Solid-Solution Nanoparticles:  Use of a Nonhydrolytic Sol−Gel Synthesis To Prepare HfO 2 and Hf x Zr 1- x O 2 Nanocrystals

作者：Jing Tang, Jason D. Fabbri, Richard D. Robinson, Yimei Zhu, Irving P. Herman, Michael L. Steigerwald, Louis E. Brus · 发表于：Chemistry of Materials · 年份：2004 · DOI：10.1021/cm049945w · 被引用次数：152 · 研究领域：Semiconductor materials and devices、Electronic and Structural Properties of Oxides、Ferroelectric and Negative Capacitance Devices

A nonhydrolytic sol−gel process closely following that of Hyeon et al. for the synthesis of ZrO 2 nanocrystals ( J. Am. Chem. Soc. 2003, 125, 6553−6557) was used to synthesize highly crystalline and monodisperse HfO 2 nanoparticles. Reactions of hafnium isopropoxide with hafnium halides at high temperature in a strongly coordinating solvent yield nanometer-sized particles of HfO 2 . The size, shape, and crystalline phase of the hafnia particles depend on both the reaction temperature and the halide. The nonhydrolytic cross-condensation method was also extended to the binary metal oxides nanocrystals, i.e., HfO 2 −ZrO 2, ZrO 2 −TiO 2, and HfO 2 −TiO 2 . Efforts to prepare nanocrystals of Hf x Zr 1 - x O 2 over a wide range of x were successful; however, this method could not be used to prepare either Zr x Ti 1 - x O 2 or Hf x Ti 1 - x O 2 . In conjunction with X-ray powder diffraction and high-resolution transmission electron microscopy, Raman spectroscopy identifies the structural phase of the nanocrystals and also proves the formation of the Hf−Zr solid solution nanoparticles via the cross-condensation method. In the case of Hf x Zr 1 - x O 2, for x < 0.5, highly monodisperse, roughly spherical particles of tetragonal Hf x Zr 1 - x O 2 were formed, while for x > 0.5, small nanorods of the monoclinic phase of the binary oxide were obtained.