A new scanning transmission X-ray microscope (STXM) optimized for cryo-spectro-tomography with soft X-rays has been designed, built and commissioned at Canadian Light Source (CLS) beamline 10ID1 (130-2700 eV). It is controlled via a new python-based software package, pySTXM. A liquid N2 goniometer (Gatan 630, -80° to 80°), mounted on a computer controlled (x,y,Theta) tilt stage allows for spectro-tomographic measurements at cryogenic temperatures (-180°C) which reduces radiation damage. The CLS cryo-STXM is unique among the set of soft X-ray STXMs currently installed around the world. Details of the cryo-STXM design and examples of its performance will be presented.
A super-polished substrate with an off-axis parabola figure was coated with a Sc/B4C/Cr multilayer. This optic was used to focus pulses of 4.3 nm photons from the Free-electron LASer in Hamburg (FLASH) at normal incidence. Beam imprints were made in poly(methyl methacrylate) to align the optic and to measure the beam profile at the focal plane. The intense interaction resulted in imprints with raised perimeters, surrounded by ablated material extending out several micrometres. These features interfere with the beam profile measurement. The effect of a post-exposure development step on the beam imprints was investigated.
Sealed nanofluidic channels with cross sections of sub-100 nm * 100 nm were created in a polymer bilayer using the
focused soft X-rays of a scanning transmission X-ray microscope and the direct write method. The width of the
nanochannels can be controlled by the area patterned in X and Y, while the height can be controlled by tuning the layer
thicknesses. Formation of the desired structures has been confirmed by near edge X-ray absorption fine structure
spectromicroscopy and scanning electron microscopy. The maximum length of the nanochannels fabricated by this
method was found to be limited by the efficiency of excavation of patterned material out of the channel, as well as the
stability of the polymer over-layer which seals it. Schemes toward interfacing these nanochannels with conventional
microfluidics are discussed.
The monochromatic zone plate focused soft X-rays of scanning transmission X-ray microscopes (STXM) can be used to
directly write patterns in common photoresists, analogous to lithography with a focused electron or ion beam. A
radiation damage spreading phenomenon when patterning with high doses was recently determined to be due to the point
spread function of the optical system (Leontowich et al., Applied Physics A: Materials Science and Processing 103, 1
(2011)). We have used this phenomenon to measure the point spread function of three different STXMs by making a
series of single pixel exposures in a photoresist at focus over a controlled dose range. Our results suggest this
measurement is sensitive to zone plate aberrations; thus, it could be valuable feedback for optimizing zone plate
fabrication schemes and STXM performance.