Pentacene evaporated

To confirm the advantages of vertical-type EETs, OSITs using pentacene or CuPc evaporated films were fabricated on glass substrates and the basic characteristics were evaluated [15,16], as detailed in Section 10.4.3. Furthermore, OSITs based on pentacene evaporated film were fabricated... 

Fig. 18 a AFM topographical images (2.5 x 2.5 (im ) of 50 mn film of pentacene evaporated on DNA-CTMA. b AFM topographical images (2.5 x 2.5 iim ) of 100 nm spin-coated film of PCBM on DNA-CTMA, (Reproduced with pennission from Elsevier and [39])... 

When the solvent evaporation is performed in a well-controlled way, sufficiently large single crystals can be obtained. This is the case for pentacene, where single crystals are grown from solution in TCB by slowly evaporating the solvent over a period of four weeks at 450 K, under a stream of ultrapure N2 gas. 

Comparing single crystal and vapor-grown devices for these two compounds is difficult, because reports on evaporated tetracene OTFTs are rather scarce [99-101], and despite several (unpublished) attempts, fabrication of an operating thin-film device from rubrene has not yet been successfully achieved. For both compounds the problem seems to arise from an improper deposition mechanism, which, in contrast with experience with pentacene and sexithiophene, does not favor two-dimensional growth. 

D. J. Gundlach, T. N. Jackson, D. G. Schlom, S. F. Nelson, Solvent-induced phase transition in thermally evaporated pentacene films, Appl. 

Figure 19.12 Left. Structure of the tandem solar cell based on pentacene and Ceo with a thin, discontinuous evaporated silver layer Incorporated for efficiency improvement. Right Power efficiency versus excitation wavelength for tandem solar cells with 2 nm silver middle layer (solid circles) and without the silver layer (open circles). The right hand scale is for the ratio of efficiency of the two cells to illustrate the significant difference in dependence on excitation wavelength. Reprinted from reference 63 with permission of the SPIE.

Pentacene can be evaporated quite conveniently by resistive heating of a tantalum crucible filled with purified pentacene powder. This procedure is ultra... 

The OFETs using inorganie gate dieleetries were prepared on a heavily doped silieon substrate, whieh also serves as the eommon gate eleetrode for all fabricated devices. The semiconducting film consists of evaporated pentacene, which is commercially available. In Figure 18.1 the transistor architecture with bottom gate and bottom drain and source contacts is shown. 

Figure 18.4 Output characteristic of an OFET with a channel length of 10 pm and a channel width of 16.8 cm, using a 127 nm thick silicon dioxide layer as gate dielectric. Before evaporating the pentacene in high-vacuum ambient, the sample was pretreated in an oxygen plasma for 30 s at 100 W plasma power.

From the area of polymer dielectrics, a sample is presented here using a commercially available and (from many microelectronic applications) well-known high-temperature polyimide. The deposition and the subsequent curing process have been described in Section 18.2.3, resulting in a 190 nm thick insulating film that showed a good chemical resistance towards diluted developer solution and acetone, so that the cathode-sputtered Au drain and source contacts can be structured as described in Section 18.2.1. The 30 nm thick pentacene layer is thermally evaporated at a deposition rate of about 0.1 nm/s and a process pressure of 1 x 10 mbar. 

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