Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high-k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum...

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics

We investigate the electronic properties of nanocrystalline cerium oxide $({\mathrm{CeO}}_{x})$ films, grown by various techniques, and we establish universal relations between them and the film structure, composition, and morphology The nanocrystalline ${\mathrm{CeO}}_{x}$ films mainly consist of ${\mathrm{CeO}}_{2}$ grains, while a considerable concentration of trivalent ${\mathrm{Ce}}^{3+}$ is distributed at the ${\mathrm{CeO}}_{2}$ grain boundaries forming amorphous ${\mathrm{Ce}}_{2}{\mathrm{O}}_{3}$ A small portion of ${\mathrm{Ce}}^{3+}$ is also located around O-vacancy sites The optical properties of the ${\mathrm{CeO}}_{x}$ films are considered, taking into account the reported band-structure calculations The fundamental gap ${E}_{g}$ of ${\mathrm{CeO}}_{x}$ is due to the indirect $\mathrm{O}2\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{Ce}4f$ electronic transition along the L high-symmetry lines of the Brillouin zone and it is correlated with the $[{\mathrm{Ce}}^{3+}]$ content, explaining the redshift of ${E}_{g}$ in nanostructured ${\mathrm{CeO}}_{x},$ which is due to the ${\mathrm{Ce}}^{3+}$ at the grain boundaries and not due to the quantum-size effect itself We also correlate the energy position of the $\mathrm{O}2\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{Ce}4f$ electronic transition, which varies up to 160-meV wide, with the lattice constant of the ${\mathrm{CeO}}_{2}$ grains We also show that the higher-order transitions are more sensitive to film composition The refractive index, far below ${E}_{g},$ is explicitly correlated with the film density, independently of the ${\mathrm{Ce}}^{3+}/{\mathrm{Ce}}^{4+}$ and O concentrations, grain size, and lattice parameter The density is also found to be the major factor affecting the absolute value of the ${\ensuremath{\varepsilon}}_{2}$ peak, which corresponds to the $\mathrm{O}2\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{Ce}4f$ electronic transition

Structure-dependent electronic properties of nanocrystalline cerium oxide films

Effect of the tungsten oxidation states in the thermal coloration and bleaching of amorphous WO3 films

Ceria is a transparent oxide suitable for various optical and optoelectronic devices. In this work, we tailor independently the refractive index n and fundamental gap Eg of nanocrystalline Ceria films by varying the substrate temperature or using Ar+ ion beams during growth with electron beam evaporation. Spectroscopic ellipsometry and x-ray reflectivity are employed to study n and Eg and to identify the physical parameters that affect them. We correlate n (varies from 1.65 to 2.15 in the studied films) with the film density through a universal, square law. The film composition strongly affects Eg, which varies from 2.8 to ∼2.0 eV. The optical absorption below 3 eV and the Eg shift are attributed to O-defect states and not to modifications in interband transitions.

Optical performance of nanocrystalline transparent ceria films

Nanotechnology is the branch of science which deals with particles ranging between 1–100 nm. These particles are called nanoparticles, and they exhibit unique electronic, optical, magnetic, and mechanical properties, which make them different from the bulk material. These properties of nanomaterials help them to find a variety of applications in the biomedical, agricultural, and environmental domains. Cerium oxide nanoparticles have gained a lot of attention as a potential future candidate for ending various kinds of problems by exhibiting redox activity, free radical scavenging property, biofilm inhibition, etc. Synthesis of these nanoparticles can be performed very easily by utilizing chemical or biological methods. But in this review, the focus is laid on the biosynthesis of these nanoparticles; as the biosynthesis method makes the cerium oxide nanoparticle less toxic and compatible with the living tissues, which helps them to find their path as an anticancer, anti-inflammatory and antibacterial agents. The pre-existing reviews have only focused on details relating to properties/applications/synthesis; whereas this review draws attention towards all the aspects in single review covering all the details in depth such as biosynthesis methods and its effect on the living tissues, along with properties, biomedical applications (diagnostic and therapeutic) and future outlook of the cerium oxide nanoparticle.

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George Atanassov

Papers

Optical properties of TiO2, Y2O3 and CeO2 thin films deposited by electron beam evaporation

Mechanical, optical and structural properties of TiO2 and MgF2 thin films deposited by plasma ion assisted deposition

Antireflection coatings on KCl single-crystal windows with low optical loss