Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Reference LCIB-ARTICLE-2007-010doi:10.1021/cr030726oView record in Web of Science Record created on 2007-02-14, modified on 2017-05-12

Inorganic and bioinorganic solvent exchange mechanisms.

The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin that the gate leakage current becomes too large. This led to the replacement of SiO2 by a physically thicker layer of a higher dielectric constant or ‘high-K’ oxide such as hafnium oxide. Intensive research was carried out to develop these oxides into high quality electronic materials. In addition, the incorporation of Ge in the CMOS transistor structure has been employed to enable higher carrier mobility and performance. This review covers both scientific and technological issues related to the high-K gate stack – the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure, their electronic structure, band offsets, electronic defects, charge trapping and conduction mechanisms, reliability, mobility degradation and oxygen scavenging to achieve the thinnest oxide thicknesses. The high K oxides were implemented in conjunction with a replacement of polycrystalline Si gate electrodes with metal gates. The strong metallurgical interactions between the gate electrodes and the HfO2 which resulted an unstable gate threshold voltage resulted in the use of the lower temperature ‘gate last’ process flow, in addition to the standard ‘gate first’ approach. Work function control by metal gate electrodes and by oxide dipole layers is discussed. The problems associated with high K oxides on Ge channels are also discussed.

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High-K materials and metal gates for CMOS applications

In the last two decades non-equilibrium spectroscopies have evolved from avant-garde studies to crucial tools for expanding our understanding of the physics of strongly correlated materials. The possibility of obtaining simultaneously spectroscopic and temporal information has led to insights that are complementary to (and in several cases beyond) those attainable by studying the matter at equilibrium. From this perspective, multiple phase transitions and new orders arising from competing interactions are benchmark examples where the interplay among electrons, lattice and spin dynamics can be disentangled because of the different timescales that characterize the recovery of the initial ground state. For example, the nature of the broken-symmetry phases and of the bosonic excitations that mediate the electronic interactions, eventually leading to superconductivity or other exotic states, can be revealed by observing the sub-picosecond dynamics of impulsively excited states. Furthermore, recent experimental...

Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium approach

In recent years Ion Beam Sputtering (IBS) has revealed itself as a powerful technique to induce surface nanopatterns with a large number of potential applications. These structures are produced in rather short processing times and over relatively large areas, for a wide range of materials, such as metals, insulators, and semiconductors. In particular, silicon has become a paradigmatic system due to its technological relevance, as well as to its mono-elemental nature, wide availability, and production with extreme flatness. Thus, this review focuses on the IBS nanopatterning of silicon surfaces from the experimental and the theoretical points of view. First, the main experimental results and applications are described under the light of the recently established evidence on the key role played by simultaneous impurity incorporation during irradiation, which has opened a new scenario for an improved understanding of the phenomenon. Second, the progress and state-of-art of the theoretical descriptions of the IBS nanopatterning process for this type of targets are discussed. We summarize the historical approach to IBS through simulation techniques, with an emphasis on recent information from Molecular Dynamics methods, and provide a brief overview of the earlier and most recent continuum models for pure and compound systems.

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Self-organized nanopatterning of silicon surfaces by ion beam sputtering

A method to accurately determine the sputter yield of the matrix from the earliest stages of a sputter profile is described Using the technique of medium-energy ion-scattering spectroscopy, this method provides data that enable a depth scale to be established from subnanometer depths onward It may be adapted to samples containing a thin amorphous surface layer (eg, a preamorphized shallow implant) or to crystalline surfaces containing a heavy-element marker layer In this Brief Report we have used this method to interpret the near-surface profile using erosion-rate data obtained from a 1-keV boron implant into a germanium preamorphized silicon (001) surface

Establishing an accurate depth-scale calibration in the top few nanometers of an ultrashallow implant profile

Medium energy ion scattering (MEIS) has been used to measure at the monolayer scale the strain profile of self-organized GaN quantum dots grown on (11–20) or a-plane AlN by molecular-beam epitaxy. By confronting the MEIS results with a structural analysis carried out by atomic force microscopy, it is established that the strain profile is anisotropic, i.e., fully elastic along [1–100] and a combination of plastic and elastic along [0001]. High resolution transmission electron microscopy measurements reveal the presence of misfit dislocations with 1/2 [0001] Burgers vector, consistent with MEIS data.

Anisotropic strain relaxation in a-plane GaN quantum dots

The quality of the interface between a HfO2 high-k gate dielectric and the Si substrate directly influences its electrical properties The chemical composition of the interfacial region of HfO2 deposited on a SiO2∕Si(100) substrate by pulsed liquid injection metal organic chemical vapor deposition at 430 and 550°C was investigated by medium energy ion scattering, angular resolved x-ray photoemission spectroscopy analysis, and high resolution transmission electron microscopy It is shown that the HfO2∕SiO2 interface is abrupt with low roughness and no silicate The interface roughness with SiO2 is found to be close to that generally measured in silicon technology (silicon oxide above silicon substrates) [E A Irene, Solid-State Electron, 45, 1207 (2001)] The analysis of the experimental results indicates that the deposition technique does not lead to the formation of an extended silicate layer at the HfO2∕SiO2 interface

Chemical interface analysis of as grown HfO2 ultrathin films on SiO2

The equations of motion are obtained for certain magnetic sources moving above a conducting plate and subject to the magnetic forces produced by the eddy currents in the plate. The effects of a small disturbance at time t=0 to a previously steady motion are investigated. It is shown that any small disturbance dies away, leaving the system in essentially the same state of steady motion as before.

Stability of Magnets Moving Above a Conducting Plane

The quality of the interface between a HfO2 high-k gate dielectric and the Si substrate directly influences its electrical properties. The chemical composition of the interfacial region of HfO2 deposited on a SiO2/Si(100) substrate by pulsed liquid injection metal organic chemical vapor deposition at 430 and 550 °C was investigated by medium energy ion scattering, angular resolved x-ray photoemission spectroscopy analysis, and high resolution transmission electron microscopy. It is shown that the HfO2/SiO2 interface is abrupt with low roughness and no silicate. The interface roughness with SiO2 is found to be close to that generally measured in silicon technology (silicon oxide above silicon substrates) [ E. A. Irene, Solid-State Electron., 45, 1207 (2001) ]. The analysis of the experimental results indicates that the deposition technique does not lead to the formation of an extended silicate layer at the HfO2/SiO2 interface

P Bailey

Papers

Establishing an accurate depth-scale calibration in the top few nanometers of an ultrashallow implant profile

Anisotropic strain relaxation in a-plane GaN quantum dots

Chemical interface analysis of as grown HfO2 ultrathin films on SiO2

Stability of Magnets Moving Above a Conducting Plane

Chemical interface analysis of as grown HfO[sub 2] ultrathin films on SiO[sub 2]