Diode-like behavior

The electrical properties of an anodic oxide are found to depend on the formation conditions and subsequent treatments such as annealing. As-prepared anodic oxides show high leakage currents and a diode-like behavior known from anodic oxides of valve metals. A short high-temperature anneal, which removes the bound hydroxyl, reduces the leakage current to values typical of thermal oxides, as shown in Fig. 5.9. 

For the serial configuration of a DSJ, such as a donor/acceptor rectifier, the I-V curves maintain a diode-like behavior, as it can be already inferred by coherent transport calculations. [265] Besides, we predict that as a result of charging effects, one conductance peak will be split into three peaks and one dip, and one current maximum into two. For a DSJ parallel configuration, due to different charging energies on the two dot sites, the stability diagrams show peculiar nesting characteristics. 

Figure 28c, d shows a schematic illustration and SEM image of a nanodevice comprising a single P3HT PCBM NW with Au and Al electrodes. The I—V characteristic curve of the single P3HT PCBM (1 2 wt%) NW in the dark shows diode-like behavior, as shown in Fig. 28e. Under illumination, the current levels were enhanced at a relatively high bias (F > 10 V), as shown in Fig. 28e. Excitons were created in the major P3HT and minor PCBM components, and they dissociated into electrons and holes under the applied electric field near the interface between P3HT and PCBM.

Rectification in an assembly designed to display diode-like behavior has been described for the binuclear complex (3) [Ru(dcb)2(Cl)-bpa-Os(bpy)2(Cl)](PF6)2, where deb is 4,4 -(COOH)2-2,2 -bipyridine and bpa is 1,2-bis(4-pyridyl)ethane, which is attached to nanocrystalline Ti02 tiu-ough the carboxylate groups associated with the Ru center. ... 

Fave, C., V. Noel, J. Ghilane, G. Trippe-AUard, H. Randriamahazaka, and J.-C. Lacroix. Electrochemical switches based on nltrathin organic films From diode-like behavior to charge transfer transparency. J. Phys. Chem. 112, 2008 18638-18643. 

Figure 3.23 An n-n heterojunction with offset gap. This heterojunction may show Schottky diode-like behavior based on injection of electrons across the spike in the conduction band. The larger potential barrier in the valence band reduces hole injection from the narrow gap material into the wider gap material. An applied voltage reduces band bending in both semiconductors.

Figure 5.11 summarizes the temperature dependent transport behavior of unipolar and ambipolar diodes based on MDMO-PPV. Below 190 K, the hole-controlled device (ITO/PEDOT and Au contact) and the ambipolar device (ITO/PEDOT and LiF-Al contact) behave identically. Trap-free SCLC transport is observed and the mobility at this temperature is estimated to be around 10-8 cm2/Vs. For the ambipolar device, a diode-like turn-on is... 

Not all diode junctions involve contacts between different doping types of the same semiconductor ( homojunctions ). The remainder, junctions between dissimilar materials or heterojunctions , are generally divided into metal/semiconductor and semiconductor/semiconductor junctions. We consider metal/semiconductor heterojunctions first. A sufficiently degenerate semiconductor behaves essentially as a metal and produces results nearly identical to the metal/semiconductor behavior. Metal/semiconductor junctions turn out to have either linear (ohmic) or diode-like current voltage characteristics and are called ohmic contacts or Schottky diodes, respectively. 

The observed I/U characteristics turn towards the behavior of antiparallel Schottky-type double diodes. A complex behavior of the I/U curves upon humidity, may indicate that two mechanisms might play the key role the mobility of H and OH ions within the fullerite lattice at high voltages and electrochemical corrosion of the fullerite in humid environment, which makes the MOSBIT structure like a galvanic battery [4,5]. 

Nanometer-Sized Electronic Devices The possible use of carbon nanotubes in nanoelectronics has aroused considerable interest. Dramatic recent advances have fueled speculation that nanotubes (SWNTs) will be useful for downsizing circuit dimensions. Because of their unique electronic properties, SWNTs can be interfaced with other materials to form novel heterostructures [156]. The simplest device one can imagine with carbon nanotubes is that involving a bend or a kink, arising from the presence of a diametrically opposite pentagon-heptagon pair. The resultant junction connects two nanotubes of different chirality and hence of different electronic structure, leading to the realization of an intramolecular device. Such a device in SWNTs is found to behave like a diode rectifier [157]. Silicon nanowire-carbon nanotube heterojunctions do indeed exhibit a rectification behavior [158]. 

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