925◦C) zones of the furnace and held for 120 hours. Un-
der those conditions gaseous iodides of Zr are formed and trans-
ported along the temperature gradient to the cold zone of the
furnace. Temperature decreasing shifts chemical balance back to
the forming of ZrSe2 which crystallizes in the cold end of the am-
poule in form of thin shiny plates. The average crystal size was
∼5mm2. The grown crystals were taken out from the ampoule,
washed with distilled water and heated under vacuum to remove
excess of selenium and iodine left on the crystal surface. Pris-
tine ZrSe2 crystals are thin gray-colored platelets, hexagonal in
The main downside of this method is the fact that due to the
more unstable nature of other butyl-alkali compounds, only butyl-
lithium solution can be easily acquired and is relatively safe to
work with, thus limiting wide usage of this method to Li inter-
calation only. Electrochemical intercalation can be performed in
an electrochemical cell where alkali metal ions are solved in an
electrolyte. This method has been applied for the transition metal
dichalcogenide NbSe2 12. Ammonia-driven intercalation is based
on the unique ability of liquid ammonia to form a stable solution
with all alkali metals without chemical interaction. Low temper-
atures are required to keep ammonia in the liquid phase and also
help to control the reaction rate and prevent destruction of crys-
tals during intercalation.
After performing intercalation one wishes to characterize spec-
troscopically the reaction product, in particular regards to the
charge transferred from the intercalant to the host derived elec-
tronic system. To that end angle-resolved photoemission spec-
troscopy (ARPES) is a key technique that allows to directly probe
the electron energy band structure. It has yielded e.g. the Fermi
level shift of the potassium doped graphite compound with KC8
shape and possess metallic shine. On the surface of large crystals
one may see spiraling growth pattern. X-ray photoemission spec-
troscopy (XPS) experiments were carried out at HESGM beamline
at Helmholtz Zentrum Berlin (HZB)20. Figure 2A shows an XPS
spectrum measured in the vicinity of the Zr and Se 3d core lev-
els confirming the chemical purity of ZrSe2 single crystals. XPS
stoichiometry13
.
spectra were measured with photon energies of 400 eV (for the
Zr 3d core level) and 290 eV (for the Se 3d core level) in the nor-
mal emission geometry. All XPS spectra were calibrated using the
Au 4f7/2 core level energy. Figure 2B shows a Laue diffraction
pattern confirming a good structural quality of grown Z rSe2 crys-
In the present work we prepare and spectroscopically study
ZrSe2 alkali metal intercalation compounds14. ZrSe2 is a semi-
conductor of recent interest as it can be grown in high quality
on high-k dielectrics and is therefore a good material for field ef-
fect transistor applications15. ARPES has also revealed that spin-
orbit coupling effects in ZrSe2 lead to a valence band splitting
of ∼300 meV in the valence band at the A point of the 3D Bril-
louin zone16. It has also been shown by ARPES that alkali metal
intercalation turns ZrSe2 into a metal both in case of Na15 and
Cs doping14,17 with similar effects observed for ZrS2 18. However
the shape of the Fermi surface has not been shown and the carrier
concentration has not been estimated. Raman spectroscopy of
doped ZrSe2 revealed shifts of the Raman active phonon modes.
However, the low wavenumber (LWN) Raman spectrum of in-
tercalated ZrSe2 has not been studied yet. Little is known re-
garding the effect of different alkali intercalants. The present
work addresses these issues. We prepare bulk Li doped ZrSe2
by butyllithium intercalation for Raman spectroscopy and surface
Li doped ZrSe2 by evaporation of Li in ultra-high vacuum condi-
tions for ARPES. Raman spectroscopy reveals phonon shifts upon
doping in agreement to previous literature. In addition we ob-
serve peculiar low wavenumber (LWN) phonons upon intercala-
tion that have not been reported so far. A mapping of the Fermi
surface of Li doped ZrSe2 by ARPES reveals a carrier concentra-
tion of 4.7×1014 cm−2. Finally, K and Cs intercalation compounds
are prepared by vapour phase intercalation and characterized by
ultra-high vacuum Raman spectroscopy. For these intercalants,
the LWN phonons are shifted in frequency pointing towards a
dopant dependent phonon mode.
tals. An overlay with a simulated diffraction pattern suggests an
expected 1T-structure (Fig. 2C). We also have carried out x-ray
diffraction to determine the lattice parameters as a = b = 3.765(2)
Angstrom and c = 6.145(3)Angstrom. These are in good agree-
ment to the literature21
.
