Magnetic nanodots from atomic Fe: Can it be done?

Abstract

Laser focusing of Fe atoms offers the possibility of creating separate magnetic structures on a scale of 10 nm with exact periodicity. This can be done by using the parabolic minima of the potential generated by a standing light wave as focusing lenses. To achieve the desired 10-nm resolution, we need to suppress chromatic and spherical aberrations, as well as prevent structure broadening caused by the divergence of the incoming beam. Chromatic aberrations are suppressed by the development of a supersonic Fe beam source with speed ratio S ‫؍‬ 11 ؎ 1. This beam has an intensity of 3 ؋ 10 15 atoms sr ؊1 s ؊1 . The spherical aberrations of the standing light wave will be suppressed by aperturing with beam masks containing 100-nm slits at 744-nm intervals. The beam divergence can be reduced by application of laser cooling to reduce the transverse velocity. We have constructed a laser system capable of delivering over 500 mW of laser light at 372 nm, the wavelength of the 5 D4 3 5 F5 atomic transition of 56 Fe we intend to use for laser cooling. Application of polarization spectroscopy to a hollow cathode discharge results in a locking system holding the laser continuously within 2 MHz of the desired frequency.

Dissipative light masks for atomic nanofabrication

“…For the final result one has to average over many realizations (typically 4000 trajectories). Between the spontaneous emission events the density-matrix elements evolve according to the set of differential equations (4) and the atomic motion is given by solving Newton's equation of motion with the instantaneous force given by equation (6). This evolution is implemented using a Runge-Kutta integration procedure of fourth order for a typical time step of δt ∼ 1 ns.…”

“…Atomic nanofabrication, a technique of direct deposition of neutral atoms using conservative far off resonance atomlight interactions, has been intensively studied in recent years. Direct deposition has already been demonstrated for sodium [1], chromium [2] and aluminium [3] while experiments with gallium [4], caesium [5], iron [6] and indium are currently under construction. In all these experiments the structures are realized by a sinusoidal conservative potential acting as an array of cylindrical lenses for the atoms.…”

One-, two-and three-dimensional nanostructures with atom lithography

“…Direct deposition atom lithography has been successfully applied to sodium atoms [18], aluminium atoms [43] and chromium atoms [20]. Laser cooling of technologically interesting candidates for nanostructures are currently investigated for iron [44] and for the group III atom gallium [45]. Indium is currently under investigation if the available optical transitions allow us to create a collimated indium beam [46].…”

Barrier-limited surface diffusion in atom lithography

“…7͒ atoms, and our group is pursuing it for Fe atoms. 8 In the case of Cr, an extensive study on structure widths was done by Anderson et al 9 They found that the structures deposited were always 20-30 nm wider than the incoming atomic beam flux distribution. Due to the confidence and thoroughness with which this atomic beam flux distribution can be calculated, they concluded that the broadening of the nanostructures must be caused by a diffusion process on the substrate.…”