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ESF provides the COST Office
through a European Commission contractCOST is supported
by the EU Framework Programme
European Network on New Sensing Technologies for Air Pollution Control
and Environmental Sustainability - EuNetAir
COST Action TD1105
Final Meeting at PRAGUE (CZ), 5-7 October 2016
New Sensing Technologies for Air Quality Monitoring
Action Start date: 01/07/2012 - Action End date: 15/05/2016 - EXTENSION: 15/11/2016
HIGH PERFORMANCE SiC-FET GAS SENSORS FOR
HIGHLY SENSITIVE DETECTION OF HAZARDOUS
INDOOR AIR POLLUTANTS
Donatella Puglisi
Participant
Linköping University / Sweden
donpu@ifm.liu.se
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Scientific context and objectives in the Action
• Background / Problem statement
Indoor air is 2x... 5x (even 100x) more polluted than outdoor air (EPA).
Adverse effects on health, environment, economy.
Inadequate ventilation
as a primary cause of
indoor air pollution.
Why Indoor Air Pollution is such an important issue?
• Brief reminder of MoU objectives:
• WG1: Development of gas-sensitive nanomaterials for detection of
specific air pollutants, and integration in gas sensor devices for indoor AQC
• WG2: Design, fabrication, testing, characterization of low-cost, high-
performance gas sensors using innovative SiC-FET sensor technology
3
Current research activities at Linköping University
• Current research topics / Problem statement:
• Highly sensitive, selective, low-cost gas sensors for indoor/outdoor AQC
applications (NOx, NH3, SO2, methane, VOCs,…), e.g.:
• Combustion control in car exhausts
• Monitoring ammonia slip in selective catalytic reduction (SCR)
systems of diesel trucks
• Sulfur dioxide monitoring in power plants
• Particle detectors
• Within SENSIndoor:
• Development of high performance SiC-FETs (LiU, SenSiC)
• Characterization of optimized sensing layers (LiU, U. Oulu, Picodeon)
• Smart operation and advanced data evaluation (USAAR)
• Field tests (ongoing)
4
SiC-FET – Transducer platform
Innovation SiC-FET: • Detection limits under threshold of legal requirements • Discrimination and quantification of specific VOCs • Stability during long-term operation
2 mm × 2 mm
Adapted from C. Bur,
Doctoral Thesis (2015)
Source of the
charge carriers
Metal contact, crucial to make a
MISFET gas sensitive
The current ID flows
from drain to source
Highly favorable for gas
sensing applications
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Fabrication of the sensing layer
Pulsed Laser Deposition (PLD)
WO3, (V2O5)
DC Magnetron Sputtering
Ir, Pt
Reproducibility of chemical composition
Control of crystal
structure, stochiometry
• Pure metal
(Ir, Pt)
• Pure metal oxide
(WO3, V2O5)
• Metal/Metal oxide
(Ir/WO3, Pt/WO3)
0 5 10 15 20 25 30 35 40 45 50 55 60
235
240
245
250
255
260
265
270
275
12.525
50100150
200
200150
10050
2512.5
Ir-gated SiC-FET @ 300 °C
Sensor
Sig
nal, I
D (
A)
Time (h)
Formaldehyde (ppb)
Sensor Signal
6
Current at a
constant voltage
Repeatability and
low ppb detection
Operating temperature
High sensor
response
10 30 40 600.00
0.05
0.10
0.15
0.20
0.25 Naphthalene
Formaldehyde
Benzene
Rela
tive
Re
spo
nse (
%)
Relative Humidity (%)
< 0.5
10 30 40 600
2
4
6
8
10
Dete
ctio
n L
imit (
pp
b)
Pt-gate SiC-FET
0 10 20 30 40 50 60
0
1
2
3
4
5
6
7
8
9
10
Det
ectio
n Li
mit
(ppb
)
Relative Humidity (%)
Formaldehyde
Benzene
Naphthalene
Ir-gate SiC-FET
330 °C
< 0.5
Pt-gate Ir-gate Detection limits under
threshold of legal
requirements
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Faster response time Higher relative response
Detection limits under
threshold of legal
requirements
Challenge addressed: extremely high sensitivity
dry air 10 20 30 40 60 20+EtOH
0
5
10
15
20
25
30
Rel
ativ
e R
espo
nse
(%)
Relative Humidity (%)
10 ppb
5 ppb
1 ppb
0.5 ppb
Ir-gate SiC-FET
Naphthalene
Morphology Surface potential
Height (nm) 60 nm ΔVpot (mV) 200 mV
10 µm
Insulator Gate Insulator Gate
ΔVpot (mV) 30 mV Height (nm) 30 nm
3 μm × 3 µm
Pt-gate Ir-gate
Degradation of sensing
layer
No degradation of sensing
layer
≈ 25 mV
Delamination
ΔVpot (mV) 30
mV
3 μm × 3 µm
Height (nm) 50
nm
≈ 10 mV Nanoparticle formation
J. Eriksson (2014)
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Challenge addressed: long-term operation
Ir-gate SiC-FET: extremely high sensitivity
and robustness!
