Examination of mechanical stability and gas sensor application of (As 2 S 3 ) 100-x (AgI) x...
1
Examination of mechanical stability and gas sensor application of (As 2 S 3 ) 100-x (AgI) x chalcogenide glasses K. Kolev 1 *, T. Petkova 1 , C. Popov 2 1 Institute of Electrochemistry and Energy Systems (IEES), Bulgarian Academy of Sciences 2 Institute of Nanostructure Technologies and Analytics (INA), University of Kassel, Germany INA inlet Analyte 1 M FC-3 M FC-2 M FC-1 Flow Cham ber sensor PC outlet M ass-flow controllers Analyte 2 valves carrier gas Electronics acquisition EXPERIMENTAL SET–UP SORPTION PROPERTIES CONCLUSIONS The surface and morphology analysis of the thin films shows that films are uniform, homogeneous, featureless and smooth both on surface and in depth The magnitude and the sign of the stress are functions of the film composition and structure as well as of the mechanical and thermomechanical properties. The bigger tensile stress of the samples with 5 % at. AgI can be related to initial incorporation of atoms with larger atomic radius into As 2 S 3 pyramidal structure. As AgI amount increases Ag atoms occupy the microvoids and thus the glass density enhances and the structure stabilizes. This densification and stabilization of the structure leads to weakening of the tensile stress and change in the sign of the mechanical stress to compressive in the samples with 25 and 30 % at. of AgI. Resonating cantilevers functionalized with amorphous (As 2 S 3 ) 90 (AgI) 10 film were exposed to vapors of different analytes, including water, VOC and ammonia, in order to study the sorption properties of the chalcogenide coating. The highest sensitivity was observed towards acetone, the analyte with one of the highest molecular weight and with the lowest dipole moment among the tested analytes. The sensor acted primarily as a microbalance distinguishing the vapors by the difference in their molecular weight with physisorption as main mechanism. The short response and recovery times together with the linear increase of the response MOTIVATION Development of new transduction principles in the sensoric technique Search for new sensitive materials New sensors with improved sensitivity, selectivity and reliability Different functionalization layers for diverse gases Electronic Sensor Cantilever sensors – a miniature version of a microbalance Fabrication process – complementary metal- oxide-semiconductor (CMOS) technology Integration of transducer, actuator and read- out in one unit Decrease of the resonance frequency with addition of mass, i.e. by sorption of gas molecules CANTILEVER–BASED CHEMICAL GAS SENSORS 2 2 2 1 2 1 1 4 K m K – spring constant of the cantilever 1 – resonance frequency before exposure 2 – resonance frequency after exposure ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support of the European Social Fund (Program “Development of human resources”) under contract BG051PO001/07/3.3- 02/58/17.06.2008). Stoney's equation: - film stress d - film thickness E Si - Young's modulus of the substrate - Poisson's ratio of the substrate D - thickness of the substrate R - curvature radius of the bending L, h - length and deflection of the cantilever beam d R D E Si 1 ) 1 ( 6 2 R L 2 h 2 2 h D D cant L d h cantilever, deflection determined by optical microscopy Focus on frame Focus on beam h h te nsile com pressive 7 m m 16m m 1 6 m m 4m m 4m m 2m m 8m m 5m m 6m m 4m m 3m m 8.5m m 4 . 6 m m 5 6 7 4 1 2 3 THEORETICAL BASIS of STRESS INVESTIGATION SURFACE and MORPHOLOGY STRESS MEASUREMENTS
-
Upload
blaise-houston -
Category
Documents
-
view
216 -
download
0
Transcript of Examination of mechanical stability and gas sensor application of (As 2 S 3 ) 100-x (AgI) x...
Examination of mechanical stability and gas sensor application of (As2S3)100-x(AgI)x chalcogenide glasses
K. Kolev1*, T. Petkova1, C. Popov2
1 Institute of Electrochemistry and Energy Systems (IEES), Bulgarian Academy of Sciences2 Institute of Nanostructure Technologies and Analytics (INA), University of Kassel, Germany
INA
inlet
Ana
lyte
1
MFC-3
MFC-2
MFC-1
Flow Chamber
sensor
PC
outlet
Mass-flow controllers
Ana
lyte
2
valv
es
carrier gas
Electronics acquisition
card
EXPERIMENTAL SET–UP
SORPTION PROPERTIES
CONCLUSIONS
The surface and morphology analysis of the thin films shows that films are uniform, homogeneous, featureless and smooth both on surface and in depth
The magnitude and the sign of the stress are functions of the film composition and structure as well as of the mechanical and thermomechanical properties.
The bigger tensile stress of the samples with 5 % at. AgI can be related to initial incorporation of atoms with larger atomic radius into As2S3 pyramidal structure.
As AgI amount increases Ag atoms occupy the microvoids and thus the glass density enhances and the structure stabilizes. This densification and stabilization of the structure leads to weakening of the tensile stress and change in the sign of the mechanical stress to compressive in the samples with 25 and 30 % at. of AgI.
Resonating cantilevers functionalized with amorphous (As2S3)90(AgI)10 film were exposed to vapors of different analytes, including water, VOC and ammonia, in order to study the sorption properties of the chalcogenide coating.
The highest sensitivity was observed towards acetone, the analyte with one of the highest molecular weight and with the lowest dipole moment among the tested analytes.
The sensor acted primarily as a microbalance distinguishing the vapors by the difference in their molecular weight with physisorption as main mechanism.
The short response and recovery times together with the linear increase of the response signals with the analyte concentration make the investigated As-S-Ag films a promising candidate for gas sensitive elements.
MOTIVATION Development of new transduction principles in the sensoric technique
Search for new sensitive materials
New sensors with improved sensitivity, selectivity and reliability
Different functionalization layers for diverse gases
Electronic Sensor
Cantilever sensors – a miniature version of a microbalance
Fabrication process – complementary metal-oxide-semiconductor (CMOS) technology
Integration of transducer, actuator and read-out in one unit
Decrease of the resonance frequency with addition of mass, i.e. by sorption of gas molecules
CANTILEVER–BASED
CHEMICAL GAS SENSORS
22
21
2
11
4 K
m
K – spring constant of the cantilever
1 – resonance frequency before exposure
2 – resonance frequency after exposure
ACKNOWLEDGMENTS
The authors gratefully acknowledge the financial support of the European Social Fund (Program “Development of human resources”) under
contract BG051PO001/07/3.3-02/58/17.06.2008).
Stoney's equation:
- film stressd - film thicknessESi - Young's modulus of the substrate - Poisson's ratio of the substrate
D - thickness of the substrateR - curvature radius of the bending
L, h - length and deflection of the cantilever beam
dR
DESi 1)1(6
2
RL2 h2
2 h
D
Dcant
L
dh
cantilever, deflection determinedby optical microscopy
Focus on frame Focus on beam
hh
tens ile com pressive
7mm
1 6 m m
16mm
4m m
4 m m2 m m
8 m m
5 m m
6 m m4 m m
3 m m
8 .5 m m
4.6mm
56
74
12
3
THEORETICAL BASIS of
STRESS INVESTIGATION
SURFACE and MORPHOLOGY
STRESS MEASUREMENTS
