Characterizing Characterizing InGaAs quantum InGaAs quantum

dot chains dot chains Tyler ParkTyler Park John Colton John Colton Jeff FarrerJeff Farrer Ken Clark Ken Clark

David MeyerDavid Meyer Scott Scott ThalmanThalman

Haeyeon YangHaeyeon Yang

APS 4CS New Mexico Institute of Mining and Technology Socorro, NM October 26-27, 2012

OutlineOutline Quantum dot (QD) overviewQuantum dot (QD) overview

Quantum dot growthQuantum dot growth

Photoluminescence (PL) Photoluminescence (PL) spectroscopyspectroscopy

Transmission electron microscopyTransmission electron microscopy

ResultsResults

Quantum Dots OverviewQuantum Dots Overview QD QD

OverviewOverview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults • Charge carriers constrained in 3 dimensions• Quantum well constrained in 1 dimension, quantum wires constrained in 2

• Many uses: optoelectronics, detectors, lasers, quantum computing…

Quantum Dots OverviewQuantum Dots Overview QD OverviewQD Overview

QD GrowthQD Growth

PL SpectroscopyPL Spectroscopy

TEMTEM

ResultsResults(photon)

he-

• Excite electrons across bandgapExcite electrons across bandgap

• “ “Trap” electrons in well/QD until Trap” electrons in well/QD until they relaxthey relax

• Released photons correspond to Released photons correspond to bandgap energybandgap energy

Quantum Dots OverviewQuantum Dots Overview QD QD

OverviewOverview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

Dong Jun Kim and Haeyon Yang,Nanotechnology,(2008).

Zh. M. Wang, et al.,Journal of Applied Physics, (2006).

110

Quantum Dot GrowthQuantum Dot Growth QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

InGaAs

• Modified Stranski-Krastanov technique• QD layer grown at a cooler temperature• Annealing process, during which QDs form• Capping layer for electronic/optical uses

Photoluminescence Photoluminescence SpectroscopySpectroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResultsDetector

Lenses

Monochromator

Lock-in Amplifie

r

Laser Chopper

Cryostat

Sample

Photoluminescence Photoluminescence SpectroscopySpectroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

capped, annealed at 460C capped, annealed at460C, 480C, and 500C

Transmission Electron Transmission Electron MicroscopyMicroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

• Preparation:

Scanning electron microscope (SEM) / Focused Ion Beam (FIB)

Mechanical thinning

Transmission Electron Transmission Electron MicroscopyMicroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

• Cross-sectional and plan view cuts• Analytical transmission electron microscopy

(chemical analysis)• Partial electron energy-loss spectroscopy (PEELS)• X-ray energy dispersive spectroscopy

(XEDS)

Transmission Electron Transmission Electron MicroscopyMicroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

Transmission Electron Transmission Electron MicroscopyMicroscopy

QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

Results and ConclusionResults and Conclusion QD OverviewQD Overview

QD GrowthQD Growth

PL PL SpectroscopySpectroscopy

TEMTEM

ResultsResults

• Obtained optical and physical information about the quantum dot chains• Found the effect of the capping layer in the quantum dot samples• Investigating quantum dot chain samples with slightly different growth properties• Working with different methods to obtain plan view cuts

Special thanks to: Felipe Rivera, Thomas McConkie, and Richard Vanfleet