semiconductor based hydrogen sensor and detecting system reporter: dr. kun-wei lin 1
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Semiconductor Based Hydrogen Sensor and Detecting System
Reporter: Dr. Kun-Wei Lin Reporter: Dr. Kun-Wei Lin
1
Outline
Part 1 IntroductionPart 1 Introduction
Part 2 ExperimentalPart 2 Experimental
Part 3 Gas Sensing Characteristics of the Different Structure –Part 3 Gas Sensing Characteristics of the Different Structure – Based SensorsBased Sensors
Part4 96Part4 96、、 9898、、 99 Projects 99 Projects some application some application
2
Part 1Part 1
Introduction
3
4
摘錄自網路
5
Hydrogen-Domestic Use
Hydrogen Storage
Hydrogen Refueling Station
Hydrogen Transportation
Hydrogen fueled aircraft
Hydrogen Fuel Cell
Hydrogen Applications
Applications of Hydrogen
Hydrogen Cylinder
Liquid hydrogen fueled aircraftHelios Prototype
http://www.mae.ufl.edu/NasaHydrogenResearch/index.php?src=h2webcourse6
IntroductionIntroduction
Application of hydrogen sensorApplication of hydrogen sensor* * Industrial fabrication processesIndustrial fabrication processes
* * Medical installationsMedical installations
* * Laboratories (especially for semiconductor fabrication)Laboratories (especially for semiconductor fabrication)
* * Hydrogen-fueled motor vehiclesHydrogen-fueled motor vehicles
Since 1976, Transistors and Schottky diodes based on Metal(Pd)-Oxide-Semiconductor(Si) MOS devices were used as hydrogen sensors.
—Lundstrom’s Group (Linkoping University, Sweden)
Ingemar Lundström
7
8
Types of Hydrogen Sensors
Gain=
Different type of gas sensors* MOS capacitors (capacitance change)
* MOS field effect transistors (threshold voltage shift)
* MOS Schottky barrier diodes (current change)
* MS Schottky barrier diodes (current change)
MetalInsulator
Semiconductor
Capacitor
Metal
Semiconductor
Schottky diode
Metal
Insulator
Semiconductor
Field-effecttransistor
S D
8
The advantages of our device compare with Si-based structure* Short response time* Obvious current variation * Operation at room temperature* widespread operating temperature
regime
9
Mechanism of Hydrogen-SensingMechanism of Hydrogen-Sensing
-+
Pd or Pt catalytic metal
Semiconductor
Surface
Pd
Interface
ΔHS
ΔHb
ΔHio
ΔHi
Oxide
H2(g)
Ha Ha
O2(g)
Oa OaOHa Ha
H2O (g)
-+
-+
Hb
H2(g) : molecular hydrogen
Ha : adsorbed hydrogen atoms on the Pd or Pt surface
Hb : hydrogen atoms in the Pd or Pt bulk
H i: hydrogen atoms at the Pd/oxide interface
10
Under atmospheric conditionsThe catalytic reaction kinetics scheme of hydrogen adsorption and desorption
Mechanism of Hydrogen-SensingMechanism of Hydrogen-Sensing
H2(g) 2Ha 2Hb 2Hi
In presence of oxygen, the addition reaction of hydrogen desorption
O2 + 2Ha 2(OHa)
OHa + Ha H2O
k1k2 k3
r1 r2 r3
where k1, k2, k3, and r1, r2 and r3 are adsorption and desorption rate constants.
11
1212
MechanismMechanism of Hydrogen-Sensingof Hydrogen-Sensing
Under steady-state conditions, b induced by hydrogen adsorption can be assumed as
ibb maxwhere b,max is the maximum change in barrier height and i is the hydrogen coverage at the interface.
2
2
1 O
H
i
i
P
PK
where K is a temperature-dependent rate constant; PH2 and
PO2 are H2 and O2 partial pressures, respectively. The reaction order 1 for temperatures above 75 and ℃ 0.5 for the lower temperatures
12
Mechanism of Hydrogen-SensingMechanism of Hydrogen-Sensing
The Langmuir form can be expressed in terms of B and Bmax as
maxmax
111
2
2
H
o
PK
P
From the relation of saturation current and barrier height, the Langmuir can also be deduced as
)ln(
1
)ln(
1
)ln(
1
0
max,0
0
max,0
0
02
2
I
IP
P
I
IK
I
I gH
o
gg
where I0g,max is the maximum saturation current at hydrogen-
contained ambient.
13
Mechanism of Hydrogen-SensingMechanism of Hydrogen-Sensing
According to the van’t Hoff equation
R
S
RT
HK
ln
where H is the change of enthalpy, S the change of entropy,
and R the gas constant.
