Zinc oxide can be called a multifunctional material thanks to its unique physical and chemical properties. The first part of this paper presents the most important methods of preparation of ZnO divided into metallurgical and chemical methods. The mechanochemical process, controlled precipitation, sol-gel method, solvothermal and hydrothermal method, method using emulsion and microemulsion enviroment and other methods of obtaining zinc oxide were classified as chemical methods. In the next part of this review, the modification methods of ZnO were characterized. The modification with organic (carboxylic acid, silanes) and inroganic (metal oxides) compounds, and polymer matrices were mainly described. Finally, we present possible applications in various branches of industry: rubber, pharmaceutical, cosmetics, textile, electronic and electrotechnology, photocatalysis were introduced. This review provides useful information for specialist dealings with zinc oxide.

Zinc Oxide-From Synthesis to Application: A Review.

Magnesium Oxide (MgO).- Zincblende Magnesium Sulphide (?-MgS).- Zincblende Magnesium Selenide (?-MgSe).- Zincblende Magnesium Telluride (?-MgTe).- Zinc Oxide (ZnO).- Wurtzite Zinc Sulphide (?-ZnS).- Cubic Zinc Sulphide (?-ZnS).- Zinc Selenide (ZnSe).- Zinc Telluride (ZnTe).- Cubic Cadmium Sulphide (c-CdS).- Wurtzite Cadmium Sulphide (w-CdS).- Cubic Cadmium Selenide (c-CdSe).- Wurtzite Cadmium Selenide (w-CdSe).- Cadmium Telluride (CdTe).- Cubic Mercury Sulphide (?-HgS).- Mercury Selenide (HgSe).- Mercury Telluride (HgTe).

Handbook on physical properties of semiconductors

Thin Friction The rubbing motion between two surfaces is always hindered by friction, which is caused by continuous contacting and attraction between the surfaces. These interactions may only occur over a distance of a few nanometers, but what happens when the interacting materials are only that thick? Lee et al. (p. 76; see the Perspective by Müser and Shakhvorostov) explored the frictional properties of a silicon tip in contact with four atomically thin quasi–two dimensional materials with different electrical properties. For all the materials, the friction was seen to increase as the thickness of the film decreased, both for flakes supported by substrates and for regions placed above holes that formed freely suspended membranes. Placing graphene on mica, to which it strongly adheres, suppressed this trend. For these thin, weakly adhered films, out-of-plane buckling is likely to dominate the frictional response, which leads to this universal behavior. A universal trend is observed for the friction properties of thin films on weakly adhering substrates. Using friction force microscopy, we compared the nanoscale frictional characteristics of atomically thin sheets of graphene, molybdenum disulfide (MoS2), niobium diselenide, and hexagonal boron nitride exfoliated onto a weakly adherent substrate (silicon oxide) to those of their bulk counterparts. Measurements down to single atomic sheets revealed that friction monotonically increased as the number of layers decreased for all four materials. Suspended graphene membranes showed the same trend, but binding the graphene strongly to a mica surface suppressed the trend. Tip-sample adhesion forces were indistinguishable for all thicknesses and substrate arrangements. Both graphene and MoS2 exhibited atomic lattice stick-slip friction, with the thinnest sheets possessing a sliding-length–dependent increase in static friction. These observations, coupled with finite element modeling, suggest that the trend arises from the thinner sheets’ increased susceptibility to out-of-plane elastic deformation. The generality of the results indicates that this may be a universal characteristic of nanoscale friction for atomically thin materials weakly bound to substrates.

Frictional Characteristics of Atomically-Thin Sheets

We fabricated a phosphor-conversion white light emitting diode (LED) using an InGaN chip that emits 400 nm near-ultraviolet (n-UV) light and phosphors that emit in the blue and yellow region. When the white LED was operated at a forward-bias current of 20 mA at room temperature (RT), the color temperature (Tcp), average color rendering (Ra), operating voltage (Vf) and luminous efficacy (ηL) were estimated to be 5800 K, 85.3, 3.2 V, and 26.1 lm/W, respectively. With increasing forward-bias current, the luminous flux increased almost linearly and was estimated to be 5.0 lm at 60 mA. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates obtained from the measured spectra remained almost constant during the forward-bias current increase from 0.5 mA to 60 mA.

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip : Semiconductors

In the age of technology, nanoparticles have proven to be one of the essential needs for development. These nanoparticles have the potential to be used for a wide variety of applications, thereby, development in improving the quality of nanoparticles, to make them more application specific, is still under research. In this regard, an important point to note is that the procedures employed in synthesizing nanoparticles require to be cost-effective and less-steps involved and have an additional advantage, i.e. they should be eco-friendly. This means that the synthesis procedure needs avoiding the use of harmful chemicals, and negligible generation of any noxious by-products. The green synthesis (biosynthesis) method employs simple procedures, easily available raw materials and ambiance for the synthesis process, where the precursors used are safe, with minute possibility for the production of harmful by-products. Considering these advantages, the current review includes a brief description on the various chemical and physical synthesis method of zinc oxide (ZnO) nanoparticles with emphasis on the biosynthesis of ZnO nanoparticles using plant extracts (and briefly microbes), the phytochemicals present in the plant extracts, the plausible mechanisms involved in the formation of ZnO nanoparticles and applications of the as-synthesized ZnO nanoparticles as photocatalysts and microbial inhibitors.

