https://doi.org/10.1140/epjp/s13360-023-04139-2
Regular Article
Humidity effect on the evolution of CsI thin films: a fractal study of rough surfaces
1
Department of Physics, Institute of Science, Banaras Hindu University (BHU), 221005, Varanasi, India
2
Department of Physics, Government P G College, 221508, Saidabad, Prayagraj, India
3
School of Earth and Environment Science, Central University of Himachal Pradesh, Shahpur Campus, 176206, Kangra, India
4
Department of Physics, University of Allahabad, 211002, Prayagraj, India
5
Natural Sciences Discipline, PDPM Indian Institute of Information Technology, Design and Manufacturing (IIITDM), 482005, Jabalpur, India
6
INFN Sezione di Trieste, Area Science Park, Padriciano 99, 34149, Trieste, Italy
7
Departimento di Fisica and INFN Bari, Politecnico di Bari, 70126, Bari, Italy
Received:
29
January
2023
Accepted:
25
May
2023
Published online:
10
June
2023
The present work aims at studying the morphological, micro-structural, compositional and fractal features of CsI thin films, for the thicknesses 30, 50, 300 and 500 nm, in two cases: (i) as-deposited and (ii) 1-h humid air aged. The average grain sizes, estimated from TEM technique, are varied between the range 313–1058 nm, and their values are found to get increased after exposing to the humid air. The interplanar spacing evaluated from a SAED pattern is lesser than the standard value for a strain-free CsI crystal which suggests that a compressive stress is acting in the film. The compositional analysis suggests that the atomic percentage of Cs:I is 1:1, and it increased by the factor of two with exposure to humidity. The surface morphological images, captured by atomic force microscopy, signify the fractal behavior of CsI films. The values of the roughness exponent and fractal dimensions are determined for both as-deposited and humid-aged CsI films. It is observed that fractal parameters no longer remain unchanged after exposure to humidity, but they do not show any monotonic decreasing or increasing nature. The value of the roughness exponent was found to be greater than 0.5 which indicates that the height fluctuations at neighboring pixels are positively correlated. It signifies the height variations at neighboring pixels exhibit persistent behavior and memory effect.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