The change of barrier height b can be rewritten as:
bH
Hb KP
KP
2/1
2/1
max,
2
21
14
Stainless Steel Chamber
Manometer Valve
Mass Flow Control
Heating Tape
Heater and Thermometer
Test Line
Sample
Exhaust
Valve
HeaterFlange
Semiconductor Parameter Analyzer
Air H2/Air Mixture
The schematic setup of the hydrogen measurement system
15
Measurement system implementationMeasurement system implementation
Agilent 4155C
半導體量測平台
感測氣瓶
1616
Measurement system implementation
1717
Part 2Part 2
Experimental
18
Fabrication of the Device
Thin films were grown by MOCVD on S.I. GaAs substrate.
Conventional photolithography and wet etching technique is used.
Thermal oxide was grown by furnace at 120oC for 60 minutes.
Metal pattern was made by the thermal evaporation method.
The dimension of device is 2.05x10-3 cm2.
Ohmic contact : AuGe Schottky contact : Pd
Ohmic Contact
Pd Schottky Contact
S.I. GaAs substrate
5000Å GaAs buffer layer
3000Å AlGaAs active layer(n=2x1017cm-3 )
Pd Schottky Contact
AuGe Ohmic Contact
50Å Thermal Oxide 300Å n+-GaAs
19
Why We Choose AlGaAs and Pd?
AlxGa1-xAs is lattice matched to GaAs, and the mole fraction of Al can be changed from 0 to 1.
The energy bandgap of AlGaAs is larger than GaAs and InP.
In compared with InGaP/GaAs and InP-based material system, the thermal oxide is more easily grown on AlGaAs/GaAs.
AlGaAs-based hydrogen sensor is suitable for higher operation temperature than InP-based system.
Pd metal shows excellent selectivity to hydrogen gas than other metals.
20
Hydrogen Sensing Mechanism
Steps of H2 sensing mechanism :
H2 molecules adsorb on Pd surface and then dissociate to atoms.
H atoms diffuse into the bulk of Pd metal.
H atoms adsorb on Pd/oxide interface and form thin dipole layer.
The barrier height is reduced by the formation of thin dipole layer.
Fermi-Level
Air Pd Metal Oxide AlGaAs
H 2 molecule
H 2 adsorb on Pd surface and
dissociate into atoms
- +- +- +
Dipole LayerH atoms
diffuse into Pd bulk
Ec
Ev
21
Current-Voltage Characteristics
The Pd/oxide/AlGaAs MOS device shows excellent performance from room temperature to 160oC
0.0 0.2 0.4 0.6 0.8 1.01E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
0.01
Forward Bias
Reverse bias
Air 15ppm (H
2/Air)
50ppm 100ppm 200ppm 500ppm 0.1% 0.5% 1%
Pd/oxide/AlGaAs MOS Schottky Diode at 95oC
Cur
rent
(A)
Applied Voltage (V)
0.0 0.2 0.4 0.6 0.8 1.01E-13
1E-12
1E-11
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
Air 15ppm 50ppm 100ppm 200ppm 500ppm 0.1% 0.5% 1%
Pd/oxide/AlGaAs at 30oC
Cur
rent
(A)
Applied Voltage (V)
22
Barrier Height at Room Temperature
In compared with InGaP-based device, the barrier height of AlGaAs-based device is larger.
InGaP 0.92eV in air 0.77eV in 1% H2/air
AlGaAs 1.05eV in air 0.84eV in 1% H2/air
0 2000 4000 6000 8000 100000.75
0.80
0.85
0.90
0.95
1.00
1.05
Barrier Height Compared with InGaP
Bar
rier H
eigh
t (eV
)
Hydrogen Concentration (ppm)
InGaP AlGaAs
23
Barrier Height Variation
100 1000 100000.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
Barrier Height Variation
Bar
rier H
eigh
t Var
iatio
n (e
V)
Hydrogen Concentration (ppm)
InGaP AlGaAs
• Barrier height variation at room temperature.
• The barrier height variation of the AlGaAs-based device is larger than the InGaP-based device from 15ppm to 1% of hydrogen gas concentration.
• Barrier height variation of InGaP & AlGaAs are 0.14 and 0.21 eV, respectively.
24
Saturation Sensitivity
Pd/oxide/AlGaAs MOS device shows very high saturation sensitivity, especially at room temperature.
Over 155 times of sensitivity can be observed in 1% H2/Air at room temperature.0 2000 4000 6000 8000 10000
0
20
40
60
80
100
120
140
160
180
Saturated Sensitivity at 0.35V Forward Bias
Sen
sitiv
ity (
S)
Hydrogen Concentration (ppm)
30oC
50oC
70oC
95oC
120oC
160oC
S = IH2 - Iair
Iair
25
Saturation Sensitivity at R.T.
