Single electron tunneling devices

Finally, metal nanopartides are under investigation as elements in future electronic nanodevices they can be used as nanowires, nanoislands and as electron confinements in single electron tunneling devices [33-35]. Therefore, the fabrication of nanopartides with very well-defined sizes and surface properties is particularly important. Molecular films at particle surfaces are essential for specific interactions between nanopartides and macromolecules, between nanopartides and substrates and for the positioning of nanopartides inside nanodectrode arrangements. Nanopartides are also of interest for nano-optoelectronic appUcations due to their spedfic optical properties. For this purpose, the synthesis of nanopartides with very small distributions in chemical composition, size and shape in microreactors is under investigation. 

Among these one of the most promising concepts is the development of single electron (SE) devices, which retain their scalability down to the molecular level. At present, due to exploitation of charging (Coulomb) effects in metallic SE devices comprising tunnel junctions with submicrometer size, individual charge carriers can be handled... 

The greatest potential appHcation for single-electron devices Hes in digital circuits. However, a number of other appHcations exist, including current standards and ultrasensitive electrometers (70,71). SETs are not unique to compound semiconductors, and in fact a great deal of work has been carried out in other material systems, including Al—AlO —A1 tunnel junctions. A review of single-electron phenomena is available (72). 

Figure 1. The tunneling of a single electron (SE) between two metal electrodes through an intermediate island (quantum dot) can be blocked of the electrostatic energy of a single excess electron trapped on the central island. In case of non-symmetric tunneling barriers (e.g. tunneling junction on the left, and ideal (infinite-resistance) capacitor on the right), this device model describes a SE box .

The invariance of IETS in an M-A-M junction vs an M-I-A-M device is exceptionally well demonstrated by the work of Reed [30], Figure 7 shows the Au-alkanedithiol-Au structure he used to create a single barrier tunnel diode. The IET spectra obtained from this device were stable and repeatable upon successive bias sweeps. The spectrum at 4.2 K is characterized by three pronounced peaks in the 0-200 mV region at 33,133, and 158 mV. From comparison with previously reported IR, Raman, and high-resolution electron energy-loss (HREEL) spectra of... 

Fig. 1. Schematic view of the nanomechanical GMR device a movable dot with a single electron level couples to the leads due to tunneling of electrons, described by the tunneling probability amplitudes TL,n(t)), and due to the exchange interaction whose strength is denoted by JL,n(t). An external magnetic field H is oriented perpendicular to the direction of the magnetization in the leads (arrows).

A schematic view of the nanomechanical GMR device to be considered is presented in Fig. 1. Two fully spin-polarized magnets with fully spin-polarized electrons serve as source and drain electrodes in a tunneling device. In this paper we will consider the situation when the electrodes have exactly opposite polarization. A mechanically movable quantum dot (described by a time-dependent displacement x(t)), where a single energy level is available for electrons, performs forced harmonic oscillations with period T = 2-k/uj between the leads. The external magnetic field is perpendicular to the orientation of the magnetization in both leads. 

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