Semiconductor/semiconductivity multilayer

Figure 29. For the latter case, it is considered that the semiconducting re-electron systems are separated by insulating hydrocarbon spacers, resulting in alternate thin layers of organic semiconductor and insulator in these monolayer assemblies. The direct current - voltage (I - V) characteristics were mea- sured for the multilayers H2Pc(R)8 and Cu-Pc(R)8 in directions perpendicular and parallel to the film plane. In both cases, the linear I - V relationships of Ohm s law were observed at low electric field and obtained DC conductivities are summarized in Table 3. The normal conductivity (ajJ were ca. 10 13 S cm-1, while the lateral ones p//) were 3.4 x 10-7 and 9.9 x 10 7 S cm 1 for films of the metal-free and copper Pc derivatives, respectively. The former (ojJ tended to decrease slightly with increase of Figure 29. Schematical illustration of the substituent alkyl chain length,...

To implement this strategy, multilayered semiconductor structures were grown by MOCVD and then processed using lithographic techniques to create trenches of 10-20 p-m. Trenches of 10 pm were used to create arrays of 34 interdigitated LED/photodiode pairs, as shown in Fig. 8. As molecules adsorb onto the surfaces of these semiconducting materials, the electronic properties of the surfaces can be altered and thus changes in current can be observed when molecules such as ammonia and sulfur dioxide adsorb onto the surfaces of the diodes. 

Besides the value of LB-films as model systems in fundamental research there are a number of potential applications for these layers. The incorporation of LB monolayers and multilayers into both metal/LB-film/metal and metal/LB-film/semiconductor (MIS) devices has recently been attracting considerable attention [237]. Structures in the first category may find application as the basis for simple photovoltaic cells or switches. When deposited onto semiconducting substrates, the fine control of the LB layer thickness permits the optimization of the efficiency of both photovoltaic and electroluminescent structures. Thicker films can be used to control the surface conductivity of a variety of semiconductors and as the basis for a field effect transistor. The three particular examples presented in this section should serve to indicate the usefulness of monomolecular insulating films in the field of microelectronics. 

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