Template-directed synthesis, characterization and electrical properties of Au–TiO₂–Au heterojunction nanowires

Abstract

The feasibility of synthesizing metal-oxide-metal (MOM) heterojunction nanowires in the Au-TiO 2-Au system is demonstrated. The synthesis method presented here entails sequential electroplating of Au and electro-deposition of amorphous titanium oxide (TiO x) inside nanoholes of anodic aluminium oxide (AAO) templates. This is followed by dissolving the template, and heat-treating the released nanowires, which results in the crystallization of the amorphous TiO x segment into nanocrystalline TiO 2. Detailed transmission electron microscopy (TEM) investigation has revealed that the nanocrystalline TiO 2 is orthorhombic (columbite) phase primarily. This synthesis method has the potential to provide better control over the characteristics and architectures of the resulting MOM nanowires. The Au-TiO 2-Au nanowires were incorporated into single-nanowire devices, fabricated using a direct-write method. Nonlinear current-voltage (I-V) responses were obtained for individual MOM nanowires. The heterojunctions in such MOM nanowires are likely to offer certain advantages over all-oxide nanowires, making the MOM nanowires potentially useful as one-dimensional building blocks in the multifunctional nanoelectronics of the future.

Fabrication and characterization of size-controlled CuTCNQ charge-transfer complex nanocrystals

“…Several novel nanostructures and nanoparticles have been fabricated and applied in this field [1][2][3][4][5][6][7][8]. However, organic semiconductors still remain a challenging objective [9][10][11].…”

Bipolar resistive switching in individual Au–NiO–Au segmented nanowires

“…1 But there is a growing demand for high-density NVRAMs in electronics that are fast, reliable, energy efficient, and immune to read-write fatigue. 1͒ developed in our laboratories [23][24][25][26][27][28] are more representative of prototypical single ReRAM memory cells. 1 One such concept for nonvolatile resistive random access memory ͑ReRAM͒ that is being pursued very actively is electric-field induced resistance change in oxides, 2-4 such as NiO, [5][6][7][8][9][10][11] TiO 2 , 12-15 Fe 2 O 3 , 10 CuO, 16 and perovskites.…”

“…23,26 Briefly, sequential segments of Au ͑ϳ6 m͒, Ni ͑ϳ900 nm͒, and Au ͑ϳ6 m͒ were electroplated ͑constant current of Ϫ0.5 mA͒ inside the nanoholes of anodic aluminum oxide templates ͑nanohole diameter of ϳ250 nm͒ ͑Anopore ® , Whatman, Inc., Florham Park, NJ͒. [23][24][25][26][27] Figure 2͑b͒ is a high-resolution TEM bright-field image of a Au/NiO interface, showing nearperfect contact between Au and NiO. These were then heat treated at 600°C for 30 min either in air ͑pO 2 = 0.2͒ or an atmosphere with pO 2 = 0.1 ͑balance N 2 ͒ to oxidize only the Ni segment to NiO.…”

Low‐Temperature Synthesis of Large‐Area, Free‐Standing Nanorod Arrays on ITO/Glass and other Conducting Substrates

“…Nanoporous AAO, however, has primarily been produced using aluminum foils, such that nanorods and nanowires of various materials have been produced by electrochemical deposition onto a thin electrode layer on the bottom of the fragile, unsupported membrane. [12,18,19] It is essential for device fabrication that templates be synthesized on supporting substrates, allowing them to be filled then etched away, leaving arrays of free-standing, aligned nanorods of uniform diameter and length electrically connected to a rigid substrate. Significant progress has been made in producing AAO templates on silicon substrates.…”