Pentacene substrate surface roughness

The substrate surface smoothness is critical to TFT performance. Device fabrication processes basically duplicate and/or worsen the surface roughness, which leads to smaller pentacene grains and results in deterioration of pentacene channel mobility. Atomic-force microscopy was used to characterize the surface roughness. Figure 15.21 shows an AFM image of our PET substrate surface before any process. The mean-square roughness and peak-to-valley roughness are 10 A and 90 A,... 

Fig. 15.21. AFM image of PET substrate surface. While visually boring, the surface roughness is sufficient to significantly reduce pentacene mobility if it is not in some way planarized.

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