Tubes, electron tunneling

Electron tubes Electron tunneling Electrooptic materials Electrooptics Electroosmosis... 

Summary. The interplay between electrical and mechanical properties of suspended, doubly clamped carbon nanotubes in the Coulomb blockade regime is studied theoretically. In this geometry, the capacitance between the nanotube and the gate depends on the distance between them. We find that the tube position changes in discrete steps every time an electron tunnels onto it. Edges of Coulomb diamonds acquire a (small) curvature. Eigenffequencies are modified by Coulomb blockade in a discrete fashion. 

The gate voltage dependence of the frequency is a stepwise function, as shown in the inset of Fig. 3. Steps occur whenever an additional electron tunnels onto the tube. For the E-nanotube, their height is MHz, which is measurable. Note, that the present submicron silicon devices are always in the weak-bending regime so that corrections due to the second term in Eq. (16) are too small to be measured. Furthermore, one should realize that frequency quantization is only observable if the frequency itself is greater than the inverse tunneling time for electrons. 

Fig. 3. Gate voltage dependence of the frequency ujq of the fundamental mode for three different values of the residual stress. Numbers are taken for the E-nanotube (see Fig. 2). The fundamental mode of an unstressed tube is 140 MHz (thin horizontal line). The inset is an enlargement of the To = 0 curve of the main figure showing step-wise increases of vn whenever an additional electron tunnels onto the tube.

Effects of nuclear dynamics on electron tunneling in redox proteins have been an important question for the biological electron transfer community. While it has been understood how nuclear dynamics controls the Pranck-Condon factor, little was known until now about how the dynamics affects the tunneling matrix element. Our results show that, when tunneling is dominated by a single pathway tube, dynamical effects are small and Pathways level calculations provide reasonable results. The situation changes when several pathway tub are important and destructive interference exists among them. In this case dynamic amplification becomes important,... 

A single-electron transistor (SET) has been prepared by Cees Dekker and coworkers (Science, 293, 76, (2001)) with a conducting nanotube. The SET is prepared by putting two bends in a tube with the tip of an AFM. Bending causes two buckles that, at a distance of 20 nm, serves as a conductance barrier. When an appropriate voltage is applied to the gate below the barrier, electrons tunnel one at a time across the barrier. 

The uniquely high mobility displayed by SWNT (146, 147) makes them attractive for applications in nanodevices, such as thin-film transistors (TFT), which could be produced by solution-processed random networks of SWNT. An optimum TFT would be composed entirely of semiconducting nanotubes, since their performance is limited by the presence of metallic tubes. It has been proposed that even below the percolation threshold of metallic tubes, electron hopping or tunneling may occur between neighboring metallic tubes (148). This electron channeling reduces the on/off ratio and therefore, the overall performance of the transistor. Removal of metallic nanotubes from the network has been achieved by electron breakdown (149, 150). 

In this equation, the connectedness criterion [A] embraces the nature of the inter-tube junctions, as it describes the efficiency of electron tunneling between adjacent tubes. The value of A is set by the electron tunneling distance [f], the value of which presumably is influenced by the temperature and by the electronic states of the CNTs, the contact potential barrier, and the electrostatic... 

Figure 6.1 Reducing the band-gap of the material within the inter-tube junction to increase the electron tunneling distance (left] and the desired final composite morphology (right].

Very little will be said here concerning the equipment aspects of plasma etching. There are three basic types of equipment which have been used a) barrel systems, b) planar systems, and c) systems in which the wafers are located downstream from the plasma to be referred to in this paper as downstream etching systems. These plasma etching configurations are shown schematically in Fig. 3.1. Often the barrel systems are used with a perforated metal tube called an etch tunnel which is shown in Fig. 3.1 a and b. The purpose of the etch tunnel is to protect the wafers from the energetic ion and electron bombardment to which waters immersed directly... 

The field ion microscope is perhaps the simplest of all atomic resolution microscopes as far as mechanical and electrical designs are concerned. The atomic resolution microscopes, at the present time, include also different types of electron microscopes,1 the scanning tunneling microscope (STM)2 and the atomic force microscope (AFM)2 Before we discuss the general design features of the field ion microscope it is perhaps worthwhile to describe the first field ion microscope,3 and a very simple FIM4 which can be constructed in almost any laboratory. The first field ion microscope, shown in Fig. 3.1, is essentially a field emission microscope5 except that it is now equipped with a palladium tube with... 

Since the nanotube is attached to the electrodes by tunneling contacts, it is in the Coulomb blockade regime. We define the energy to add the nth electron to the tube as Sn = Wn - Wn i. Then, if the nanotube contains n > 0 electrons, the conditions that current can not flow (is Coulomb blocked) are... 

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