SummaryWe demonstrate compact full-field soft X-ray transmission microscopy with sub 60-nm resolution operating at λ = 2.48 nm. The microscope is based on a 100-Hz regenerative liquid-nitrogen-jet laser-plasma source in combination with a condenser zone plate and a micro-zone plate objective for highresolution imaging onto a 2048 × 2048 pixel CCD detector. The sample holder is mounted in a helium atmosphere and allows imaging of both dry and wet specimens. The microscope design enables fast sample switching and the sample can be prealigned using a visible-light microscope. High-quality images can be acquired with exposure times of less than 5 min. We demonstrate the performance of the microscope using both dry and wet samples.

We studied current-voltage characteristics of long one dimensional Josephson junction chains with Josephson energy much larger than charging energy, EJ ≫ EC. In this regime, typical IV curves of the samples consist of a supercurrent branch at low bias voltages followed by a voltage-independent chain current branch, I Chain at high bias. Our experiments showed that I Chain is not only voltageindependent but it is also practically temperature-independent up to TC. We have successfully model the transport properties in these chains using a capacitively shunted junction model with nonlinear damping.

Cold development was applied to improve the resolution in a trilayer resist that is used for the fabrication of state-of-the-art soft x-ray microscopy zone plates. By decreasing the temperature of the hexyl acetate developer to −50 °C, 11 nm half-pitch gratings have been resolved in the electron-beam resist ZEP 7000. 12 nm half-pitch gratings have been successfully transferred, via the intermediate SiO2 hardmask, into the bottom polyimide layer by CHF3 and O2 reactive ion etching. The trilayer resist, including optimized cold development, has finally been used in an electroplating-based process for the fabrication of nickel zone plates. Zone plates with down to 13 nm outermost zone width have been fabricated and 2.4% average groove diffraction efficiency has been measured for zone plates with 15 nm outermost zone width and a nickel height of 55 nm.

We report on a novel condenser for full-field transmission x-ray microscopes that use synchrotron radiation from an undulator source. The condenser produces a Koehler-like homogeneous intensity distribution in the sample plane and eliminates object illumination problems connected with the high degree of spatial coherence in an undulator beam. The optic consists of a large number of small linear diffraction gratings and is therefore relatively easy to manufacture. First imaging experiments with a prototype condenser were successfully performed with the Twinmic x-ray microscope at the Elettra synchrotron facility in Italy.

We report on a compact interferometer for the water-window soft-x-ray range that is suitable for operation with laser-plasma sources. The interferometer consists of a single diffractive optical element that focuses impinging x rays to two focal spots. The light from these two secondary sources forms the interference pattern. The interferometer was operated with a liquid-nitrogen jet laser-plasma source at lambda=2.88 nm. Scalar wave-field propagation was used to simulate the interference pattern, showing good correspondence between theoretical and experimental results. The diffractive optical element can simultaneously be used as an imaging optic, and we demonstrate soft-x-ray microscopy with interferometric contrast enhancement of a phase object.