The saturation sensitivity is decreased with increasing the applied voltage.
Generally, the saturated sensitivity is increased with increasing the hydrogen concentration.
The saturated sensitivity is almost unity when the applied voltage is over 0.8V.0 2000 4000 6000 8000 10000
-20
0
20
40
60
80
100
120
140
160
180
Saturated Sensitivity at Several Apply Voltage
Sen
sitiv
ity (S
)
Hydrogen Concentration (ppm)
0.3V 0.4V 0.5V 0.6V 0.7V 0.8V
26
Transient Response at 30oC
The applied voltage is 0.35V.
Even at room temperature, the studied device shows good transient response characteristics under extremely low hydrogen concentration of 15 ppm H2/Air.
The maximum current of the studied device varies from 1.5x10-8 to 7.7x10-7 A under the condition of Air and H2/Air, respectively.
0 1000 2000 3000 4000 5000 6000 7000 8000
0.0
1.0x10-7
2.0x10-7
3.0x10-7
4.0x10-7
5.0x10-7
6.0x10-7
7.0x10-7
8.0x10-7
Transient Response of Pd/Oxide/AlGaAs at 30oC
Cur
rent
(A)
Time(sec)
Conc.of H2/Air
15ppm 50ppm 100ppm 200ppm 500ppm 0.1% 0.5% 1%
0 1000 2000 3000 40008.0x10
-9
1.0x10-8
1.2x10-8
1.4x10-8
1.6x10-8
1.8x10-8
2.0x10-8
2.2x10-8
2.4x10-8
27
Transient Response at 95oC & 160oC
0 1000 2000 3000 4000
5.0x10-6
1.0x10-5
1.5x10-5
2.0x10-5
2.5x10-5
3.0x10-5
3.5x10-5
4.0x10-5Transient Response of Pd/Oxide/AlGaAs at 95oC
Cur
rent
(A)
Time(sec)
15ppm 50ppm 100ppm 200ppm 500ppm 1000ppm 5000ppm 10000ppm
0 1000 2000 3000 40001.0x10-4
1.5x10-4
2.0x10-4
2.5x10-4
3.0x10-4
3.5x10-4
4.0x10-4
4.5x10-4Transient Response of Pd/Oxide/AlGaAs at 160oC
Time(sec)
15ppm 50ppm 100ppm 200ppm 1000ppm 5000ppm 10000ppm
28
Response of 1% Hydrogen
τa : adsorption time constant,
τb : adsorption time constant are defined as the times reach e-1 of the final steady-state current values.
0 5000 10000 15000 20000 250001E-8
1E-7
1E-6
1E-5
1E-4
1E-3
Transient Response of 1% Hrdrogen Gas
Air purge in
H2/Air purge in
160oC
120oC
95oC
70oC
50oC
30oC
Cur
rent
(A)
Time (sec)
τa τb
30oC 66 50
50oC 26 18
70oC 11 10
95oC 10 8
120oC 8 6
160oC 2 1.5
29
Conclusion
At room temperature, the extremely hydrogen concentration of 15ppm can be easily detected.
The detected transient-state response characteristic of 15ppm H2/air at room temperature is first reported.
The reverse current exhibit a highly sensitivity linearity, the current change from 1x10-10A(air) to 1x10-8A(1%) at 95oC.
High sensitivity of 155 under 0.3V and 1% H2/air can be obtained at room temperature.
The studied device shows a promise for high sensitivity, low leakage current, wide temperature operation regime and fast response speed for hydrogen sensor application.
30
Comparative studies of hydrogen sensing performance of Pd/InGaP MOS and MS
Schottky diodes
31
The X-ray energy dispersive spectrometer (EDS 能量散射 ) analysis
32
Measured I-V characteristics of the studied Pd/InGaP MOS Schottky diode
Measured I-V characteristics of the studied Pd/InGaP MOS Schottky diode, at T=400K, under atmospheric condition with
different hydrogen concentrations.
The inset of this figure shows the corresponding forward I-V characteristics of studied device at different temperature of 300, 400, 500, 550, and 600K,
respectively.
33
Measured I-V characteristics of the studied Pd/InGaP MS Schottky diode (400K)
Measured I-V characteristics of the studied Pd/InGaP MS Schottky diode, at T=400K, under atmospheric condition with different hydrogen
concentrations.
The current variation of MOS structure is lager than that of MS Schottky diode. This is attributed to the reduction of the leakage current resulting from the improved interface properties under the presence of interficial
oxide layer.
34
Barrier height as a function of hydrogen concentration in air
35
as a function of
)ln(
1
)ln(
1
)ln(
1
0
max,0
0
max,0
0
02
2
I
IP
P
I
IK
I
I gH
o
gg
From slopes and intercepts, the equilibrium constant K values are obtained as 3.01, 1.38, and 0.7 for the Pd-MOS Schottky diode at 350,
400, and 450K, respectively.
