Large Magnetoresistance in C60-based spin-valve transistors

A. BEDOYA-PINTO; M. GOBBI; F. GOLMAR; R. LLOPIS; F. CASANOVA; L. HUESO

Donostia

Workshop; WORKSHOP ON NANOMAGNETISM AND SPINTRONICS; 2012

CIC nanoGUNE

Organic semiconductors (OS) have emerged as a promising material class for spintronic applications [1], mainly due to their weak spin relaxation mechanisms which result in long spin lifetimes. While recent efforts have focused on the spin injection and transport in organic semiconductors, there are few reports about the intrinsic properties of the molecular material. In particular, the fact that OSs behave as ordinary semiconductors has not been yet fully exploited in hybrid semiconductor spintronic applications. In this work, we report the achievement of a spin-valve transistor (SVT) which employs C60 as a semiconducting collector. The SVT represents one of the most successful spintronic devices based on the combination between ferromagnetic materials and semiconductors [2]. SVTs are 3 terminal devices with the same scheme of a metal base transistor: a hot electron current is injected into the device by an emitter, and a ferromagnetic metal base modulates the amount of current reaching the collector. In this configuration, the current can be modulated not only by the applied gate voltage, but also by the magnetic field (magnetocurrent). We show that the C60-based SVT, composed of an Al/Al203/Co/Cu/Py/C60/Al multilayer, perform as state-of-the-art inorganic SVT, with a magnetocurrent (MC) reaching 89% at room-temperature. The MC shows a strong dependence on the bias voltage at the emitter, the latter corresponding to the energy of the injected hot-electrons. Moreover, we show that this MC value can be enhanced by the application of a proper voltage at the collector, reaching in principle an infinite value, with 0 current in the off-state. The energy barrier at the C60/metal interface resembles a conventional Schottky barrier, and its height is determined by measuring the hot-electron emitter voltage as a function of collector current in a three- terminal configuration. These results demonstrate that C60 has the same functionality of an ordinary n- type band-like semiconductor and can be well integrated in further hybrid spintronic devices. References [1] V. A. Dediu, L. E. Hueso, I. Bergenti, and C. Taliani, Nature Materials, 8 707 (2009) [2] R. Jansen, Journal of Physics D: Applied. Physics 36 R289 (2003)