Programmable Conductance Switching and Negative Differential Resistance in Nanoscale Organic Films
- PDF / 176,881 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 56 Downloads / 183 Views
I9.34.1
Programmable Conductance Switching and Negative Differential Resistance in Nanoscale Organic Films Troy Graves-Abe and J.C. Sturm Department of Electrical Engineering Princeton Institute for the Science and Technology of Materials Princeton University Princeton, NJ 08544, U.S.A. ABSTRACT Thin (12-nm) self-assembled films of the insulating molecule 11-mercaptoundecanoic acid (MUA) were contacted by gold electrodes in a sandwich structure. Current-voltage scans of the resulting devices revealed symmetric negative differential resistance (NDR) with peaks at ±3 V and large peak current densities of up to 104 A/cm2. Devices could be programmed reversibly into nonvolatile high- and low-conductance states by applying 1-ms voltage pulses of 4 V and 10 V, respectively; this conductance could be probed non-destructively with voltages below 2.5 V. A conductance ratio of 103 between the high- and low-conductance states was measured. The NDR is attributed to the dynamic alteration of the device conductivity as the voltage is scanned. Devices fabricated with one gold and one aluminum electrode displayed NDR only for positive bias on the gold electrode, which supports a model in which the observed programming and NDR is due to the movement of gold in the film leading to the formation and destruction of conductive pathways through the insulating layer. INTRODUCTION The demand for increasingly sophisticated mobile electronic devices has led to great interest in new forms of nonvolatile electronic memory to overcome the performance limitations of the dominant CMOS-based memory technologies [1,2]. Recently, a number of memory technologies based on organic compounds have been demonstrated [3]. Organic devices have several features, including low fabrication costs and material properties that can be tailored to meet specific requirements, that make them attractive candidates for next-generation memory arrays. In this work, we report on novel organic devices that display negative differential resistance (NDR) and programmable, non-volatile conductance switching with characteristics that are promising for potential memory application. The devices consist of a thin (12-nm) film of the insulating molecule 11-mercaptoundecanoic acid (MUA) sandwiched between metal electrodes. The relationship between the NDR and a related programmable conductance switching was investigated with pulsed and low-frequency current-voltage measurements. We also present current-voltage measurements on devices made with different electrode metals. EXPERIMENTAL DETAILS Devices were fabricated by depositing a thin film of gold onto a silicon substrate by thermal evaporation (with a 5-nm titanium layer for adhesion). Multiple self-assembled layers of 11mercaptoundecanoic acid (MUA) (purchased from Aldrich) were grown on the gold film by alternate immersions in millimolar ethanol solutions of MUA and Cu(ClO4)2 (purchased from
I9.34.2
Aldrich), resulting in repeated bi-layers of MUA and copper [4,5]. Following the growth of 7-8 layers of MUA (total thickness
Data Loading...
