Abstract
By means of the state-of-the-art reactive oxide molecular beam epitaxy, we synthesized (001)- and (111)-orientated polar LaNiO3 thin films. In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO3 and iso-polarity LaAlO3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. For largely polar (111)-orientated films, we showed that iso-polarity LaAlO3 (111) substrate was more suitable than Nb-doped SrTiO3. In situ reflection high-energy electron diffraction, ex situ high-resolution X-ray diffraction, and atomic force microscopy were used to characterize these films. Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO3 based superlattices.
Highlights
Our results show that special attentions need to be paid to grow high-quality oxide films with polar orientations, which can prompt the explorations of all-oxide electronics and artificial interfacial engineering to pursue intriguing emergent physics like proposed interfacial superconductivity and topological phases in LaNiO3 based superlattices
LNO is widely explored as conductive electrode materials[10,11,12,13] as well as building bricks of various superlattices in pursuing all-oxide electronics and emergent physics.[14,15,16,17]
Though with the similar nominal thickness, diffraction peaks of the film on LAO is sharper than these on niobium-doped SrTiO3 (Nb-STO): the (111) peak full width at half maximum (FWHM) of the film on LAO was estimated to be around 0.91◦ by Gauss fitting, while that of the film on Nb-STO was around 1.53◦. These observations suggest that LAO substrate is more suitable than Nb-STO in terms of growing (111)-orientated LNO films, which can be understood in regard to polar continuity on LAO and discontinuity on Nb-STO [Fig. 5(a)]
Summary
Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy In order to avoid the interfacial reconstructions induced by polar catastrophe, screening metallic Nb-doped SrTiO3 and iso-polarity LaAlO3 substrates were chosen to achieve high-quality (001)-orientated films in a layer-by-layer growth mode. High-quality LNO films were achieved via sputtering[8,9] and pulsed laser deposition (PLD).[15,17,25,26] Compared to these two techniques, the state-of-the-art reactive oxide molecular beam epitaxy (OMBE) is a low-energy deposition method, and can control the growth at atomic scale which can essentially allow the fabrication of high-quality thin films and superlattices with sharp interfaces.[27,28,29,30,31]
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