Nanofabrication of x-ray diffractive optics using electron beam lithography requires a complex process of electron exposure optimization and resist development. Thermal scanning probe lithography (TSPL) offers a high resolution, maskless, gray scale patterning method with reduced complexity. Thin diffractive optics with high efficiency for the extreme ultraviolet (EUV) and soft x-ray (SXR) photon range could be fabricated by combining TSPL with a single etching step if the TSPL resist, polyphthalaldehyde (PPA), can be used as an etch mask to direct-etch the pattern into a substrate using reactive ion etching. This condition critically depends on high etch selectivity between the substrate and the PPA, because TSPL resolution deteriorates as the PPA patterning depth increases beyond tens of nanometers. In this work, the authors have evaluated the etch selectivity for PPA and Si3N4 using SF6/C4F8 gases and the influence of process parameters, including gas flow rate, vacuum pressure, radio frequency bias power, and inductively coupled plasma power. The experimental results indicate that an etch selectivity of 7 (Si3N4:PPA) is achievable, and the authors demonstrate that diffractive optics for EUV/SXR can be fabricated in only two steps.

The development of devices that exhibit both superconducting and semiconducting properties is an important endeavor for emerging quantum technologies. We investigate superconducting nanowires fabricated on a silicon-on-insulator (SOI) platform. Aluminum from deposited contact electrodes is found to interdiffuse with Si along the entire length of the nanowire, over micrometer length scales and at temperatures well below the Al–Si eutectic. The phase-transformed material is conformal with the predefined device patterns. The superconducting properties of a transformed mesoscopic ring formed on a SOI platform are investigated. Low-temperature magnetoresistance oscillations, quantized in units of the fluxoid, h/2e, are observed.

Nanoscale superconducting quantum interference devices (nano-SQUIDs) with Dayem bridge junctions and a physical loop size of 50 nm have been engineered in boron-doped nanocrystalline diamond films using precision Ne-ion beam milling. In an unshunted device, the nonhysteretic operation can be maintained in an applied field exceeding 0.1 T with a high flux-tovoltage transfer function, giving a low flux noise 0.14 / Hz noise 0 ϕ μ ϕ = at 1 kHz and a concurrent spin sensitivity of 11 spins/ Hz . At elevated magnetic fields, up to 2 T, flux modulation of the nano-SQUID output voltage is maintained but with an increase in period, attributed to an additional phase bias induced on the nano-SQUID loop by up to 16 vortices per period penetrating the nano-SQUID electrodes.