James T. Goldbach

Nanofabrication of integrated magnetoelectronic devices using patterned self-assembled copolymer templates

Conventional lithographic exposure is used to selectively degrade regions of a self-assembled diblock copolymer film to obtain a honeycomblike nanoporous array template with arbitrary lateral design. Combined with other lithographic process steps, this enables the fabrication of arrays of nanostructures interfaced to electrical probes for device applications. To demonstrate, a unique magnetotransport device is fabricated, consisting of an array of electrodeposited Co nanowires standing atop a thin gold film patterned into a four-probe resistor configuration. Magnetoresistance measurements, performed at various temperatures and magnetic field orientations, reveal the coexistence of anisotropic magnetoresistance and giant magnetoresistance.

Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1Terabit∕in.2 The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15nm) and interwire spacing (24nm), whereas nanowire length (typically 50to1000nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7kOe at 300K. Magnetic and structural characterizations suggest that these properties arise from an improved degree...

Terabit Density Cobalt Nanowire Arrays With Tunable Magnetic Properties

Nanoporous templates made from diblock copolymer films are used for electrochemical fabrication of hexagonal arrays of vertical cobalt magnetic nanowires at terabit/in 2 density. The nanowire diameter and areal density are determined by the copolymer molecular weight, whereas the nanowire length and internal crystal morphology are controlled through the dc electrodeposition growth process. The array magnetic properties can be modified substantially by electrodeposition p H conditions while keeping wire size and interwire distance constant. Optimum p H control results in preferential growth of c-axis oriented crystallites with large perpendicular coercivity. The appearance of exchange bias behavior, exhibited at low temperatures, is also investigated.