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WO3: porous or thin film? PLD depositions at Univ. Oulu
• Porous as-deposited WO3 layers by
PLD at RT and (a) p(O2) = 0.2 mbar or
(b) 0.08 mbar (SEM images).
(a) (b)
(a) (b)
The gate contact is processed by sputter deposition of porous Ir on top of WO3 (Ir/WO3).
The gate contact is pure WO3.
• Dense WO3 thin films deposited in-situ by PLD at 450 °C and (a) p(O2) = 0.02 mbar or (b) 0.05 mbar (AFM images).
• Poor sensitivity and lack of selectivity due to
• Wide band gap, high resistivity, low reactivity of the MOX
• Short life time, lack of stability
• Addition of a noble metal to enhance sensitivity and selectivity
• Ir is among the most effective catalysts for sensing reducing
gases (e.g. HC)
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Temperature dependence
6 8 10 12 14 16359
360
361
362
363
364
Sensor
Sig
nal, I
D (
A)
Time (h)
Linear region
VDS
= 1.0 V
201
202
203
204
205
206
1010
50
100Saturation regionV
DS = 4.0 V
Ir/WO3 SiC-FET
300 °C
C6H
6 (ppb)
100
5010
0 1 2 3 4 50
100
200
300
400
500
600
700
400°C
350°C300°C
250°C
200°C
150°C
Dra
in C
urr
en
t (
A)
Drain-Source Voltage (V)
Ir/WO3-gated
SiC-FET Oper. point
Sat. reg.
Effect of the electrical
operating point
Electrical characterization
0 50 100 150 200 2500.0
0.5
1.0
1.5
2.0
2.5
225 °C
300 °C
S
enso
r R
esp
on
se
, I D
(
A)
Concentration of Benzene (ppb)
Ir/WO3 SiC-FET
Linear region
Onset of saturation
300 °C
225 °C
Gas tests
10 50 1000.0
0.5
1.0
1.5
2.0
2.5
Ir/WO3 SiC-FET
300 °C
Sensor
Respo
nse, I D
(
A)
Concentration of Benzene (ppb)
Linear region
Onset of saturation region
Saturation region
D. Puglisi et al., Mat. Sci. Forum 858 (2016) 997-1000.
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Sensitivity Ir vs Ir/WO3 SiC-FETs
10 1000
1
2
3
4
5
6
7
8
SiC-FET
300 °C
R
ela
tive R
esponse (
%)
Formaldehyde (ppb)
Ir
Ir/WO3
10 100
Benzene (ppb)
Ir
Ir/WO3
SiC-FET
300 °C
D. Puglisi et al., Conf. Proc. Indoor Air 2016.
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Discrimination of naphthalene independent of ethanol’s presence
M. Bastuck et al., Thin Solid Films (2016), in press.
Challenge addressed: Enhanced selectivity
to naphthalene with Ir/WO3
0 10 20 30 40 50 60 700
2
4
6
eth
anol (p
pm
)
0 10 20 30 40 50 60 70
time (h)
0
10
20
30
40
naphth
ale
ne (
ppb)
Gas exposure profile
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Field test setup Montessoriskolan Trilobiten, Linköping
Jun. – Sept. 2016
~80 cm
FET 3S electronics
FM-801
CH2O monitor
Mini-PC/
Computer stick
4G modem
NI-DAQ 6215
SenseAir CO2 Temp.
Hum.
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Screenshot of the field test running
VDS = 4V
ID
Temp. cycles
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Research Facilities available for current research
• Clean room, ISO 6 (magnetron sputtering, lithography, CVD, etc.)
• Sensor processing and characterization (gas mixing systems,
readout electronics, bonding machine, spot welding, scribers,
thermal evaporation, shadow masks, optical microscopes, AFM,
SEM, etc.)
• Hardware and software for data acquisition and data analysis
• Gas bottles: CH2O, C6H6, CO, NO, NO2, NH3, N2, O2, synthetic air
• Other facilities available at: Saarland University, SenSiC,
University of Oulu, Picodeon, 3S
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Suggested R&I Needs for future research
Research direction
• Field tests: evaluation and testing
• Networking / complementary cooperation
• Dissemination of results / press release within and outside Europe, web
R&I Needs
• Creation of a sustainable environment for the future generations and ourselves: healthy, comfortable, energy-efficient
• Development of low cost, user-friendly sensors/sensor systems for detection of specific hazardous VOCs (formaldehyde is hot topic) – today CO2, TVOC
Innovation SiC-FET
• Versatile technology – operation over a wide temperature range
• Extremely high sensitivity – detection limits under threshold of current legal requirements
• Enhanced selectivity through optimization of the sensing layer and dynamic operation (TCO) – discrimination and quantification (formaldehyde, benzene, naphthalene)
Benefits
• Our SiC-FET sensor will work as a switcher: for on demand ventilation, «below threshold» means ventilation not needed – low cost, energy-efficient, user-friendly
Acknowledgements
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Thank you for your attention! incl. STSM at USAAR (2013)