Electronic structure of delta-doped La:SrTiO3 layers by hard x-ray photoelectron spectroscopy
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(a) Experimental geometry, including sample configuration with a La0.06Sr0.94TiO3 doped delta layer embedded in undoped SrTiO3. (b) Survey spectra obtained with a photon energy of 4990 eV and covering a range of 0-1000 eV binding energy from a thick 30 nm La-doped STO film (red curve) and from the delta-doped layer of (a) with the same La concentration (blue curve). Various peaks are labeled. The spectra have been offset vertically for clarity. A blowup of the La 3d region for both samples is also shown.
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Core level and valence band spectra of 30-nm-thick La:STO and the delta-doped layer of Fig. 1(a). (a) La 3d, obtained at 4990 eV for the thick sample, and at both 4990 and 3237 eV for the delta-doped layer. Spectra obtained with 4990 eV for (b) Ti 2p, with the inset showing the low-binding-energy Ti3+ features, (c) Sr 3p, and (d) the valence band region. All spectra are normalized to the peak maxima. The La 3d spectra of the delta-doped sample have been generated by subtracting a linear background from the measured spectra. The small differences between the blue spectra in (a) and the other two were found to be a short-term beam instability that led to experimental artifacts in intensity. None of our other data was affected by this problem.
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