Synthesis of III-V nanocrystals (NCs) is proved to be much more difficult than II-VI nanocrystals by either colloidal or gas phase methods. Although arsenides and phosphides have been synthesized with relative success, production of good quality stibnides and nitrides still poses many challenges. The reported stibnide and nitride NCs in literature usually suffer from agglomeration, low purity and incorrect stoichiometry. Furthermore, the photoluminescence properties of these NCs haven’t been elaborated well and quantum yield measurements are scarce. In this work, we propose unique way of synthesizing pure and bare III-V semiconductor NCs in gas phase with a low temperature plasma (LTP). We focus on the synthesis of GaSb, GaN, GaSbN and InN NCs. The method diverges from the previously reported syntheses of semiconductor NCs, since use of vapor precursors is avoided. Instead, bulk pieces of the constituent metals are evaporated and by subsequent condensation, aerosols were formed. These aerosols of Ga, Sb, In and nitrogen were used as precursors. Produced aerosols were sent into a flow-through Ar LTP reactor. Downstream of the plasma, free-standing and crystalline III-V semiconductor NCs with a narrow size distribution were observed to be formed. Stoichiometry was found to be adjustable by manipulating the input aerosol concentrations and input plasma power. The produced powder was extensively analyzed with transmission electron microscopy, scanning electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. In the case of GaN, preliminary photoluminescence (PL) measurements showed a feint band-edge emission, but a bright emission peak centered at 450 nm was also observed. Extended PL measurements for other III-Vs will be presented, along with a detailed study of the effect of operation parameters and reactor design on the size, stoichiometry and PL properties of the produced NCs. The mechanism of the formation of the compound semiconductor NCs from the source aerosols in the LTP will also be discussed.

Synthesis of pure and bare III-V Nanocrystals from bulk metals in a low temperature plasma

2019 Spring National Meeting

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