Lanthanum hexaboride nanoobelisks

A single-crystalline LaB₆ nanoobelisks with different pyramidal tip heights and diameters were synthesized by a metal-catalyzed chemical vapor decomposition (CVD) method. Preferential growth of nanoobelisks is obtained at the lower-temperature growth zone and at a frequency of greater than 95%. Nanoobelisks with much shorter pyramidal tops and uniform width along the length of the shaft are obtained at a higher-temperature growth zone away from the La precursor. Dark regions indicating high z material are found at the ends of most nanoobelisks and nanowires, while the presence of boron and lanthanum in the appropriate regions of there structures is observed. Growth of only flat-topped, uniform-diameter nanoobelisks farther downstream illustrates the importance of precursor flux change in the geometries of material tip growth.