Epitaxial La_0.7Sr_0.3MnO₃ thin films grown on SrTiO₃ buffered silicon substrates by reactive molecular‐beam epitaxy

Abstract

La 0.7 Sr 0.3 MnO 3 (LSMO) thin films (with a thickness of 10, 20, 60, 75, and 100 nm) were grown on SrTiO 3 (STO)-buffered silicon (001) substrates by reactive molecular-beam epitaxy. Xray diffraction (XRD) revealed the heterostructures to be fully epitaxial with orientation relationship (001) LSMO jj (001) STO jj (001) Si and [100] LSMO jj [100] STO jj [110] Si. Root mean square roughness was about 0.5 nm as measured by atomic force microscopy (AFM) for films of 10-75 nm thicknesses, and about 1 nm for the 100 nm thick LSMO film.Normalized Hooge parameters in the (0.95 AE 0.25) Â 10 À30 -(3.41 AE 0.71) Â 10 À30 m 3 range were measured at 300 K, which are comparable to the noise level typically measured in the best LSMO films on (001) STO substrates. Overall these very low noise LSMO films with thicknesses in the 10-100 nm range grown on STO/Si showed properties rivaling those of LSMO films deposited on (001) STO single crystal substrates, thus demonstrating their potential use for LSMO-based devices on silicon substrates.

Enhanced electrical and magnetic properties in La0.7Sr0.3MnO3thin films deposited on CaTiO3-buffered silicon substrates

“…Insulating behavior over the whole temperature range is observed. This leads us to conclude that both the electrical and magnetic properties are enhanced compared to those reported in high epitaxial quality La 0.7 Sr 0.3 MnO 3 films deposited on SrTiO 3 buffered Si substrates, 39 where T MI and T C values were 350 K and 330 K, respectively. We ascribe the enhancement of these properties to the fact that the La 0.7 Sr 0.3 MnO 3 cell is under compressive in-plane strain on CaTiO 3 /Si as predicted by Millis et al 57 and also experimentally observed in Ref.…”

“…The normalized Hooge parameters α H /n was then measured to be (4.2 ± 0.6) × 10 −31 m 3 at 300 K, which is about two times lower than the one measured in La 0.7 Sr 0.3 MnO 3 films of comparable thickness deposited on SrTiO 3 /Si with α H /n values of (9.8 ± 0.6) × 10 −31 m 3 at 300 K and only two times higher than the one measured in La 0.7 Sr 0.3 MnO 3 films of comparable thickness deposited on SrTiO 3 single crystal substrates with α H /n values of (2.47 ± 0.6) × 10 −31 m 3 . 39,58,59 In conclusion, we have shown the promise of epitaxial (100) p -oriented CaTiO 3 as a buffer layer for the integration of functional oxides having the perovskite structure with silicon. Specifically, we have grown high-quality epitaxial La 0.7 Sr 0.3 MnO 3 films on CaTiO 3 /Si.…”

“…This is the lowest value reported for manganite films of comparable thickness grown on silicon substrates. 39,[44][45][46][47] The microstructure of the La 0.7 Sr 0.3 MnO 3 /CaTiO 3 /Si epitaxial heterostructure was studied by TEM. Figure 5(a) shows the overall microstructure of the specimen, including an amorphous SiO x layer, which formed in situ by the diffusion of oxygen through the growing epitaxial film and oxidation of the underlying silicon substrate during the film growth.…”

“…Electrical low-frequency noise measurements were performed at 300 K in the same way as previously described. 39,58,59 The La 0.7 Sr 0.3 MnO 3 /CaTiO 3 /Si thin film was patterned by UV photolithography and argon ion etching to form a 50 µm wide and 150 µm long strip, which includes two gold pads for supplying the current and two gold pads at which the voltage was measured in a four-probe geometry. bias currents.…”

“…We demonstrate here that La 0.7 Sr 0.3 MnO 3 films deposited on CaTiO 3 /Si indeed showed enhanced electrical properties (e.g., lower electrical resistivity and 1/ f noise, and high temperature of the metal-to-insulator transition) as well as enhanced magnetic properties (higher Curie temperature) compared to other epitaxial La 0.7 Sr 0.3 MnO 3 thin films deposited on buffered silicon substrates. [33][34][35][36][37][38][39] We grew epitaxial CaTiO 3 thin films on (100) Si by reactive molecular-beam epitaxy (MBE). The native SiO 2 layer was removed from the (100) Si substrate using a strontium assisted process.…”