viewing multiple unit cells in crystalmaker

#Viewing multiple unit cells in crystalmaker full

Approximately 75% examined nanowires were found to have planar defects, while the remaining 25% were planar defect-free-like.

#Viewing multiple unit cells in crystalmaker full

In our previous study, about one hundred as-synthesized boron carbide nanowires were subjected to TEM study, during which each nanowire was examined throughout the full tilting range allowed by the configuration of our microscope. However, due to the complicated rhombohedral crystal structure, detailed structural characterization especially on planar defects that could greatly affect the properties of boron carbide 1D nanostructures has not yet gained enough attention, and the structure–property relations have not been established. Field emission, photoluminescence, mechanical, and thermal conductivity properties of these 1D nanostructures were reported. Most reported boron carbide 1D nanostructures were synthesized by carbothermal reduction or chemical vapor deposition at approximately 1,100☌. īoron carbide 1D nanostructures have attracted increasing attention in the last few years because of their potential applications in nanocomposites and thermoelectric energy conversion. , ZnO, CdSe) whose crystal structures are either cubic or hexagonal. To date, most planar defect-related studies have been focused on 1D nanostructures made of silicon, silicon carbide, III-V (e.g. However, due to the sophistication of the TEM technique, sometimes, experimental artifacts could be erroneously interpreted or lead to controversy. So far, transmission electron microscopy (TEM) has been one major technique commonly used to characterize the structure of individual 1D nanostructures and reveal the nature of planar defects. Thus, it is crucial to know their nature such as existence, distribution, and orientation within each 1D nanostructure while establishing the structure–property relations. In addition to assisting the growth of nanostructures, these defects can affect the mechanical, electrical, thermal, and optical properties of 1D nanostructures. Planar defects, such as stacking faults and twins, naturally exist in some as-synthesized one-dimensional (1D) nanostructures. Understanding the true nature of planar defects is essential in tuning the properties of these nanostructures through manipulating their structures. Our study calls attention to researchers to be extremely careful when studying nanowires with potential planar defects by TEM. The approach greatly alleviates tedious TEM examination of the nanowire and helps to establish the reliable structure–property relations. To identify fault orientations (transverse faults or axial faults) of those nanowires whose planar defects are not revealed by TEM, a new approach is developed based on the geometrical analysis between the projected preferred growth direction of a nanowire and specific diffraction spots from diffraction patterns recorded along the axial or short diagonal directions out of the (001) plane (off-zone condition). However, in most cases, these three characteristic directions are not parallel to the viewing direction when boron carbide nanowires are randomly dispersed on TEM grids. Due to the unique rhombohedral structure of boron carbide, planar defects are only distinctive when the viewing direction is along the axial or short diagonal directions (,, or 1 ¯ 10) within the (001) plane (in-zone condition).

The simplified reason of this invisibility is that the viewing direction during TEM examination is not parallel to the (001)-type planar defects. , no presence of characteristic defect features like modulated contrast in high-resolution TEM images and streaks in diffraction patterns. Results show that these defects can easily be invisible, i.e. In this work, planar defects (twins or stacking faults) in boron carbide nanowires are extensively studied by transmission electron microscopy (TEM). The physical properties of nanostructures strongly depend on their structures, and planar defects in particular could significantly affect the behavior of the nanowires.