1. Characterizing InGaAs quantum dot chains Tyler Park John Colton Jeff Farrer Ken Clark Jeff Farrer Ken Clark David Meyer Scott Thalman Haeyeon Yang APS 4CS New Mexico Institute of Mining and Technology Socorro, NM October 26-27, 2012

2. Outline  Quantum dot (QD) overview  Quantum dot growth  Photoluminescence (PL) spectroscopy  Transmission electron microscopy  Results

3. Quantum Dots Overview  QD Overview  QD Growth  PL Spectroscopy  TEM  Results Charge carriers constrained in 3 dimensions Quantum well constrained in 1 dimension, quantum wires constrained in 2 Many uses: optoelectronics, detectors, lasers, quantum computing…

4. Quantum Dots Overview  QD Overview  QD Growth  PL Spectroscopy  TEM  Results (photon) h e-e- Excite electrons across bandgap Excite electrons across bandgap “Trap” electrons in well/QD until they relax “Trap” electrons in well/QD until they relax Released photons correspond to bandgap energy Released photons correspond to bandgap energy

5. Quantum Dots Overview  QD Overview  QD Growth  PL Spectroscopy  TEM  Results

6. Quantum Dots Overview  QD Overview  QD Growth  PL Spectroscopy  TEM  Results Dong Jun Kim and Haeyon Yang, Nanotechnology,(2008). Zh. M. Wang, et al., Journal of Applied Physics, (2006). 110

7. Quantum Dot Growth  QD Overview  QD Growth  PL Spectroscopy  TEM  Results InGaAs Modified Stranski-Krastanov technique QD layer grown at a cooler temperature Annealing process, during which QDs form Capping layer for electronic/optical uses

8. Photoluminescence Spectroscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results Detector Lenses Monochromator Lock-in Amplifier Laser Chopper Cryostat Sample

9. Photoluminescence Spectroscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results capped, annealed at 460  C capped, annealed at 460  C, 480  C, and 500  C

10. Transmission Electron Microscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results Preparation: Scanning electron microscope (SEM) / Focused Ion Beam (FIB) Mechanical thinning

11. Transmission Electron Microscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results Cross-sectional and plan view cuts Analytical transmission electron microscopy (chemical analysis) Partial electron energy-loss spectroscopy (PEELS) X-ray energy dispersive spectroscopy (XEDS)

12. Transmission Electron Microscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results

13. Transmission Electron Microscopy  QD Overview  QD Growth  PL Spectroscopy  TEM  Results

14. Results and Conclusion  QD Overview  QD Growth  PL Spectroscopy  TEM  Results 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