Nanocarbons show great promise for establishing the next generation of Joule heating systems, but suffer from the limited maximum temperature due to precociously convective heat dissipation from electrothermal system to surrounding environment. Here we introduce a strategy to eliminate such convective heat transfer by inserting highly stable and conductive microcapsules into the electrothermal structures. The microcapsule is comprised of encapsulated long-chain alkanes and graphene oxide/carbon nanotube hybrids as core and shell material, respectively. Multiform carbon nanotubes in the microspheres stabilize the capsule shell to resist volume-change-induced rupture during repeated heating/cooling process; and meanwhile enhance the thermal conductance of encapsulated alkanes which facilitates an expeditious heat exchange. The resulting microcapsules can be homogeneously incorporated in the nanocarbon-based electrothermal structures. At a dopant of 5%, the working temperature can be enhanced by 30% even at a low voltage and moderate temperature, which indicates a great value in daily household applications. Therefore, the stable and conductive microcapsule may serve as a versatile and valuable dopant for varieties of heat generation systems.

Despite being one of the most promising amorphous semiconductors, indium-gallium-zinc oxide (IGZO) has been mostly studied in transistors at low frequencies with limited effort on high-speed diodes. In this letter, the IGZO Schottky diodes with different active areas are fabricated in co-planar microwave waveguides on glass substrates at room temperature. By reducing the area of the diode, the cutoff frequency at zero bias can be improved. We are able to show that the diode with the active area of 200 μm ² has an intrinsic cutoff frequency beyond 20 GHz. By connecting the diode with a load, the rectifying circuit also exhibits a cutoff frequency of 4.2 GHz with the input power of 15 dBm. Simulations based on the diode properties are performed to include intrinsic and extrinsic components, and the results agree well with the experimental data.

Thin film transistors (TFTs) have been fabricated using magnesium zinc oxide (MgZnO) layers deposited by atomic layer deposition at 200 °C. The composition of the MgZnO is systematically modified by varying the ratio of MgO and ZnO deposition cycles. A blue-shift of the near band-edge photoluminescence after post-deposition annealing at 300 °C indicates significant activation of the Mg dopant. A 7:1 ratio of ZnO:MgO deposition cycles was used to fabricate a device with a TFT channel width of 2000 μm and a channel length of 60 μm. This transistor yielded an effective saturation mobility of 4 cm²/V s and a threshold voltage of 7.1 V, respectively. The on/off ratio was $1.6\times {10}^6$ and the maximum interface state density at the ZnO/SiO₂ interface is $\sim 6.5\times {10}^{12}$ cm⁻².

Polycrystalline zinc oxide (ZnO) thin-film transistors with a Ta ₂ O ₅ high- k gate dielectric layer are fabricated by radio-frequency magnetron sputtering at room temperature. Under the optimal deposition conditions, the devices show saturation mobility values over 50 cm ² /Vs, an ON/OFF ratio of , and a subthreshold voltage swing of 0.29 V/decade at a low operating voltage of 4 V. This is, to the best of our knowledge, one of the highest field-effect mobility values achieved in ZnO-based thin-film transistors by room-temperature sputtering. The stability of the devices is also examined and the sensitive dependence of the carrier mobility on the deposition conditions is discussed.