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The fabrication and magnetic properties of arrays of short nanowires are reviewed. The arrays consist of electrodeposited ferromagnetic cylinders with aspect ratios of up to 3 and diameters of 57–180 nm. Their hysteresis loops are characterized and their remanent states are related to the predictions of a three-dimensional micromagnetic model, which shows a transition from a single-domain ‘flower’ state to a lower-remanence ‘vortex’ state with increasing diameter. The shapes of the array hysteresis loops are governed by interactions between the particles. The switching fields of small Ni cylinders can be described using a dynamic micromagnetic model.

Macroscopic and microscopic switching characteristics are obtained for 100 nm period arrays of Ni nanomagnets with a mean switching field (coercive field) of 710 Oe. Magnetic force microscopy in combination with micromagnetic theory shows that inhomogeneities in the particle shapes result in an intrinsic standard deviation in switching fields of 105 Oe, while the interactions between neighboring nanomagnets broaden the distribution to 276 Oe, equivalent to a squareness of 0.8 in the bulk hysteresis loop. The switching field distribution is consistent with curling as the switching mechanism.

The magnetic properties of a 100-nm-period large-area array of regular, 30-nm polycrystalline nickel particles have been studied. The particles are found to reverse incoherently, and their hysteresis behavior has been compared with a computational model over a range of temperatures. Excellent agreement with the model is obtained, indicating that switching of the particles is dominated by the reversal of approximately 10-nm-diameter volumes within each particle. These switching volumes are identified with the columnar grains in the polycrystalline nickel, showing that the microstructure determines the magnetic behavior of the particles. This explains the anisotropy distribution and the onset of superparamagnetism in the sample. Incoherent reversal occurs even though the particles are only 1.5 times the exchange length in nickel, a size at which nearly uniform rotation is expected to occur if the particles were homogeneous.

A variable size nanoscale particle sieve with openings between 2 and 50 nm has been used for determining, selecting, and manipulating the size of large liquid helium clusters in the range from 7×103 to 3×106 atoms. The variable openings of the sieve are obtained by rotating a nanofabricated free-standing transmission grating with a 100 nm period and 50 nm wide slits around an axis parallel to the slits. The new nano-sieve can be applied to clusters of various species as well as to large molecules with sizes down to 2 nm.

Proton and {alpha}-particle energy spectra were measured in coincidence with evaporation residues from 252 and 295 MeV {sup 58}Ni+{sup 112}Sn fusion reactions. Residues were separated from the beam using an electrostatic deflector and detected with surface barrier detectors. Light charged particles were detected with arrays of NaI detectors. Statistical model calculations based on standard parameter choices reproduce the spectra from the cold, low spin {sup 170}Pt{sup *} system. The effects of employing different methods of calculating transmission coefficients were explored. The optical model, ingoing wave boundary condition model, and a simple one-dimensional barrier penetration model from a fusion systematics analysis produce comparable satisfactory predictions. The Hill-Wheeler approximation for transmission coefficients gives unrealistic results for protons.

The magnetic behavior of two different 100 nm period arrays of Ni pillars has been characterized using vibrating sample magnetometry and magnetic force microscopy. The samples have similar aspect ratios of approximately two but different particle dimensions, leading to differences in the strength of magnetostatic interactions. The experimental results were compared with a simulation based on an Ising-like simple interaction model.

A method is presented for the fabrication of large-area arrays of magnetic particles with 100 nm period, using achromatic interferometric lithography combined with etching, electrodeposition, or an evaporation and liftoff processes. These “nanomagnet” arrays have applications in patterned magnetic media, in magnetic memories, and for studies of particle interactions.

Magnetic hysteresis loops have been measured for a 100 nm period array of 35 nm diameter nickel pyramids formed by interferometric lithography. Results are compared with a computational model which describes a square array of Stoner-Wohlfarth particles. This allows the distribution of particle anisotropies and easy axis directions, and the switching mechanism, to be inferred.

