Graphene improves ZnO:Sm nanocomposite dielectric conductivity by up to seven orders of magnitude

Researchers at Romania’s National Institute for Research and Development in Microtechnologies (IMT-Bucharest), working with the “Petru Poni” Institute of Macromolecular Chemistry in Iasi, the Horia Hulubei National R&D Institute for Physics and Nuclear Engineering’s Extreme Light Infrastructure-Nuclear Physics facility, the National University of Science and Technology POLITEHNICA Bucharest, and Hellenic Mediterranean University in Greece, have shown that adding small amounts of graphene to samarium-doped zinc oxide (ZnO:Sm) nanocomposites raises dielectric conductivity by up to seven orders of magnitude, from around 10⁻⁹ S/cm for pure ZnO to 10⁻³–10⁻² S/cm at the highest graphene loadings tested.

ZnO is a widely used wide-bandgap semiconductor (~3.37 eV) valued for its thermal and chemical stability, low cost, and non-toxicity, with applications spanning optoelectronics, energy, environmental remediation, antibacterial textiles, and pharmaceuticals. Its practical use in electronic, energy, and thermoelectric applications, though, is limited by relatively low electrical conductivity stemming from a low charge-carrier concentration. Researchers have previously addressed this through doping, engineered oxygen vacancies, nanostructuring, and surface functionalization. Doping with trivalent rare-earth ions such as Sm3+ improves conductivity by inducing structural defects and oxygen vacancies that modulate carrier concentration, while separately, incorporating graphitic carbon into ZnO matrices has been shown to improve charge transport and suppress electron-hole recombination, given graphene’s high carrier mobility, large surface area, and strong conductivity. According to the authors, combining rare-earth doping with graphene in a single ZnO system has been little studied, and no prior work had looked specifically at electrospun Sm-doped ZnO modified with low graphene loadings.

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