Temperature-Dependent Nonlinear Damping in Palladium Nanomechanical Resonators.

Advances in nanofabrication techniques have made it feasible to observe damping phenomena beyond the linear regime in nanomechanical systems. In this work, we report cubic nonlinear damping in palladium nanomechanical resonators. Nanoscale palladium beams exposed to a H2 atmosphere become softer and display enhanced Duffing nonlinearity as well as nonlinear damping at ultralow temperatures. The damping is highest at the lowest temperatures of ∼110 mK and decreases when warmed up to ∼1 K. We experimentally demonstrate for the first time temperature-dependent nonlinear damping in a nanomechanical system below 1 K. This is consistent with a predicted two-phonon-mediated nonlinear Akhiezer scenario with a ballistic phonon mean free path comparable to the beam thickness. This opens up new possibilities to engineer nonlinear phenomena at low temperatures.

Weak Antilocalization and Quantum Oscillations of Surface States in Topologically Nontrivial DyPdBi(110)Half Heusler alloy.

Recently, a number of ternary half-Heusler compounds have been predicted independently by several research groups as candidates for 3D topological insulators. In this work, we report the observation of a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hall-marks of topological surface states, and Shubnikov-de Hass (SdH) quantum oscillations in <110> oriented DyPdBi (DPB) thin films grown on MgO (100) substrates. The films prepared by pulsed laser deposition technique under the optimized conditions, showed a textured structure with (110) planes parallel to the (100) plane of MgO. The measured WAL effect follows the Hikami-Larkin-Nagaoka (HLN) model and the extracted values of phase coherence length (lϕ) and α are ~420 nm and ~-0.52 respectively. The power law variation of lϕ (~T-0.46) indicates the presence of the 2D surface states in DPB film. The Dirac nature of the surface states is further confirmed by Landau-level fan diagram analysis of SdH oscillations of the magneto-transport data. This analysis shows a finite Berry phase of 0.90π ± 0.16, reasonably close to the expected π value. Sheet Carrier density, ns ~ 2.56 × 1012 cm-2, calculated from the SdH oscillations (fSdH ~ 106 T) and Hall measurements agree well with each other. These findings demonstrate that the half Heusler DPB thin films (~15-20 nm) can be used as a suitable material for investigating the novel intrinsic quantum transport properties of surface Dirac fermions.

Polyarylenesulfonium Salt as a Novel and Versatile Nonchemically Amplified Negative Tone Photoresist for High-Resolution Extreme Ultraviolet Lithography Applications.

The present report demonstrates the potential of a polyarylenesulfonium polymer, poly[methyl(4-(phenylthio)-phenyl)sulfoniumtrifluoromethanesulfonate] (PAS), as a versatile nonchemically amplified negative tone photoresist for next-generation lithography (NGL) applications starting from i-line (λ ∼ 365 nm) to extreme ultraviolet (EUV, λ ∼ 13.5 nm) lithography. PAS exhibited considerable contrast (γ), 0.08, toward EUV and patterned 20 nm features successfully.