The equilibrium constant K is decreased as the temperature is
increased.
0ln
10
I
I g 2/1
2
HP
36
The corresponding K values of the studied Pd-MS Schottky diode are 2.36, 2.11, and 1.85 at 350,
400, and 450K, respectively.
The equilibrium constant K is decreased as the temperature is increased.
The interface coverage i is
decreased with elevating the temperature at the same hydrogen partial pressure.
The water production rate is increased with increasing the
operating temperature.
0ln
10
I
I g as a function of 2/1
2
HP
37
lnK as a function of the reciprocal of temperature
According to the van’t Hoff equation
R
S
RT
HK
ln
where H is the initial heat of hydrogen adsorption, S the change of entropy, and R
the gas constant.
From slopes of this plot, the calculated H values for Pd/InGaP MOS and MS Schottky diodes are 355
and 65.9 meV/atom, respectively.
38
i/(1-i) as a function of
The change of barrier height b
can be rewritten as:
bH
H
KP
KP
2/1
2/1
max
2
21
The calculated max values are
163, 103, 88.6, and 82 meV for Pd-MOS Schottky diode at 300, 350,
400, and 450K, respectively.
2/1
2HP
39
Transient response curves
Transient response curves upon the introduction and removal of 97, 537, and 9090ppm H2/air gases of
the studied Pd/InGaP MOS
Schottky diode at 400K.
With increasing the hydrogen concentration from 97 to 9090ppm H2/air, the response time constant
of adsorption (a) for the studied
MOS Schottky diode is decreased from 35 to 5.4 sec.
40
Transient response curves
Transient response curves upon the introduction and removal of 97, 537, and 9090ppm H2/air gases of
the studied Pd/InGaP MS Schottky
diode at 400K.
With increasing the hydrogen concentration from 97 to 9090ppm H2/air, the response time constant of
adsorption (a) for the studied MS
Schottky diode is decreased from 64 to 7.8 sec.
41
Transient response curves
The transient response curves of the studied MOS Schottky diode at 350 and 400 K vary gradually increase.
This implies that the coverage sites at the Pd metal and oxide interface are not all occupied and the water production rate is lower
than adsorption rate.
At a higher temperature of 600K, the interface coverage sites are all occupied and the water production rate is larger than the adsorption rate.
42
Transient response curves
At low temperature of 350K, the unsaturated behaviors of
transient response are found.
At 400 and 500K, due to the absence of interface coverage site in MS Schottky diode, the adsorption and absorption on the Pd surface are depend on the temperature and the Pd
surface property.
43
The Pd/InGaP hydrogen sensors based on the MOS and MS Schottky diodes have been fabricated and studied. The studied devices exhibit significantly wide operating temperature regimes.
Even at 300K and low hydrogen concentration of 15ppm H2/air, the
remarkable hydrogen detection can be observed.
Under the presence of oxide layer in device structure, the hydrogen detection sensitivity is improved.
From the van’t Hoff equation, heats of hydrogen adsorption are 355 and 65.9 meV/atom for studied MOS and MS-type devices, respectively.
These values confirm that hydrogen atoms populated at the interface between Pd metal and oxide layer causes the improved hydrogen detection characteristics of MOS type structure.
Summary
44
Comparative studies of hydrogen sensing performance of Pd- and Pt- InGaP MOS Schottky diodes
45
Current-voltage (I-V) characteristics of Pd-InGaP MOS Schottky diode hydrogen sensor
The forward currents of the studied Pd-InGaP MOS Schottky diode are substantially increased with increasing the hydrogen
concentration and temperature.
The current variations of InGaP Schottky diode based on Pd metal are more sensitivite than those of Pt metal under low hydrogen concentration (< 937 ppm H2/air)
and low operating temperature (T<
400 K) regimes.
46
Current-voltage (I-V) characteristics of Pt-InGaP MOS Schottky diode hydrogen sensor
The forward currents of the studied Pt-InGaP MOS Schottky diode are substantially increased with increasing the hydrogen concentration and temperature.
At high operating temperature, the Pt/InGaP sensor has better detecting properties. Particularly, at 600K, the current variations of Pt/InGaP Schottky diode are significantly higher than those of
Pd/InGaP Schottky diode.
47
Current variation as a function of hydrogen concentration
Current variation as a function of hydrogen concentration for Pd-InGaP Pd-InGaP MOS Schottky diode hydrogen sensors at
different temperature.
Upon exposing to low hydrogen concentration ambient, however, the Pd-InGaP Schottky exhibits better hydrogen detecting
capability.
