Skutterudites CoSb3 are considered interesting candidates for thermoelectric applications, because the filling of guest atoms into the cage-like structure has the potential to improve its thermoelectric properties by an increased phonon scattering, which reduces the thermal conductivity. This, however, requires that a high electrical conductivity is maintained. In this study, we performed resistivity, Hall effect, and fluctuation spectroscopy measurements on polycrystalline thin films of semiconducting YbzCo4Sb12 with 0<z<0.27. Our aim is to better understand the conventional dc electronic transport but also the low-frequency dynamical properties of the charge carriers. The electronic properties are highly sensitive to the filling factor z as well as other parameters, e.g., the Sb content. The resistivity can be described by Mott variable range hopping at low temperatures. A large 1/f noise level suggests an influence of the granularity of the polycrystalline thin films. By analyzing the 1/f-noise and two-level fluctuations, which are abundant for filled samples annealed at 500 °C, we are able to determine the energy distribution of the relevant electronic switching processes. A likely explanation for the observed low-frequency dynamics is capture/emission processes of impurities with a broad distribution within the energy gap.

1.
T. M.
Tritt
, “
Thermoelectric phenomena, materials, and applications
,”
Annu. Rev. Mater. Res.
41
,
433
448
(
2011
).
2.
M. S.
Dresselhaus
,
G.
Chen
,
M. Y.
Tang
,
R. G.
Yang
,
H.
Lee
,
D. Z.
Wang
,
Z. F.
Ren
,
J.-P.
Fleurial
, and
P.
Gogna
, “
New directions for low-dimensional thermoelectric materials
,”
Adv. Mater.
19
,
1043
1053
(
2007
).
3.
T. C.
Harman
, “
Quantum dot superlattice thermoelectric materials and devices
,”
Science
297
,
2229
2232
(
2002
).
4.
R.
Venkatasubramanian
,
E.
Siivola
,
T.
Colpitts
, and
B.
O'Quinn
, “
Thin-film thermoelectric devices with high room-temperature figures of merit
,”
Nature
413
,
597
602
(
2001
).
5.
M.
Christensen
,
N.
Lock
,
J.
Overgaard
, and
B. B.
Iversen
, “
Crystal structures of thermoelectric n- and p-type Ba8Ga16Ge30 studied by single crystal, multitemperature, neutron diffraction, conventional x-ray diffraction and resonant synchrotron x-ray diffraction
,”
J. Am. Chem. Soc.
128
,
15657
15665
(
2006
).
6.
G. S.
Nolas
,
D. T.
Morelli
, and
T. M.
Tritt
, “
Skutterudites: A phonon-glass-electron crystal approach to advanced thermoelectric energy conversion applications
,”
Annu. Rev. Mater. Sci.
29
,
89
116
(
1999
).
7.
J. O.
Sofo
and
G. D.
Mahan
, “
Electronic structure of CoSb3: A narrow-band-gap semiconductor
,”
Phys. Rev. B
58
,
15620
15623
(
1998
).
8.
H.
Anno
,
T.
Sakakibara
,
Y.
Notohara
,
H.
Tashiro
,
T.
Koyanagi
,
H.
Kaneko
, and
K.
Matsubara
, “
Preparation and thermoelectric properties of CoSb3 thin films on GaAs(100) substrate
,” in
Proceedings of the 16th International Conference on Thermoelectrics (ICT)
(
1997
).
9.
D.
Mandrus
,
A.
Migliori
,
T. W.
Darling
,
M. F.
Hundley
,
E. J.
Peterson
, and
J. D.
Thompson
, “
Electronic transport in lightly doped CoSb3
,”
Phys. Rev. B
52
,
4926
4931
(
1995
).
10.
D. T.
Morelli
,
T.
Caillat
,
J.-P.
Fleurial
,
A.
Borshchevsky
,
J.
Vandersande
,
B.
Chen
, and
C.
Uher
, “
Low-temperature transport properties of p-type CoSb3
,”
Phys. Rev. B
51
,
9622
9628
(
1995
).
11.
T.
Caillat
,
A.
Borshchevsky
, and
J.-P.
Fleurial
, “
Properties of single crystalline semiconducting CoSb3
,”
J. Appl. Phys.
80
,
4442
(
1996
).
12.
S. R.
Sarath Kumar
,
D.
Cha
, and
H. N.
Alshareef
, “
Lattice dynamics and substrate-dependent transport properties of (In, Yb)-doped CoSb3 skutterudite thin films
,”
J. Appl. Phys.
110
,
083710
(
2011
).
13.
E. S.
Toberer
,
A.
Zevalkink
, and
G. J.
Snyder
, “
Phonon engineering through crystal chemistry
,”
J. Mater. Chem.
21
,
15843
(
2011
).
14.
