How the Complex Network of Specklegram Deciphers Intra‐Film Thermal Induced Dynamics?

Abstract

The present work deciphers the potential of the graph and its features in the speckle-based nondestructive evaluation of intra film thermal-induced dynamics. The molybdenum oxide film, prepared by sputtering technique, containing nanorods is subjected to thermal stress from 30-50 °C and the specklegrams are recorded. The co-occurrence matrix (CM) and heat map analyses of the specklegrams by dividing the temperature range into four intervals of 5 °C each reveal that the thermal stress drives the film from a less stable to a more stable state from the third to the fourth temperature interval. The CM analysis indicates the thermal-induced rearrangements among the nanorods of the film. By extracting frames from the videograph of the speckle pattern during temperature variation, a complex network is constructed, taking the middle column of each frame as a node. The graph features also become minimum in the third interval and increase in the fourth interval revealing that the film moves to a more ordered state under thermal stress. The analysis of the specklegram by CM, heat map, and graph suggests that graph features present a high sensitivity compared to the other methods.