Organometallic synthesis of gallium-arsenide crystallites, exhibiting quantum confinement

Abstract

The optical spectra of semiconductor crystallites whose dimension is comparable to the bulk exciton diameter show quantum confinement effects.'"To date, experimental studies of nanometer-size crystallites have been restricted to 11-VI and I-VI1 semiconductors, while 111-V semiconductors, including one of the most important direct band gap semiconductors, GaAs, have not yet been studied in this form, because of the numerous difficulties encountered in their preparation.Compared to the I-VI1 and 11-VI semiconductors, the 111-Vs have a greater degree of covalent bonding, a less ionic lattice, and larger exciton diameters (the exciton diameter in GaAs is 190 8, compared to 60 8 for CdS).For this reason, quantum size effects on the optical spectra have been predicted to be more pronounced in the 111-V class of materials than in the TI-VIS,' and crystallites of GaAs are more likely to find application in optical devices than CdS cluster^.^$^In this paper we present the first documented preparation of relatively monodisperse, redissolvable, crystalline, nanometer-size particles of GaAs.'Oyl]The nanocrystals were prepared in polar organic solvents, using a reaction developed by Wells and co-~orkers.~~9'~GaCl, and As(SiMe3), react in hydrocarbons to give solid products, which on heating afford GaAs.I3 Our X-ray diffraction experiments on the black GaAs powder prepared in this manner show that the domain size is 100 8.We carried out the same (16)