Scanning-helium-ion-beam lithography with hydrogen silsesquioxane resist

A scanning-helium-ion-beam microscope is now commercially available. This microscope can be used to perform lithography similar to, but of potentially higher resolution than, scanning electron-beam lithography. This article describes the control of this microscope for lithography via beam steering/blanking electronics and evaluates the high-resolution performance of scanning helium-ion-beam lithography. The authors found that sub-10 nm-half-pitch patterning is feasible. They also measured a point-spread function that indicates a reduction in the micrometer-range proximity effect typical in electron-beam lithography.National Science Foundation (U.S.). Graduate Research Fellowship Progra

Precision Cutting and Patterning of Graphene with Helium Ions

We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on $Si/SiO_2$ substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with ~15 nm feature sizes.Engineering and Applied SciencesPhysicsOther Research Uni

Charged Particle Lithography for the Fabrication of Nanostructured Optical Elements

This thesis work focuses on nanostructured optical elements for light and matter waves that have been fabricated using helium ion beam lithography and electron beam lithography. The motivation of this thesis has been to develop new optical elements and to contribute with foundational work to instrumentation and characterization of nanostructures. The work has been carried out at the University of Bergen, Nanostructure Laboratory and at the Massachusetts Institute of Technology, Nanostructure Laboratory. The thesis is based on five papers published in international, peer reviewed, Web of science journals. The thesis defender is sole first author on paper I-IV and shared first author on paper V. Paper I presents the first helium ion beam lithography patterning on a non-horizontal surface. Such patterning is possible because of the large field of depth in a helium ion beam instrument. Comparable writing cannot be performed with standard electron beam lithography. Patterning on curved or tilted surfaces is potentially very useful in a range of devices e.g. optical lenses, and is fundamentally an attractive property. Paper II presents a systematic scanning-electron-microscopy study of the charging effect in metal nanostructures on insulating surfaces. Negative charging is found to induce a measurement error in the measured dimensions of the nanostructures comparable to a de-magnified image. In paper III, the optical response of metal nanoparticles mediated by the localized surface plasmon resonance effect are studied using integrating spheres, and the influence of the fabrication method on the optical properties is discussed. Paper IV and V describe optical elements for matter waves. In Paper IV a high-transmission atom sieve for focusing neutral helium atoms is fabricated, showing that focusing below 10 nm should in principle be possible. Paper V demonstrates fast resolution change in the focusing neutral helium microscope by inserting collimating apertures. Without changing the properties of the neutral helium beam and without breaking the vacuum a resolution change by a factor of 4.4 is demonstrated

Modeling the point-spread function in helium-ion lithography

We present here a hybrid approach to modeling helium-ion lithography that combines the power and ease-of-use of the Stopping and Range of Ions in Matter (SRIM) software with the results of recent work simulating secondary electron (SE) yield in helium-ion microscopy. This approach traces along SRIM-produced helium-ion trajectories, generating and simulating trajectories for SEs using a Monte Carlo method. We found, both through simulation and experiment, that the spatial distribution of energy deposition in a resist as a function of radial distance from beam incidence, i.e. the point spread function, is not simply a sum of Gauss functions.Semiconductor Research Corporation. Nanoscale Research InitiativeNational Science Foundation. Graduate Research Fellowship Progra

Helium Ion Microscopy

Helium Ion Microcopy (HIM) based on Gas Field Ion Sources (GFIS) represents a new ultra high resolution microscopy and nano-fabrication technique. It is an enabling technology that not only provides imagery of conducting as well as uncoated insulating nano-structures but also allows to create these features. The latter can be achieved using resists or material removal due to sputtering. The close to free-form sculpting of structures over several length scales has been made possible by the extension of the method to other gases such as Neon. A brief introduction of the underlying physics as well as a broad review of the applicability of the method is presented in this review.Comment: Revised versio

Nanoladder cantilevers made from diamond and silicon

We present a "nanoladder" geometry that minimizes the mechanical dissipation of ultrasensitive cantilevers. A nanoladder cantilever consists of a lithographically patterned scaffold of rails and rungs with feature size $\sim$ 100 nm. Compared to a rectangular beam of the same dimensions, the mass and spring constant of a nanoladder are each reduced by roughly two orders of magnitude. We demonstrate a low force noise of $158 (+62)(-42)\,$zN and $190 (+42)(-33)\,$zN in a one-Hz bandwidth for devices made from silicon and diamond, respectively, measured at temperatures between 100--150 mK. As opposed to bottom-up mechanical resonators like nanowires or nanotubes, nanoladder cantilevers can be batch-fabricated using standard lithography, which is a critical factor for applications in scanning force microscopy