Abstract
The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A pseudo-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of ~104 monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.
Highlights
By analyzing surface fluctuations of CdTe films deposited on polyimide (Kapton) substrates, we reveal that the observed transient regime is characterized by Gaussian statistics, a constant roughness in time and no spreading of correlations through the system
Similar results are obtained by estimating ξ from the first zeros of the slope-slope correlation function, as done, e. g., in refs. These results demonstrate that the first regime is a pseudo-steady state (PSS), not described by the EW equation, for which 1/z = 0.5 is expected[22], while 1/z ≈ 0 is found here
We have analyzed the kinetic roughening of CdTe films deposited on Kapton substrates at relatively low temperature and intermediate deposition rate
Summary
By analyzing surface fluctuations of CdTe films deposited on polyimide (Kapton) substrates, we reveal that the observed transient regime is characterized by Gaussian statistics, a constant roughness in time and no spreading of correlations through the system. After a long characteristic time tc, corresponding to the deposition of ~104 monolayers of CdTe, correlations and height fluctuations start developing, yielding an asymptotic growth in the KPZ class.
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