2.1.1 Lithium intercalation
Figure 1B depicts a sketch of Lithium intercalation by the con-
ventional butyllithium method22. A ZrSe2 crystal was immersed
into 1M n-butyllithium solution in hexane for 72h, washed with
hexane and stored under Ar. The intercalated crystal turns blue
and its surface begins to degrade. The Li doped crystals undergo
deintercalation if exposed to atmosphere.
2.1.2 Vapour phase intercalation
Figure 1C depicts a photograph and a sketch of vapour phase in-
tercalation. Potassium and caesium intercalations were carried
out in this way. The alkali metal and ZrSe2 crystals were placed
into an evacuated Pyrex ampoule. The ampoule was placed into
a thermal gradient of 150-200◦C for 96h. Alkali vapor interacts
with ZrSe2 and metal atoms diffuse into the layered structure.
During this process direct contact of the crystals with molten
metal was avoided since high reaction rates affect the crystal qual-
ity. The intercalated crystals turn blue and readily deintercalate if
exposed to air.
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Fig. 2 A) X-ray photoelectron spectra of as-synthesized ZrSe2. The Zr 3d and Se 3d peaks are shown. B) Laue diffraction pattern of as-synthesized
ZrSe2. The open circles depict calculations of diffraction spots. C) Sketch of the crystal structure of the 1T phase (Zr in blue, Se in red).
Fig. 3 ARPES (T = 20 K) scan along the high symmetry ΓM line of A) pristine and B) Li-doped ZrSe2. C) Fermi surface mapping (a symmetrization
has been applied). The blue points denote the experimental ARPES maxima and the red line an elliptical fit. The area of the ellipse has been used
to determine the charge carrier concentration (see text). The photon energy was hν = 36 eV in all spectra. D) High-resolution ARPES spectra parallel
to the ΓM direction showing a splitting in the conduction band. E) Raman spectra of pristine and Li-doped ZrSe2 measured with a green (λ=532 nm)
laser. F) Low wavenumber Raman spectra of pristine and Li-doped ZrSe2 (λ=633 nm). All Raman spectra were recorded at room temperature.
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2.1.3 Lithium deposition
ond method that is a bit easier to apply works by reloading the
intercalated samples into an ampoule with a flat surface (Hilgen-
berg) inside an Ar box. This ampoule is sealed by wax and trans-
ferred out of the Ar box. We have performed Raman spectroscopy
of samples prepared in both ways and did not find a difference
in the obtained spectra. Figure 3E depicts Raman spectra of pris-
tine and Li doped ZrSe2. Upon doping with alkali metals, the
characteristic peaks of A1g and Eg modes are shifted to lower and
higher wavenumbers, respectively. This observation is in good
agreement to previous data27. In the case of low frequency Ra-
man spectra (Figure 3F) one can see low energy Raman modes at
51 cm−1 and 71 cm−1 appearing after doping. Interestingly, there
are two more weak Raman modes present in pristine ZrSe2 at
240 cm−1 and 260 cm−1 (Figure 3E). These have been assigned
For the ARPES experiments, several monolayers of lithium were
evaporated from a commercial SAES getter source onto the sur-
face of ZrSe2. The doping was performed in an ultra-high vacuum
(UHV) chamber in steps up to the maximum Fermi level with the
sample at 20 K. The amount of Li was calibrated by a quartz micro
balance.
