Metallic nanoparticles in a polymeric matrix: Electrical impedance switching and negative differential resistance

Future organic electronic and nanoelectronic applications will need organic memories as the devices and circuits get more complex. However, until very recently there has been limited research on the subject. Recent discoveries allow organic bistable devices to be used for nonvolatile memory applications [1]. We present a memory device concept that utilizes metallic nanoparticles dispersed in an insulating matrix. The simple structure allows one-step active layer deposition and thus paves the way for roll-to-roll processing. The main objective of this work is to develop memory units that can be manufactured in a rapid and economical fashion. The printing process offers tools for this purpose, but requires air-stable materials. Thus the use of gold nanoparticles (Figure 1) in a polystyrene matrix is a feasible alternative. However, other materials are also investigated. Figure 1: Gold nanoparticle with polystyrene tails (left) and a TEM picture, which shows that the particles are evenly distributed in the polymer matrix (right). Even distribution of nanoparticles is a requirement for optimal device operation. The TEM picture in Figure 1 shows that the gold particles spread evenly in the matrix. A resistance switching phenomenon can be observed in this nanoscale composite when contacted in a sandwich structure. Although the switching is still inconsistent, the negative differential resistance is consistent, which can also be utilized in a memory device. (Figure 2) Figure 2: I-V characteristics of a Au-particle memory device. 1. Himadri S. Majumdar, Jayanta K. Baral, Ronald Österbacka, Olli Ikkala, and Henrik Stubb, Fullerene-based bistable devices and associated negative-differential-resistance effect, Organic Electronics 6 (2005) 188-192.