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A study was conducted to explore the physics and modeling of temperature dependence of various parasitic resistances in SiGe heterojunction bipolar transistors down to 30 K. The analysis of experimental data revealed that the bound state fraction factor is temperature dependent and could be applied to allow compact modeling of resistances from 30 to 300 K for moderately-doped regions.

A method is described that has allowed for the easy modification of design-kit-supplied models to predict and optimize mutual thermal coupling using commonly available CAD tools such as Cadence and Spectre. This method is used for optimizing a multitransistor SiGe PA cell in a 180-nm second-generation 120-GHz-peak [f.sub.T] SiGe technology for thermal balancing.

The noise behavior resulting from impact ionization (II) is assessed at room temperature for silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) with box Ge profile, featuring a maximum transit frequency of [f.sub.T] = 80 GHz. The noise parameters (NPs) measured over a wide range of collector-emitter voltages revealed that the weak avalanche model is accurate to capture II noise in examined SiGe HBTs.

The nitrogen composition dependence of the characteristics of TaN/HfLaON/[Hf.sub.1-x-y][N.sub.x][O.sub.y]/Si[O.sub.2]/Si MONOS memory devices is discussed. A wider memory window and a smaller high-temperature decay rate are observed in the [Hf.sub.0.3][N.sub.0.2][O.sub.0.5] MONOS devices.

Several studies are conducted to investigate the thermal stability of fully silicides (FUSI) NiSi/HF-based high-k gate stacks, when exposed to typical back-end-of-line (BEOL) nitrogen. The analysis reveals that the Ni diffusion through dielectrics in the Si channel is highly supported by the relatively weaker Ni-Ni bonds associated with Ni-rich phases coupled with grain boundary diffusion of liberated Ni.

Several in situ techniques are used to study the formation and degradation of NiSi films, when different alloying metals with a high melting point, like W, Ti and Ta, are added to pure Ni films in different concentrations at different temperatures. The results demonstrate the improvement in the morphological stability of the films on addition of such metals, which further increases the activation energy for NiSi formation.

A tight-binding parameter extraction scheme that is suitable for the modeling of intermetallic alloy systems is implemented. Augmented by a fitted repulsive energy contribution that takes the form of embedded atom potential, the tight-binding total energy method is applied in Monte Carlo simulations to compute the coefficients of thermal expansion for Mo3Si.

Several theoretical studies are conducted to explain the different thermoelectric properties exhibited by the nanostructured [Si.sub.1-x][Ge.sub.x] alloys. An increase in the phonon scattering probability of the grain boundaries is shown to lead to significant enhancement of the current state of the alloys.

Atom probe tomography study of clustering in the Al-Mg-Si system is described by understanding the impact of natural aging, preaging and alloy composition on the clustering behavior of solute atoms. Preaging has promoted the formation of clusters with an Mg:Si ratio close to 1 in both alloys, while natural aging has produced clusters with Mg:Si ratios similar to those of the alloys.

The power loss of two-dimensional hole gas (2DHG) due to acoustic phonons via deformation potential coupling and Pekar mechanism is calculated by considering the temperature dependent screening. Hot phonon effect has reduced the power loss of 2DHG and the power loss calculations are carried out for different carrier concentrations.

The dislocation structure at the initial stage of relaxation of [Ge.sub.x][Si.sub.1-x] films (x = 0.4-0.8) grown on Si(001) substrates tilted at 6 [degree] to the nearest (111) plane is analyzed. Samples annealed at higher temperatures contain misfit dislocation (MD) segments, which has lost their contrast on one of the TEM images taken to detect edge dislocation segments in the two-wave diffraction mode but do not coincide with the direction [110].

The article explains the magnetic, as well as the magnetothermodynamic properties of [Ho.sub.5][Si.sub.4] compounds. The heat capacity of the material is shown to be completely dependent on the temperature.

Several studies are conducted to explain the structure, magnetic properties and the magnetocaloric effect observed in the various [Nd.sub.5][Si.sub.3] compounds. The compounds are shown to be extremely beneficial for a large number of magnetic refrigeration applications.

The article explains the microstructure, as well as the mganetocaloric effects of the various La[Fe.sub.10.8][Co.sub.0.7][Si.sub.1.5][C.sub.0.2] compounds observed at different annealing times. The grains of the compounds are shown to considerably increase with an increase in the annealing time.

The magnetron cosputtering technique is employed to explain the various postannealing effects on the properties of the different hydrogenated amorphous Si(Mn) magnetic semiconductors. Annealing is shown to lead to a significant enhancement in the saturation magnetization, electrical conductivity and carrier concentration of the semiconductors.

The article explains the synthesis and the properties of the various La[(Fe,Co,Si).sub.13] bulk alloys and ribbons that are shown to exhibit high temperature magnetocaloric effects. The peak of magnetic entropy change taking place in these ribbons is shown to be smaller in the ribbons as compared to the annealed ingot counterparts.

