CPM Seminar

Oxide nanoelectronics for non-volatile memories

Andreas Rüdiger

Laboratory of ferroelectric nanoelectronics
INRS-EMT

The commercial success of oxide electronics has been primarily driven by their dielectric properties as in high performance capacitors or tunable dielectrics. More recently, ultrafast ferroelectric RAM (FeRAM) became available based on the hysteretic remnant polarization in ferroelectrics. Despite the fact that the charge transport properties of oxides can be tuned from wide band-gap insulators to superconductors it has not been until lately that these properties are considered for resistive RAMs (RRAM) in which information is reversibly stored in two distinct resistance states.

In order to determine the scaling of the memory properties [1,2], the microscopic mechanism needs to be quantitatively understood which requires a careful local investigation of the electronic properties as only possible by scanning probe techniques. While ferroelectric properties are investigated down to a lateral resolution of a few nanometers by piezoresponse force microscopy [3] and related techniques, the charge transport properties are monitored by conductive AFM [4]. We will address recent findings on the electronic properties of binary and ternary oxides for resistive and FeRAM, respectively, and on systems where both effects are observed simultaneously [5]. Our focus is on the scaling limits of both material systems as well as on the fundamental resolution limits of scanning probe for this purpose.

[1]A. Rüdiger, T. Schneller, A. Roelofs, S. Tiedke, T. Schmitz, R. Waser, Nanosize ferroelectric oxides - tracking down the superparaelectric limit, Applied Physics A, 80, 1247-1255 (2005)
[2]R. Waser, A. Rüdiger, Pushing towards the digital storage limit, Nature Materials, 3, 81-82, 2004
[3]S. Clemens, S. R�hrig, A. Rüdiger, T. Schneller, R. Waser, Embedded ferroelectric nanostructure arrays, Nanotechnology, 20 (2009) 075305013109
[4]L. Yang, C. Kuegeler, K. Szot, A. Rüdiger, R. Waser, The influence of copper electrode on the resistive switching effect in TiO₂ thin films studied by conductive force microscopy, Applied Physics Letters, 95 (2009)
[5]A. Petraru, H. Kohlstedt, A. Rüdiger, P. Meuffels, K. Szot, R. Waser Perimeter effect in resistively switching PZT capacitors, Applied Physics Letters, 92 (2008) 062907