A PRESENTATION OF … SIZE-SELECTED COMPOUND SEMICONDUCTOR QUANTUM DOTS BY NANOPARTICLE CONVERSION BRENT WACASER, KIMBERLY A DICK, ZEILA ZANOLLI, ANDERS GUSTAFSSON, KNUT DEPPERT AND LARS SAMUELSON Andrew Cardes 3/7/07

Claims of Innovation  Group at Lund University in Sweden.  Development of a novel technology:  Called nanoparticle conversion  Produce semiconductor QD  Dot size, surface density, position, & material system are all independently controlled  Spatial positioning realized

Strankski-Krastanow Growth Materials of QD & substrate Density Particle Size

Nanoparticle Conversion Overview Independent Particle Formation Aerosol Evaporation Particle Generator

Results & Analysis Figure 3. (a) AFM and (b) SEM image of QDs taken from a sample converted from In aerosol particles with an average diameter of 30 nm. The average QD height (measured by AFM) is 18±3 nm and the diameter (measured by SEM) is 31±3 nm. (c) SEM image of circular areas containing QDs produced from an EBL pattern and evaporation of 2 nm In followed by lift off. The pattern consisted of columns of circular areas separated by 2 μ m on each side. In each column the circular areas were the same size. The diameter of the circular areas was decreased from left to right by 10 nm. The part of the pattern in the image results from 180, 170, and 160 nm circular areas.

Results & Analysis Figure 4. TEM image of a InAsP QD converted from a nominally 30 nm In particle on a Si substrate. In this sample, it was not possible to determine if this image is taken of a ‘whole’ QD or if the QD has been partially milled away during the sample preparation. The image is taken along a [11¯2] pole of the Si substrate. The contrast of the lattice fringes of the QD is somewhat blurred by the amorphous carbon surrounding the QD, which comes from the TEM sample preparation. Figure 5. PL spectra taken from individual QDs converted from In nanoparticles at ∼ 5 K in a micro PL set-up. (a) Spectra from four different QDs converted from different sized In nanoparticles, with diameters labelled to the left side of the spectra. (b) PL of the 30 nm QD depicted in (a) at lower laser excitation powers (the relative power, P, is indicated to the left of the spectra). The highest excitation power density of the laser, 1000 P, was used for all the samples in (a). Note that there are at least two distinct peaks, 1.37 eV at lower and 1.41 eV at higher excitation power densities.

Conclusions  QD can be produced through a process that decouples dot size, density, and material limitations.  Dots with crystalline structure can be achieved with multiple materials.  Patterned arrays are possible.  Quantum confinement can be achieved.  Blinking is observed. Thank you!