Question

Nanowires are high aspect-ratio metal or semiconducting wires with diameters on the order of 1 to 100 nanometers and typical lengths of 1 to 100 microns. Nanowires likely will be used in the future to create high-density electronic circuits. Nanowires can he fabricated from ZnO. ZnO has the wurtzite structure. The wurtzite structure is a hexagonal lattice with four atoms per lattice point at Zn (0, 0, 0), Zn (2/3, 1/3, 1/2), O (0, 0, 3/8), and O (2/3, 1/3, 7/8). How many atoms are there in the conventional unit cell? If the atoms were located instead at Zn (0, 0, 0), Zn (1/3, 2/3, 1/2), O (0, 0, 3/8), and O (1/3, 2/3, 7/8), would the structure be different? Please explain. For ZnO, the unit cell parameters are a = 3.24 A and c = 5.19 A. A typical ZnO nanowire is 20 nm in diameter and 5 mu m long. Assume that the nanowires are cylindrical. Approximately how many atoms are there in a single ZnO nanowire? Sketch the ion arrangement on the (110) plane of ZnS (with the zinc blende structure) and compare this arrangement to that on the (110) plane of CaF_2 (with the flourite structure). Compare the planar packing fraction on the (110) planes for these two materials.

Answer 1