SYNTHESIS AND CHARACTERIZATION OF BINARY AND TERNARY III-V QUANTUM DOTS

Quantum dots of InP, GaP, GaInP2, and GaAs with diameters ranging from 20-80 Angstrom can be synthesized as well-crystallized nanoparticles with bulk zinc blende structure. The synthesis is achieved by heating appropriate organometallic precursors with stabilizers in high boiling solvents for several days to produce QDs, which can then be dissolved in nonpolar organic solvents to form transparent colloidal QD dispers ions. The high sample quality of the InP and Gap QDs results in excito nic features in the absorption spectra; excitonic features could not b e observed for GaAs or GaInP2 QDs. The GaP and GaInP2 QD colloids exhi bit very intense (quantum yields of 15-25%) visible photoluminescence at room temperature. The photoluminescence for InP QDs preparations sh ow two emission bands: one band is in the visible at the band edge of the QD, and a second band appears above 800 nm. The near-IR PL is attr ibuted to deep traps, presumably phosphorus vacancies on the QD surfac e. This band can be removed after controlled addition of etchant; subs equently, very intense band-edge emission (quantum yield 30%), which i s tunable with particle size, is obtained. The QDs were characterized by TEM, SAXS, AFM, powder X-ray diffraction, steady-state optical abso rption and photoluminescence spectroscopy, ps to ns transient photolum inescence spectroscopy, and fs to ps pump-probe absorption (i.e., hole -burning) spectroscopy.