羟氨苄青霉素引起大疱性类天疱疮样疹

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

We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.

Structural (n,m) determination of isolated single wall carbon nanotubes by resonant Raman scattering

Porous anodic aluminum oxide: anodization and templated synthesis of functional nanostructures.

Instabilities in semiconductor heterostructure growth can be exploited for the self-organized formation of nanostructures, allowing for carrier confinement in all three spatial dimensions. Beside the description of various growth modes, the experimental characterization of structural properties, such as size and shape, chemical composition, and strain distribution is presented. The authors discuss the calculation of strain fields, which play an important role in the formation of such nanostructures and also influence their structural and optoelectronic properties. Several specific materials systems are surveyed together with important applications.

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Structural properties of self-organized semiconductor nanostructures

A novel C-MOS compatible silicon gas flow sensor using porous silicon for thermal isolation has been designed and fabricated. The small sensor size combined with the very good thermal isolation by porous silicon assure fast response, with a time constant of the order of 1.5 ms. The principle of operation is based on heat transfer from a polysilicon resistor to the fluid and the detection of the flow-induced temperature difference by Al/polysilicon thermopiles, integrated at both sides of the heater. The sensor has been evaluated in nitrogen flows from 0 to 0.4 m/s. The sensitivity per heating power is 6.0 mV/(m/s)W and the responsivity is 0.65 V/W. The noise equivalent power and the minimum detectable velocity are 1.5×10 −8 W/Hz 1/2 and 4.1×10 −3 m/s, respectively. The chip size is 1.1 mm×1.5 mm.

Novel C-MOS compatible monolithic silicon gas flow sensor with porous silicon thermal isolation

Metal–insulator–semiconductor structures with a layer of silicon nanocrystals embedded within the SiO2 layer at a tunneling distance from a p-type silicon substrate and fabricated using chemical vapor deposition, oxidation, and annealing, exhibited charge trapping, determined from the capacitance–voltage (C–V) characteristics, which abruptly increased at fields above 2.5 MV/cm. Electrons or holes are trapped when biasing the structure into inversion or accumulation, respectively, and retention of trapped charge is demonstrated. The I–V characteristics exhibit an N-shaped form, indicating screening effects due to charging; an initial current spike, attributed to transient charging of nanocrystals, occurs at the same voltage causing abrupt C–V shift increase, with Fowler–Nordheim current rising at higher voltages. These structures are promising for memory device applications.

Charging effects in silicon nanocrystals within SiO2 layers, fabricated by chemical vapor deposition, oxidation, and annealing

Thin films of the high-k dielectric Y2O3 are grown on Si (001) substrates by e-beam evaporation in ultrahigh vacuum (UHV), aiming at correlating structural quality with electrical behavior. Films grown at high temperature of ∼450 °C have reproducibly good epitaxial crystalline quality although they exhibit poor electrical behavior. The best electrical properties are measured in films grown at a low to intermediate temperature range around 200 °C, although these films have inferior structural quality, exhibiting texturing or polycrystallinity. A possible explanation for the observed low leakage current (∼10−6 A/cm2 at +1 V) in these films is the presence of a thick (15–20 A) and uniform interfacial amorphous layer typically formed during growth because of the oxidation of the silicon substrate. This layer is significantly reduced in samples grown at high temperature, while it almost disappears after in situ annealing to 650 °C in UHV, producing sharp interfaces and very good, stoichiometric crystalline Y2O3 epitaxial layers.

Structural and electrical quality of the high-k dielectric Y2O3 on Si (001): Dependence on growth parameters

Si/SiO2 superlattices on oxidized silicon wafers were fabricated by successive cycles of silicon deposition and high-temperature thermal oxidation. Silicon films were deposited by low-pressure chemical vapor deposition at 580 °C. As-deposited silicon was amorphous, and it exhibited two weak photoluminescence (PL) peaks in the visible range, a stable one at ≅650 nm and an unstable one at 530–550 nm. By oxidation at 900 °C, a drastic increase of the stable PL peak was observed with an initial redshift from 650 to 800–900 nm and a subsequent blueshift down to 680–700 nm. Its position and intensity depended on the oxidation time. For prolonged oxidation, PL disappeared. The observed PL is attributed to silicon crystallites passivated by oxygen. Localized states at the Si/SiO2 interface limit the emitted wavelength. The PL peak from superlattices was at the same position as from one bilayer, while a superlinear increase in PL intensity was observed by increasing the number of bilayers.

Photoluminescence from nanocrystalline silicon in Si/SiO2 superlattices

In this work, the thermal properties of suspended porous silicon (PS) micro-hotplates are investigated. The micro-hotplates are fabricated by a novel technique, based on the isotropic etching of silicon under a PS layer, in a high-density plasma reactor. Suspended PS micro-hotplates with integrated heaters have been fabricated and characterized. Both the supporting beams and the rim surrounding the membrane are made of PS. This results in minimization of the thermal losses to the substrate. Very high local temperatures on the micro-hotplates (higher than 600 °C) with very low power consumption (only a few tens of mW) have been obtained, due to the very low thermal conductivity of PS, which is comparable to that of thermal oxide and it is much lower than that of silicon nitride, typically used for thermal sensor applications.

Androula G. Nassiopoulou

Papers

Novel C-MOS compatible monolithic silicon gas flow sensor with porous silicon thermal isolation

Charging effects in silicon nanocrystals within SiO2 layers, fabricated by chemical vapor deposition, oxidation, and annealing

Structural and electrical quality of the high-k dielectric Y2O3 on Si (001): Dependence on growth parameters

Photoluminescence from nanocrystalline silicon in Si/SiO2 superlattices

Thermal properties of suspended porous silicon micro-hotplates for sensor applications