Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

/pdf/prospects-of-colloidal-nanocrystals-for-electronic-and-3dxpyhl3r7.pdf

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectrics in thin-film form. The authors introduce the current state of development in the application of ferroelectric thin films for electronic devices and discuss the physics relevant for the performance and failure of these devices. Following this the review covers the enormous progress that has been made in the first-principles computational approach to understanding ferroelectrics. The authors then discuss in detail the important role that strain plays in determining the properties of epitaxial thin ferroelectric films. Finally, this review ends with a look at the emerging possibilities for nanoscale ferroelectrics, with particular emphasis on ferroelectrics in nonconventional nanoscale geometries.

/pdf/physics-of-thin-film-ferroelectric-oxides-3zmqphtpv1.pdf

Physics of thin-film ferroelectric oxides

We present a review of current research on the optical properties of ZnO nanostructures. We provide a brief introduction to different fabrication methods for various ZnO nanostructures and some general guidelines on how fabrication parameters (temperature, vapor-phase versus solution-phase deposition, etc.) affect their properties. A detailed discussion of photoluminescence, both in the UV region and in the visible spectral range, is provided. In addition, different gain (excitonic versus electron hole plasma) and feedback (random lasing versus individual nanostructures functioning as Fabry-Perot resonators) mechanisms for achieving stimulated emission are described. The factors affecting the achievement of stimulated emission are discussed, and the results of time-resolved studies of stimulated emission are summarized. Then, results of nonlinear optical studies, such as second-harmonic generation, are presented. Optical properties of doped ZnO nanostructures are also discussed, along with a concluding outlook for research into the optical properties of ZnO.

Optical properties of ZnO nanostructures.

The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin (1.4 nm) that its leakage current is too large. It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (κ) or 'high K' gate oxides such as hafnium oxide and hafnium silicate. Little was known about such oxides, and it was soon found that in many respects they have inferior electronic properties to SiO2 ,s uch as a tendency to crystallise and a high concentration of electronic defects. Intensive research is underway to develop these oxides into new high quality electronic materials. This review covers the choice of oxides, their structural and metallurgical behaviour, atomic diffusion, their deposition, interface structure and reactions, their electronic structure, bonding, band offsets, mobility degradation, flat band voltage shifts and electronic defects. The use of high K oxides in capacitors of dynamic random access memories is also covered.

/pdf/high-dielectric-constant-oxides-cotu2e70vd.pdf

High dielectric constant oxides

The scaling of complementary metal oxide semiconductor transistors has led to the silicon dioxide layer, used as a gate dielectric, being so thin (14?nm) that its leakage current is too large It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (?) or 'high K' gate oxides such as hafnium oxide and hafnium silicate These oxides had not been extensively studied like SiO2, and they were found to have inferior properties compared with SiO2, such as a tendency to crystallize and a high density of electronic defects Intensive research was needed to develop these oxides as high quality electronic materials This review covers both scientific and technological issues?the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure and reactions, their electronic structure, bonding, band offsets, electronic defects, charge trapping and conduction mechanisms, mobility degradation and flat band voltage shifts The oxygen vacancy is the dominant electron trap It is turning out that the oxides must be implemented in conjunction with metal gate electrodes, the development of which is further behind Issues about work function control in metal gate electrodes are discussed

https://iopscience.iop.org/article/10.1088/0034-4885/69/2/R02/pdf

High dielectric constant gate oxides for metal oxide Si transistors

The synthesis of nc-Si by reactive evaporation of SiO and subsequent thermal induced phase separation is reported. The size control of nc-Si is realized by evaporation of SiO/SiO2 superlattices. By this method an independent control of crystal size and density is possible. The phase separation of SiO into SiO2 and nc-Si in the limit of ultrathin layers is investigated. Different steps of this phase separation are characterized by photoluminescence, infrared absorption and transmission electron microscopy measurements. The strong room temperature luminescence of nc-Si shows a strong blueshift of the photoluminescence signal from 850 to 750 nm with decreasing crystal size. Several size dependent properties of this luminescence signal, like decreasing radiative lifetime and increasing no-phonon transition properties with decreasing crystal size are in good agreement with the quantum confinement model. Er doping of the nc-Si shows an enhancement of the Er luminescence at 1.54 µm by a factor of 5000 compared to doped SiO2 layers. The decreasing transfer time for the nc-Si to Er transition with decreasing crystal size can be understood as additional proof of increasing recombination probability within the nc-Si for decreasing crystal size.

/pdf/synthesis-and-size-control-of-si-nanocrystals-by-sio-sio2-t2ayvcbmzi.pdf

Synthesis and size control of Si nanocrystals by SiO/SiO2 superlattices and Er doping

Summary form only given. Nanoscaled structures play a major role in optoelectronic and semiconductor research with many applications already in a commercial state. Today's Si nanocrystals research is focused on the preparation of Si nanocrystals embedded in an oxide host. Methods applied for preparation are Si ion implantation into high quality oxides, sputtering of Si rich oxides or reactive evaporation of Si rich oxides. Using these methods the Si crystal size is controlled by the Si content in the SiO/sub 2/ matrix. Crystal size and number cannot be controlled independently. in addition, there is only a limited control of the size distribution. We present a new process that allows the size controlled preparation of silicon nanocrystals on 4 inch wafers.

Si based highly luminescent photonic structures

Silicon carbide carbonization layers were grown on (100) silicon substrates at intermediate pressures and comperatively low propane concentrations in hydrogen by application of a slow temperature ramp. Scanning and transmission electron microscopy (SEM and TEM) studies of the SiC/Si interfaces revealed pyramidal voids and micropipes, only voids or none of these Si out-diffusion defects depending on the specific CVD parameters. (orig.) 8 refs.

Formation and prevention of micropipes and voids in CVD carbonization experiments on (100) silicon

Phase separation and thermal crystallization of SiO/SiO 2 superlattices result in ordered arranged silicon nanocrystals. The preparation method enables independent control of particle size as well as of particle density and spatial position by using a constant stoichiometry of the layers. Infrared absorption and photoluminescence spectra are measured as a function of annealing temperature to study the phase separation process. Three photoluminescence emission bands are observed. A band centered at 560 nm is found in as-prepared samples and vanishes for annealing above 700 o C. A second band around 760 nm to 890 nm is detected for annealing temperatures above 500 o C. The superlattices show a strong luminescence and a size dependent blue shift in the visible and near-infrared region after crystallization for temperatures above 900 o C. The origin of the different photoluminescence bands at different phase separation stages of ultra thin SiO x layers are discussed based on transmission electron microscopy investigations and on correlations seen in photoluminescence spectra and infrared absorption. In addition, we report the PECVD preparation of amorphous SiO/SiO 2 superlattices which show a similar size dependent luminescence after crystallization.

Highly luminescent Si quantum dots: new ways for size, position, and density control

http://www-old.mpi-halle.mpg.de/mpi/publi/pdf/2251_97.pdf

Properties of pulsed laser deposited optical coatings

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