CrSi and CrSi2 films grown by MBE on Si(111) and Si(001) substrates at different Cr to Si flow’s ratio: Crystal and phonon structure and thermoelectric properties

Thin (16.2–30.8 nm) and thick (47.8–261.0 nm) nanocrystalline films of CrSi, CrSi 2 , and their mixtures were grown by molecular beam epitaxy (MBE) at temperatures of 350–450 °C on Si(001) and Si(111) substrates. Based on the results of the crystal structure studies, the samples were divided into three groups: (1) CrSi 2 films; (2) CrSi films and (3) films containing two phases CrSi and CrSi 2 .The formation of silicide phases was confirmed by Raman scattering spectroscopy data at a laser wavelength of 633 nm. A critical thickness of chromium silicide films (30.8 nm) was established, below which the 2D thermoelectromotive force model does not provide correct values of film’s thermoelectric parameters. In the CrSi 2 film (261 nm), the Seebeck coefficient (190 μV/K) and power factor (0.4 mW/(m·K²)) were achieved at 420 K. For thick (63–81.6 nm) CrSi films, the maximum Seebeck coefficient (50 μV/K) and power factor (1.0–1.3 mW/(m·K²)) are observed at T = 450 K. It has been shown for the first time that the addition of CrSi 2 phase to a c-CrSi one leads to an increase in the Seebeck coefficient (70–75 μV/K) and power factor (1.69 mW/(m·K²)) at temperature range of 200–420 K. A comparison with other silicide thermoelectrics showed that this is due to a simultaneous increase in conductivity in the c-CrSi phase and an increase in the Seebeck coefficient in nanocrystalline CrSi 2 . The obtained power factor values make c-CrSi/CrSi 2 films a promising material for room temperature thermoelectric applications.