G. A.
Slack
, in
Thermoelectrics Handbook: Macro to Nano
, edited by
D. M.
Rowe
(
CRC Press
,
1995
).
15.
C.
He
,
M.
Daniel
,
M.
Grossmann
,
O.
Ristow
,
D.
Brick
,
M.
Schubert
,
M.
Albrecht
, and
T.
Dekorsy
, “
Dynamics of coherent acoustic phonons in thin films of CoSb3
,”
Phys. Rev. B
89
,
174303
(
2014
).
16.
Y.
Li
,
C.
Ren
,
P.
Xiong
,
S.
von Molnár
,
Y.
Ohno
, and
H.
Ohno
, “
Modulation of noise in submicron GaAs/AlGaAs Hall devices by gating
,”
Phys. Rev. Lett.
93
,
246602
(
2004
).
17.
A. L. E.
Smalley
,
S.
Kim
, and
D. C.
Johnson
, “
Effects of composition and annealing on the electrical properties of CoSb3
,”
Chem. Mater.
15
,
3847
3851
(
2003
).
18.
M.
Daniel
,
C.
Brombacher
,
G.
Beddies
,
N.
Jöhrmann
,
M.
Hietschold
,
D.
Johnson
,
Z.
Aabdin
,
N.
Peranio
,
O.
Eibl
, and
M.
Albrecht
, “
Structural properties of thermoelectric CoSb3 skutterudite thin films prepared by molecular beam deposition
,”
J. Alloys Compd.
624
,
216
225
(
2015
).
19.
J. H.
Scofield
, “
AC method for measuring low-frequency resistance fluctuation spectra
,”
Rev. Sci. Instrum.
58
,
985
993
(
1987
).
20.
J.
Müller
, “
Fluctuation spectroscopy—A new approach for studying low-dimensional molecular metals
,”
ChemPhysChem
12
,
1222
1245
(
2011
).
21.
N. F.
Mott
, “
Conduction in non-crystalline materials
,”
Philos. Mag.
19
,
835
852
(
1969
).
22.
Y.
Kajikawa
, “
Conduction model covering non-degenerate through degenerate polycrystalline semiconductors with non-uniform grain-boundary potential heights based on an energy filtering model
,”
J. Appl. Phys.
112
,
123713
(
2012
).
23.
M.
Lonsky
,
S.
Heinz
,
J.
Müller
,
M.
Daniel
, and
M.
Albrecht
, “
1/f- and random telegraph noise of thermoelectric CoSb3 skutterudite thin films
,” in
2015 International Conference on Noise and Fluctuations (ICNF)
(
2015
).
24.
F.
Hooge
, “
1/f noise is no surface effect
,”
Phys. Lett. A
29
,
139
140
(
1969
).
25.
B.
Raquet
, “
Electronic noise in magnetic materials and devices
,” in
Spin Electronics
(
Springer
,
Berlin, Heidelberg, New York
,
2001
).
26.
S.
Kogan
,
Electronic Noise and Fluctuation in Solids
(
Cambridge University Press
,
New York
,
1996
).
27.
P.
Dutta
,
P.
Dimon
, and
P.
Horn
, “
Energy scales for noise processes in metals
,”
Phys. Rev. Lett.
43
,
646
649
(
1979
).
28.
B.
Shklovskii
, “
Theory of noise for hopping conduction
,”
Solid State Commun.
33
,
273
276
(
1980
).
29.
B.
Shklovskii
, “
1/f noise in variable range hopping conduction
,”
Phys. Rev. B
67
,
045201
(
2003
).
30.
J. G.
Massey
and
M.
Lee
, “
Low-frequency noise probe of interacting charge dynamics in variable-range hopping boron-doped silicon
,”
Phys. Rev. Lett.
79
,
3986
3989
(
1997
).
31.
A. L.
McWhorter
,
in Semiconductor Surface Physics
, edited by
R. H.
Kingston
(
University of Pennsylvania Press
,
1957
), p.
207
.
32.
J. R.
Kirtley
,
T. N.
Theis
,
P. M.
Mooney
, and
S. L.
Wright
, “
Noise spectroscopy of deep level (dx) centers in GaAs-AlxGa1xAs heterostructures
,”
J. Appl. Phys.
63
,
1541
(
1988
).
33.
J.
Müller
,
S.
von Molnár
,
Y.
Ohno
, and
H.
Ohno
, “
Decomposition of 1/f noise in AlxGa1x/GaAs Hall devices
,”
Phys. Rev. Lett
96
,
186601
(
2006
).
34.
J.
Müller
,
Y.
Li
,
S.
von Molnár
,
Y.
Ohno
, and
H.
Ohno
, “
Single-electron switching in AlxGa1xAs/GaAs Hall devices
,”
Phys. Rev. B
74
,
125310
(
2006
).
You do not currently have access to this content.