While existing mobile networks use frequencies up to 2.5 GHz, network of the 5th generation (5G) will work in the frequency range from 24 to 72 GHz. It will allow data transfer speed up to 20 gbps (gbps is the abbreviation of gigabits per second). Filters for such high frequencies require among others materials tuning of the permittivity using high electric field and low dielectric losses.
The research team of Stanislav Kamba, in collaboration with American and German colleagues, succeeded in developing a new material with such properties. It consists of a succession of atomic layers of SrTiO3, BaTiO3 and SrO (see figure below).
The layers were deposited using molecular beam epitaxy on DyScO3 substrate, which induces a mechanical strain of about 1%. Today’s best microwave tunable dielectric parameters were achieved in films of (SrTiO3)5(BaTiO3)SrO. The Czech team participated mainly in the characterization of the thin films in the terahertz (1012 Hz) frequency range, in the explanation of the low dielectric losses and of the high tunability of the permittivity. Results were published on 23rd December 2019 in the journal Nature Material.
Schema of crystal structures of investigated (SrTiO3)n-1(BaTiO3)1SrO films and their view in scanning transmission electron microscope. The best microwave and terahertz properties were achieved in the films with n = 6. Yellow octahedra depict TiO6 layers, green and red points mark atoms of Sr and Ba.
Institute of Physics of the Czech Academy of Sciences
kamba [at] fzu [dot] cz,
tel. +420 266 052 957,
ORCID ID: https://orcid.org/0000-0003-4699-869X
N.M. Dawley, E.J.Marksz, A.M. Hagerstrom, G.H. Olsen, M.E. Holtz, V. Goian, C. Kadlec, J. Zhang, X. Lu, J.A. Drisko, R. Uecker, S. Ganschow, C.J. Long, J.C. Booth, S. Kamba, C.J. Fennie, D.A. Muller, N.D. Orloff and D.G. Schlom, Nature Materials, https://doi.org/10.1038/s41563-019-0564-4