Synthesis And Characterization Of InP Colloidal Quantum Dots

Recently, semiconductor quantum dots (QDs) are attracting more and more interest due to their many novel properties, such as quantum size effect and surface effect. But the preparation of high quality semiconductor QDs remains a major stumbling block for the investigation of QDs. Up to now, researchers have approached many ways to produce semiconductor QDs, in these ways the colloid route should be the best one. Most previous work has been restricted to II-VI colloidal QDs, while III-V QDs have not been extensively studied because of difficulties with their preparation.In this paper, the history, status and future of the preparation of III-V QDs are presented first. And we introduce three approaches on preparation semiconductor QDs and point out the advantages of colloid route after comparing these approaches.We analyze the mechanics of the QDs'growth in details. The formation of colloidal QDs can be divided into three general steps: nucleation, growth and passivation. For a monodisperse sample, the nucleation event must be well separated in time from the growth step. The initial prepared QDs maybe of wide size distribution, so it is necessary to narrow the size distribution using size selective precipitation.We use the dehalosilylation reaction of InCl3 and P(Si(CH3)3)3 in trioctylphosphine oxide (TOPO) to produce InP colloidal QDs. Toluene/methanol served as the solvent system are used to isolate InP colloidal QDs with narrower size distribution.X-ray diffraction (XRD) patterns indicate that as-synthesized InP QDs are highly crystallized, and their lattice structure are zinc blend, the same as bulk InP materials. Transmission electron microscopy (TEM) results show the InP QDs are spherical or roughly spherical; the particles are dispersed and separate entities showing little agglomeration and no fusing. We also measured the average diameter and the size distribution of the QDs using the TEM pictures. The best results are 25? and standard deviation is 20.4%. The UV-vis absorption spectra and photoluminescence spectra both exhibit blue shift as the QD size decreases which indicated marked quantum confinement effect.