Transport properties across the La2∕3Ca1∕3MnO3∕SrTiO3 heterointerface

Abstract

The transport properties across La 2/3 Ca 1/3 MnO 3 / SrTiO 3 ͑LCMO/STO͒ heterostructures with different thicknesses of the STO insulating barrier have been studied by using atomic force microscopy measurements in the current sensing ͑CS͒ mode. To avoid intrinsic problems of the CS method we have developed a nanostructured contact geometry of Au dots. The conduction process across the LCMO/STO interface exhibits the typical features of a tunneling process. The analysis of I͑V͒ curves by using the Simmons model allows us to determine the barrier height ͑ 0 Ϸ 0.6 eV͒ of STO barriers. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2833760͔Complex oxides have attracted much interest recently because they show a broad spectrum of intrinsic functionalities that allow envisaging the development of a new generation of oxide-based electronic, magnetic, and magnetoresistive devices. 1,2 Among them manganese perovskites occupy a prominent place due to their very peculiar properties, such as the colossal magnetoresistive response and the half metallic character. Nevertheless, the successful implementation of oxide-based devices requires preserving bulklike magnetic and transport properties at surfaces and interfaces. Thus, the physics and chemistry of surfaces and interfaces become a subject of primary interest since they can drastically modify magnetic and electronic properties reducing the performances of thin films and multilayered structures due to chemical inhomogeneity, strain, charge transfer, or spin exchange interactions. 3,4 Interfacial effects are especially relevant in manganitebased magnetic tunneling junctions where not only electronic but also magnetic properties are important. Due to the strong orbital-lattice coupling lattice strain effects may be very important in manganites 5 thus, playing a relevant role on the degradation of the magnetic properties. 6 However, other causes, such as polar discontinuity across the interface, may also be important. 7 In this sense, recent theoretical studies predict the appearance of electronic phase segregation with the formation of a spin-and orbital-ordered insulator phase at the manganite-insulator interface due to the reduction of carriers at the interface. 8 In this work we have carefully analyzed the transport properties across SrTiO 3 ͑STO͒ insulating barriers on top of La 2/3 Ca 1/3 MnO 3 ͑LCMO͒ films at room temperature by using atomic force microscopy ͑AFM͒ working in the current sensing ͑CS͒ mode. To avoid intrinsic problems of the CS method we have developed a nanostructured contact geometry of Au dots. The conduction process across the LCMO/ STO/Au heterostructure exhibits the typical features of a tunneling process. The analysis of I͑V͒ curves by using the Simmons model allows us to determine the barrier height, 0 Ϸ 0.6 eV, in good agreement with previous reports for STO tunneling barriers.LCMO epitaxial thin films of about 60 nm thick have been grown by rf sputtering on top of ͑001͒ STO substrates ͓T D = 800°C and a pressure of 330 mTorr ͑Ar+ 20% O 2...

Polymer assisted deposition of epitaxial oxide thin films

“…Jain et al 107 2) the height of the barrier, E=0.4 eV. 108 The latter value was very close to the obtained in barriers of STO deposited by PLD 110 , demonstrating that ultra-thin layers of LCO prepared by PAD retained a good insulator character and can be used as tunneling barriers in combination with LSMO at room temperature.…”

“…This is an important drawback for the stacking of these materials in a multilayer heterostructure. However, c-axis oriented single phase of nominal composition of Ca 115 The growth of the ordered structure from the substrate interface is due to the bottom-up slow crystallization of an epitaxial rock-salt layer on top of the LAO substrate, with a relationship (001) BiORS||(001)LAO; [110]BiORS ||[100]LAO. Int.…”

Tunnel Conduction in Epitaxial Bilayers of Ferromagnetic LaCoO3/La2/3Sr1/3MnO3 Deposited by a Chemical Solution Method

“…This problem is overcome using the nanostructured contact geometry so that injected current depends only on the size of the Au dots. Conductive AFM measurements using contact geometry have been achieved so far in Au/LCMO interfaces fabricated by sputtering. − …”

Effect of Incident Light on Transport Properties of Pulsed Laser Deposited Manganite Thin Films

“…The energy of UV light is ~ 4.48 eV which is higher than the barrier height of LCMGO/Si p-n junction. The barrier height of LCMGO/Si p-n junction is ~3.9 eV, calculated using ø0=WLCMGO− øSi [26]. Where, WLCMGO is the work function of the LCMGO (~ 4.88 eV) and øSi is the electron affinity of Si (~0.9 eV).…”

“…There are various theoretical models and mechanisms available to understand the charge transport behaviour of the materials, thermionic emission: I = AT 2 exp (-[{ΦBq (qV / 4πεd) 1/2 } /KT] [14], hopping conduction mechanism: I α V [14], Space Charge Limited conduction (SCLC) mechanism: ISCLC = 9μεrε0θ V 2 /8d 3 [26], (iv) Schottky barrier: I = AT 2 exp (-[ψ-(q 3 V / 4πε0k) 1/2 / KBT [21], and (v) Simmons model : I α V n [27] etc. The Simmons model is best fitted in reverse bias mode of I-V characteristics for all the grown thin films.…”