Charge effect in point projection images of carbon fibres

Abstract

Nanometre‐sized carbon fibres across holes have been observed in a lensless point projection field‐emission microscope operating between 100 and 300 eV. At sufficiently high magnification fringe patterns appear; with the help of simulations we show that they are strongly dependent on the charge density of the fibres. These patterns are characterized by an odd number of fringes with a central fringe that becomes very bright as the charge increases. Average diameter and linear charge density have been obtained with remarkable precision from analysis of fringes. Charge distribution from the middle to the edge of fibres has been investigated as well as narrowings at localized places on the fringe pattern. From these two examples, the limits of the models used for the simulations and those of the data acquisition system are discussed. Finally, this work emphasizes the fact that the fringe pattern masks the actual form of the fibre and that it is necessary to take account of the charge effect to interpret this diffraction pattern.

Electron Beam Coherency Determined from Interferograms of Carbon Nanotubes

“…At large tip-object distances, the patterns of the first group looked rather similar to the Fresnel fringes generated by a narrow strip, simulated by Prigent et al, 13 as shown in Figure 7(a). The tip approach changed the Fresnel-like fringe patterns into fringes of equal spacing, as shown in Figure 7(b), indicating that the MWCNT began to function as an electron biprism at small tip-object distances.…”

Vanadium Pentoxide Nanorods Anchored to and Wrapped with Graphene Nanosheets for High‐Power Asymmetric Supercapacitors

“…Figure 1) and leads to a constricted (or widened) projection image. In LEEPS images of carbon fibers and nickel nanowires, a positive object charging was found 19, 20…”

“…At high magnification the image is dominated by interference and must be treated as an in‐line hologram 16–18. LEEPS has been used for the imaging of nanoscale objects, such as single‐polymer fibers, DNA, carbon nanotubes, and metal NWs 6, 15, 19–21. Due to the low electron energy, the LEEPS image is very sensitive to electric fields surrounding the object.…”

Characterization of nanowires with the low energy electron point source (LEEPS) microscope

“…Since then, several groups explored its experimental and theoretical foundations. Experimental imaging has been performed with carbon fibers [7,8], carbon nanotubes [9][10][11][12], and thin metal wires [13]. Holographic imaging of single polymer fibers [14] and of unstained individual DNA molecules [15,16] was also reported.…”

“…In the case of electrostatic charging it was shown that the corresponding image distortions are correctable by an appropriate reconstruction scheme [11,24,25]. The alteration of LEEPS images by electrostatic charges might be used to map linear charge distributions along nanowires or nanotubes as shown by Dorozhkin and Dong [26].…”