Jahresbericht 2005 - IPHT Jena

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typically used thermoelectric materials BiSb and
Sb with materials of higher thermoelectric figures
of merit, which moreover have higher temperature
stabilities. For the prediction of sensor properties
by parametric thermal modeling the transport
coefficients of these materials have to be
characterized up to 300 °C. The according measurement
equipment shall be built in 2006.
The high-effective ternary BiSbTe was chosen
as thermoelectric p-material. It was sputtered
by dc technology under optimized conditions.
Thereby a power factor of P = α 2 σ = 1.9 10 –3 W/
(m K 2 ) (Seebeck coefficient α = 189 µV/K and
electrical conductivity σ = 53 540 (Ω m) –1 ) was
obtained at room temperature. In a first run sensors
of TS 80 type were manufactured for high
temperature applications with this technology
using CuNi as n-material. However, some problems
appeared in the wet-chemical patterning of
the BiSbTe films, which can most likely be attributed
to the specific sputtering conditions. The
averaged responsivity S = 51 V/W is enhanced
by a factor of 1.6 compared with BiSb/Sb and
the temperature coefficient of responsivity is
lowered by a factor of 2.7 in the room temperature
range. Sensors of this type were delivered
for testing and qualifying to the project partner
Micro-Hybrid Electronic.
Nanotechnologies for the functionalization
of ceramic materials (FANIMAT-nano)
(E. Kessler, U. Dillner)
FANIMAT-nano represents one so-called “growth
core” in the Program “Innovative Regional
Growth Cores” launched by the Federal Ministry
of Education and Research (BMBF). This is a
development support program aimed towards
regional cooperations with platform technology
and important features which make them unique
in their field of competence. The target region of
FANIMAT-nano is the region Jena-Hermsdorf in
the federal state Thuringia. Within the FANIMATnano
growth core, the Thermal Microsensors
group at IPHT Jena is involved in a project called
“Structurable ceramic thin films for high-temperature
stable infrared (HT-IR) sensors” which started
in September 2005. Our partners in this project
are the Hermsdorf Institute for Technical
Ceramics (HITK) and the Micro-Hybrid Electronics
GmbH (MHE), also located in Hermsdorf.
The development objectives of this project
include the creation and characterization of
structurable polyceramic or solgel thin film materials
which can be integrated in the stacks of
functional layers of thermoelectric infrared
microsensors as high-temperature resistant
absorber layers and isolation or passivation layers,
respectively. Furthermore, the development
of thermopile sensor chips with operating temperatures
up to 250 °C employing those ceramic
films is envisioned. Investigations of these chips
MIKROSYSTEME / MICROSYSTEMS
in vacuum-tight sensor housings are planned to
test the compatibility of the ceramic films with
high-temperature interconnection and packaging
techniques. Thus, the project combines the competence
of the three partners HITK (ceramic
nano-powders), IPHT (thermoelectric sensor
functional layers) and MHE (interconnection and
packaging techniques).
In 2005, first investigations concerning new
absorber layers were carried out. The absorption
coefficients of several high-temperature resistant
layers supplied by HITK and based on different
materials were measured at IPHT using a FTIRspectrometer.
Moreover, the morphology of the
layers was characterized by SEM (see Fig. 3.5).
For layers of a special soot, absorption coefficients
exceeding 90% were found in the wavelength
range between 8 and 14 µm.
Fig. 3.5: A SEM micrograph of a special hightemperature
resistant soot absorber layer.
Calorimetric space debris detector
(E. Kessler, V. Baier, U. Dillner, A. Ihring)
A detector array of 16 × 16 thermopile sensors
based on the TS100/Flow design was developed
as an integrated part of a breadboard model of a
new type of in-situ space debris and meteoroid
detector to determine the impact energy of
micron-sized particles by calorimetric measurements
(see Fig. 3C on the color page). The partners
of this project are the eta_max Space
GmbH, Braunschweig, the Physikalisch-Technische
Bundesanstalt, and the TU Braunschweig.
The thermopile array is completed with an appropriate
plate absorber array supported by small
spacing columns of 20 µm height made of SU-8
and thermally connected to the sensitive areas of
the thermopiles each to convert the kinetic energy
of the impacting particles into a temperature
increase. An estimate of an average thermal
effect gives temperature rises of 2…3 mK which
can be clearly detected by the thermopiles. Initial
tests using laser pulse heating were successfully
performed.