Photo Induced Surface Modulation in Amorphous Materials
MSc. Ugis Gertners (ISSP UL Laboratory of Optical Recording)
Amorphous chalcogenide semiconductors (As-S, As-Se, Ge-S, Ge-Se e.g.) thin films causes increasing interest as promising material for data optical recording and processing. Significant changes of photo-induced optical properties, such as the refractive index (Δn to 0.8), viscosity, micro hardness and bandgap changes (ΔEg to 0.4eV) in these materials make it possible to perform phase as well as amplitude recording thin films. Photo-induced changes in chalcogenide semiconductors are related to the transformation of chemical bonds, which determines the high resolution (~104 mm-1) of the material [1-2]. The listed things are those that make amorphous chalcogenides as competitive materials for optical recording in holography, as well as in making optical elements of the surface relief in nanolithography, and also in data transmission and storage in information technology. Recent studies have shown that soft material (such as amorphous chalcogenide) exposure to light forms a significant deformation [3], which is associated with the susceptibility to radiation. This process is reversible and the obtained deformation is not a density effect, because the entry can be deleted thermally - by heating [3], as well as optically - by illuminating the sample [4]. The dissertation is based on this phenomenon, which objective is to do a research on the amorphous chalcogenide susceptibility to light. As one of the research methods, a direct holographic record will be used, i.e., creating surface relief or holographic grating in chalcogenides directly during the recording without any additional processing, like etching. Complete development of this method opens wide range of usage possibilities in optical element production and utilization, as well as in introduction of new and innovative technologies. There is still a lot of interesting phenomena in amorphous chalcogenide that are not well understood and explained in a microscopic level and so this work will be directly involved in the process of research. Record efficiency dependence from its parameters (intensity, polarization) and recording conditions will be examined. Optical properties for obtained nanostructures will be studied, such as transmission, reflection, diffraction efficiency, etc. The obtained structures will be viewed by atomic force microscopy, determining their shape and size.
[1] R. P. Wang, Amorphous Chalcogenides: Advances and Applications: Pan Stanford Publishing, 2014.
[2] K. Tanaka and K. Shimakawa, Chalcogenide Semiconductors and Related Materials: Springer, New York, 2011.
[3] V. Palyok, I. A. Szabó, D. L. Beke, and A. Kikineshi, Surface grating formation and erasing on a-Se films, Appl Phys A, vol. 74 (5), pp. 683-687, 2002.
[4] U. Gertners and J. Teteris, Photo-induced Mass Transfer in Chalcogenides, IOP Conf. Series: Materials Science and Engineering, vol. 23, p. 012007, 2011.