I build graphene FET biosensors in the Nano3 cleanroom, from bare silicon to wire-bonded die.
I'm a third-year B.S. NanoEngineering student in the Department of Chemical and Nano Engineering at UC San Diego. My work sits where semiconductor processing meets sensing: I fabricate graphene field-effect transistors in the cleanroom and use them to detect hormones in sweat at picomolar levels.
I've run the full process flow myself, from SC-1 cleaning and maskless lithography through e-beam evaporation, PECVD, and reactive ion etching to wire bonding and probe-station testing. This site documents each step, the physics behind the device, and the study notes I keep on semiconductor fabrication.
I'm looking for internships in semiconductor process engineering, device fabrication, and biosensing.
Both started in November 2026 and build directly on my cleanroom work.
Two labs, one device platform. In the Lal Lab I use GFETs to detect hormones. In the Vazquez Mena Lab I add quantum dots to give them an optical sensing mode.
Prof. Ratnesh Lal Lab
Manuscript under review · GFET detection of estradiol and cortisolSide-gated GFET operation, the Dirac point, the electric double layer, and how aptamer binding turns into a measurable voltage shift.
The fabrication sequence I run in the UCSD Nano3 cleanroom. Each linked step has its own write-up with the recipe and the physics behind it.
| Step | Process | Tool / recipe | Purpose |
|---|---|---|---|
| 01 | Substrate clean | SC-1 · DIW:NH₄OH:H₂O₂ 5:1:1 | Remove organics and particles from (100) Si wafers. |
| 02 | Resist coat | AZ1529 · LOR5B/AZ1518 bilayer | Single layer for oxide etch; bilayer gives an undercut for lift-off that spares the graphene. |
| 03 | Lithography | Heidelberg MLA · 250–350 mJ/cm² | Maskless patterning, with dose tuned to resist thickness. |
| 04 | Metal contacts | Temescal e-beam · Cr 20 nm / Au 180 nm | Cr adhesion layer and Au contacts under high vacuum, then lift-off. |
| 05 | Passivation | Oxford PECVD · SiH₄/N₂O, 350 °C | Deposit SiO₂ to protect the leads. |
| 06 | Oxide etch | Trion ICP-RIE · CF₄/Ar, 9 mTorr | Fluorine radicals plus ion bombardment for an anisotropic profile that opens the channel and pads. |
| 07 | Graphene transfer | APS Cu etch · PMMA support | Move CVD graphene onto the device, then remove PMMA and anneal. |
| 08 | Package | Wire bonder · custom PCB | Bond working dies for electrical characterization and biosensing. |
| 09 | Inspect and test | Optical microscopy · probe station | Find defects and cross-check them against I–V results to trace failure modes. |
Order shown is a representative flow. Transfer and passivation order varies by device design. Cleanroom overview →
Photolithography, Plasma Etching, Thin-Film Processing, Semiconductor Physics, Nanochemistry.
Budgeting and funding proposals for KSEA events, and growing a 60+ member soccer club with an 80% return rate.
Leadership details →A series I write to teach myself the fundamentals behind the tools.