Micrograph of the September from the Journal of Sol-Gel Science and Technology

Each month, the ISGS Newsletter features an interesting and striking micrograph (or series of micrographs) chosen from a recent issue of the Journal of Sol-Gel Science and Technology or from unpublished sources such as PhD theses, etc (with full attribution given). If you know of any interesting images that might be suitable, please contact the ISGS Newsletter Editor for inclusion. The micrographs can be optical, SEM, TEM, AFM, etc, and a brief description of the samples should be provided.

This month’s images are taken from three different papers in the latest issue of JSST and once again highlight the breadth of sol-gel science and technology, together with the areas in which our community is making an impact.

The first is taken from the work of Gegova-Dzhurkova, Nesheva, Dzhurkov, Šćepanović, GrujićBrojčin, Bineva, Mihailov, Levi, Manolov and Popović entitled “Modification of surface morphology and lattice order in nanocrystalline ZnO thin films prepared by spincoating sol–gel method” (JSST, (2021) 100, 55-67, https:// doi.org/10.1007/s10971-021-056356), which explores the effect of drying in a hot-air flow (90-95 oC) and laser annealing on key properties of ZnO films, including internal stress, crystallinity and defect density. The optical micrographs at the top (with each micrograph displaying a viewing field ca. 50 μm in width) show the wrinkled morphology obtained in the absence of the hot-air-drying step (a) compared to the unwrinkled morphology obtained using an intermediate hot-air-drying step (b) to evaporate volatiles. An AFM image further illustrating the wrinkled morphology is also shown (c).

The second series of micrographs is from the work of Choudhary and Deepak. This paper, entitled “Investigation of time-dependent stability and surface defects in sol–gel derived IGZO and IZO thin films” (JSST, (2021), 100, 132-146, https://doi.org/10.1007/s10971021-05615-w), explores the effect of gallium doping and ageing on the optical and electrical properties of indium gallium zinc oxide thin films deposited by spincoating. The as-processed films were typically uniform, transparent and amorphous when viewed under an optical microscope, with roughness below 2 nm. However, while they remained structurally and electrically stable with time, slight changes in morphology were evident after 13 days, with optical microscopy revealing some dark spots which were found to have high indium content. AFM studies of these defects revealed intriguing morphologies, with the effect being more evident in the absence of gallium doping.