Growth, characterization and electrical properties of epitaxial erbium silicide

Abstract

Molecular beam epitaxy (MBE) growth of erbium silicide (ERS) thin films on (111) silicon surface and their characterization are discussed. We demonstrated that continuous and monocrystalline films can be prepared by co-deposition of both erbium and silicon in a 1:2 ratio, on either high or room temperature (RT) silicon substrates, followed by solid phase epitaxy (SPE). Using X-ray diffraction (XRD), transmission electron microscopy (TEM), transmitted electron diffraction (TED) and Rutherford backscattering spectrometry (RBS) we identified the silicide as ErSi 2− x , i.e. erbium disilicide with a large concentration of vacancies. The films were shown to be monocrystalline with possible vacancy ordering. The Si/ErSi 2 /Si structures were subsequently prepared and shown to have a minimum RBS channelling yield χ min value of about 5% for erbium in ErSi 2− x and of 7% for the overgrown silicon. The resistivity of epitaxial ErSi 2− x films was found to be about 35 micro ohm cm at RT. The Hall coefficient was found to change sign (at about 150 K) which was explained in terms of a two-band conduction model. At about 4.5 K both resistivity and Hall coefficient exhibit anomalies associeted with magnetic ordering of erbium atoms demonstrated by divergence of the magnetic susceptibility. The Schottky diodes made on p-silicon show excellent rectifying properties, with a barrier height of 0.74±0.01 eV. The diodes on n-silicon were ohmic at RT and rectifying at low temperatures with a barrier height of 0.29±0.01 eV. Possible electronic applications of ERS are also discussed.