Planar Device Structure

Furthermore, we have extended the planar device structure to localise the interface where the switching appears. An additional contact stripe was located in the gap between the existing two metal contact stripes. In this case, the distance between the two parallel metal contacts was 15 pm. The middle electrode was positioned between them and had a width of 5 pm. The contacts were covered with Cu(TCNQ) by complete conversion of a previously deposited Cu layer. 

Polyimides formed by thermolysis of poly(amic acids) have proven to be the least successful of planarizing polymers because their high glass transition temperatures limit flow and conformability to the device topography. However, this high is a performance advantage. For example, polyimides have been used to planarize device structures where the thermal stability of the polymer allows it to remain on the final device. 

The ability to integrate an electro-optic material with other optical devices, e.g. light sources and detectors, and with electronic drive circuits is important. Integrability implies that the electro-optic materials and the processing of these materials are compatible with the other components, and that electrical and optical interconnects can be fabricated. Polymer glasses are widely used in the fabrication of electronic devices and device interconnects. Polymers are also used as photoresists and as dielectric interlayers for electrical interconnects. As a result, a body of knowledge already exists concerning planarization methods of polymers on substrates, the definition of microscopic features, and the fabrication of microstructures in planar polymer structures. 

A simple example of this is the case of a molecule (modeled as an oscillating dipole) close to a perfect mirror. If the dipole is parallel to the mirror, destructive interference between directly emitted light and reflected light causes a reduction in the radiative rate. In the presence of competing nonradiative decay processes, this leads to a reduction in the efficiency of emission. The variation of radiative rate with position and orientation for a molecule within an arbitrary planar dielectric structure has been modeled by Crawford.81 This model has been applied to polymer LEDs by Burns et al.,82 and Becker et al.,83 who predict significant variations in the efficiency of radiative decay in polymer LEDs depending on the distribution of exciton generation within the device. 

The LEDs discussed so far have all been simple planar structures, typically on glass substrates. The unique processing advantages of conjugated polymers also allow a range of novel device structures to be considered, some of which are discussed here. 

One of the basic challenges in the fabrication of highly non-planar devices lies in the preparation only a few methods have so far been explored to produce deeply structured thin films on a flat substrate and—in a second step—to produce a continuous coverage on a deeply structured substrate. In Section 6.3, some of the possible fabrication processes will be discussed. 

The planar structure was fabricated as follows the glass substrate was carefully cleaned as described above. A 300 nm metal layer was deposited onto the substrate by e-beam evaporation. Next, the metal layer was patterned by standard photolithography. After metal etching, the device structure contained two parallel metal stripes that served as contacts. The distance between the two stripes was 10 pm. Then, a Cu-stripe with a thickness of 70 nm was e-beam evaporated onto the contacts. Finally, the substrate was immersed into the TCNQ/acetonitrile solution. The device was kept in the TCNQ/acetonitrile solution until the Cu layer was completely converted into Cu(TCNQ). Finally, the substrate was rinsed with acetone and dried with nitrogen. Figure 27.10 shows a schematic drawing of the device. 

At the next stage of our studies, we developed a new robust method for rolling lithographically defined planar strained heterofilms in preset directions to obtain 3D-free-standing shells of even more complex geometry and properties (Fig. 4). Precise micro- and nanotubes, and also other precise nanoshells can be used as building blocks for more complex device structures. Like molecules, such building... 

Device structure (a) and schematic energy level diagram (b) of a tandem organic PV cell with CuPc-Cjo planar-mixed molecular HJs. 

A key point regarding electrochemical sensors is the fabrication process. These devices are usually obtained by means of sintering techniques to achieve pellet structures (Kida et al., 2000), and some authors even combine thin- or thick-film techniques to fabricate some elements such as electrodes (Salam et al., 1998). But the great potential of the use of planar configurations has made them more usual in the literature (Ramfrez-Salgado and Fabry, 2003, Fergus, 2008). Planar devices ease the fabrication process so... 

Solar cells can directly convert solar energy into electricity, which is clean and inexhaustible. Generally, the solar cells are built with a planar sandwiched structure on the rigid substrate, which restricts their applications in many fields. Flexible polymer substrates, such as poly(ethyleneterephthalate) (PET), poly(ethylenenaphthalate) (PEN), and polydimeth-ylsiloxane (PDMS), have been widely used to fabricate flexible solar cells. With high stability and flexibility, the solar cells can easily integrate with other portable or wearable devices to significantly extend their applications. 

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