Several studies are conducted to explain the impact of interstitial nitrogen on the phase transition and the magnetocalroic effect observed in the Mn(As,Si) systems. The Curie temperature of the systems is shown to increase with nitrogen atoms and decrease with silicon addition.

Several studies are conducted to explain the magnetic properties and the magnetocaloric effect of the different La[Fe.sub.11.2][Co.sub.0.7][Si.sub.1.1][C.sub.x] materials. The refrigerant capacity of the materials is shown to decrease with an increase in the C content of the materials.

Several magnetization measurements are conducted to explain the magnetic properties and the magnetocaloric effects observed in the antiferromagnetic ErTiSi compounds. These compounds are shown to be extremely beneficial for magnetic refrigeration applications.

A simple analytical expression is proposed that can predict in-plane and cross-plane values of thermal conductivity of superlattices from an approximate analytical expression that has joined a model expansion of the Boltzmann equation with a combination of the acoustic mismatch model and diffuse mismatch model for thermal boundary resistance. Extra attention is given to the low thermal conductivity predicted in the Si/Ge large period range, which current microscale models have failed to predict but are described in the present model.

Different types of scattering mechanisms are applied to compare an optimal value of the Seebeck coefficient in three, two, and one dimensions for Si/SiGe, [Bi.sub.2][Te.sub.3], PbTe, and SrTi[O.sub.3]. The increases in the thermoelectric power factor of nanostructures are attributed to the increase in the magnitude of the integrated density of states (DOS) and not the change in shape.

The acoustic detection method applied to the study of the magnetocaloric effect in Gd and [Gd.sub.5][([Ge.sub.1-x][Si.sub.x]).sub.4] compounds, is explored in the temperature range from 230 to 360 K and for magnetic fields up to 20 kOe. The acoustic method which is able to distinguish a second-order phase transition from a first-order magnetic-crystallographic one, is observed to show good sensitivity to detect spurious material in small quantities.

A study was conducted to examine the diffusion of silicon (Si) and germanium (Ge) in silicon-germanium [Si.sub.1-x][Ge.sub.x]-isotope heterostructures with Ge contents (where x = 0, 0.05, 0.25, 0.45, and 0.70) at a temperature range between 690 and 1270 degree [Celsius]. The significantly more pronounced diffusional jumps observed for Ge atoms compared to those of Si is explained with an increasing contribution of vacancies to self-diffusion in [Si.sub.1-x][Ge.sub.x] with x.

Aberration-corrected scanning-transmission electron microscopy (STEM) was used to determine the atomic structure in a Ni-diffused Si (001) surface layer. The results from STEM provide insight into the tetrahedral interstitial voids of a Si crystal occupied by Ni atoms, dissociation of Si atoms in the surface layer and the formation of Ca[F.sub.2]-type Ni[Si.sub.2] lattice at substrate temperature which matched the surface layer.

The dependence of the vibrational modes in rapid thermal chemical vapor deposited [Si.sub.1-x-y][Ge.sub.x][C.sub.y] films on the substitutional carbon concentration is analyzed by using Raman and infrared spectroscopy. The introduction of C into thin SiGe layers has reduced the average lattice constant and the results have confirmed the increase in the probability of creating third-nearest-neighbor pairs with increasing carbon content.

Lattice dynamics (LD) calculations and molecular dynamics (MD) simulations are used to predict the thermal resistance of semiconductor Si and Ge thin films. The results revealed that the ballistic and diffusive differences between the Ge/Si/Ge structures could be predicted by considering the frequency dependence of the phonon mean free paths.

The composition of [beta]- precipitates in an Al-Mg-Si alloy is examined by using atom probe tomography, ab initio density functional calculations and quantitative electron diffraction. Ab initio calculations have shown that replacing the [Si.sub.3]-site by aluminum has led to energetically favorable compositions consistent with the other phases in the precipitation sequence.

Several experimental and theoretical studies are conducted to explain the short time transient thermal behavior of the various solid-state microrefrigerators. The interplay existing between the Peltier and Joule effects is also discussed.

Nanodifferential scanning calorimetry (nano-DSC) at ultrarapid scan rates in a temperature-time regime not accessible with conventional apparatus is used to study the multilayer and bilayer Ni/Si thin films. The results indicated that use of heating rate [greater than] 10,000 degree [Celsius/s might open new routes for intermetallic micro- and nanofabrication of Ni/Si thin films, at temperatures well below those prevailing during explosive silicidation.

A combined materials science-electrical characterization of single crystalline Pr[O.sub.2](111)/Si(111) heterostructures are carried out to study the influence of postdeposition annealing in 1 bar oxygen at 300-600 degree [Celsius] on the dielectric properties of Pr[O.sub.2](111)/Si(111). The results from the temperature-dependent J-V studies indicated that the formation of the single crystalline Pr[O.sub.2]/amorphous Pr-silicate bilayer structure on Si(111) resulted in improved insulating properties and strong electrical instability phenomena in the form of a Maxwell-Wagner instability and dielectric relaxation.