3 Spectroscopic characterization
3.1 Angle-resolved photoemission spectroscopy
Alkali metal doping of ZrSe2 leads to changes in electronic and
crystal structure which can be observed using ARPES. ARPES was
performed at the BaDElPh beamline23 of the Elettra synchrotron
in Trieste (Italy) with linear s− and p− polarisation at temper-
atures of 20 K. The crystal surfaces were prepared in-situ in a
vacuum better than 5×10−11mbar and at liquid He temperatures
by cleaving with a top post inside the analysis chamber. Imme-
diately after the cleave we determined the high-symmetry direc-
tions through low-energy electron diffraction. ARPES data taken
from pristine ZrSe2 are shown in Figure 3A and reveals a semi-
to two-phonon processes24
. Upon doping we can not observe
them any more which points towards a loss of the resonance con-
dition for two phonon scattering upon shifting the Fermi level.
Notably, Raman measurements at several spots across the sam-
ples revealed that the intercalated samples are homogeneous.
3.2.2 Cs and K intercalated ZrSe2
Along with well-known Li intercalation we performed K and Cs in-
tercalation from the vapour phase into bulk ZrSe2 crystals. These
Raman spectra are shown in Figure 4A an display similar effects
as in the lithium doping cases, i.e. the shifting of A1g and Eg
phonon modes. The phonon energy shift upon doping was exten-
sively investigated for example for graphene28. It has been shown
for graphene that there are two main contributions: one is the
lattice expansion which causes a downshift. The second contribu-
tion is the phonon self energy which can change with doping. We
speculate that a similar reasoning might be applied for ZrSe2, too.
Interestingly, the low-wavenumber Raman modes for Li, K and Cs
intercalants appear at different energies. For the K intercalated
ZrSe2, we observe them at 38 cm−1 and 62 cm−1 respectively, and
for Cs intercalated ZrSe2 a broad mode around 60 cm−1 appears.
These modes have not been reported so far and could in principle
be a result of one or several following reasons: 1) changes in the
lattice structure and defect formation upon interaction with the
alkali metal 2) dopant derived vibrations and 3) electronic Raman
scattering. The high structural quality of doped samples as e.g.
evidenced by ARPES makes 1) unlikely. Moreover, the tempera-
ture of the Raman measurements was room temperature which
makes 3) unlikely. Since there is a distinct dopant dependence
which shifts the phonons to lower wavenumber with increasing
dopant mass, we speculate that the LWN phonon modes belong
to alkali ion vibrations.
conductor band structure with the valence band maximum at the
Γ point of the Brillouin zone. Upon doping by Li this picture dras-
tically changes and the Fermi level moves into the previously un-
occuppied conduction band. Most importantly, at the M point in
the BZ, a parabolic band appears which crosses the Fermi energy.
This clearly indicates a transition from semiconducting to metal-
lic electronic properties. In order to estimate the charge carrier
density on the ZrSe2 layers, we performed ARPES mapping of
the Fermi surface. The Fermi surface map (hν = 36 eV) is shown
in Figure 3C. This photon energy corresponds to the A point of
the 3D BZ. A fit o f t he A RPES m axima u sing a n e llipse allows
to calculate the charge carrier density equal to 4.7 × 1014 elec-
trons per square centimeter. Figure 3D depicts a cut through the
pocket (hν = 22 eV). A splitting of the conduction band by about
100 meV can be seen which we tentatively attribute to spin-orbit
coupling16. Assuming a complete charge transfer for each Li ion,
we estimate a stoichiometry of about 1 Li per two unit cells.
