scanning near-field optical microscopy

Organic-inorganic halide perovskites are materials of high interest for the development of solar cells.

Learning more about the relationship between the electrical properties and the chemical compositions of perovskite at the nanoscale can help to understand how the interrelations of both can affect device performance and contribute to an understanding on how to best design perovskite active layer structures.*

For the article “Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy” Ting-Xiao Qin, En-Ming You, Mao-Xin Zhang, Peng Zheng, Xiao-Feng Huang, Song-Yuan Ding, Bing-Wei Mao and Zhong-Qun Tian used correlative infrared-spectroscopic nanoimaging ( IR-spectroscopy ) by scattering-type scanning near-field optical microscopy ( s-SNOM ) and Kelvin probe force microscopy ( KPFM ) to contribute to the discussion whether nanometer-sized grain boundaries (GBs) in polycrystalline perovskite films play a positive or negative role in solar cell performance.*

The integrated KPFM and s-SNOM measurements were performed by the authors to acquire the surface potential and infrared near-field image simultaneously through a single-pass scan and thereby learn more about the relationships between the electrical properties and spectral information at the grain boundaries of the investigated material ( polycrystalline CH₃NH₃Pbl₃ perovskite films ).*

The results of the correlated s-SNOM and KPFM imaging presented in the article show that the electron accumulations are enhanced at the grain boundaries (GBs) of the investigated polycrystalline perovskite film, particularly under light illumination which would assist in electron-hole separation and therefore would be a positive influence on the performance of the solar cell.*

NanoWorld conductive platinum-iridium coated Arrow AFM probes ( Arrow-NCPt ) were used to perform the s-SNOM IR imaging.

Figure 4 from “Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy” by Ting-Xiao Qin et al.
Correlative KPFM and s-SNOM nanoimaging on perovskite.
a AFM topography (1 μm × 1 μm); b Contact potential difference (CPD); and c simultaneously acquired infrared near-field image; d one-dimensional line profiles of the topography, CPD and infrared near-field amplitude along the white dashed lines marked in a–c. The scale bars are 200 nm.
NanoWorld Arrow-NCPt AFM probes were used to perform the s-SNOM IR imaging — Figure 4 from “Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy” by Ting-Xiao Qin et al.
**Correlative KPFM and s-SNOM nanoimaging on perovskite**.
a AFM topography (1 μm × 1 μm); b Contact potential difference (CPD); and c simultaneously acquired infrared near-field image; d one-dimensional line profiles of the topography, CPD and infrared near-field amplitude along the white dashed lines marked in a–c. The scale bars are 200 nm.

*Ting-Xiao Qin, En-Ming You, Mao-Xin Zhang, Peng Zheng, Xiao-Feng Huang, Song-Yuan Ding, Bing-Wei Mao and Zhong-Qun Tian
Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy
Light: Science & Applications volume 10, Article number: 84 (2021)
DOI: https://doi.org/10.1038/s41377-021-00524-7

Please follow the external link to read the whole article: https://rdcu.be/clg7f

Open Access : The article “Quantification of electron accumulation at grain boundaries in perovskite polycrystalline films by correlative infrared-spectroscopic nanoimaging and Kelvin probe force microscopy” by Ting-Xiao Qin, En-Ming You, Mao-Xin Zhang, Peng Zheng, Xiao-Feng Huang, Song-Yuan Ding, Bing-Wei Mao and Zhong-Qun Tian is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/.

Launching and manipulation of polaritons in van der Waals materials offers novel opportunities for applications such as field-enhanced molecular spectroscopy and photodetection.*

Particularly, the highly confined hyperbolic phonon polaritons (HPhPs) in h-BN slabs attract growing interest for their capability of guiding light at the nanoscale. An efficient coupling between free space photons and HPhPs is, however, hampered by their large momentum mismatch.*

In the article “Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas” P. Pons-Valencia, F. J. Alfaro-Mozaz, M. M. Wiecha, V. Biolek, I. Dolado, S. Vélez,P. Li, P. Alonso-González, F. Casanova, L. E. Hueso, L. Martín-Moreno, R. Hillenbrand and A. Y. Nikitin show that resonant metallic antennas can efficiently launch HPhPs in thin h-BN slabs. Despite the strong hybridization of HPhPs in the h-BN slab and Fabry-Pérot plasmonic resonances in the metal antenna, the efficiency of launching propagating HPhPs in h-BN by resonant antennas exceeds significantly that of the non-resonant ones.