48
Current variation as a function of hydrogen concentration
Current variation as a function of hydrogen concentration for Pt-InGaP MOS Schottky diode hydrogen sensors at different temperature.
By comparing with the hydrogen sensing response from current variations, generally, the Pt/InGaP Schottky diode is more sensitive to hydrogen than the
Pd-InGaP Schottky diode.
49
Barrier height as a function of hydrogen concentration
Barrier height as a function of hydrogen concentration for Pd-InGaP MOS Schottky diode hydrogen sensor at
different temperature.
The barrier height variation is significant under low hydrogen concentration for Pd-InGaP MOS Schottky
diode.
50
Barrier height as a function of hydrogen concentration
Barrier height as a function of hydrogen concentration for Pd-InGaP MOS Schottky diode hydrogen sensor at different temperature.
Under the hydrogen-contained ambient, the Pt-InGaP Schottky diode exhibits a relatively large reduction of b magnitude
especially in high hydrogen
concentration regimes.
51
lnK as a function of the reciprocal of temperature
Under this operating temperature region, the hydrogen adsorption processes of both studied devices are exothermic. Hence, as the temperature is increased, the hydrogen responses are unfavorable. Above 450K, on the contrary, the slope of the studied Pd/InGaP Schottky diode is negative. It is known that the contact belongs to Schottky type if the interface reaction heat is positive. Yet, an Ohmic contact is found for negative interface
reaction heat.
52
Theoretical Modeling
ac HH 21
2
Under atmospheric conditions, the hydrogen adsorbed on Pd surface reacting with oxygen to form water can
be expressed as:
ac
a OHHO ][22 22 OHHOH c
aa 23
Based on the rate equations of hydrogen-oxygen reaction under
steady-state conditions, These rate equations describing the Pd surface with oxygen present are :
dt
d
N
Nccc
N
SF
dt
d i
s
iOHSOSSSOHO
S
HHS 32
21
0 2)441(2
22
OSSOHOS
OOO cN
SF
dt
d 2
20 )441(2
22
OHSOSOH cc
dt
d 32
53
Fogelberg and Petersson proposed a model:
Theoretical Modeling
Ni Number of sites per area at the interface
N* Number of sites per area at the Pd surface
S0H2 Sticking coefficient for hydrogen
S0O2 Sticking coefficient for oxygen
HS Heat of adsorption for hydrogen at the Pd surface
Hb Heat of adsorption for hydrogen in the Pd bulk
Hi0 Initial heat of adsorption for hydrogen at the Pd/oxide interface
The molecular flux towards the surface and given by
mkT
PF
2
where k is the Boltzman constant and T the temperature. P denotes the partial pressure of molecular hydrogen or molecular oxygen and m the
mass of molecular hydrogen or molecular oxygen. 54
Theoretical Modeling
The rate equation for hydrogen at the interface can be expressed as
)1()1( 5
*
4
*
Sii
iSi
i cN
Nc
N
N
dt
d
where N* is the concentration of sites in the transition state, i the coverage of
hydrogen at the interface.
Under steady-state condition
0dt
d
dt
d
dt
d OHOS
By substituting O and OH, then S can be solved by
0234 EDCBA SSSS
55
Theoretical Modeling
])1(1284)1(648[ 21
2
3
222121
3
222
0 22 cc
ccccc
c
cc
N
SFA
S
OO
]16)1[(64])1(164[ 2221
3
2021
3
222
0 2222 cccc
c
N
SFcc
c
cc
N
SFB
S
OO
S
HH
22
0
3
22020 22222
22 4)1()(168 cN
SF
c
c
N
SFc
N
SFC
S
HH
S
HH
S
OO
23
220 )1()(16 22 cc
c
N
SFD
S
HH
0E
i can be obtained by the isotherm
)]exp(1[
)exp(
kT
HHkT
HH
SiSS
SiS
i
56
Comparisons with Experiments
The experimental result shows good agreements with theoretical data especially at lower hydrogen
partial pressure regime. Under higher hydrogen partial pressures, the interface coverage i
saturates and deviates from the predict behaviors.
This indicates that the i is
decreased with elevating the temperature under the same hydrogen partial pressure. As the i
becomes high enough then the Hi
decreases to Hb which results in
the accumulation of hydrogen
atoms at the Pd bulk. 57
The hydrogen sensing performances of Pd- and Pt-InGaP MOS Schottky diodes have been systematically studied and compared under steady-state condition at different temperature.
The Pd-InGaP Schottky diode exhibits large current variation and change of barrier height under low hydrogen concentration ambient.
The Pt-InGaP Schottky diode shows better high-temperature performances and larger hydrogen detection regimes.
The initial heat of adsorption of Pd- and Pt-InGaP Schottky diodes are 355 and 364.8meV/atom, respectively.
