LaNiO₃ films with tunable out-of-plane lattice parameter and their strain-related electrical properties

Abstract

97 39286LaNiO 3 (LNO) thin films were grown using pulsed laser deposition. The c-axis, i.e., out-of-plane lattice parameter of the films was controlled reproducibly by using different substrate materials and by variation of oxygen partial pressure and growth temperature. The out-of-plane (c-axis) strain of LNO deposited on LaAlO 3 with increasing oxygen pressure changed from positive to negative. All the films show an excellent metallic conductivity with positive resistivity temperature coefficient. Lowest resistivity was about 300 mV cm. At high and low temperatures, the resistivity is explained by electron-phonon scattering and electron-electron interaction, respectively. In addition, the resistivity shows a clear dependence on the c-axis strain of LNO films. With increasing strain, the resistivity increases. However, this effect is much more pronounced for negative c-axis strain.Strain-dependent resistivity of LNO films on LAO at the indicated measurement temperatures. The inset is a typical AFM image of the LNO film surface.1 Introduction The conduction band of perovskite nickelates (RNiO 3 , where R ¼ rare earth) is formed by the overlap of the Ni 3d orbitals and the O 2p orbitals. Most perovskite nickelates exhibit a temperature-driven metal-toinsulator transition [1,2], which is related to the strongly distorted perovskite structure and the size of the rare-earth ion R [3, 4]. However, LaNiO 3 (LNO) is the only member that remains metallic down to the lowest temperatures [5]. For this reason, LNO is an excellent candidate for use as an electrode in oxide electronics, in particular at low temperature. The primitive cell of bulk LNO is rhombohedral with angle a ¼ 60.498. It is reasonably well approximated by a pseudocubic cell with a ¼ 0.3838 nm. Several efforts have been undertaken to prepare LNO thin films by sputtering [6], pulsed laser deposition (PLD) [7], molecular beam

Multiple strain-induced phase transitions inLaNiO3thin films

“…The in-plane lattice parameters (a) in Table I [25] and Wei et al [26] and extensively discussed for manganite thin films [27], which are both consistent with the ω scans presented above. These features can also be identified in the 35 nm films.…”

“…In Figs , it can be appreciated that the q z values are smaller than those of the substrate (brightest spots), and a double-peak associated with the film emerges [25,26]. The in-plane lattice parameters (a) in Table I [25] and Wei et al [26] and extensively discussed for manganite thin films [27], which are both consistent with the ω scans presented above.…”

Modeling the conductivity around the dimensionality-controlled metal-insulator transition in LaNiO3/LaAlO3 (100) superlattices

“…The epitaxial LNO films show (100) out-of-plane crystalline orientation and in-plane epitaxial relationship similar to those of our previous work. 16 Combining the optimized LNO and LAO growth, [LNO/LAO] 10 (100) SLs were fabricated. Fig.…”

Confinement-driven metal-insulator transition and polarity-controlled conductivity of epitaxial LaNiO3/LaAlO3 (111) superlattices

“…Hence, a possible reason for the enhancement of resistivity of SLs on STO could be the slight expansion of their in-plane lattice constants, which leads to larger Ni-O-Ni bond lengths. 22 However, the transport behavior of SLs on LAO substrate cannot be described by the 2D Mott VRH model because the calculated hopping distance is much smaller than the localization length. The criterion R hop /a > 1 is not fulfilled for [6/7] 10 SL on LAO which undergoes a metal-insulator transition with the sheet resistance around 25.8 kX/(.…”

“…Motivated by the above mentioned, promising theoretical predictions, 11,12 together with recent experimental progress in epitaxial growth of LNO-based films and SLs, 19,22 we present here (111) [LNO m /LAO n ] l SLs (m and n indicate the number of unit cells, respectively, thereafter referred to as [m/n] l ). The stacking periodicity is repeated l times to adjust the total superlattice thickness.…”