3.2 Raman spectroscopy
3.2.1 Butyllithium intercalated ZrSe2
The Raman spectra of pristine ZrSe2 that we obtained under am-
bient conditions fit the literature data very w ell24. Alkali metal
intercalated ZrSe2 can not be measured in ambient conditions be-
cause of the high reactivity with air. We have overcome this prob-
lem in two ways. One is that we have made use of an ultra-high
vacuum (UHV) Raman system25,26. Samples were taken from the
ampoules and mounted on a wobble stick in a vacuum suitcase in-
side a glove box. Then, these samples were transferred into the
UHV Raman without exposure to air. UHV-Raman was performed
in the back-scattering geometry using a commercial Raman sys-
tem (Renishaw) integrated in a homebuilt optical chamber where
the exciting and Raman scattered light were coupled into the vac-
uum using a long-working distance microscope objective with an
NA of ∼0.426. The laser power on the sample was 1 mW. A sec-
4 Conclusions and outlook
In conclusion we have synthesized Li doped ZrSe2 by butyllithium
intercalation from the liquid phase and by evaporation of Li in
UHV conditions onto the ZrSe2 surface. For the bulk sensitive Ra-
man spectroscopy, the samples intercalated by butyllithium have
been used. For the surface sensitive ARPES method Li evapora-
tion in UHV has been applied. Upon Li doping, the semiconduc-
tor ZrSe2 becomes metallic which is evidenced by the appearance
of an elliptical Fermi surface around the M point in the 2D BZ.
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Fig. 4 A) Raman modes of pristine and intercalated (Li, K, Cs) ZrSe2 (λ=532 nm). B) Low-frequency Raman spectrum (λ=633 nm). All Raman spectra
were recorded at room temperature.
Also the phonon system of ZrSe2 undergoes changes, in particular
phonon energy shifts of the Raman active A1g and Eg phonons are
observed. We also observe the appearance of new low wavenum-
ber modes in the Raman spectrum whose origin is tentatively at-
tributed to dopant derived vibrations. The connection of these
new modes to the intercalant is corroborated by their appearance
for K and Cs intercalants at slightly different frequencies.
6 J. Wilson, F. D. Salvo and S. Mahajan, Advances in Physics,
1975, 24, 117–201.
7 E. Marseglia, International Reviews in Physical Chemistry,
1983, 3, 177–216.
8 R. Zhang, J. Waters, A. K. Geim and I. V. Grigorieva, Nature
Communications, 2017, 8, 15036.
9 G. Abelan, C. Neiss, V. Lloret, S. Wild, J. C. Chacon-Torres,
K. Werbach, F. Fedi, H. Shiozawa, A. Goerling, H. Peterlik,
T. Pichler, F. Hauke and A. Hirsch, Angewandte Chemie Inter-
national Edition, 2017, 56, 15267–15273.
Conflict of interest
There are no conflicts to declare.
10 M. Chhowalla, H. S. Shin, G. Eda, L.-J. Li, K. P. Loh and
H. Zhang, Nat Chem, 2013, 5, 263–275.
5 Acknowledgements
K.N., N.E., B.S., A.F. and A.G. acknowledge the ERC grant no.
648589 ’SUPER-2D’, funding from DFG project CRC 1238 (project
A1) and DFG project GR 3708/2-1. The research leading to these
results has received funding from the European Community’s
Horizon 2020 Programme under grant agreement n. 730872
(CALIPSOplus). A.N. and C.W. acknowledge STN programme
(Karlsruhe Institute of Technology) for a partial support of these
experiments. We thank HZB and Elettra for the allocation of syn-
chrotron radiation beamtimes.
11 G. Ding, G. Y. Gao, Z. Huang, W. Zhang and K. Yao, Nanotech-
nology, 2016, 27, 375703.
12 E. Hitz, J. Wan, A. Patel, Y. Xu, L. Meshi, J. Dai, Y. Chen, A. Lu,
A. V. Davydov and L. Hu, ACS Applied Materials & Interfaces,
2016, 8, 11390–11395.
13 A. Grüneis, C. Attaccalite, A. Rubio, D. V. Vyalikh, S. L.
Molodtsov, J. Fink, R. Follath, W. Eberhardt, B. Büchner and
T. Pichler, Phys. Rev. B, 2009, 80, 075431.
14 H. Starnberg, Acta Physica Polonica A, 2001, 100, 301–318.
15 M. J. Mleczko, C. Zhang, H. R. Lee, H.-H. Kuo, B. Magyari-
Köpe, R. G. Moore, Z.-X. Shen, I. R. Fisher, Y. Nishi and E. Pop,
Science Advances, 2017, 3, year.
