Metylammonium Lead Bromide Perovskite Single Crystals: Scanning Probe Microscopy Studies
Parmenio Boronat a, Ismael Fernández a, Clara Aranda a b, Jesús Ortiga a, Ana Cros a, Núria Garro a, Pablo P. Boix a
a Institut de Ciències de Materials (ICMUV), c/ Catedràtic José Beltrán, 2, Paterna (València), Spain
b Institute of Advanced Materials (INAM), Universitat Jaume I, Castellón, Spain.
Proceedings of Sustainable Metal-halide perovskites for photovoltaics, optoelectronics and photonics (Sus-MHP)
València, Spain, 2022 December 12th - 13th
Organizers: Teresa S. Ripolles and Hui-Seon Kim
Poster, Parmenio Boronat, 043
Publication date: 15th November 2022

Scanning probe microscopies (SPM) are powerful tools for the study of new materials as they can image several interactions simultaneously with nanometer resolution. This reaches far beyond the capabilities of other techniques and has helped in clarifying some complicated problems. Recent developments in the synthesis methods of  metal halide perovskites (MHP) have allowed a fast and feasible production of bulk and thin-film monocrystals which present new distinctive properties that are still under investigation. In this work, we focus on MAPbBr3 bulk and thin-film single crystal (TFSC) and use several SPM to study their topography (AFM), electrostatic interaction (EFM), surface potential (KPFM) and conductivity (C-AFM). By these means, three problems have been tackled: surface degradation and passivation, and MEMristor behavior.  Concerning surface degradation, flat surfaces have been generally observed in fresh MAPbBr3 TFSC samples, but after some days, terraces and lumps appear over the surface, which may be a signal of lead (II) bromide salts formation [1]. Light response of passivated bulk MAPbBr3 [2] samples has been studied too. By focusing red and green lasers on their surface, surface photovoltage (SPV) has been found to be significant for green light but has a negligible response for red light.

Finally, TFSC perovskites can present MEMristor behavior as reported in literature [3]. A MEMristor device changes from high-resistance to low-resistance states through a resistive switching (RS) [4].  RS phenomena has been studied using conductive AFM tips. The measured IV curves show the characteristic MEMristor hysteresis loop. Furthermore, sub-micrometer changes in the sample structure and chemical composition have been observed not only with AFM, but also with EFM and KPFM, direct signatures of conduction filaments forming through the layer which may lead to RS.

Spanish MICINN/AEI under project PID2019-104272RB-C53/AEI/10.13039/501100011033

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