We review the nucleation and growth of different Ga₂O₃polymorphs with several techniques, giving practical guidelines for their synthesis.

We prepared by molecular-beam epitaxy and studied structures of InAs quantum dots embedded in InxGa1−xAs confining layers. The structures were designed so that the strain of quantum dots could be controlled independently of In composition of confining layers. In such a way, we single out the effect of strain in quantum dots on the energy of photoluminescence emission. We show that strain can be effectively used to tune the emission energy of quantum dots, and that room-temperature emission at 1.3 μm can be obtained. Our results suggest that by quantum-dot strain engineering, it will be possible to extend emission wavelength beyond 1.55 μm.

We present a complete study both by experiments and by model calculations of quantum dot strain engineering, by which a few optical properties of quantum dot nanostructures can be tailored using the strain of quantum dots as a parameter. This approach can be used to redshift beyond $1.31\mu \mathrm{m}$ and, possibly, towards $1.55\mu \mathrm{m}$ the room-temperature light emission of InAs quantum dots embedded in InGaAs confining layers grown on GaAs substrates. We show that by controlling simultaneously the lower confining layer thickness and the confining layers’ composition, the energy gap of the quantum dot material and the band discontinuities in the quantum dot nanostructure can be predetermined and then the light emission can be tuned in the spectral region of interest. The availability of two degrees of freedom allows for the control of two parameters, which are the emission energy and the emission efficiency at room temperature. The $\mathrm{In}\mathrm{As}∕\mathrm{In}\mathrm{Ga}\mathrm{As}$ structures were grown by the combined use of molecular beam epitaxy and atomic layer molecular beam epitaxy; their properties were studied by photoluminescence and photoreflectance spectroscopies and by atomic force microscopy; in particular, by means of photoreflectance not only the spectral features related to quantum dots were studied but also those of confining and wetting layers. The proposed approach has been used to redshift the room-temperature light emission wavelength up to $1.44\mu \mathrm{m}$ . The optical results were analyzed by a simple effective-mass model that also offers a rationale for engineering the properties of structures for efficient long-wavelength operation.

Two-dimensional (2D) materials such as graphene, transition metal dichalcogenides, and boron nitride have recently emerged as promising candidates for novel applications in sensing and for new electronic and photonic devices. Their exceptional mechanical, electronic, optical, and transport properties show peculiar differences from those of their bulk counterparts and may allow for future radical innovation breakthroughs in different applications. Control and reproducibility of synthesis are two essential, key factors required to drive the development of 2D materials, because their industrial application is directly linked to the development of a high-throughput and reliable technique to obtain 2D layers of different materials on large area substrates. Among various methods, chemical vapour deposition is considered an excellent candidate for this goal thanks to its simplicity, widespread use, and compatibility with other processes used to deposit other semiconductors. In this review, we explore the chemical vapour deposition of MoS₂, considered one of the most promising and successful transition metal dichalcogenides. We summarize the basics of the synthesis procedure, discussing in depth: (i) the different substrates used for its deposition, (ii) precursors (solid, liquid, gaseous) available, and (iii) different types of promoters that favour the growth of two-dimensional layers. We also present a comprehensive analysis of the status of the research on the growth mechanisms of the flakes.