Based on the Temkin isotherm model, the experimental results of hydrogen coverage i are consistent with theroretical data over three order
of magnitudes of hydrogen partial pressure.
Summary
58
59
A High Electron Mobility Transistor A High Electron Mobility Transistor (HEMT) hydrogen Sensor with a (HEMT) hydrogen Sensor with a
Pt-Oxide- AlPt-Oxide- Al0.240.24GaGa0.760.76As MOS StructureAs MOS Structure
59
05-05-21
HEMT Device Structure and ProcessHEMT Device Structure and Process
Drain
Source
Gate
Gate Pad
S.I. GaAs substrate
5000Å undoped GaAs buffer
150Å undoped In0.15Ga0.85As channel layer
45Å undoped Al0.24Ga0.76As spacer
δ(n+) = 4x1012 cm-2
200Å Al0.24Ga0.76As Schottky layer (n=3x1017 cm-3)
600Å GaAscap layer oxide layer
n+ = 2x1018 cm-3Pt
Au/Ge/Ni Au/Ge/Ni
60
0.0 0.5 1.0 1.5 2.0
0
1
2
3
4
5
6
7
VGS
=-0.6V
VGS
=-0.3V
VGS
=0V
VGS
=-0.3/step
T=30oCA
G=1.4x100m2
air 14ppm H
2/air
98ppm H2/air
980ppm H2/air
9970ppm H2/air
Dra
in C
urre
nt
I D (m
A)
Drain-Source Voltage VDS
(V)
Current-Voltage CharacteristicsCurrent-Voltage Characteristics
0.0 0.5 1.0 1.5 2.0
0
1
2
3
4
5
6
7
VGS
=-0.9V
VGS
=-0.6V
VGS
=-0.3V
VGS
=0V
VGS
=-0.3/stepA
G=1.4x100m2
T=160oC
Drain-Source Voltage VDS
(V)D
rain
Cur
rent
I D
(mA
)
air 14ppm H
2/air
98ppm H2/air
980ppm H2/air
9970ppm H2/air
22 thGS
G
GnDS VV
L
CWI
61
Drain Saturation Current Sensitivity SDrain Saturation Current Sensitivity SJJ
10 100 1000 10000
10-1
100
101
VGS
= 0V & VDS
= 1.2V
30oC
72oC
112oC
160oC
Hydrogen Concentration (ppm H2/air)
Dra
in S
atu
rati
on
Cu
rren
t S
ensi
tiv
ity
S J (A
/mm
-pp
m H 2/a
ir)
2H
air,DS2H,DSJ C
JJS
Hydrogen concentration ↑ → SJ ↓ → Current Variation Saturation
T ↑ → SJ ↓ → Low Hydrogen Concentration Limitation↑
62
-1.5 -1.0 -0.5 0.0 0.5 1.0
0
50
100
150
200
250
VDS
= 1.2V
T = 30oC
Dra
in S
atu
rati
on C
urr
ent
I D (
mA
/mm
)
Tra
nsc
ond
uct
ance
g m
(m
S/m
m)
Gate-Source Voltage VGS
(V)
air 14ppm H
2/air
98ppm H2/air
980ppm H2/air
9970ppm H2/air 0
50
100
150
200
250
ggm m & I& IDSDS V.S. V V.S. VGSGS
gm decay
63
10 100 1000 10000
0
30
60
90
120
Th
resh
old
Vo
lta
ge S
hif
t
Vth (
mV
)
Hydrogen Concentration (ppm H2/air)
30oC
72oC
112oC
160oC
10 100 1000 10000
10-5
10-4
10-3
VDS
=1.2V & VGS
=0V
D
ra
in S
atu
ra
tio
n C
urren
t V
aria
tio
n
ID
S (A
)
Hydrogen Concentration (ppm H2/air)
30oC
72oC
112oC
160oC
Vth & IDS V.S. CH2
Hydrogen concentration ↑ → ∆Vth ↑ Linear relation with ln(CH2) T ↑ → ∆Vth ↓
Leakage current
64
20 40 60 80 100 120 140 160
1011
1012
1013
Temperature (oC)
Inte
rface
Ad
sorb
ed S
ite
n i (cm
-2)
14ppm H2/air
98ppm H2/air
494ppm H2/air
980ppm H2/air
9970ppm H2/air
Hydrogen Adsorbed Sites
s
inpV
T ↑ → Interface adsorption sites ↓
~10%
~70%
~80%
65
0.5 1.0 1.5 2.0 2.5 3.0 3.5
20
40
60
80
100
120
Inverse Square Root of Hydrogen Partial Pressure
PH
2
-0.5 (Torr-0.5)
Inve
rse
Thre
shol
d V
olta
ge S
hift
1 / V
tn (
V-1)
30oC
52oC
72oC
Langmuir Adsorption Model Analysis
