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

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

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

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.

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

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 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

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.

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 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

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

Photodiode Fabrication Process

Photodiode Fabrication Process

Photodiode Fabrication Process

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

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

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.

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.

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 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