The influence of gas cluster ion beam surface etching on the chemical and electronic structure of perovskite Emily Albert 1 , Dongguen Shin 1 , Patrick Amsalem 1 , Fengshuo Zu 1 , Norbert Koch 1,2 1 Humboldt-Universität zu Berlin, Germany, 2 Helmholz-Zentrum Berlin, Berlin, Germany Understanding the interface electronic properties in halide perovskites (HaP) - based optoelectronic devices is of major importance to optimize their efficiency and functionality. However, reaching the substrate / HaP thin film interface is challenging and can eventually be achieved by physical etching of the typically 500 nm thick thin films. While standard depth profiling with argon ions results in massive damage of the HaP, we investigated the impact of gas cluster ion beams (GCIB) on methylammonium lead iodine (MAPbI 3 ) and characterized the etched surface by photoelectron spectroscopy and atomic force microscopy. We analyzed the evolution of MAPbI 3 thin films (450 - 500 nm thick) electronic and chemical properties as a function of sputtering time and kinetic energy per argon atom, using selected settings of 10 keV/˜3000 and 5 keV/˜6000 Ar atoms per cluster. The first setting showed the formation of PbI 2 and Pb 0 after just 1h of exposure as well as a shift in the secondary electron cut off (SECO) and valence band (VB) onset. After 33h, the film showed no perovskite like properties anymore with a remaining inhomogeneous film of ˜100 nm thickness. The second setting showed neither chemical degradation nor a shift in the SECO after 1h of exposure. Following 13h, evidence of the formation of PbI 2 as well as Pb 0 appeared together with a shift in the SECO and VB onset. After 32h, the film still exhibited a thickness of ˜400 nm. Consequently, the utilized settings showed that there is a trade off between the etching depth and the degradation of the perovskite film. While gas cluster ion beam sputtering seems not to be suitable for the depth profiling of MAPbI 3 , the second setting with 5keV/˜6000 argon atoms per cluster could potentially be utilized for cleaning the perovskite surface, in the view of fundamental surface studies.
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© The Author(s), 2023
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