Lightweight porous silica foams with extreme-low dielectric permittivity and loss for future 6G wireless communication technologies

• Published in: Nano research Vol. 14; no. 5; pp. 1450 - 1456
• Main Authors: Pálvölgyi, Petra S., Sebők, Daniel, Szenti, Imre, Bozo, Eva, Ervasti, Henri, Pitkänen, Olli, Hannu, Jari, Jantunen, Heli, Leinonen, Marko E., Myllymäki, Sami, Kukovecz, Akos, Kordas, Krisztian
• Format: Journal Article
• Language: English
• Published: Beijing Tsinghua University Press 01.05.2021; Springer Nature B.V
• Subjects: 6G mobile communication; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Cellulose; Chemistry and Materials Science; Communications systems; Condensed Matter Physics; Dip coatings; Electronic devices; Foams; Frequency filters; Immersion coating; Lightweight; Materials Science; Metals; Metamaterials; Micropatterning; Nanofibers; Nanotechnology; Permittivity; Research Article; Shadow masks; Silica; Silicon dioxide; Slabs; Sol-gel processes; Substrates; Terahertz frequencies; Thin films; Wireless communication systems; Wireless communications; silica foams; low-permittivity materials; templated sol-gel synthesis; 6G telecommunication; low-loss dielectrics
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-020-3201-2

In the next generation wireless communication systems operating at near terahertz frequencies, dielectric substrates with the lowest possible permittivity and loss factor are becoming essential. In this work, highly porous (98.9% ± 0.1%) and lightweight silica foams (0.025 ± 0.005 g/cm 3 ), that have extremely low relative permittivity ( ε r = 1.018 ± 0.003 at 300 GHz) and corresponding loss factor (tan δ < 3 × 10 −4 at 300 GHz) are synthetized by a template-assisted sol-gel method. After dip-coating the slabs of foams with a thin film of cellulose nanofibers, sufficiently smooth surfaces are obtained, on which it is convenient to deposit electrically conductive planar thin films of metals important for applications in electronics and telecommunication devices. Here, micropatterns of Ag thin films are sputtered on the substrates through a shadow mask to demonstrate double split-ring resonator metamaterial structures as radio frequency filters operating in the sub-THz band.