Depth mapping of metallic nanowire polymer nanocomposites by scanning dielectric microscopy

• Published in: Nanoscale 2021-06, Vol.13 (22), p.1116-1126
• Main Authors: Balakrishnan, Harishankar, Millan-Solsona, Ruben, Checa, Marti, Fabregas, Rene, Fumagalli, Laura, Gomila, Gabriel
• Format: Article
• Language: English
• Subjects: Conductors; Diameters; Electronics; Gelatin; Microscopy; Nanocomposites; Nanowires; Nondestructive testing; Optimization; Permittivity; Photovoltaic cells; Polymers; Silver; Solar cells; Spatial distribution; Thick films
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d1nr01058a

Polymer nanocomposite materials based on metallic nanowires are widely investigated as transparent and flexible electrodes or as stretchable conductors and dielectrics for biosensing. Here we show that Scanning Dielectric Microscopy (SDM) can map the depth distribution of metallic nanowires within the nanocomposites in a non-destructive way. This is achieved by a quantitative analysis of sub-surface electrostatic force microscopy measurements with finite-element numerical calculations. As an application we determined the three-dimensional spatial distribution of ∼50 nm diameter silver nanowires in ∼100 nm−250 nm thick gelatin films. The characterization is done both under dry ambient conditions, where gelatin shows a relatively low dielectric constant, r ∼ 5, and under humid ambient conditions, where its dielectric constant increases up to r ∼ 14. The present results show that SDM can be a valuable non-destructive subsurface characterization technique for nanowire-based nanocomposite materials, which can contribute to the optimization of these materials for applications in fields such as wearable electronics, solar cell technologies or printable electronics. The depth mapping of metallic nanowires buried in polymer nanocomposites can be achieved in a non-destructive way and with nanoscale spatial resolution with scanning dielectric microscopy.