Zinc oxide (ZnO) is a fascinating wide band gap semiconductor material with many properties that make it widely studied in the material science, physics, chemistry, biochemistry, and solid-state electronics communities. Its transparency, possibility of bandgap engineering, the possibility to dope it into high electron concentrations, or with many transition or rare earth metals, as well as the many structures it can form, all explain the intensive interest and broad applications. This review aims to showcase ZnO as a very versatile material lending itself both to bottom-up and top-down fabrication, with a focus on the many devices it enables, based on epitaxial structures, thin films, thick films, and nanostructures, but also with a significant number of unresolved issues, such as the challenge of efficient p-type doping. The aim of this article is to provide a wide-ranging cross-section of the current state of ZnO structures and technologies, with the main development directions underlined, serving as an introduction, a reference, and an inspiration for future research.

The fabrication of low-resistance and thermal stable ohmic contacts is important for realization of reliable SiC devices. For then-type SiC, Ni-based metallization is most commonly used for Schottky and ohmic contacts. Many experimental studies have been performed in order to understand the mechanism of ohmic contact formation and different models were proposed to explain the Schottky to ohmic transition for Ni/SiC contacts. In the present review, we summarize the last key results on the matter and post open questions concerning the unclear issues of ohmic contacts ton-type SiC. Analysis of the literature data and our own experimental observations have led to the conclusion that the annealing at high temperature leads to the preferential orientation of silicide at the heterointerface (0001)SiC//(013)δ-Ni2Si. Moreover, we may conclude that onlyδ-Ni2Si grains play a key role in determining electrical transport properties at the contact/SiC interface. Finally, we show that the diffusion barriers with free diffusion path microstructure can improve thermal stability of metal-SiC ohmic contacts for high-temperature electronics.

Thin polycrystalline ZnO films are deposited onto Si (100) substrates by means of DC reactive sputter deposition from a Zn target in an argon–oxygen mixture. The influences of the oxygen content in the mixture and of the total gas pressure in the reactor during deposition as well as of applying postgrowth annealing in an oxygen flow at elevated temperatures on the structural, chemical, and electrical properties of the obtained films are discussed. Three types of thin‐film structures were obtained: a porous polycrystalline Zn layer, a porous polycrystalline ZnO layer and a dense ZnO film. The porous Zn layer grew at oxygen content less than 33% and upon annealing in an oxygen flow at 400, 600, and 800 °C transformed to porous polycrystalline ZnO films. For oxygen contents ≥33% the obtained films were dense and polycrystalline with a 00.2 dominating orientation. X‐ray diffraction (XRD), scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), and Hall effect measurements were applied to characterize the obtained films.

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Phone: þ48 22 5487942 1 Â 10 8 V/&, respectively for C and Al implantation. Characterization by XRD, Raman and photoluminescence spectroscopy provides evidence that implantation damages the crystal lattice, yielding insulating properties. It is demonstrated that the isolation is stable up to 600 8C. We also demonstrate AlGaN/GaN HEMTs on semi-insulating Ammono-GaN substrates working both in DC (I DS ¼ 800 mA/mm) and RF (up to 6.5 GHz) mode with isolation prepared by means of the described approach.

The recent rapid development of transparent electronics, notably displays and control circuits, requires the development of highly transparent energy storage devices, such as supercapacitors. The devices reported to date utilize carbon-based electrodes for high performance, however at the cost of their low transparency around 50%, insufficient for real transparent devices. To overcome this obstacle, in this communication highly transparent supercapacitors were fabricated based on ZnO/MnO nanostructured electrodes. ZnO served as an intrinsically transparent skeleton for increasing the electrode surface, while MnO nanoparticles were applied for high capacitance. Two MnO synthesis routes were followed, based on the reaction of KMnO with Mn(Ac) and PAH, leading to the synthesis of β-MnO with minority α-MnO nanoparticles and amorphous MnO with embedded β-MnO, respectively. The devices based on such electrodes showed high capacitances of 2.6 mF cm and 1.6 mF cm, respectively, at a scan rate of 1 mV s and capacitances of 104 μF cm and 204 μF cm at a very high rate of 1 V s, not studied for transparent supercapacitors previously. Additionally, the Mn(Ac) devices exhibited very high transparencies of 86% vs. air, far superior to other transparent energy storage devices reported with similar charge storage properties. This high device performance was achieved with a non-acidic LiCl gel electrolyte, reducing corrosion and handling risks associated with conventional highly concentrated acidic electrolytes, enabling applications in safe, wearable, transparent devices.

In this paper, the results of detailed X-ray photoelectron spectroscopy (XPS) studies combined with atomic force microscopy (AFM) investigation concerning the local surface chemistry and morphology of nanostructured ZnO thin films are presented. They have been deposited by direct current (DC) reactive magnetron sputtering under variable absolute Ar/O2 flows (in sccm): 3:0.3; 8:0.8; 10:1; 15:1.5; 20:2, and 30:3, respectively. The XPS studies allowed us to obtain the information on: (1) the relative concentrations of main elements related to their surface nonstoichiometry; (2) the existence of undesired C surface contaminations; and (3) the various forms of surface bondings. It was found that only for the nanostructured ZnO thin films, deposited under extremely different conditions, i.e., for Ar/O2 flow ratio equal to 3:0.3 and 30:3 (in sccm), respectively, an evident and the most pronounced difference had been observed. The same was for the case of AFM experiments. What is crucial, our experiments allowed us to find the correlation mainly between the lowest level of C contaminations and the local surface morphology of nanostructured ZnO thin films obtained at the highest Ar/O2 ratio (30:3), for which the densely packaged (agglomerated) nanograins were observed, yielding a smaller surface area for undesired C adsorption. The obtained information can help in understanding the reason of still rather poor gas sensor characteristics of ZnO based nanostructures including the undesired ageing effect, being of a serious barrier for their potential application in the development of novel gas sensor devices.

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