Initial Sticking Coefficient Attenuation of Gases in Carbon Monoxide - - PowerPoint PPT Presentation

Initial Sticking Coefficient Attenuation of Gases in Carbon Monoxide Sensing on Pt80Au14Ti6

• Dr. rer. nat. Roniyus Marjunus, S.Si., M.Si.

2nd International Conference on Applied Sciences, Mathematics and Informatics Bandar Lampung, 8th August 2018

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Carbon Monoxide Gas naturally in atmosphere (< 0.001%) & produced by human activities e.g. in fire accident

• 1. Motivation

toxic, colorless, odorless Tolerated Concentration: 30 ppm Solid State Sensor need sensor Resistance Based Sensor Work Function Based Sensor

• freedom of sensing material
• detect chemisorbed/weakly

bound physisorbed at room/high temperatures.

• heating is not obligatory
• low power consumption

X X X X √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √

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• 2. Introduction

Loss Signal Problem and its Solution The sensitive layer loses its signal after 24 hours in air and can be refreshed by annealing at 170oC for 10 minutes in air. Attenuation of Initial Sticking Coefficient It is suspected causing the loss signal problem. Pt80Au14Ti6 It was already investigated as CO sensitive layer in normal atmosphere as a work function change based sensor at room temperature. The Aim of This Research Finding the attenuation factor of initial sticking coefficient of gases.

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• 3. Basic Theories

Work Function

E EF Evac Clean Surface E EF Evac Reducing gas e E EF Evac Oxidizing gas e

vac F

E E − = Φ

• ld

F new F

E E − = ∆Φ

(Korotchenkov, 2011) where: Φ : work function (eV) Evac : vacuum energy level (eV) EF : Fermi energy level (eV) ∆Φ : work function change (eV)

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Kelvin Probe

• 3. Basic Theories, cont.

sensitive layer Vibrating reference electrode I CPD

(Korotchenkov, 2011)

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Floating Gate Field Effect Transistor (FG-FET)

Hybrid Mounted Top Electrode Air Gap p-channel MOSFET in the transistor-well (n) Floating Gate Sensitive Film

• 3. Basic Theories, cont.

Capacitance-well (n) Substrate (p-Si)

Bottom Electrode Oxide Passivation Guard Ring

(Korotchenkov, 2011)

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Pt80Au14Ti6

• 3. Basic Theories, cont.

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• 3. Basic Theories, cont.

Adsorption, Reaction, Dissociation and Desorption

Surface Coverage Change Rate of:

• 1. Adsorption Process
• 2. AB as product of A and B
• 3. A as dissociation of AB

( )

     − − = kT E mkT P S dt d

a 2

exp 2 1 π σ Θ Θ

B A r r AB

exp Θ Θ υ Θ      − = kT E dt d

AB diss diss A

exp Θ υ Θ      − = kT E dt d Θ υ Θ      − = kT E dt d

d d exp

• 4. Desorption Process

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• 3. Basic Theories, cont.

Reaction Mechanism Model

• Adapting from Water Gas Shift Reaction (WGSR)
• State of the art: 18 reactions were filtered from 60 of WGSRs by Callaghan.
• This research: Callaghan’s reactions + 2 of WGSRs + 1 new reaction = 21 reactions.
• Every reaction: forward and reverse reactions.
• One way reaction: reaction energy parameter and Arrhenius coefficient.
• Every material: 42 energy parameters and Arrhenius coefficient.

Example: 9 coupled differential equations.

( )

mkT P F

n x x

π σ Θ 2 1− =

       − = kT E r

N r,

• r

f N r,

• r

f N r,

• r

f

exp υ

CPD

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Attenuation Factor (fadj1) of Initial Sticking Coefficient

Reports: Oxygen can diffuse in Pt fadj1=1-0.00585exp(5.76664Osub) Loss Signal Problem Pt(100)(1x1) hex-Pt(100) O atom Pt atom (1) (2) (3)

• 4. Results and Discussions

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• 4. Results and Discussions, cont.

Simulation with/without Attenuation Factor (fadj1)

t (hours)

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Conclusion

1.The Reaction Mechanism Model is in agreement with the experiment results. 2.Initial Sticking Coefficient should be adjusted with the attenuation factor. 3.Attenuation factor of the Initial Sticking Coefficient is fadj1=1- 0.00585exp(5.76664Osub).

Acknowledgement

Thank to: 1.Ministerium of Research, Technology and Higher Education, Republic of Indonesia. 2.Universität der Bundeswehr München, Jerman.

• 6. Conclusion & Acknowledgement

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Thank You for Your Attention Vielen Dank für Ihre Aufmerksamkeit