Arrays of cylindrical magnetic particles have been made using interference lithography combined with electrodeposition. The cylinders are made from Ni, Co, CoP, or CoNi, with diameters of 57--180 nm, aspect ratios of 0.4--3, and array periods of 100--200 nm. The remanent states of the cylinders correspond to single-domain ``flower'' states or to magnetization vortices depending on the particle size and aspect ratio. Experimental data are in good agreement with a magnetic-state map calculated using a three-dimensional micromagnetic model, which shows the remanent state as a function of particle size and aspect ratio. The interactions between the particles, and their switching-field distribution, have been quantified.

The development of micro- and nanofabrication, their applications, and their dependent industries has progressed to a point where a bifurcation of technology development will likely occur. On the one hand, the semiconductor industry (at least in the USA) has decided to develop EUV and SCALPEL to meet its future needs. Even if the semiconductor industry is successful in this (which is by no means certain) such tools will not be useful in most other segments of industry and research that will employ nanolithography. As examples, MEMS, integrated optics, biological research, magnetic information storage, quantum-effect research, and multiple applications not yet envisioned will not employ the lithography tools of the semiconductor industry, either because they are too expensive, insufficiently flexible, or lacking in accuracy and spatial-phase coherence. Of course, direct-write electron-beam lithography can meet many of these non-semiconductor-industry needs, but in other cases a technique of higher throughput or broader process-latitude is necessary. Our experience at MIT in applying low-cost proximity x-ray nanolithography to a wide variety of applications leads us to conclude that this technology can provide an alternative path of a bifurcation. A new projection lithography technique, zone-plate-array lithography (ZPAL), does not require a mask, can operate from UV to EUV to x-rays, and has the potential to reach the limits of the lithographic process.

Patterns of 50 nm lines and spaces were demonstrated by low energy electron beam proximity lithography using 47-nm-thick poly methyl methacrylate (PMMA) and stencil masks fabricated by achromatic interference lithography (AIL). The result indicates the validity of the resolution analysis previously reported and the resolution capabilities of low energy electron beam proximity projection lithography (LEEPL) as a 50 nm node technology.

We describe initial steps we have taken in the development of zone-plate-array lithography (ZPAL), a proposed new paradigm for sub-100 nm lithography. The optimal implementation of ZPAL would employ an undulator emitting soft x rays of 4.5 nm wavelength. However, we have opted to concentrate initially on the major uncertainties associated with ZPAL: (1) fabrication of a large array of zone plates with a center-to-center spacing accuracy finer than the minimum zone width, (2) multiplexing of input beams to the individual zone plates, and (3) coordination of that multiplexing with precision motion of a substrate stage. We fabricated arrays of pure-phase zone plates suitable for the 193 nm output of an ArF laser, and conducted exposure tests using a modified Michelson configuration for focusing the zone plate array on the substrate. We also show the first example of simplistic writing. We show that the micromirror array manufactured by Texas Instruments, for use in projection displays, has dimensions and switching characteristics close to those needed for an ultimate ZPAL system.

Achromatic interferometric lithography is the preferred approach for producing large‐area, spatially coherent 100 nm period gratings and grids. We report on improvements to processes which have enabled exposure areas of ≊10 cm2. In addition, we report on the fabrication of 100 nm period free‐standing gold gratings.

For the fabrication of periodic structures with spatial periods of 100 nm or less, achromatic interferometric lithography is preferred over other lithographic techniques. We report on processes we have developed, using achromatic interferometric lithography, to fabricate large‐area coherent gratings and grids with spatial periods of 100 nm.

The relative diffraction peak intensities of He atoms with an incident beam energy of 65 meV diffracted from a microfabricated 100 nm-period transmission grating are analyzed using both Fresnel and Fraunhofer diffraction theory. The projected slit width could be varied from 50 nm down to less than 1 nm by inclining the grating at angles up to Q 0542° with respect to the incident beam. Good agreement between calculated and measured peak intensities, up to the sixth order, is obtained by accounting for random deviations in the slit positions, and averaging over the velocity spread of the incident beam as well as the spatial extent of the nozzle beam source. It is demonstrated that He atom beam diffraction together with simple transmission measurements is an excellent means of characterizing such gratings including a detailed determination of the slit width, the bar shape, and random as well as periodic disorder.