Youngjun Kweon / Research
Research · Jul 2025 – Present

Oscar Vazquez Mena Lab

Integrating 2D materials, nanostructures, and advanced nanoarchitectures for next-generation electronic, optical, biological, and biomedical devices.

Lab website ↗GFET hormone biosensor project →GFET device physics →

The lab

Core expertise: 2D atomic materials, nanofabrication, semiconductor processing, photovoltaics, and biosensing.

Area Focus
2D materials Studying and integrating graphene, MoS₂, and h-BN for ultrathin, high-mobility, low-power devices.
Acoustic metamaterials Using semiconductor fabrication to build 3D acoustic metamaterials that operate above the MHz range.
Quantum dots Exploring the size-dependent optical properties of quantum dots for photodetectors, solar cells, and light-emitting devices.
3D nanostructuring Developing vertically ordered nanostructures for photodetectors, solar cells, and light-emitting devices.
Photovoltaics and optoelectronics Using graphene's tunable electronic properties for light harvesting, tunable junctions, and optoelectronic devices.
Nanobiosensing Building highly sensitive platforms from graphene and plasmonic metal nanoparticles to detect biomolecular interactions.

The overall goal is to combine nanomaterials with advanced fabrication to create devices with new electrical, optical, acoustic, and biological functions.

My work

  • Fabricated CdSe quantum-dot photonic structures to integrate with GFET devices as an additional sensing modality, correlating source–drain current with optical-intensity changes from quantum-dot photoluminescence quenching.
  • Fabricated back-gated GFET devices for an additional sensing mechanism.
  • Optimized graphene transfer (APS Cu etch), PMMA removal, and annealing to improve GFET response and repeatability.
  • Evaluated how graphene transfer, annealing, and QD deposition each affect downstream device performance.

Example data: CdSe photoluminescence

Photoluminescence of CdSe / graphene / biomolecule stacks.

Measurement regions

PL was measured at six locations per chip to compare emission across interfaces:

Region Stack
M1, M2 CdSe only, on Si
M3, M4 CdSe + graphene, on Si
M5, M6 CdSe + graphene, on Au
Figure 3. Chip layout (samples SL2, SL8, SL9) with PL measurement points.
Figure 3. Chip layout (samples SL2, SL8, SL9) with PL measurement points.

PL intensity by region

  • Emission peaks near 550 nm. The CdSe-only regions (M1, M2) are brightest, while the regions with graphene (M3–M6) are markedly lower.
  • This trend is consistent with graphene quenching CdSe photoluminescence.
Figure 4. PL intensity vs. wavelength for regions M1–M6 (sample SL2).
Figure 4. PL intensity vs. wavelength for regions M1–M6 (sample SL2).

The aptamer-based hormone biosensor I work on is written up in full on the Lal Lab page.