Carbon often appears in Si in concentrations above its solubility. In this article, we propose a comprehensive model that, taking diffusion and clustering into account, is able to reproduce a variety of experimental results. Simulations have been performed by implementing this model in a Monte-Carlo atomistic simulator. The initial path for clustering included in the model is consistent with experimental observations regarding the formation and dissolution of substitutional C-interstitial C pairs (C s-C i). In addition, carbon diffusion profiles at 850 and 900°C in carbon-doping superlattice structures are well reproduced. Finally, under conditions of thermal generation of intrinsic point defects, the weak temperature dependence of the Si interstitial undersaturation and the vacancy supersaturation in carbon-rich regions also agree with experimental measurements.

In order to simulate the diffusion kinetics during thermal treatments in SiGe heterostructures, a physically-based atomistic model including chemical and strain effects has been developed and implemented into a nonlattice atomistic kinetic monte carlo (KMC) framework. This model is based on the description of transport capacities of native point defects (interstitials and vacancies) with different charge states in SiGe alloys in the whole composition range. Lattice atom diffusivities have been formulated in terms of point defect transport, taking into account the different probability to move Si and Ge atoms. Strain effects have been assessed for biaxial geometries including strain-induced anisotropic diffusion, as well as charge effects due to strain-induced modifications of the electronic properties. Si-Ge interdiffusion in heterostructures has been analyzed from an atomistic perspective. A limited set of physical parameters have been defined, being consistent with previously reported ab initio calculations and experiments. The model has been implemented into a nonlattice KMC simulator and the relevant implementation details and algorithms are described. In particular, an efficient point defect mediated Si-Ge exchange algorithm for interdiffusion is reported. A representative set of simulated interdiffusion profiles are shown, exhibiting good agreement with experiments.

The hydrogen bonds involving sulfur in the furfuryl mercaptan monohydrate are compared with the interactions originating from the hydroxyl group in furfuryl alcohol. The dimers with water were created in a supersonic jet expansion and characterized using microwave spectroscopy and supporting molecular orbital calculations. In furfuryl alcohol-water, a single isomer is observed, in which the water molecule forms an insertion complex with two simultaneous hydrogen bonds to the alcohol (O-H⋅⋅⋅O ) and the ring oxygen (O -H⋅⋅⋅O ). When the alcohol is replaced by a thiol group in furfuryl mercaptan-water, two isomers are observed, with the thiol group preferentially behaving as proton donor to water. The first isomer is topologically equivalent to the alcohol analog but the stronger hydrogen bond is now established by water and the ring oxygen, assisted by a thiol S-H⋅⋅⋅O hydrogen bond. In the second isomer the sulfur group accepts a proton from water, forming a O -H⋅⋅⋅S hydrogen bond. Binding energies for the mercaptan-water dimer are predicted around 12 kJ mol weaker than in the alcohol hydrate (B3LYP-D3(BJ)). The non-covalent interactions in the furfuryl dimers are dominantly electrostatic according to a SAPT(0) energy decomposition, but with increasing dispersion components in the mercaptan dimers, which are larger for the isomer with the weaker O -H⋅⋅⋅S interaction.

Water forms weak H-bonds with thenyl compounds, simultaneously retaining internal mobility in the dimer.

Room temperature conductance transients in the SiN x :H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder-induced gap-state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model. © 1997 American Institute of Physics. ͓S0003-6951͑97͒03732-7͔Presently, ultrathin silicon dioxide gates ͑30-40 Å͒ are required as a consequence of the reduction in the ultralargescale-integration ͑ULSI͒ silicon device dimensions. On the other hand, silicon nitride, Si 3 N 4 , has been successfully used as an insulator with different III-V semiconductors. Two important properties of silicon nitride ͑Si 3 N 4 ͒ make it a candidate to substitute silicon dioxide, SiO 2 , in ultrathin dielectric structures: silicon nitride has a higher dielectric constant and exhibits a better performance as a diffusion barrier than silicon dioxide. Nevertheless, the interface between Si 3 N 4 and Si is not as well known as the SiO 2 /Si interface and significantly higher densities of interfacial states are always displayed by the silicon nitride/silicon structure.In this letter we report for the first time the existence of conductance transients in Al/Si 3 N 4 /Si structures. As we show later, this behavior is related to the existence of a spatial distribution of interface states. We use metal-insulatorsemiconductor ͑MIS͒ diodes in which a 550-Å-thick SiN x :H film was directly deposited on ͗100͘ n-type silicon by electron-cyclotron-resonance ͑ECR͒ plasma at 200°C. Silicon nitride films have been fabricated with a wide composition range 1 from Si-rich to near stoichiometric and N-rich films. For compositions far from the stoichiometry the hydrogen content increases and the number of electrically active defects in the film increases due to the distortion in bonds induced by hydrogen, 2 in spite of the dangling bond saturation that it produces. In a previous work 3 we have proved by capacitance-voltage ͑C-V͒ and deep-level transient spectroscopy ͑DLTS͒ studies that the electrical properties of these films are closely related to hydrogen content. We observed hysteresis phenomena in the C-V curves. This behavior has been previously reported by Lau et al. 4 and may be understood by the defect model suggested by Hasegawa et al. 5,6 These authors proposed that the interface states are distributed both in energy and in space. This distribution is called disorder-induced gap-state ͑DIGS͒ continuum. Emission and capture of free electrons by states located far from the interface can occur by mean of tunneling mechanisms.7 When bias varies from inversion to accumulation, electrons in the semiconductor conduction band are captured by emptied interface states, whereas when moving in the opposite direction electrons are emitted from filled ...