No abstract

Cross-linked poly(dimethylsiloxane) (PDMS) was irradiated with a Xe2*-excimer lamp (172 nm) under ambient conditions. The irradiation in combination with the formed ozone results in an oxidation of PDMS to SiO2 at the polymer−air interface. The surface properties of the irradiated surfaces were studied by means of contact angle measurements, infrared spectroscopy, and X-ray photoelectron spectroscopy. The photochemical conversion of surface methylsilane groups to silanol groups is responsible for the large increase in surface free energy. Subsequent degradation of the polymer and formation of SiO x was monitored by infrared spectroscopy. As determined by X-ray photoelectron spectroscopy, the binding energy shifts reach values corresponding to SiO2. The atomic ratio concentration O:Si changes from about 1:1 (PDMS) to about 2:1 (SiO2). On the basis of the XPS and IR results, the photochemical reaction pathway from PDMS to silicon oxide via surface silanol groups is discussed. The strict linearity of the contact angle versus irradiation time and the clear dependence from irradiation intensity allows the tuning of the chemical surface functionalities.

The electrical conductivity of dense and nanoporous zirconia‐based thin films is compared to results obtained on bulk yttria stabilized zirconia (YSZ) ceramics. Different thin film preparation methods are used in order to vary grain size, grain shape, and porosity of the thin films. In porous films, a rather high conductivity is found at room temperature which decreases with increasing temperature to 120 °C. This conductivity is attributed to proton conduction along physisorbed water (Grotthuss mechanism) at the inner surfaces. It is highly dependent on the humidity of the surrounding atmosphere. At temperatures above 120 °C, the conductivity is thermally activated with activation energies between 0.4 and 1.1 eV. In this temperature regime the conduction is due to oxygen ions as well as protons. Proton conduction is caused by hydroxyl groups at the inner surface of the porous films. The effect vanishes above 400 °C, and pure oxygen ion conductivity with an activation energy of 0.9 to 1.3 eV prevails. The same behavior can also be observed in nanoporous bulk ceramic YSZ. In contrast to the nanoporous YSZ, fully dense nanocrystalline thin films only show oxygen ion conductivity, even down to 70 °C with an expected activation energy of 1.0 ± 0.1 eV. No proton conductivity through grain boundaries could be detected in these nanocrystalline, but dense thin films.

During the growth of oxide thin films by pulsed laser deposition, a strong oxygen substrate-to-film transfer has been experimentally observed for SrTiO 3 and LaAlO 3 thin films epitaxially grown on 18 O exchanged SrTiO 3 and LaAlO 3 substrates by secondary ion mass spectrometry depth profiling. This oxygen transfer effect can seriously change the respective thin film properties. Taking the oxygen substrate contribution to the overall oxygen balance into account, original ways to design material properties of oxide thin films can be envisioned like a controlled charge carrier doping of SrTiO 3 thin films.

We present direct, real-time observations of emergent magnetic monopole dynamics in highly frustrated artificial spin ice.

No abstract

No abstract

Many in-memory computing frameworks demand electronic devices with specific switching characteristics to achieve the desired level of computational complexity. Existing memristive devices cannot be reconfigured to meet the diverse volatile and non-volatile switching requirements, and hence rely on tailored material designs specific to the targeted application, limiting their universality. “Reconfigurable memristors” that combine both ionic diffusive and drift mechanisms could address these limitations, but they remain elusive. Here we present a reconfigurable halide perovskite nanocrystal memristor that achieves on-demand switching between diffusive/volatile and drift/non-volatile modes by controllable electrochemical reactions. Judicious selection of the perovskite nanocrystals and organic capping ligands enable state-of-the-art endurance performances in both modes – volatile (2 × 106 cycles) and non-volatile (5.6 × 103 cycles). We demonstrate the relevance of such proof-of-concept perovskite devices on a benchmark reservoir network with volatile recurrent and non-volatile readout layers based on 19,900 measurements across 25 dynamically-configured devices.