Evidence for power-law dominated noise in vacuum deposited CaF2

Breakdown of dynamic scaling in surface growth under shadowing

Using Monte Carlo simulations and experimental results, we show that for common thin film deposition techniques, such as sputter deposition and chemical vapor deposition, a mound structure can be formed with a characteristic length scale, or "wavelength" lambda, that describes the separation of the mounds. We show that the temporal evolution of lambda is distinctly different from that of the mound size, or lateral correlation length xi. The formation of a mound structure is due to nonlocal growth effects, such as shadowing, that lead to the breakdown of the self-affinity of the morphology described by the well-established dynamic scaling theory. We show that the wavelength grows as a function of time in a power law form, lambda approximately t(p), where p approximately equals 0.5 for a wide range of growth conditions, while the mound size grows as xi approximately t(1-z), where 1/z varies depending on growth conditions.

Statistical characterization of thermally evaporated rough CaF2 films

Thermal deposition of CaF2 onto a glass substrate creates a nanoscale rough surface. A series of samples with differing nominal CaF2 film thicknesses have been fabricated, and the topography has been investigated using atomic force microscopy. Measured values for the statistical characterization of the samples are presented including the exponents describing the scaling behavior of the surfaces. We find that the roughness exponent alpha=0.88+/-0.03 , the growth exponent beta=0.75+/-0.03 , and the dynamical exponent z=alpha/beta=1.17+/-0.06 . We also measure the multifractal spectra and nearest neighbor height difference probability distribution. The results are consistent with noise dominated by a power-law distribution with exponent mu+1 approximately equal to 4.6. Profilometer measurements were used to determine the porosity phi of the deposited films, which we find to be constant for all film thicknesses with phi approximately 0.46 .