Effect of Fe ion implantation on the thermoelectric properties and electronic structures of CoSb(3) thin films

In the present study, thin films of single-phase CoSb(3) were deposited onto Si(100) substrates via pulsed laser deposition (PLD) method using a polycrystalline target of CoSb(3). These films were implanted by 120 keV Fe-ions with three different fluences: 1 × 10(15), 2.5 × 10(15) and 5 × 10(15) ions per cm(2). All films were characterised by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), Rutherford backscattering (RBS) spectrometry and X-ray absorption spectroscopy (XAS). XRD data revealed that the ion implantation decreased the crystalline nature of these films, which are recovered after the rapid thermal annealing process. The Seebeck coefficient S vary with the fluences in the temperature range of 300 K to 420 K, and is found to be highest (i.e., 254 μV K(−1)) at 420 K for the film implanted with 1 × 10(15) ions per cm(2). The high S and low resistivity lead to the highest power factor for the film implanted with 1 × 10(15) ions per cm(2) (i.e., 700 μW m(−1) K(−2)) at 420 K. The changing of the sign of S from negative for the pristine film to positive for the Fe-implanted samples confirm that the Fe ions are electrically active and act as electron acceptors by replacing the Co atoms. XAS measurements confirm that the Fe ions occupied the Co site in the cubic frame of the skutterudite and exist in the 3+ oxidation state in this structure.