Development of a new single-step process for the production of SnO_1tn2 based gas sensors [Elektronische Ressource] = Entwicklung eines neuartigen einstufigen Herstellungsprozesses für Gassensoren auf SnO_1tn2-Basis / vorgelegt von Thorsten Sahm

Tsahm

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2007
• Nombre de lectures: 20
• Langue: Deutsch
• Poids de l'ouvrage: 13 Mo

Extrait

Development of a new
single-step process for the production
of SnO based gas sensors 2

Entwicklung eines neuartigen
einstufigen Herstellungsprozesses
für Gassensoren auf SnO Basis 2


D I S S E R T A T I O N


der Fakultät für Chemie und Pharmazie
der Eberhard-Karls-Universität Tübingen

zur Erlangung des Grades eines Doktors
der Naturwissenschaften

2007

vorgelegt von

Thorsten Sahm




























Tag der mündlichen Prüfung: 12.07.2007
Dekan: Prof. Dr. Lars Wesemann
1. Berichterstatter: PD Dr. Udo Weimar
2. Berichterstatter: Prof. Dr. Günter Gauglitz










Thefirst90%oftheworkneed90%ofthetime.
Theresttakestheother90%.
Yogi Berra





Table of contents

1. Introduction................................................................................................... 1
1.1 Motivation....................................................................................................2
1.2 Scope of the work ........................................................................................5
2. MOX sensors: an overview ...........................................................................3
2.1 Sensing materials....................................................................................... 12
2.1.1SnO ............................................................................................................................132
2.2 SnO – gas interaction............................................................................... 152
2.2.1Oxygen........................................................................................................................18
2.2.2Water...........................................................................................................................20
2.2.3Methane ......................................................................................................................21
2.2.4Carbonmonoxide......................................................................................................21
2.2.5Ethanol .......................................................................................................................22
2.3 Effect of doping......................................................................................... 23
2.4 Synthesis of metal oxides.......................................................................... 24
2.5 Deposition methods.................................................................................. 26
2.5.1Vapourdeposition.....................................................................................................27
2.5.2Sol$gelbasedmethods ..............................................................................................28
2.5.3Classicalmethodsforthickfilms ............................................................................29
2.6 The role of filters ....................................................................................... 30
2.7 The FSP approach..................................................................................... 31
3. Experimental............................................................................................... 35
3.1 Sensor fabrication ...................................................................................... 36
3.1.1Flamespraypyrolysis(FSP).....................................................................................37
3.1.2Screenprinting...........................................................................................................43
3.1.3Spincoating................................................................................................................45
3.2 Sensor characterisation ............................................................................. 46
3.2.1Scanningelectronmicroscopy(SEM) ....................................................................47
3.3 Sensor performance................................................................................... 47
3.3.1Dcelectricalmeasurements .....................................................................................47
3.3.2Catalyticconversionmeasurements........................................................................49
3.3.3Stabilitytests...............................................................................................................50
3.3.4Simultaneousworkfunctionandresistancemeasurements ................................50
4. Material characterisation ............................................................................ 57
4.1 Powder characterisation............................................................................ 58
4.1.1UndopedSnO ..........................................................................................................582

4.1.2Pt$dopedSnO ...........................................................................................................622
4.2 Directly deposited layer characterisation ................................................. 65
4.2.1Differentlayerthicknesses .......................................................................................65
4.2.2Multilayerdeposition ...............................................................................................68
4.3 Summary.................................................................................................... 72
5. Results & discussion................................................................................... 73
5.1 Feasibility study of FSP material .............................................................. 74
5.1.1Propanal......................................................................................................................74
5.1.2CO...............................................................................................................................76
5.1.3NO .............................................................................................................................782
5.1.4Summary.....................................................................................................................78
5.2 Simultaneous work function and resistance measurements.................... 79
5.2.1COandhumidity.......................................................................................................80
5.2.2Oxygen........................................................................................................................85
5.2.3Summary.....................................................................................................................89
5.3 Influence of deposition method................................................................ 90
5.3.1Temperaturedependency.........................................................................................90
5.3.2Concentrationdependency ......................................................................................92
5.3.3Summary.....................................................................................................................94
5.4 Effect of platinum doping......................................................................... 95
5.4.1LowCOconcentrationrange..................................................................................96
5.4.2HighCOconcentrationrange .................................................................................97
5.4.3Catalyticconversionmeasurements........................................................................98
5.4.4Stabilitytests.............................................................................................................101
5.4.5Summary...................................................................................................................104
5.5 Grain size effect........................................................................................105
5.5.1InfluenceonCOsensing........................................................................................105
5.5.2Summary...................................................................................................................106
5.6 Layer thickness dependency....................................................................107
5.6.1Reproducibility.........................................................................................................107
5.6.2UndopedSnO ........................................................................................................1082
5.6.3Pt$dopedSnO .........................................................................................................1112
5.6.4Summary...................................................................................................................112
5.7 Multilayer sensors ....................................................................................112
5.7.1Dcelectricalcharacterisation .................................................................................113
5.7.2Catalyticconversionmeasurements......................................................................115
5.7.3Filtereffectonsel