Three-dimensional structure of twinned and zigzagged one-dimensional nanostructures using electron tomography

Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique 3-dimensional (3D) structures of twinned Zn₃P₂ (tetragonal) and InAs (zinc blende) nanowires synthesized by the vapor transport method. The Zn₃P₂ nanowires adopt a unique superlattice structure that consists of twinned octahedral slice segments having alternating orientations along the axial [111] direction of a pseudocubic unit cell. The apices of the octahedral slice segment are indexed as six equivalent 〈112〉 directions at the [111] zone axis. At each 30 degrees turn, the straight and zigzagged morphologies appear repeatedly at the 〈112〉 and 〈011〉 zone axes, respectively. The 3D structure of the twinned Zn₃P₂ nanowires is virtually the same as that of the twinned InAs nanowires. In addition, we analyzed the 3D structure of zigzagged CdO (rock salt) nanowires and found that they include hexahedral segments, whose six apices are matched to the 〈011〉 directions, linked along the [111] axial direction. We also analyzed the unique 3D structure of rutile TiO₂ (tetragonal) nanobelts; at each 90 degree turn, the straight morphology appears repeatedly, while the inbetween twisted form appears at the [011] zone axis. We suggest that the TiO₂ nanobelts consist of twinned octahedral slices whose six apices are indexed by the 〈011〉/〈001〉 directions with the axial [010] direction.