MSD1 Senior Design Project- Oxygen Gas SensorP09051

Samuel Shin

Jeremy Goodman

Sponsor: RIT uE & EE department

Project Guide: Professor Slack

AgendaProject descriptionHigh Level Customer Needs/ Eng

SpecsConcept Description & RationaleSystem ArchitectureHigh Risk AssessmentDetailed Assembly

◦ Emitter and Receiver Circuit◦ Photodiode Fabrication

Testing ResultsFuture Plans

Project DescriptionOxygen gas detection via fluorescence

quenching.Based on Tris-Ruthenium[II](dichloride) material

incorporated in an oxygen-permeable polymer◦ Responds to gaseous %Oxygen which changes

fluorescent intensity and lifetime◦ Higher O2 conc = decreased intensity and lifetime

Method has been researched and is widely used◦ Expensive◦ Equipment not readily available to everyday user

Plan is to design a complete cost & size- efficient sensor system for the measurement of % Oxygen

High Level Customer Needs / Eng SpecsProvide consistent measurement results

◦LED pulse width at 100ms◦Entering wavelength at 455nm

Cost and size-effective◦Commercially available LED source◦Standard electronic components for signal

conditioning◦Low-cost, high performance optical filters◦RIT SMFL designed/built photodetector◦Ru(dpp) polymer created in RIT Chem dept.

Concept Description/ RationaleIncorporate the

entire system inside a light-tight box

Inject fixed amounts of nitrogen and oxygen to exhibit an environment with fixed %Oxygen

System Architecture

Input Signal (100ms pulse width from function generator)

LED Pulsing Circuit (455nm)

Ru(dpp) Thin Film (fluorescent material) – emitting wavelength of 613nm

Optical & Signal Conditioning

Amplified Signal in Oscilloscope (I or V vs. Time)

High Risk AssessmentStill a proof of concept

◦ Design will have to be modified to match needs Unclear Parameters will exist

Where noise is coming from, etc

Materials◦ Creating Ru(dpp) polymer has to be done

with help from a faculty memberFunding

◦ Assembly of chamber, gas canisters needed.

◦ Difficult to obtain funds

Final Results- LED Emitter CircuitCircuit assembled

to exhibit a steady source of LED light, in a set fixed pulse.◦Used a power

PMOSFETCompleted

assembly using vectoboard and soldering components.

V 1

TD = 0

TF = 5 nP W = 1 mP E R = 1 0 m

V 1 = 5

TR = 5 n

V 2 = 1

M 1

M b re a k P

V 25 v d c

0

R 12 . 6

0

D 1D 1 N 4 1 4 9

0

V

I

V

Final Results- Receiver Circuit Circuit assembled to

receive the light source and transfer it into voltage output.

Used photovoltaic amplifier circuit configuration.

Completed assembly using vectoboard and soldering components.

Completed circuit demonstration in lab, and also with complete light-tight box.◦ Used commercial

photodiode for test.

Photodiode PlanningTwo Architectures – 4” n-type

silicon◦Lateral (Finger) Diode

Small Active Area Fast Response Time

◦Planar Diode Large Active Area Slow Response Time Tunable Junction Depth (Wavelength

Selectable)

Fabricated in the RIT SMFL

Photodiode Design

N-Type Wafer P+ Implant

N+ Implant

Finger Contacts

LATERAL PHOTODIODE

N-Type Wafer

P-Well Implant

Contact Ring

PLANAR PHOTODIODE

Photodiode Fabrication Process

Photodiode Fabrication Process

Photodiode Fabrication Process

Photodiode Results - Responsivity

Planar responsivity >2x greater than Lateral!

400 500 600 700 800 900 1000 11000

0.1

0.2

0.3

0.4

0.5

Wavelength (nm)

Pow

er (

A/W

)

PlanarLateral

PLANAR

LATERAL

>2xDifferenc

e

Wavelength

Resp

onsi

vit

y (

A/W

)

↑ Active AreaTuned Junction↑ Responsivity

GREATER SIGNAL!

BUT↑ DARK CURRENT!

Photodiode Results - Capacitance

Planar capacitance much higher than Lateral

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 00

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2x 10

4

Voltage (V)

Cap

acit

ance

per

un

it A

rea

(pF

/cm

2)

Planar

Lateral

PLANAR

LATERAL

↑ Surface Area↑ Capacitance↑ Response Time

SLOWER DIODE!

Photodiode ConclusionPlanar diode had increased

responsivity◦Higher Signal from Fluorescence

Signal◦Higher Dark Current

Lateral diode had low capacitance◦Fast Response TimePlanar likely candidate for Fluorescence

Spec.

Testing ResultsPlan was to assemble a tight flow

chamber with valves with oxygen and nitrogen flowing in.

Emitter and receiver circuit showed proper required behavior as outlined in specifications and customer needs.

Limited testing environment available, but still showed a change in intensity, as specified.

Strong / Weak Points of Design/ Room for future research & improvement

Strong points of final design◦Was able to exhibit a possible, more

affordable alternative.◦Introduced cost effective fabrication

method of photodiode. Weak points & places for

improvements ◦Actual testing of chamber

incomplete◦Abnormal behavior in emitter circuit◦Needed more people in respective

fields◦Needed more funding

Conclusion

Project descriptionHigh Level Customer Needs/ Eng SpecsConcept Description & RationaleSystem ArchitectureHigh Risk AssessmentDetailed Assembly

◦ Emitter and Receiver Circuit◦ Photodiode Fabrication

Testing ResultsStrengths & weakness of design, plans for

future research