Their results provide fundamental insights into the launching of HPhPs in thin polar slabs by resonant plasmonic antennas, which will be crucial for phonon-polariton based nanophotonic devices.*

A commercial s-SNOM setup in which the oscillating (at a frequency Ω≅270kHz) metal-coated (Pt/Ir) AFM tip (NanoWorld ARROW-NCPt) was illuminated by p-polarized mid-IR radiation, was used.*

Figure 4 from “Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas” by P. Pns-Valencia et al. :
Near-field imaging of the HPhPs launched by the gold antenna. a Schematics of the s-SNOM setup. b Illustration of antenna launching of HPhPs. The spatial distribution of the near-field (shown by the red and blue colors) is adapted from the simulation of Re(Ez). c Topography of the antenna. d Simulated near-field distribution, |E(x, y)|, created by the rod antenna on CaF2 (the field is taken at the top surface of the antenna). Scale bars in c, d are 0.5 μm. e, h Experimental near-field images. f, i Simulated near-field distribution |Ez(x, y)| (taken 150 nm away from the h-BN slab). g, j Simulated near-field distribution |Ez(z, y)| taken in the cross-section plane along the center of the rod antenna. In e–g ω = 1430 cm−1, while in h–j ω = 1515 cm−1. The scale bars in e–i are 2 μm and in g, j are 0.1 μm (vertical) and 0.5 μm (horizontal). The length of the antenna in all panels is L = 2.29 μm — Figure 4 from “Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas” by P. Pons-Valencia et al. :
Near-field imaging of the HPhPs launched by the gold antenna. a Schematics of the s-SNOM setup. b Illustration of antenna launching of HPhPs. The spatial distribution of the near-field (shown by the red and blue colors) is adapted from the simulation of Re(Ez). c Topography of the antenna. d Simulated near-field distribution, |E(x, y)|, created by the rod antenna on CaF2 (the field is taken at the top surface of the antenna). Scale bars in c, d are 0.5 μm. e, h Experimental near-field images. f, i Simulated near-field distribution |Ez(x, y)| (taken 150 nm away from the h-BN slab). g, j Simulated near-field distribution |Ez(z, y)| taken in the cross-section plane along the center of the rod antenna. In e–g ω = 1430 cm−1, while in h–j ω = 1515 cm−1. The scale bars in e–i are 2 μm and in g, j are 0.1 μm (vertical) and 0.5 μm (horizontal). The length of the antenna in all panels is L = 2.29 μm

*P. Pons-Valencia, F. J. Alfaro-Mozaz, M. M. Wiecha, V. Biolek, I. Dolado, S. Vélez,P. Li, P. Alonso-González, F. Casanova, L. E. Hueso, L. Martín-Moreno, R. Hillenbrand, A. Y. Nikitin
Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas
Nature Communications 2019; 10: 3242
doi: 10.1038/s41467-019-11143-7

Please follow this external link to read the full article: http s://www.ncbi.nlm.nih.gov/pmc/articles/PMC6642108/

Open Access: The paper « Launching of hyperbolic phonon-polaritons in h-BN slabs by resonant metal plasmonic antennas » by P. Pons-Valencia, F. J. Alfaro-Mozaz, M. M. Wiecha, V. Biolek, I. Dolado, S. Vélez,P. Li, P. Alonso-González, F. Casanova, L. E. Hueso, L. Martín-Moreno, R. Hillenbrand and A. Y. Nikitin is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.