1. MSD1 Senior Design Project- Oxygen Gas Sensor
Samuel Shin
Jeremy Goodman
Sponsor: RIT uE & EE department
Project Guide: Professor Slack

2. Agenda Project description High Level Customer Needs/ Eng Specs
Concept Description & Rationale
System Architecture
High Risk Assessment
Detailed Assembly
Emitter and Receiver Circuit
Photodiode Fabrication
Testing Results
Future Plans

3. Project Description Oxygen 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

4. High Level Customer Needs / Eng Specs
Provide 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.

5. Concept Description/ Rationale
Incorporate the entire system inside a light-tight box
Inject fixed amounts of nitrogen and oxygen to exhibit an environment with fixed %Oxygen

6. 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)

7. High Risk Assessment Still a proof of concept Materials Funding
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 member
Funding
Assembly of chamber, gas canisters needed.
Difficult to obtain funds

8. Final Results- LED Emitter Circuit
Circuit assembled to exhibit a steady source of LED light, in a set fixed pulse.
Used a power PMOSFET
Completed assembly using vectoboard and soldering components.

9. 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.

10. Photodiode Planning Two 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

11. Photodiode Design PLANAR PHOTODIODE P-Well Implant Finger Contacts
N+ Implant
Contact Ring
N-Type Wafer
N-Type Wafer
P+ Implant
LATERAL PHOTODIODE

12. Photodiode Fabrication Process

13. Photodiode Fabrication Process

14. Photodiode Fabrication Process

15. Photodiode Results - Responsivity
Planar responsivity >2x greater than Lateral!
↑ Active Area
Tuned Junction
↑ Responsivity
GREATER SIGNAL!
BUT
↑ DARK CURRENT!
PLANAR
>2x
Difference
Responsivity (A/W)
LATERAL
Wavelength

16. Photodiode Results - Capacitance
Planar capacitance much higher than Lateral
↑ Surface Area
↑ Capacitance
↑ Response Time
SLOWER DIODE!
PLANAR
LATERAL

17. Photodiode Conclusion
Planar diode had increased responsivity
Higher Signal from Fluorescence Signal
Higher Dark Current
Lateral diode had low capacitance
Fast Response Time
Planar likely candidate for Fluorescence Spec.

18. Testing Results
Plan 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.

19. 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

20. Conclusion Project description High Level Customer Needs/ Eng Specs
Concept Description & Rationale
System Architecture
High Risk Assessment
Detailed Assembly
Emitter and Receiver Circuit
Photodiode Fabrication
Testing Results
Strengths & weakness of design, plans for future research