Scaling Behavior of Surface Roughness

The framework we adopted for measuring the scaling behavior from AFM images is the following. The 2-D power spectral density (PSD) of the Fast Fourier Transform of the topography h x, y) is estimated [54], then averaged over the azimuthal angle (p to yield the radial PSD (/) as detailed in [55]  

From the Wiener-Kinchine theorem, the integrated PSD yields the r.m.s. roughness vs the length/scale r  

the mean height (/z)=0, Eq. (6.1) is calculated on an image with scan length L, f is the spatial frequency (i.e. the inverse distance), and /max is the Nyquist frequency. The analysis for the relevant scaling properties (viz. correlation length, roughness exponent, etc.) can be carried out either on the roughness (6-7) 

6 Electronic Structure and Eneigy Transfer in Solid a-Sexithienyl 

Experiments on transport, injection, electroluminescence, and fluorescence probe the spatial correlation within the film, therefore we expect that their response will be sensitive to the self-affinity of the film. This approach, which we proved useful in the analysis of AFM data of conjugated molecular thin films grown in high vacuum, has never been applied to optical and electrical techniques on these systems and might be an interesting route to explore. We have started to assess die influence of different spatial correlations in thin films on the optical and the electro-optical properties, as it will be described in the next section. 

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