Semiconductor/semiconductivity array

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. 

Considering the merits and demerits of both semiconducting devices and SAW-type devices, an array with both a semiconductor and a SAW device might be designed as a useful means of detecting odors, including those of CWAs. 

Figure 2 Structure of the polymer grid triode with the various layers. (1) and (5) are the cathode and anode (pixel) arrays, respectively. The other layers are continuous films common to all the PGTs within the array (2) and(4) are semiconducting layers, poly(2-methoxy-5-(2 -ethyl-hexyloxy)-1,4-phenylene vinylene), MEH-PPV, and (3) is the common grid network filled with semiconductor (3 ).

Undoped conjugated polymers have an anisotropic, quasi-one-dimensional electronic structure with the tt electrons coupled to the polymer backbone via electron-phonon interactions. The overlapping of TT- (also TT -) electron wave functions forms a valence band (conduction band) with a gap size of typically 2-4 eV, corresponding to the conventional semiconductor gap. As a result, undoped conjugated polymers (hereafter called simply semiconducting polymers) exhibit the electronic and optical properties of semiconductors in combination with the mechanical properties of general polymers, making them potentially useful for a wide array of applications. 

A third major innovation in polymer physics during the past decade is the recognition that because they are quasi-one-dimen-sional materials, some polymers exhibit collective semiconducting ground states(5,8). In contrast to the pervasive effects of disorder in almost all polymers, however, the occurrence of collective phenomena is uncommon. Specifically, it is characteristic of macromolecules like polyacetylene which have experienced a symmetry-lowering structural modification that introduces a semiconductor gap into what would have been a metallic electronic excitation spectrum. Moreover, in such materials the consequences of disorder can be dramatically different from those noted in the previous lecture. Thus, in this third and final lecture we examine the destruction of the collective semiconducting ( Peierls ) ground state in doped polyacetylene by the interaction of the conduction electrons with a disordered array of donors or acceptors. 

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