Semiconductor Based Hydrogen Sensor and Detecting System Reporter: Dr. Kun-Wei Lin 1.

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

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


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


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


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)


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)


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

)


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,


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,


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 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


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


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:


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


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


])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

)


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

)


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

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.




93

HydrogenSensing

chipMSC-51

bluetooth

alarm

LCD display

Client

bluetooth

Server

98 project

94

98 project

95

99 project

96

99 project

97

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

Semiconductor Based Hydrogen Sensor and Detecting System Reporter: Dr. Kun-Wei Lin 1.

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Transcript of Semiconductor Based Hydrogen Sensor and Detecting System Reporter: Dr. Kun-Wei Lin 1.