Atomic layer deposition (ALD) is a thin film technology that in the past two decades rapidly developed from a niche technology to an established method. It proved to be a key technology for the surface modification and the fabrication of complex nanostructured materials. In this Progress Report, after a short introduction to ALD and its chemistry, the versatility of the technique for the fabrication of novel functional materials will be discussed. Selected examples, focused on its use for the engineering of nanostructures targeting applications in energy conversion and storage, and on environmental issues, will be discussed. Finally, the challenges that ALD is now facing in terms of materials fabrication and processing will be also tackled.

Low dimensional materials have been examined as electrocatalysts for the hydrogen evolution reaction (HER). Among them, two-dimensional Transition Metal Dichalcogenides (2D-TMDs) such as MoS 2 have been identified as potential candidates. However, the performance of TMDs towards HER in both acidic and basic media remains inferior to that of noble metals such as Pt and its alloys. This calls for investigating the influence of controlled defect engineering of 2D Hydrothermal synthesis 6.5ű0.04

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SummaryA study of transmittance and photoluminescence spectra on the growth of oxygen-rich ultra-thin ZnO films prepared by atomic layer deposition is reported. The structural transition from an amorphous to a polycrystalline state is observed upon increasing the thickness. The unusual behavior of the energy gap with thickness reflected by optical properties is attributed to the improvement of the crystalline structure resulting from a decreasing concentration of point defects at the growth of grains. The spectra of UV and visible photoluminescence emissions correspond to transitions near the band-edge and defect-related transitions. Additional emissions were observed from band-tail states near the edge. A high oxygen ratio and variable optical properties could be attractive for an application of atomic layer deposition (ALD) deposited ultrathin ZnO films in optical sensors and biosensors.

Since the first report on ultraviolet lasing from ZnO nanowires (NWs), [1] remarkable effort has been dedicated to the development of novel synthesis routes for 1D ZnO nanostructures. Ordered arrays of 1D ZnO NWs have a promising future as applications in electronic and optoelectronic devices, because they are expected to improve the performance of various nanodevices such as short-wavelength lasers, [1] nanostructured solar cells, [2,3] electroluminescent, [4] and field-emission devices.[5]What is now a relevant area of focus in nanoscience involves the preparation of higher-order assemblies, arrays, and superlattices of these 1D nanostructures. [6] Recently, many efforts have focused on the integration of 1D nanoscale building blocks into 3D architectures. Hollow urchin-like ZnO NWs that combine properties of 3D and 1D materials may emerge as a more interesting alternative than simple arrays of NWs due to the higher specific surface and porosity, [7] especially for application in dye and semiconductor-sensitized solar cells. [3,8] To date, there are only two strategies to synthesize hollow urchin-like ZnO NWs. The first one [9] is a wet-chemical route that uses a modified Kirkendall process, by which zinc powders that are spherical in shape are transformed into hollow urchin-like ZnO NWs dispersed in solution. The second strategy [10][11][12] is based on the calcination of metallic Zn microsphere powders at relatively high temperature (500-750 8C). With these two approaches, ZnO nanostructures are often randomly distributed (in size and organization), which may limit their practical applications as building blocks in nanodevices. Nevertheless, it is essential for the fabrication of nanodevices to assemble NW-structured hollow spheres with a uniform size in ordered arrays, since such an organisation combines the merits of patterned arrays and nanometer-sized materials. Until now, a suitable technique is still missing for the fabrication of ordered arrays of hollow urchin-like ZnO NWs with tunable sizes.In this paper, we report on a novel approach to fabricate well-ordered hollow urchin-like single-crystal ZnO NWs with controlled NW and core dimensions. The method combines the formation of a polystyrene (PS) microsphere colloidal mono/ multilayer and the electrodeposition of ZnO NWs, followed by the elimination of the PS microspheres, which play the role of a template. It is shown that the light scattering properties of such an ordered architecture exceed those of ZnO NW arrays. Applications as 3D building blocks in the field of nanostructured solar cells are discussed.Mono/multilayers of PS spheres covering conductive substrates have been used as templates to electrodeposit inverse opal structures. [13,14] In such cases the nucleation of ZnO took place at the interstitial sites (on a conductive substrate) between the PS spheres leading to different morphologies depending on the employed method. Our strategy of electrodeposition differs from those previously described by the mode of nucleation and growth. In our ...

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Nanolaminates are of great interest for their unique properties such as high dielectric constants and advanced mechanical, electrical, and optical properties. Here we report on the tuning of optical and structural properties of Al 2 O 3 /ZnO nanolaminates designed by atomic layer deposition (ALD). Structural properties of nanolaminates were studied by SEM, GIXRD, and AFM. Optical characterization was performed by transmittance and photoluminescence (PL) spectroscopy. Complex study of monolayer properties was performed by ellipsometry. Optical constants for Al 2 O 3 and ZnO monolayer were calculated. The band gap of ZnO single layers and the excitonic PL peak position were shifted to the UV region related to quantum confinement effects. No peaks in the UV region were observed in nanolaminates with 2 nm ZnO single layer thickness due to fully depleted region in small crystalline grains (<2 nm). The improved room temperature photoluminescence of nanolaminates makes them prominent materials for optical biosensors applications.

Raman spectroscopy of a single 40 nm 3C‐SiC nanowire (NW) has been achieved at room temperature with the use of surface‐enhanced Raman scattering (SERS). The structure used to enhance the Raman scattering process is based on a tungsten tip covered by a thin gold layer; a NW is attached to the apex of this tip. The specific dimensions of the SiC NWs (diameters are a few tens of nanometers and lengths are a few micrometers) allow us to study several parts of an individual NW according to the lateral resolution of the Raman microspectrometer. High‐resolution transmission electron microscopy (HRTEM) images show both atomic arrangements in the SiC NWs with growth predominantly in the [111] direction and abundant structural defects. Effort has been focused on the correlation between the Raman spectroscopic profiles and the structural deformations. The Fano interference features of the sharp phonon lines have been used to evaluate the free carrier concentration.