References
1 M. S. Dresselhaus and G. Dresselhaus, Advances in physics,
2002, 51, 1–186.
16 M. Moustafa, A. Ghafari, A. Paulheima, C. Janowitz and
R. Manzkea, Journal of Electron Spectroscopy and Related Phe-
nomena, 2013, 189, 35–39.
2 N. B. Hannay, T. H. Geballe, B. T. Matthias, K. Andres,
P. Schmidt and D. MacNair, Phys. Rev. Lett., 1965, 14, 225–
226.
17 H. E. Brauer, H. I. Starnberg, L. J. Holleboom and H. P.
Hughes, Journal of Physics: Condensed Matter, 1995, 6, 7741–
7760.
3 T. E. Weller, M. Ellerby, S. S. Saxena, R. P. Smith and N. T.
Skipper, Nat. Phys., 2005, 1, 39–41.
4 N. Emery, C. Hérold, M. d’Astuto, V. Garcia, C. Bellin, J. F.
Marêché, P. Lagrange and G. Loupias, Phys. Rev. Lett., 2005,
95, 087003.
18 A. Ghafari, C. Janowitz and R. Manzke, Journal of Physics:
Condensed Matter, 2013, 25, 315502.
19 H. Schäfer, Chemische Transportreaktionen, Verlag Chemie,
Weinheim, 1962.
5 G. L. Doll, J. S. Speck, G. Dresselhaus, M. S. Dresselhaus,
K. Nakamura and S. Tanuma, Journal of Applied Physics, 1989,
66, 2554–2558.
20 A. Nefedov and C. Wöll, Advanced Applications of NEXAFS
Spectroscopy for Functionalized Surfaces. In: Bracco G., Holst
1–6 | 5

Dalton Transactions
Page 6 of 7
View Article Online
DOI: 10.1039/C7DT03756B
B. (eds) Surface Science Techniques., Springer, Berlin, Heidel-
berg, 2013, vol. 51, pp. 277–303.
25 B. V. Senkovskiy, A. V. Fedorov, D. Haberer, M. Farjam, K. A.
Simonov, A. B. Preobrajenski, N. Martensson, N. Atodiresei,
V. Caciuc, S. Blügel, A. Rosch, N. I. Verbitskiy, M. Hell, D. V.
Evtushinsky, R. German, T. Marangoni, P. H. M. van Loos-
drecht, F. R. Fischer and A. Grüneis, Advanced Electronic Ma-
terials, 2017, 1600490.
21 C. R. Whitehouse and A. A. Balchin, physica status solidi (a),
1978, 47, K173–K176.
22 D. W. Murphy, F. J. D. Salvo, J. George W. Hull and J. V.
Waszczak, Inorganic Chemistry, 1976, 15, 17–21.
23 L. Petaccia, P. Vilmercati, S. Gorovikov, M. Barnaba, A. Bianco,
D. Cocco, C. Masciovecchio and A. Goldoni, Nuclear Instru-
ments and Methods in Physics Research Section A: Accelerators,
Spectrometers, Detectors and Associated Equipment, 2009, 606,
780–784.
26 A. Grüneis, B. Senkovskiy, A. Fedorov, M. Hell and S. Michel,
in Reference Module in Chemistry, Molecular Sciences and
Chemical Engineering, Elsevier, 2017.
27 P. C. Klipstein, C. M. Pereira and R. H. Friend, Philosophical
Magazine Part B, 1987, 56, 531–539.
28 M. Lazzeri and F. Mauri, Phys. Rev. Lett., 2006, 97, 266407.
24 S. Manas-Valero, V. Garcia-Lopez, K. C. Andres and M. Gal-
biati, Applied sciences, 2016, 6, 264.
6 |
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