Mechanically exfoliated low-layered [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$]: A single-crystalline p-type transparent conducting oxide

Abstract

Transparent conducting oxides (TCOs) are essential components of optoelectronic devices and various materials have been explored for highly efficient TCOs having a combination of high transmittance and low sheet resistance. Here, we focus on a misfit thermoelectric oxide [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$] and fabricate the transparent low-layered crystals by a mechanical tape-peeling method using the single-crystalline samples. From the transmittance measurement, we find that the thickness of low-layered samples is several orders of hundred nanometers, which is comparable with the estimation from the scanning electron microscopy images. Compared to the previous results on the polycrystalline and $c$-axis oriented transparent films, the electrical resistivity is reduced owing to the single-crystalline nature. The figure of merit for the transparent conducting materials in the present low-layered samples is then evaluated to be higher than the values in the previous reports. The present results on the low-layered single-crystalline [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$] may offer a unique class of multi-functional transparent thermoelectric oxides.

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References in corpus (3)

• Electric Field Effect in Atomically Thin Carbon Films
• Crossover from itinerant to localized states in the thermoelectric oxide [Ca${}_2$CoO${}_3$]${}_{0.62}$[CoO${}_2$]
• Nonlinear transport associated with spin-density-wave dynamics in Ca${}_3$Co${}_4$O${}_9$