Fermi electron wave packet interference images on carbon nanotubes at room temperature

Abstract

We report on the structure and electronic properties of single wall carbon nanotubes tips with atomically spatial resolution. Scanning tunneling microscopy shows topographic images of closed tips with a variety of geometrical structure; these include round, conical, as well as tips with a messy shape. Standing wave pattern of the charge density is observed at the tube cap which is formed due to constructive interference between the electronic states and its reflection on the nanotube tips. Atomically resolved images show asymmetry in the charge density that decay out within 6 nm away from the cap. These distinctive tip states do not exist elsewhere on the tube and are related to the presence of topological defects at tube ends.

The electronic properties of suspended single wall carbon nanotubes

“…The reason is that the larger the bias window the more phase randomization occurs due to summing over more electron states that enter the bias window. In our previous STM study on supported tubes, we observe similar oscillation close to the nanotube ends [6], however there is a fundamental difference between this and oscillations on unsupported nanotubes. In the first type there is damping factor, which washes the interference pattern within 6 nm away from the nanotube edge while the second type we see no damping ''on the suspended portion''.…”

“…A band asymmetry around the zero bias and a shift and broadening in van Hove singularities were attributed to a signature of nanotube-substrate interaction [2]. Another signature of substrate-nanotube interactions is the short-range modulation of electron waves close to nanotube edges [6] and defects [7,8]. Although transport experiments on SWNT and theoretical calculations verify that the coherence length is of order of micron, STM experiments deduce a short coherence length of less than 3 nm.…”

Ring-shaped images as a result of nonuniform field emission from capped carbon nanotubes

“…There is a visible similarity between these diagrams and the STM measurements of Ref. 16. While the current explanation of such images relies entirely on the tight binding electronic model 16 and are viewed as a projection of the intimate atomic structure of the CNT, the similarity with the diagrams of Fig.…”

“…16. While the current explanation of such images relies entirely on the tight binding electronic model 16 and are viewed as a projection of the intimate atomic structure of the CNT, the similarity with the diagrams of Fig. 6 at least indicates that the contribution of the quasifree electrons to the net experimental results should not be ruled out.…”

Quantum size dependence of electron distribution on carbon nanotubes and its influence on field emission

“…͑13͒ has recently become available for direct experimental investigation through scanning tunneling microscopy ͑STM͒ techniques. 12 The main goal of the present study is to examine the electron axial density defined by Eq. ͑13͒ and the implications of the electron quantum confinement on the field emitted electron energy spectrum.…”