The magnetic properties and magnetocaloric effects of the [Gd.sub.6][Co.sub.2][Si.sub.3] alloy are examined. [Gd.sub.6][Co.sub.2][Si.sub.3] has undergone a reversible second-order magnetic transition with a Curie temperature at room temperature.

The magnetic, magnetocaloric, and magnetoelastic properties of La[Fe.sub.11.57][Si.sub.1.43][B.sub.x] compounds are studied by using magnetization and strain gauge techniques. The studies have shown that the characteristics of the magnetocaloric effect of La[Fe.sub.11.57][Si.sub.1.43] is adjusted by a change in B concentration in the La[Fe.sub.11.57][Si.sub.1.43][B.sub.x] system.

Modified Deal-Grove model is used for extracting the parabolic rate constants related to the oxygen diffusion at different temperature and the activation energy of oxygen diffusivity finding that oxygen diffusion is still the rate-limiting step. The oxidation behavior is attributed to the strain effects associated with the volume change in converting Si/SiGe to Si[O.sub.2]/mixed oxide at different oxidation stages.

An analytically modeled mechanism of strain relief of pseudomorphic [Si.sub.1-x][Ge.sub.x]/Si(100) heterostructures by [Si.sup.+] ion implantation and annealing is presented. The detrimental effect of local amorphization of the SiGe layer on its relaxation and on strain transfer to the Si-cap layer is also addressed.

The oxidation of ultrathin strained silicon layers grown on relaxed [Si.sub.0.9][Ge.sub.0.1] substrates under high thermal budget conditions in [N.sub.2]O ambient at 800 degree [Celsius] is reported. The results suggested that the observed high density of interface traps is attributed to the two existing interfaces of the strained Si layer, the Si[O.sub.2]/strained-Si and the strained-Si/[Si.sub.0.9][Ge.sub.0.1].

A thermometric-fieldmetric method is developed by which Fe-Si laminations are characterized under either alternating or rotational excitation up to peak induction. The power losses at high inductions are determined by measuring the rate of rise of the specimen temperature and the imperfect adiabatic behavior of the material is accounted for by the physical modeling of the thermal diffusion process.

Interlayer exchange couplings are examined for [Co.sub.2]Fe[Al.sub.0.5][Si.sub.0.5]/Cr/[Co.sub.2]Fe[Al.sub.0.5][Si.sub.0.5] trilayers films grown on MgO (001) single crystal and thermally oxidized Si substrates. Strong exchange couplings are observed for the films with the Cr spacer layer and the relationship of interlayer couplings with the structure is discussed.

A high resolution transmission electron microscopy was used to study the structures of the GeSi/Si(001) islands overgrown with the Si capping layer of different thicknesses at temperature 300 degree Celsius. The defect-free Si capping layer with flat surface could be obtained by two-step deposition of 20-nm-thick Si capping layer, first deposited at a low temperature of 300 degree Celsius followed by 70-nm-thick Si capping layer deposition at a high temperature of 640 degree Celsius.

Nonequilibrium molecular dynamics (NEMD) simulations are performed in order to understand the effect of factors such as tensile versus compressive straining on the thermal conductivity of Si-Ge superlattices at three different temperatures. Compressive and tensile strains are important factors in tailoring the thermal conductivity of the superlattices and the straining has reduced the thermal conductivity.

The thermal conductivity of Si/SiGe superlattice films is evaluated. The studies have shown that the interface resistance due to the interface scattering/roughness has dominated the effective thermal conductivity, especially when the superlattice period is small.

The velocity and activation energy of dislocation motions in phosphorous (P)-implanted silicon-germanium (SiGe)/silicon (Si) heterostructures with a Ge are determined by using an etching method and the x-ray Lang topography method. The reduction in the velocities and the increase in the activation energies of the dislocation motions are attributed to the generation of microdefects, which has provided resistance to the gliding motion of a threading dislocation.

High undercooling is achieved in bulk eutectic [Ni.sub.70.2][Si.sub.29.8] alloy melt by using glass fluxing and cyclic superheating. The forming process of quasiregular microstructure is shown to be due to a transition from faceted-faceted to nonfaceted-nonfaceted eutectic concurring with increasing undercooling.

Ultrathin Si and SiGe films on insulator are used as templates for preparing hybrid metal/semiconductor rolled-up tubes and structured Cr films are thermally evaporated on SiGe- and Si-on-insulator substrates. A cross section of a Cr/SiGe tube is examined by transmission electron microscopy and electron energy loss spectroscopy.

The ability of molecular-dynamics simulation to analyze the thermal transport in Si-Ge alloys is examined. The results have major implications for using classical molecular-dynamics simulations for predicting properties of alloy materials near and below the Debye temperature.

The effect of Nd and Co substitution on magnetic entropy changes and hysteresis losses is examined for the cubic Na[Zn.sub.13]-type La[Fe.sub.13]-type La[Fe.sub.13-x][Si.sub.x] compounds. The Co-doped Na[Zn.sub.13]-type LaNdFeSi compounds might be a suitable candidate for magnetic refrigerant near room temperature.