The nanoscale interface between multi-component (Ag–Au–Cu–Pd–Pt) alloy nanoparticles on MoS2 sheets increase its work function making an ohmic contact into Schottky with gold electrodes. This drastically enhances response towards hydrogen gas.

Hydrogen is known to diffuse through particular planes of ZnO crystals. However, in spite of being an established gas sensor material, such diffusion related effects have not been reported in gas sensor properties of ZnO in the literature to the best of our knowledge. Here, we report a prominent overshoot observed in the response transients of single crystalline large ZnO microrods sensor upon exposure to hydrogen gas. This overshoot intensity and time has been found to vary systematically with the temperature as well as gas concentration. In spite of larger size of rods (diameter ≈1–3 µm), it shows a very high response of nearly 950% for 1000 ppm hydrogen at 300 °C. The observed overshoot is very prominent at temperatures below 300 °C. This unusual behavior has been attributed to the bulk diffusion of atomic hydrogen into the subsurface of ZnO microrods. The coefficient of diffusivity, estimated from the time of overshoot, is found to be typically 10−15 m2 s−1, at 250 °C, and its thermal activation energy has been found to be 0.22 eV. The lack of grain boundaries within the microrods and surface gradient driven diffused hydrogen species have been proposed as the origin of unusual overshoot profiles.

The paper investigates the magnetic behavior of chromium doped SnO2 Dilute Magnetic Semiconductor (DMS) nanoparticles, through structural, spectroscopic, and magnetic studies. A non-equilibrium solution combustion method is adopted to synthesize 0–5 at. % Cr doped SnO2 nanoparticles. The detailed spectroscopic studies on the system using micro-Raman spectroscopy, x-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy along with the structural analysis confirm the presence of Cr in 3+ oxidation state, which substitutes at Sn4+ site in SnO6 octahedra of the rutile structure. This doping is found to enhance the defects in the system, i.e., oxygen vacancies. All the synthesized SnO2 nanoparticles (with or without dopants) are found to exhibit Room Temperature Ferromagnetism (RTFM). This occurrence of RTFM is attributed to the magnetic exchange interaction through F-centers of oxygen vacancies as well as dopant magnetic impurities and explained through the Bound Magnetic Polaron (BMP) model of DMS systems. Nonetheless, as the doping of Cr is further increased beyond 2%, the solubility limit is achieved. This antiferromagnetic exchange interaction from interstitial Cr dopants dominates over the BMP mechanism and, hence, leads to the decrease in the net magnetic moment drastically.

No abstract

Miniaturized chemical sensors are of immense utility for low-power-consuming, on-chip-integrable functional devices. In this letter, complementary metal oxide semiconductor (CMOS)-compatible fabrication of a suspended Ni/NiO nanobeam gas sensor device showing a selective response to hydrogen gas at room temperature is reported. The dimensions of the suspended Ni beam are 100 nm × 1 μm, and the thickness varied from 15 and 20 nm. Further, it is oxidized using either thermal oxidation or plasma oxidation. The selective response obtained is a nearly 50% change in resistance for 5000 ppm of H2 at 25 °C in plasma-oxidized-sputtered Ni films. The joule heating results in thermal oxidation viz-a-viz electromigration of Ni metal self-functionalization and helps in the selective response toward hydrogen.