Nonthermal plasma synthesis of semiconductor nanocrystals

Semiconductor nanocrystals have attracted considerable interest for a wide range of applications including light-emitting devices and displays, photovoltaic cells, nanoelectronic circuit elements, thermoelectric energy generation and luminescent markers in biomedicine. A particular advantage of semiconductor nanocrystals compared with bulk materials rests in their size-tunable optical, mechanical and thermal properties. While nanocrystals of ionically bonded semiconductors can conveniently be synthesized with liquid phase chemistry, covalently bonded semiconductors require higher synthesis temperatures. Over the past decade, nonthermal plasmas have emerged as capable synthetic approaches for the covalently bonded semiconductor nanocrystals. Among the main advantages of nanocrystal synthesis in plasmas is the unipolar electrical charging of nanocrystals that helps avoid or reduce particle agglomeration and the selective heating of nanoparticles immersed in low-pressure plasmas. This paper discusses the important fundamental mechanisms of nanocrystal formation in plasmas, reviews the range of synthesis approaches reported in the literature and discusses some of the potential applications of plasma-synthesized semiconductor nanocrystals.