A review on bio-synthesized zinc oxide nanoparticles using plant extracts as reductants and stabilizing agents.

The structural and optical properties of the ZnO, Al-doped ZnO, Ga-doped ZnO, and In-doped ZnO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and ultraviolet-visible spectroscopy. All the nanorods grew with good alignment on the ZnO seed layers and the ZnO nanorod dimensions could be controlled by the addition of the various dopants. For instance, the diameter of the nanorods decreased with increasing atomic number of the dopants. The ratio between the nearband-edge emission (NBE) and the deep-level emission (DLE) intensities (INBE/IDLE) obtained by PL gradually decreased because the DLE intensity from the nanorods gradually increased with increase in the atomic number of the dopants. We found that the dopants affected the structural and optical properties of the ZnO nanorods including their dimensions, lattice constants, residual stresses, bond lengths, PL properties, transmittance values, optical band gaps, and Urbach energies.

https://www.koreascience.or.kr:443/article/JAKO201316349188725.pdf

Effects of Doping with Al, Ga, and In on Structural and Optical Properties of ZnO Nanorods Grown by Hydrothermal Method

ZnO seed layers were deposited on a quartz substrate using the sol-gel method, and Al-doped ZnO (AZO) nanorod array thin films were grown on the ZnO seed layers by the hydrothermal method with different Al concentrations ranging from 0 to 2.0 at. %. The structural and blue emission properties of the ZnO and AZO nanorod array thin films were investigated using scanning electron microscopy (SEM), x-ray diffraction, Ultraviolet-visible spectroscopy, and photoluminescence (PL). Al doping greatly affects the morphology of AZO nanorod array thin films. For an Al concentration of 2.0 at. %, it can be clearly seen from the SEM image that the hexagonal shape has changed into a prism-like shape. In the PL spectra, it is clear that the intensity ratio of the near-band-edge emission to the deep-level emission (DLE) increases as the Al concentration increases up to 2.0 at. %. The DLE peak (about 2.80 eV) in the blue emission region is found for the AZO nanorod array thin films. The transmittance spectra show that as compared to the ZnO nanorod array thin films, the AZO nanorod array thin films exhibited significantly improved transmittance in the visible region and a blue shift of the absorption edge.

Structural and blue emission properties of Al-doped ZnO nanorod array thin films grown by hydrothermal method

by change in the In content, especially at the In content of 3 at.%. The values of direct band gap were decreased with increase in the In content. The width of localized states in the optical band gap of the indium-doped ZnO thin films were changed with In content and the Urbach energy (EU) was changed inversely with optical band gap of the indium-doped ZnO thin films.

/pdf/growth-and-characterization-of-indium-doped-zinc-oxide-thin-1vtpx1jb8u.pdf

Growth and Characterization of Indium-Doped Zinc Oxide Thin Films Prepared by Sol-Gel Method

Zinc oxide (ZnO) thin films with different thicknesses were grown on Si and porous silicon (PS) by plasma-assisted molecular beam epitaxy (PA-MBE). The effects of the thickness and PS on the properties of the ZnO thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The ZnO thin films grown on PS exhibit a very smooth surface morphology even at a growth time of 5 min, which indicates that the films are in the 2D mode of grain growth. It is suggested that the optical properties, as well as the structural properties, of the ZnO thin films are enhanced by introducing PS. Also, the structural and the optical properties are improved as the thickness is increased.

Thickness Dependence of Properties of ZnO Thin Films on Porous Silicon Grown by Plasma-assisted Molecular Beam Epitaxy

Nanocomposites composed of nano-fibrous ZnO thin films and porous silicon (PS) were prepared and examined by atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) to investigate their structural and optical properties. PS, consisting of irregular and random nanosized-pores, was prepared by electrochemical anodization. The nano-fibrous ZnO thin films were grown on PS by the sol-gel spin-coating method. The texture coefficient (TC
 (hkl)) of the nano-fibrous ZnO thin films was calculated to determine the preferred orientation. The nano-fibrous ZnO thin films were grown with a c-axis preferred orientation. The residual stress in the films was reduced in the case of PS. The observed broad PL emission peak from 460 to 598 nm was attributed to coupled emission from ZnO to PS. The results show that white light luminescence with blue, green, and red emission peaks having highly uniform intensities can be obtained from the nanocomposite via a relatively simple and low-cost sol-gel spin-coating method.

Giwoong Nam

Papers

Effects of Doping with Al, Ga, and In on Structural and Optical Properties of ZnO Nanorods Grown by Hydrothermal Method

Structural and blue emission properties of Al-doped ZnO nanorod array thin films grown by hydrothermal method

Growth and Characterization of Indium-Doped Zinc Oxide Thin Films Prepared by Sol-Gel Method

Thickness Dependence of Properties of ZnO Thin Films on Porous Silicon Grown by Plasma-assisted Molecular Beam Epitaxy

White light emission from nano-fibrous ZnO thin films/porous silicon nanocomposite