max,max,
25.0
5.0
111 2
2ththe
O
Hth VVK
P
PV
66
2.9 3.0 3.1 3.2 3.3
0.1
0.2
0.3
0.4
72oC
52oC 30oC
Slope = 0.50135 (K-1)Intercept = -1.24201
Loga
rith
mic
Val
ue o
fE
quili
briu
m C
onst
ant l
n K
e
Inverse Absolute Temperature 1000/T (1/K)
Van’t Hoff Equation Analysis
R
S
RT
HKln
00
e
Van’t Hoff equation
Ho (MOS) =-8.32KJ/mole
67
0 5 10 15 20 25 30 35
0.8
1.0
1.2
1.4
1.6
1.8
H2 off
H2 on
9970ppm H2/air
160oC112oC
72oC
30oC
Dra
in C
urr
en
t I
D (
mA
)
Response Time (1000 sec)
VDS
= 1.2VV
GS = -0.3V
Transient Response V.S. Temperature
Oxygen effect
T ↑ → a↓ Higher H2 dissociation rate
68
AlGaAs-Based τa (sec)
Pt MOS HEMT 135
Pt MOS Schottky 296
Pt MS Schottky 330
Transient Response ComparisonTransient Response Comparison
69
Gray system
For given data sequence is found by 1-AGO as
for ,where the , from(1),it is easy to recover as
}1for ,0)({ Kkkx
Kk 1
)1()(=)( ∑1=
)1( k
n
nxkx
)()1( kx
)1(=)1()1( xx
)()1( kx
)2()1(-)()( )1()1( kxkxkx
This operation is called 1-IAGO
70
Gray system
By and ,a gray difference equation is fourmed as
where
and
)(kx )()1( kx
)3(=)(+)( )1( bkazkx
)4()]1(+)([5.0=)( )1()1()1( kxkxkz
)5()(=][1
yBBBb
aTT
71
Gray system
where and
the can solve as
)()1( kx
)6())1(()( )1()1( a
be
a
bxkx ka
1)(
1)3(
1)2(
)0(
)0(
)0(
kz
z
z
B
)(
)3(
)2(
)0(
)0(
)0(
kx
x
x
y
72
Gray system
The estimate of , ,is then obtained by 1-IAGO as
The GM (1,1) model is simple, and sample less.However, the disadvantage is only
apply to less information .
)(kx )(ˆ kx
)7()1(-)()(ˆ )1()1( kxkxkx
73
GM(1,1) ModelGM(1,1) Model
求一階差分方程式之通解
原始序列X(0)(k),求出累加生成序列X(1)(k)
建立一階差分方程式
接著透過矩陣B與矩陣y求出發展係數a和b
進行一次反累加生成,求出建模後序列
The flow of GM(1,1) modeling
74
Gray system
0 2 4 6 8 10
0
5
10
15
20
25
30
35
40
Da
ta
Value
1-AGO Process Origin Data
The compare of origin data and 1-AGO process.
75
GPM ModelGPM Model
Since the measured hydrogen sensing data is a series of non-negative sequence, we assume that data.Then the preprocess by 1-AGO is used and the
hydrogen series data could be obtained as: (1)Substitute (1) into 2-degree polynomial equation,
one can obtain that (2)
}31 ,)({1
)1( kiDD
k
i
31,)( 2)1( kforcbkakkD
76
GPM Model
The coefficient of the 2-degree polynomial equation, i.e., a, b, and c, in (2) could be found from the matrix as: The coefficient of the 2-degree polynomial equation, i.e., a, b, and c, in (2) could be found from the matrix as:
1
)1(
)1(
)1(
139
124
111
)3(
)2(
)1(
D
D
D
c
b
a(3)(3)
Finally, the output developed grey hydrogen sensing model, based on first-order inverse accumulated generating operation (1-IAGO), could be presented as:
Finally, the output developed grey hydrogen sensing model, based on first-order inverse accumulated generating operation (1-IAGO), could be presented as:
(k) -1)+(k 1)+(k (1)^(1)^^
DDD (4)(4)
77
GPM Model
78
GPDM Model
79
80
Design of gas sensing micro-system
The proposed gas sensing micro-system.
