Effects of post‐growth annealing on physical properties of SrRuO₃ thin film grown by MOCVD

Abstract

6392 3003We report on the annealing effects on strontium ruthenate thin films deposited on SrTiO 3 using liquid-delivery metalorganic chemical vapor deposition (MOCVD). The results of high resolution X-ray diffraction (HR-XRD), Raman spectroscopy, atomic force microscopy (AFM), and electrical resistivity, before and after a post-growth annealing process were analyzed and compared. XRD and Raman spectroscopy for the asdeposited film revealed that the film had c-axis orientation and contained RuO 2 as secondary phase. Single phase SrRuO 3 could be obtained by annealing the film at 700 8C. Annealing at higher temperatures up to 850 8C leads to ruthenium deficiency, which is revealed by an increase in the out-of-plane lattice parameter, while at even higher annealing temperatures a decrease in the outof-plane lattice parameter was detected might be due to diffusion of Ti from the substrate. The electrical resistivity increased with increasing annealing temperature up to 950 8C and showed typical metallic temperature dependence, while for the film annealed at 1000 8C a semiconductor-like behavior was observed.

Structural and transport properties of SrRuO3 thin films grown by MOCVD on (001) SrTiO3 substrates: The role of built-in strain and extra phases

“…The reduced resistivity value for sample 2 is caused by the existence of the RuO 2 (bulk RuO 2 has a resistivity of = 35 cm [26]) and Ru ( = 12 cm [27]) impurity phases. This is in agreement with our recent observation that the anneal-related loss of the RuO 2 impurity phase leaves a stoichiometric SrRuO 3 layer of higher resistivity [15]. This observation is also consistent with the results of Lee and Tsai [14], who found that the sheet resistivity of SRO thin films decreases with the increase of the ruthenium content by changing the chemical ratio of Ru/(Sr + Ru) and, finally, the Curie transition kink even vanishes.…”

“…The reduction of the vertical lattice parameter for sample 3 is caused by partial plastic relaxation of the layer due to defects which are induced by the incorporation of the extra phase Sr 3 Ru 2 O 7 and the low O 2 supply during deposition. On the other hand, the slight increase of the lattice parameter of sample 3 in comparison with sample 2 could be caused by Ru-deficiency, as observed recently [15]. Dabrowski et al [18] also reported that Ru vacancies decrease the average interatomic Ru-O distance and rotation of the RuO 6 octahedra as Sr atoms relax towards the Ru vacancy increases the unit cell volume.…”

“…We have previously reported on the effect of post-growth annealing on SrRuO 3 MOCVD films containing RuO 2 as an extra phase [15]. The main results were that, first, single phase SrRuO 3 could be obtained by annealing the film at 700 • C while, second, a thermal annealing at higher temperatures, up to 850 • C, led to ruthenium deficiency.…”

Origin of abnormal structural transformation in a (BiPb)FeO3/SrRuO3/SrTiO3 hetero-structure probed by Rutherford backscattering

“…While Raman scattering has been employed to investigate the phase transformation and soft modes in the bulk BiFeO 3 , Raman spectra from (BiPb)FeO 3 layers are in general difficult to obtain since an underlying perovskite SrRuO 3 /SrTiO 3 structure overwhelms the scattering signal emanating from the top (BiPb)FeO 3 layers. By subtracting the contributions arising solely from the SrRuO 3 /SrTiO 3 structure, it is possible to obtain the contribution of the (BiPb)FeO 3 layer in the Raman signal 17 . Figure 1a shows one of the representative Raman spectra of the (BiPb)FeO 3 /SrRuO 3 /SrTiO 3 heterostructure grown at T g  = 650 °C ( x ) as well as the base SrRuO 3 /SrTiO 3 ( y ) structure.…”

Electronic band structure of (111) SrRuO3 thin films: An angle-resolved photoemission spectroscopy study

“…Overall, both fitting MDC dispersion and analysis of real and the imaginary part of the self-energy consistently points towards the existence of a kink around -44 meV. Remarkably, the position of this kink is comparable to the energy of the B 2g phonon mode (354 cm −1 = 43.9 meV) that corresponds to the motion of apical oxygen ions 41 . Meanwhile, in (001) SRO films, the kink is attributed to the coupling between electron and in-plane oxygen vibration-driven A g (540 cm −1 = 67 meV) mode 23 .…”