Fig. 1: Sample structure and enhanced THz emission of Pt1-x(MgO)x/CoFeB heterostructures.
a Schematic diagram of our spintronic terahertz emitter in the experiment, with femtosecond laser incident from the substrate side along the z-direction and the applied magnetic field along the x-direction. b XRD θ-2θ patterns for Pt1−x(MgO)x single layer with different x. c X-ray photoemission spectroscopy (XPS) for Pt 4 f peaks in a Pt0.93(MgO)0.07 single layer. d Cross-sectional high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image and energy-dispersive x-ray spectroscopy (EDS) mapping of Pt, Mg, and O. The white line in the lower left corner is the scale, and the length of the white line corresponds to the actual length of 10 nm. e Cross-sectional high-resolution transmission electron microscopy image of a magnetic stack of Pt0.93(MgO)0.07(5)/ CoFeB(4)/MgO(1.5). The white line in the lower left corner is the scale, and the length of the white line corresponds to the actual length of 10 nm. f THz waveforms generated by Pt1-x(MgO)x(3)/CoFeB(4) structure with different MgO content. g Comparison between the time-domain THz signal from the Pt0.93(MgO)0.07(3)/CoFeB(4) (solid red line), Pt(3)/CoFeB(4) (deep red dotted line) and that from the ZnTe crystal (light red dash-dot line), at the same pump power. h Fourier spectra obtained from the Pt0.93(MgO)0.07(3)/CoFeB(4) (solid red line), Pt(3)/CoFeB(4) (deep red dotted line) and ZnTe crystal (light red dash-dot line). The data in f are shifted horizontally for clarity.
