| AVS 65th International Symposium & Exhibition | |
| Advanced Ion Microscopy Focus Topic | Thursday Sessions |
| Session HI+AS-ThM |
| Session: | Advanced Ion Microscopy & Surface Analysis |
| Presenter: | Yongtao Liu, University of Tennessee |
| Authors: | Y.L. Liu, University of Tennessee L. Collins, Oak Ridge National Laboratory R. Proksch, Asylum Research an Oxford Instruments Company S. Kim, Oak Ridge National Laboratory B.R. Watson, University of Tennessee B.L. Doughty, Oak Ridge National Laboratory T.R. Calhoun, University of Tennessee M. Ahmadi, University of Tennessee A.V. Ievlev, Oak Ridge National Laboratory S. Jesse, Oak Ridge National Laboratory S. Retterer, Oak Ridge National Laboratory A. Belianinov, Oak Ridge National Laboratory K. Xiao, Oak Ridge National Laboratory J. Huang, Oak Ridge National Laboratory B.G. Sumpter, Oak Ridge National Laboratory S.V. Kalinin, Oak Ridge National Laboratory B.H. Hu, University of Tennessee O.S. Ovchinnikova, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory |
| Correspondent: | Click to Email |
Hybrid organic-inorganic perovskites (HOIPs) have recently attracted attention due to its success in optoelectronics, largely due to power conversion efficiency, which has exceeded 20% in a short time. Recently, the appearance of twin domains in MAPbI3 has been described ambiguously in a number of investigations. While all previous publications are limited in the descriptions of ferroelectric and/or ferroelastic nature, given (i) the correlation of defect chemistry and ferroelasticity, (ii) the coupling of ferroelectricity and ionic states, the chemistry of this twin domain can no longer be ignored. In earlier investigations, the twin domain size is revealed in the range of 100 nm- 400 nm, well in the detectability of helium ion microscopy secondary ion mass spectrometry (HIM-SIMS) (spatial resolution ~10 nm). Therefore, in this work, we correlate HIM-SIMS with multiple image techniques to unveil the chemical nature of the twin domain in MAPbI3 perovskite.
Our scanning probe microscopy (SPM) studies indicate the variation of elasticity and energy dissipation between domains. Moreover, correlating SPM with scanning electron microscope (SEM), we observed smooth topography and twin domain contrast in SEM image, simultaneously, indicating the twinning contrast in SEM image is not due to morphology. These results allow us to suppose the chemical variation between twin domains, suggesting the need of clarifying the chemical difference between domains.
Using HIM-SIMS, which combines high-resolution imaging <0.25 nm of helium ion microscopy with the chemical sensitivity of secondary ion mass spectrometry (SIMS), we can detect ion distribution with a spatial resolution of 10 nm, allowing us to quantitatively explore the chemical composition of the twin domains (100 nm-400 nm). A HIM-SIMS using two gas field ionization sources (He+ and Ne+) was utilized for mass-selected chemical imaging of perovskite samples as well as identification of chemical species by spectrum collection in this study. In a positive mode measurement, CH3NH3+ (m/z~32) chemical map shows that the CH3NH3+concentration differs both in grains and twin domains, however, the Pb+ (m/z~208) distributes uniformly. These results clarify that the chemical variation between domains originates from CH3NH3+ segregation. For the most relevant for the optoelectronic applications of HOIPs, we have shown that this chemical variation affects HOIPs’ interaction with light. Combining HIM-SIMS with multiple image techniques, this work offers insight into the fundamental behaviors of the twin domain in MAPbI3, as well as a new line of investigative thought in these fascinating materials.