81
Gas Sensor Device
Interface of sensor device(top view)
82
Sensing electrode(layer2)
Sensing area(layer1)
Heater(layer3)
Gas Sensor Device
Integrated gas sensor
83
Sensing area
Sensing electrode
Analysis circuit
Float structure
Sensing array
Heater
Si -sub
The SEM picture of the sensor arrays (before catalytic metal deposition)
84
Device Fabrication
The SEM picture of the sensor (after catalytic metal deposition)
85
Device Fabrication
Device Fabrication
Microphotograph of the sensor array
86
IC Microphotograph
Microphotograph of the sensor chip
87
Experimental Results and Discussion
The typical output current-voltage (I-V) characteristics of the studied device under air and 1% H2/air hydrogen gas at 25 .℃
88
-0.2 0.0 0.2 0.4 0.6 0.8-5.0x10-4
0.0
5.0x10-4
1.0x10-3
1.5x10-3
2.0x10-3
Sen
sing
out
put(
A)
Voltage(v)
H2(1%)
AIR
88
The measured hydrogen sensing response of 1% H2/air extract from sensor device.
89
Experimental Results and Discussion
感測訊號
輸出訊號
89
Detecting system
Input Transducer Signal Processing Output Transducer
SENSORS AMP MIX ADC DEMIX DRIVE ACTUATORSDAC
MICRO COMPUTER CONTROL
DIGITAL SIGNAL PROCESSING/ SECONDARY PARAMETER COMPENSATION/DATA HANDING
90
MSC-51 硬體部分 主要元件
• LCD• ADC0804
藍芽 (BC04)96、 98、 99 年度教育部產學計畫案
91
Circuit schematic
10uF
12MHZ
30P
30P
10K
+5V
EA/VP31
X119
X218
RESET9
P10 1P11 2P12 3P13 4P14 5P15 6P16 7P17 8
VCC40
VSS20
P00 39P01 38P02 37P03 36P04 35P05 34P06 33P07 32
WR16RD17INT013
MCS-51
D1
百位
D2
十位
D3
個位
D0
千位
A7B1C2D6
LT3BI/RBO4RBI5
a 13b 12c 11d 10e 9f 15g 14
74LS47
A2B3
E
1
Y0 4Y1 5Y2 6Y3 7
74LS139
Vin(-) 7DB0 (LSB)18DB117 Vin(+) 6
DB216DB315DB414
A-GND 8DB513DB612DB7 (MSB)11
Vref/2 9INTR
5
CLK-R 19CS1
RD2CLK-IN 4WR3 GND
10
VCC
20
ADC0804
220X7
Q1Q2
Q3Q4
10KX4
P1.4P1.5
P1.0P1.1P1.2P1.3
P0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7
+5V
+5V
2907X4
DOT
220
2K
10K
150pF
VR5K
+5V
+5V
解析度為0.02V
3.9V
VR10K
2.55V
10uF
12MHZ
30P
30P
10K
+5V
EA/VP31
X119
X218
RESET9
P10 1P11 2P12 3P13 4P14 5P15 6P16 7P17 8
VCC40
VSS20
P00 39P01 38P02 37P03 36P04 35P05 34P06 33P07 32
WR16RD17INT013
MCS-51
D1
百位
D2
十位
D3
個位
D0
千位
A7B1C2D6
LT3BI/RBO4RBI5
a 13b 12c 11d 10e 9f 15g 14
74LS47
A2B3
E
1
Y0 4Y1 5Y2 6Y3 7
74LS139
Vin(-) 7DB0 (LSB)18DB117 Vin(+) 6
DB216DB315DB414
A-GND 8DB513DB612DB7 (MSB)11
Vref/2 9INTR
5
CLK-R 19CS1
RD2CLK-IN 4WR3 GND
10
VCC
20
ADC0804
220X7
Q1Q2
Q3Q4
10KX4
P1.4P1.5
P1.0P1.1P1.2P1.3
P0.0P0.1P0.2P0.3P0.4P0.5P0.6P0.7
+5V
+5V
2907X4
DOT
220
2K
10K
150pF
VR5K
+5V
+5V
解析度為0.02V
3.9V
VR10K
2.55V
92
Portable Hydrogen Detector(96)
The portable hydrogen detector miniature. The LCD display shows the hydrogen concentration of 15ppm and the related voltage is 1.196V.
The portable hydrogen detector miniature. The LCD display shows the hydrogen concentration of 15ppm and the related voltage is 1.196V.
The portable hydrogen detector miniature. The LCD display shows the hydrogen concentration of 200ppm and the related voltage is 3.0V.
The portable hydrogen detector miniature. The LCD display shows the hydrogen concentration of 200ppm and the related voltage is 3.0V.
93
HydrogenSensing
chipMSC-51
bluetooth
alarm
LCD display
Client
bluetooth
Server
98 project
94
98 project
95
99 project
96
99 project
97
98
99
100
致謝特別感謝成功大學劉文超特聘教授的指導與鼓勵感謝劉文超教授、陳慧英教授帶領之研究團隊感謝國科會以及教育部經費補助感謝 CIC、NDL 以及 NCHC感謝一路上幫助坤緯的朋友、同事以及學生們
謝謝聆聽
101