Substrate temperature, pentacene

Pentacene thin films grown with PLD under vacuum ( 10 Torr) and at substrate temperatures ranging from 300 to 473 Khave been obtained using again a KrF excimer laser (248 nm), operated at 50 Hz and with a power of 6-8 W. Relatively... 

The channel layer is 50-nm-thick pentacene deposited in the vacuum sublimation system at ambient substrate temperature with fine metal masks. After deposition of pentacene thin film, 30-nm-thick gold layers are deposited as source and drain though fine metal masks. 

Aromatic hydrocarbon pentacene is important for application in OTFTs as it has superior field effect mobility, good semiconducting behavior, and stability [153], The chemical structure is shown in Fig. 6.10. Pentacene semiconductor films can be fabricated by sublimation in a vacuum deposition system. Optimization of the fabrication parameters, such as the substrate temperature and deposition rate, can yield a highly ordered pentacene film with improved device performance. Oriented films have optical and electrical anisotropies. 

Figure 18.5 Output characteristic of an OFET with 1000 pm channel width and 5 pm channel length on a 120 nm thick TEOS oxide layer. The thickness of the pentacene film is about 60 nm, deposited at a substrate temperature of 60 °C and a deposition rate of 0.3 nm/s at 7.4 X 10 mbar chamber pressure.

The temperature dependence of the critical island size for pentacene on Si02 was explored by Tejima et al. [44] and the results are displayed in Figure 5.1.11. The same scaled island size distributions are shown in Figure 5.1.11a for four different substrate temperatures at a constant thickness of -0.2 ML. The curves corresponding to critical island sizes of one, two, and three are shown and it is clear that the different substrate temperatures used result in different critical island sizes. The scaled island densities for thick pentacene layers are plotted as a function of... 

A -sulfinylacetamide 297 in greater than 90% yield when a catalytic amount of methyltrioxorhenium is employed. Futhermore, the hetero-Diels-Alder adduct is highly soluble in both chlorinated and ethereal solvents. A detailed investigation of the retro-Diels-Alder reaction of 298 by thermogravimetric analysis revealed an onset temperature of 120 °C and complete conversion of bicycle 298 to pentacene 296 at 160 °C, which are temperatures compatible with the polymer supports typically used in electronics applications. The electronic properties of these newly prepared OTFTs are similar to those prepared by traditional methods. Later improvements to this chemistry included the use of A -sulfinyl-/< r/-butylcarbamate 299 as the dienophile <2004JA12740>. The retro-Diels-Alder reaction of substrate 300 proceeds at much lower temperatures (130 °C, 5 min with FlTcatalyst 150 °C, Ih with no catalyst). 

Generally, in the first monolayer on (coinage) metals pentacene and other planar aromatic molecules were found to adsorb with their aromatic ring plane parallel to the substrate. A detailed discussion of the molecule/metal interaction probed by means of low temperature STM can be found in Chapter 12 by Soubatch et al. The preference for such a planar adsorption geometry can be... 

Figure 11.7 Stmcture and morphology of pentacene films grown on Au(l 11). (a) SEM micrograph of 2 nm grown at room temperature together with (b) STM data (U= -2Y, I = 15 pA) showing the stmcture of the first monolayer (indicated by I) between the islands formed (indicated by II). A similar morphology was also obtained for films grown at various conditions, (c) 30 nm (15 nm/min). The resulting islands reveal characteristic orientations relative to the substrate as shown schematically in (d).

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