We report on the electroforming in resistively switching nanocrosspoint devices made of a reactively sputtered TiO2 thin film between Pt and Ti/Pt electrodes, respectively. As most resistance switching materials, TiO2 needs to be electroformed before it can be switched. This paper presents and compares current and voltage controlled electroforming with regard to the polarity. We show that a current-driven electroforming with negative polarities leads into the switchable high resistive state without need for a current compliance. These devices show an improved stability and reliability in bipolar resistive switching performance.

There is an increasing interest in developing and characterizing multifunctional materials, as they exhibit rich physical and chemical properties and offer exciting opportunities, for example, to miniaturize integrated devices and extend the potential of establishing nanoarchitecture concepts. [ 1 , 2 ] In this context, multiferroic materials [ 3 ] which combine two or more ferroic functionalities are promising for applications in fi elds such as spintronics and non-volatile data storage. [ 4 ] As recently demonstrated [ 5 ] ferromagnetic-ferroelectric multiferroics can be advantageously used to encode the information in electric polarization and magnetization giving rise to a four logic state memory. The coupling between magnetic and electrical properties leads to additional versatility for related devices, such as electric fi eld-controlled magnetic data storage. [ 6 ] The recent emergence of Bi-based double perovskite thin fi lms, such as Bi 2 FeCrO 6 (BFCO) [7][8][9] and Bi 2 CoMnO 6 , [ 10 ] with strong magnetic behavior at room temperature, create opportunities to practically apply multiferroics. In competition with rival technologies, downscaling the feature size of multifunctional materials is an important step to achieve very high-density memory devices. [ 11 , 12 ] However, conventional patterning and lithography techniques applied to these materials with complex multiphase structure often damage or induce changes in stoichiometry, affecting the quality (and thus the properties) of the as-grown fi lm.Non-conventional patterning techniques, such as microcontact printing, [ 13 ] nanoimprint, [ 14 ] and nanostencil patterning, [ 15 , 16 ] are being increasingly explored. Compared to traditional methods (e.g., electron-beam lithography and focused ion beam lithography), they are simpler, faster and even cheaper. In addition, they offer a better process fl exibility and compatibility with several applications, [ 13 ] as they do not require post-deposition etching processes.Here we demonstrate the controlled epitaxial growth by pulsed laser deposition (PLD) of ordered arrays of sub-micrometer BFCO multiferroic structures on niobium-doped SrTiO 3 (Nb-STO) substrates, through a nanostencil, i.e., a shadow mask with nanometer-scale features. We show that the asgrown structures retain their room temperature multifunctional (ferroelectric and magnetic) character even at submicrometer dimensions. Our work represents an important step towards the successful integration of nanometer-scale multiferroic elements in current microelectronics and future nanoelectronics.Growth through a nanostencil allows a simpler parallel and resist-free patterning of complex oxides (as opposed to resistbased methods; see Experimental Section). To obtain large arrays (square millimeters) of multiferroic BFCO nano structures we fi rst optimized the PLD parameters to obtain stoichiometric, epitaxial BFCO multiferroic thin fi lms on single crystal STO substrates, [ 7 , 17 ] and under conditions compatible with stencil technology (e.g....

A novel test facility for the efficient evaluation of microelectromechanical system (MEMS) switches and the development of alternative contact materials is described. The facility utilizes the upper cantilever from commercial MEMS contact switches, and tests these against alternative bottom contact materials within a modified atomic force microscope (AFM). The test closely approximates the real switch, but can accommodate a wider range of test conditions and contact materials. The facility allows alternative contact materials to be easily and quickly incorporated, and therefore evaluated by measuring the number of cycles to failure. The evolution of the wear surfaces of the switch contact materials under test can also be easily examined. In order to demonstrate the facility, the evolution of the contact resistance and wear of a commercial RF MEMS cantilever with Au contacts was monitored under accelerated test conditions, comparing the behavior of Au bottom contacts to an alternative Au-Ni alloy contact material. The Au-Ni (20 at.%) alloy displayed reduced wear rates and improved switch cycle lifetimes compared to pure Au, while retaining acceptable values of contact resistance.

No abstract

No abstract

We present the fabrication method and the electrical performance of nanoscale crosspoint junctions for two different metal/ oxide/ metal configurations. 100 x 100 nm² small cells were fabricated by e-beam lithography and nanoimprint lithography (NIL), respectively. The electrical results show switching speeds of less than 10 ns for the SET and RESET operations, and resistance changes of several orders of magnitude. Additionally, the resistance state of TiO 2 thin films reveal a strong dependence on the switch signal and demonstrates a retention time of up to 10 5 s at room temperature and 85°C. The tested materials and fabrication steps are in good accordance with current and future CMOS technology and provide a way to achieve low cost, high density non-volatile memory.

No abstract

This paper presents a damascene process for the fabrication of titanium micro/nanostructures and nanowires with adjustable thickness down to 2 nm. Their depth is precisely controlled by chemical-mechanical planarization together with in-process electrical characterization. The latter, in combination with a model of the titanium resistivity versus thickness, allows control of the metal line depth in the nanometer range. In summary, we have developed a planarization end point detection method for metal nanostructures. In addition, the model adopted covers geometrical influences like oxidation and ageing. The fabricated titanium nanowire test structures have a thickness ranging from 2 to 25 nm and a width ranging between 15 and 230 nm.