D. Haubrich

Pattern generation with cesium atomic beams at nanometer scales

We have demonstrated that a cesium atomic beam can be used to pattern a gold surface using a self assembling monolayer (SAM) as a resist. A 12.5 μm period mesh was used as a proximity mask for the atomic beam. The cesium atoms locally change the wetability of the SAM, which allows a wet etching reagent to remove the underlying gold in the exposed regions. An edge resolution of better than 100 nm was obtained. The experiment suggests that this method can either be used as a sensitive position detector with nanometer resolution in atom optics, or for nanostructuring in a resist technique.

Species-selective microwave cooling of a mixture of rubidium and caesium atoms

We have sympathetically cooled a small sample of 133Cs atoms with 87Rb to below 1??K. Evaporative cooling was realized with microwave radiation driving the Rb ground-state hyperfine transition. By analysing the sympathetic cooling dynamics, we derive a lower limit of the modulus of the Rb?Cs interspecies triplet s-wave scattering length of 200?a0. For temperatures below 5??K we observe strong non-exponential losses of the Cs sample in the presence of the Rb sample.

Optical Trapping in a Cesium Cell with Linearly Polarized Light and at Zero Magnetic Field

We have found that linearly polarized light can be used efficiently for optical trapping of cesium atoms in a magnetic-quadrupole field. The number and density of atoms of the trapped samples are comparable to a standard magneto-optical trap with σ+-σ- polarized light, but the influence of the magnetic-quadrupole strength is strikingly different. When the polarization of counterpropagating light beams is orthogonal, trapping is observed also for zero magnetic field.

Magnetostatic traps for charged and neutral particles

We have constructed magnetostatic traps from permanent magnets for trapping charged and neutral atoms. Two storage experiments are presented: a compact Penning trap for light ions and magnetic trapping of single neutral atoms. The dynamics of cold neutral atoms and their loss mechanisms in a quadrupole magnetostatic trap are discussed.

Advancing atomic nanolithography: cold atomic Cs beam exposure of alkanethiol self-assembled monolayers

We report the results of a study into the quality of functionalized surfaces for nanolithographic imaging. Self-assembled monolayer (SAM) coverage, subsequent post-etch pattern definition and minimum feature size all depend on the quality of the Au substrate used in atomic nanolithographic experiments. We find sputtered Au substrates yield much smoother surfaces and a higher density of {111} oriented grains than evaporated Au surfaces. A detailed study of the self-assembly mechanism using molecular resolution AFM and STM has shown that the monolayer is composed of domains with sizes typically of 5-25 nm, and multiple molecular domains can exist within one Au grain. Exposure of the SAM to an optically-cooled atomic Cs beam traversing a two-dimensional array of submicron material masks ans also standing wave optical masks allowed determination of the minimum average Cs dose (2 Cs atoms per SAM molecule) and the realization of < 50 nm structures. The SAM monolayer contains many non-uniformities such as pin-holes, domain boundaries and monoatomic depressions which are present in the Au surface prior to SAM adsorption. These imperfections limit the use of alkanethiols as a resist in atomic nanolithography experiments. These studies have allowed us to realize an Atom Pencil suitable for deposition of precision quantities of material at the micro- and nanoscale to an active surface.

Diffraction by cold atoms

We have observed diffraction of a laser probe beam by a trapped sample of cold atoms. The effect is only visible in the vicinity of a resonance line. The observed diffraction pattern arises from interference of the incident and scattered light wave, allowing reconstruction of geometric properties of the trapped sample from the holographic record.

Atom Lithography with Cesium Atomic Beams

Optical lithography is the dominant method of manufacturing lateral microand nanostructures in nearly all areas of technology, but it is predicted to be limited to feature sizes of about 100 nm due to diffraction. At this scale the miniaturization is not yet impaired by quantum limits of the substrates and materials used for construction, i.e. transistors will still be governed by the same physical laws as the currently available components. Therefore nanofabrication of known devices may continue beyond this border without a conceptual change of important components involved, provided suitable lithographic processes with sub 100 nm resolution are available. According to the “roadmap” published by the semiconductor industry [1] it is expected that the technological 100 nm barrier will be reached by 2005. The applicability of sub 100 nm methods for nanostructure fabrication will not only be determined by technological and physical reasons, however, but more importantly by economical factors.

Atom optical properties of magnetic components

Efficmt bear steering components far paramagnetic atoms CUI be manufacrured from permanent magnets. In contrast to atom optical components denved from light forces permanent magnetic components do not need any supplies, they have large apenures, and rpontilneous cmissroe is absent. Mayetic acceleration i s one ardor of magnitude smaller than typlcal accelerations by gpantaneous light farces, but the maximum momentum transfer can be increased through extended components or by loucrhg the longrludunal vclucity of the atoms. With strong rare carth permanent magnets we have built lenses [ I ] .ind nllrrors (fig. 1) for atomic bcams. Our lenses have ibcill lengths in the centimcler regims for sloniic ~elocillrs of abour 70 mis and a opening ofseveral miilimeters. Hexapolc I C ~ S C S can bc iiscd for fociising anid ~magmg with B monachromaric atomic beam 121. It is wll known 111 hght optics that minors haw fewer aberratrons thla lenses. A magnetic mirror for aloin 0pOcs has been constructed from B periodic airily of milgnctic slabs with alternating direction uf lhe magnetization. The dwice has a length of 90 mm and reilccts ces~um a t o m with B vclocicy component of up LO 5 nvs perpendicular to the mirror surface.