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Materials Science and Engineering B
journal homepage: www.elsevier.com/locate/mseb
Enhance of electrical properties of resistive switches based on Sr0.1 Ba0.9 TiO3 and TiO2 thin ﬁlms by employing a Ni–Cr alloy as contact
E. Hernández-Rodríguez a,∗ , A. Márquez-Herrera a , M. Meléndez-Lira b, M. Zapata-Torres a
Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del IPN, Legaria #694 Col. Irrigación C.P., 11500 México D.F., Mexico Departamento de Física, CINVESTAV-IPN, Apartado Postal 14-740, 07000 México D.F., Mexico
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We have investigated the electric-ﬁeld-induced resistance-switching phenomena of ReRAM cellsbased on Sr0.1 Ba0.9 TiO3 and TiO2 thin ﬁlms fabricated by rf-sputtering technique. Thin ﬁlms were sandwiched between Pt, Ti and nichrome bottom electrode and Cu top electrode. The I–V measurements at room temperature are non-linear and hysteretic. Cells based on Sr0.1 Ba0.9 TiO3 present a unipolar resistanceswitching phenomenon and it is symmetric with respect to the voltage polarity, while cellsbased on TiO2 have a bipolar resistance-switching with asymmetric behavior. From the I–V measurements we demonstrated that the nichrome enhances the resistance-switching characteristics of the cells. A reduction of the voltage needed to achieve the HRS–LRS and LRS–HRS transitions are found and a very clear transition between these states is accomplished, in comparison with ReRAM cells fabricated withPt and Ti electrodes, whose voltage values are large and no clear transitions are presented. This improvement in resistance-switching behavior can be explained due to O2 vacancies formed in the interface because higher afﬁnity for oxygen of nickel and chromium. © 2010 Elsevier B.V. All rights reserved.
Article history: Received 17 March 2010 Received in revised form 13 May 2010 Accepted 19 May2010 Keywords: Oxides Metal–insulator–metal structures Electrical measurements Sputtering
Electric-ﬁeld-induced switching of resistance is very promising for potential applications in future high-performance non-volatile memory, known as resistance random access memory (ReRAM) [1,2]. ReRAM has several advantages, such as low-power consumption, high operation speed, long retention time, andespecially due to its three-dimensional multistack structure . This resistanceswitching behavior has been reported in various materials, such as metal oxides [4–9] and transition metal perovskites [10,11]. Many models were proposed such as the modiﬁcation of the Schottky barrier height by trapped charge carriers , formation of a conductive ﬁlamentary path , electrical-ﬁeld-inducedmigration of oxygen vacancies , carriers tunneling between crystalline defects , etc. However, much research is still required, from which the reversible transition mechanisms can be investigated deeply and the memory performance can be optimized. In attempt to optimize resistive switching, in this work we proposed the nichrome as suitable electrode because it fulﬁlls the requirements forconstruction of ReRAM memories, such as thermal stability  and good adhesion provided by chromium , and in contrast to Pt, Al, Cu, Ag and Au electrodes, nichrome has low price. ReRAM cells were prepared with Sr0.1 Ba0.9 TiO3 (BST) and TiO2 thin ﬁlms using nichrome as the bottom electrode and Cu as the top electrode and their resistive switching were compared with cells using Pt and
∗Corresponding author. Tel.: +52 555 7296000. E-mail address: email@example.com (E. Hernández-Rodríguez). 0921-5107/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2010.05.017
Ti as bottom electrodes prepared using the same method and under same deposition conditions. Sr0.1 Ba0.9 TiO3 and TiO2 thin ﬁlms were fabricated by rfmagnetron sputtering in an Ar/O2 plasma. The...