Near-Field Magneto-Photoluminescence of Singe Self-Organized Quantum Dots.
- PDF / 2,464,595 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 84 Downloads / 241 Views
Z6.8.1/N8.8.1/T6.8.1
Near-Field Magneto-Photoluminescence of Singe Self-Organized Quantum Dots. A. M. Mintairov, A. S. Vlasov and J. L.Merz. Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA ABSTRACT We present results obtained using low temperature near-field scanning optical microscopy for the measurements of Zeeman splitting and the diamagnetic shift of single self-organized InAs/AlAs, InAs/GaAs and InP/GaInP quantum dots. The measurements allow us to relate the bimodal size distribution of InAs dots with variations in In content. For single InP QDs we observed a strong circular polarization at zero magnetic field accompanied with a negative energy shift, suggesting that strong internal magnetic fields exist in these QDs. INTRODUCTION Near-field scanning optical microscopy (NSOM) allows one to extend the spatial resolution of optical experiments far beyond the light diffraction limit, which opens new possibilities for nanoscale characterization. Combining this with high magnetic fields allows the use of NSOM to study structural parameters and spin fine structure of exciton states.1,2,3,4 In the present paper we study the observed bimodal size distribution of InAs/GaAs and InAs/AlAs QDs by addressing the size and In content of individual dots using near-field magnetophotoluminescence (NMPL). We also report for the first time the NMPL measurements of single InP/GaInP QDs. EXPERIMENTAL DETAILS We used 50-300 nm diameter tapered fiber tips with an Al coating of 50-200 nm thickness and transmission 10-4-10-2 (see Fig.1). The taper of the single mode fibers were prepared using a pulling technique, which provides apertures 150-300 nm. To make smaller apertures (down to 50 nm) we etch the tips after pulling. -1
10 -2 5x10
Fig. 1. Transmission of the nearfield fiber probes (solid circles) at 631 nm. Straight lines show best results reported in literature. Insert shows transmission spectra of 150 and 70 nm diameter tips taken using 250W Halogen lamp as the source.
-2
-3
10 -4 5x10
Throughput
Throughput
10 -3 5x10
-4
10 -5 5x10
1E-3
70 nm
1E-4
150 nm 600 700 800 Wavelength (nm)
-5
10
30
40
50 60 70 8090100
200
300
Aperture, nm
An Oxford CryoSXP cryogenic positioning system was used for 3D scanning.
Z6.8.2/N8.8.2/T6.8.2
The near-field photoluminescence (NPL) spectra were taken in collection-illumination mode at 10 K under excitation of the 514.5 nm Ar-laser line. Spectra were measured using a CCD detector together with a 270 mm focal length monochromator. The excitation power was 150 µW, which provided power densities generally below the emission threshold of QD excited states (
Data Loading...
