X-ray focusing below 3 nm with aberration-corrected multilayer Laue lenses.

Multilayer Laue lenses are volume diffractive optical elements for hard X-rays with the potential to focus beams to sizes as small as 1 nm. This ability is limited by the precision of the manufacturing process, whereby systematic errors that arise during fabrication contribute to wavefront aberrations even after calibration of the deposition process based on wavefront metrology. Such aberrations can be compensated by using a phase plate. However, current high numerical aperture lenses for nanometer resolution exhibit errors that exceed those that can be corrected by a single phase plate. To address this, we accumulate a large wavefront correction by propagation through a linear array of 3D-printed phase correcting elements. With such a compound refractive corrector, we report on a point spread function with a full-width at half maximum area of 2.9 × 2.8 nm2 at a photon energy of 17.5 keV.

Inverted Hartmann mask made by deep X-ray lithography for single-shot multi-contrast X-ray imaging with laboratory setup.

This paper reports on the fabrication and characterization of an inverted Hartmann mask and its application for multi-contrast X-ray imaging of polymer composite material in a laboratory setup. Hartmann masks open new possibilities for high-speed X-ray imaging, obtaining orientation-independent information on internal structures without rotating the object. The mask was manufactured with deep X-ray lithography and gold electroplating on a low-absorbing polyimide substrate. Such an approach allows us to produce gratings with a small period and high aspect ratio, leading to a higher spatial resolution and extension towards higher X-ray energies. Tuning the manufacturing process, we achieved a homogeneous patterned area without supporting structures, thus avoiding losses on visibility. We tested mask performance in a laboratory setup with a conventional flat panel detector and assessed mask imaging capabilities using a tailored phantom sample of various sizes. We performed multi-modal X-ray imaging of epoxy matrix polymer composites reinforced with glass fibers and containing microcapsules filled with a healing agent. Hartmann masks made by X-ray lithography enabled fast-tracking of structural changes in low absorbing composite materials and of a self-healing mechanism triggered by mechanical stress.

Shack-Hartmann wavefront sensors based on 2D refractive lens arrays and super-resolution multi-contrast X-ray imaging.

Different approaches of 2D lens arrays as Shack-Hartmann sensors for hard X-rays are compared. For the first time, a combination of Shack-Hartmann sensors for hard X-rays (SHSX) with a super-resolution imaging approach to perform multi-contrast imaging is demonstrated. A diamond lens is employed as a well known test object. The interleaving approach has great potential to overcome the 2D lens array limitation given by the two-photon polymerization lithography. Finally, the radiation damage induced by continuous exposure of an SHSX prototype with a white beam was studied showing a good performance of several hours. The shape modification and influence in the final image quality are presented.

Inverted Hartmann mask for single-shot phase-contrast x-ray imaging of dynamic processes.

In this Letter, we present the application of the inverted Hartmann mask for time-resolved single-shot phase-contrast x-ray imaging. The inverted Hartmann mask is a periodic array of free-standing gold pillars. The array is manufactured by UV lithography and electroplating. Time-resolved measurements are performed for imaging of pulsed laser ablation in liquids using white-beam synchrotron radiation. The inverted Hartmann mask in combination with a single-shot imaging technique provides sufficient differential phase contrast even at very short exposure times. It can be effectively used for phase-contrast x-ray imaging of fast dynamic processes with temporal resolution on the millisecond scale.

Single-Shot Multicontrast X-ray Imaging for In Situ Visualization of Chemical Reaction Products.

We present the application of single-shot multicontrast X-ray imaging with an inverted Hartmann mask to the time-resolved in situ visualization of chemical reaction products. The real-time monitoring of an illustrative chemical reaction indicated the formation of the precipitate by the absorption, differential phase, and scattering contrast images obtained from a single projection. Through these contrast channels, the formation of the precipitate along the mixing line of the reagents, the border between the solid and the solution, and the presence of the scattering structures of 100-200 nm sizes were observed. The measurements were performed in a flexible and robust setup, which can be tailored to various imaging applications at different time scales.

Lithographic Performance of Aryl Epoxy Thermoset Resins as Negative Tone Photoresist for Microlithography.

Photoresists (or photo-resins) are the main and most important raw material used for lithography techniques such as deep X-ray (DXRL), ultraviolet (UVL), deep-UV (DUVL), and extreme UV (EUVL). In previous work, we showed how complicated could be the synthesis of the resins used to produce photoresist. In this study, we follow up on the strategy of tuning deep and macro levels of properties to formulate photo-resins. They were developed from a primary basis, using epoxy resins, a solvent, and a photoinitiator in several concentrations. The formulations were evaluated initially by the UVL technique, using a squared pattern of 2.3 mm2. The most suitable compositions were then studied in a pattern structure varying from 50 down to 1 µm width, applying UVL and DUVL. The patterned structures were compared with the chemical composition of the photo-resins. Considering the deep level of properties, polydispersion, and epoxidation degree were evaluated. Regarding the macro level of properties, the concentration of photoinitiator was studied. Promising results have been achieved with the control of the deep and macro levels methodology. By means of UV lithography, it was possible to note, for a large feature size above 2.0 mm2, the formulations presented good quality structures with a broad range of epoxidation degrees and photoinitiator concentrations, respectively from 3 to 100% (mol·molpolymer-1) and from 10 to 40% (mol·molpolymer-1). For structures smaller than 50 µm width, the composition of the photo-resins may be restricted to a narrow range of values regarding the formulation. The results indicate that the polydispersion of the oligomers might be a significant property to control. There is a tendency to better outcome with a low polydispersity (resins P1 and P2). Regarding UV and deep-UV irradiation, the best results were achieved with UV. Nevertheless, for DUV, the sensitivity seems to be more intense, leading to well-defined structures with over-exposure effects.

Epoxy Resins for Negative Tone Photoresists.

One of the types of negative tone photoresists is composed of at least a catalyst, a solvent, and epoxy resin. This is the primary raw material for lithography technology. To ensure high-quality pattern transfer in the lithography process, it is crucial to control the properties of the photoresist. In this work, a set of resins based on Bisphenol-A were synthesized. The obtained resins have been characterized regarding the chain size and its derivative products. As a second step, an epoxidation reaction was performed and the epoxy groups were quantified. The profile of the resins, obtained by mass spectroscopy (ESI-µ-TOF-MS), showed that it is possible to tune the chain sizes of the polymers and their derivate by controlling the parameters of the polymerization reaction. Three profiles of resins were achieved in this study. Nuclear magnetic resonance (NMR) indicates an epoxidation in the range of 96%, when comparing the phenolic peak intensity before and after the reaction. Differential Scan Calorimetry (DSC) measurements confirmed the different oligomer profiles of resins, showing different glass transition temperatures.

Structural and Thermal Characterisation of Nanofilms by Time-Resolved X-ray Scattering.

High time resolution in scattering analysis of thin films allows for determination of thermal conductivity by transient pump-probe detection of dissipation of laser-induced heating, TDXTS. We describe an approach that analyses the picosecond-resolved lattice parameter reaction of a gold transducer layer on pulsed laser heating to determine the thermal conductivity of layered structures below the transducer. A detailed modeling of the cooling kinetics by a Laplace-domain approach allows for discerning effects of conductivity and thermal interface resistance as well as basic depth information. The thermal expansion of the clamped gold film can be calibrated to absolute temperature change and effects of plastic deformation are discriminated. The method is demonstrated on two extreme examples of phononic barriers, isotopically modulated silicon multilayers with very small acoustic impedance mismatch and silicon-molybdenum multilayers, which show a high resistivity.