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The present study focuses mainly on non-electrochemical investigation of thin barrier-like oxide films formed under different pulse frequencies. The TEMinvestigation principally shows amorphous oxide films, which are dense and free of pores. The various pulse experiments have no influence on these film properties. The oxide growth factor was calculated to 1.06 nmV-1 in all cases. The microstructure (crystallographic orientation, grain boundaries) of the underlying substrate does not affect the oxide films. Independent of the pulse frequency, electrolyte species are not incorporated into the oxide films. The evidenced differences in the filmthickness are caused by intrinsic peculiarities of the high-field mechanismof growing oxide. [ABSTRACT FROM AUTHOR]

The mechanism of graphitic ordering of atomic C on Ni was investigated at temperatures ranging from room temperature to 550 °C. The C/Ni films were prepared by ion beam sputtering. Their structure has been determined by Rutherford backscattering spectrometry/nuclear reaction analysis, X-ray photoelectron spectroscopy, Raman spectroscopy and cross-sectional transmission electron microscopy. A temperature-induced and a Ni-induced enhancement of graphitic ordering is demonstrated. The Ni-effect is responsible for the formation of a bi-layer structure of the C films at higher deposition temperatures. In the bi-layers, C forms graphenic planes parallel to the Ni surface within a thickness range of 1–2 nm. Further deposited C grows preferentially perpendicular to the surface. The results are discussed on the basis of hyperthermal atom deposition, surface diffusion, metal-induced crystallization and dissolution-precipitation. Our findings point to a dominating role of surface diffusion-assisted crystallization in the carbon ordering process. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the nitrogen content on the thermal stability and degradation mechanisms of Ta–Si–N diffusion barriers was studied using methods that prove Cu interdiffusion. On the one hand, glancing angle X-ray diffraction was applied to detect Cu3Si formation after annealing of Cu/Ta–Si–N/Si layer stacks. On the other hand, a combined secondary ion mass spectroscopy and transmission electron microscopy analysis of Ta–Si–N/Cu/Ta–Si–N/SiO2/Si samples was performed. For a detailed investigation of the microstructure evolution, the crystallization behavior of both Cu-capped and uncapped Ta–Si–N/Si samples was analyzed using X-ray diffraction. In the case of an uncapped Ta73Si27 film, Si interdiffusion from the substrate precedes the layer crystallization. The substrate influence on the crystallization process decreases with increasing N content x N of the Ta–Si–N layer. Using Cu/Ta–Si–N/Si samples, a critical temperature for Cu silicide formation was determined. This temperature increases with increasing N content of the Ta–Si–N barrier. In the case of Ta–Si–N films with x N >25 at.%, Cu interdiffusion into the substrate occurs before a significant barrier crystallization is observed. For Ta–Si–N layers with x N ≤25 at.%, no indications for Cu diffusion before crystalline phase formation were detected. [Copyright &y& Elsevier]

The influence of N content on the crystallization behavior of initially amorphous Ta–Si–N diffusion barriers deposited with a thickness of 10 nm between Cu and SiO2 was investigated by means of glancing angle X-ray diffraction (XRD), glow discharge optical emission spectroscopy (GD-OES), transmission electron microscopy (TEM), and graphite furnace atomic absorption spectrometry (GF-AAS) after annealing for various times at a temperature of Tan=600 °C. For a Ta73Si27 film, only Ta silicide phases (Ta5Si3, Ta2Si) are formed, whereas all barriers containing nitrogen crystallize primarily into a Ta nitride. Si is not incorporated into this phase but diffuses mostly into the Cu film. Although the crystalline Ta nitride grows mainly within the original barrier region, it does not form a continuous layer. For barriers with a N content xN≥25 at.%, the annealing time necessary to start the crystallization increases and the formed Ta nitride phases become N-richer (Ta2N→Ta5N6). A Ta30Si18N52 layer maintains its amorphous structure even after annealing for tan=100 h. With increasing N content in the barrier, the thermal stability against Cu diffusion is improved. [Copyright &y& Elsevier]

Structural changes at annealing temperatures (Tan) of 500–1,100°C were investigated for thin Ta films which were sputter-deposited onto pure Si substrates and onto thermally oxidized Si. In the as-deposited state, the Ta layers predominantly consist of metastable tetragonal β-Ta, whereby the [001] texture is independent of the substrate material. At lower annealing temperatures, the microstructural evolution is essentially the same for both Ta films. Incorporation of O atoms causes an increase of the intrinsic compressive stress, and diffusion of C atoms into the Ta layer leads to the formation of Ta2C. Additionally, a partial transformation of the original β-Ta phase into a second phase with tetragonal unit cell (denoted as β′-Ta) occurs. For the Ta/Si system, the formation of a Ta–Si intermixing layer is initiated at Tan=550°C, and nucleation of crystalline TaSi2 occurs at Tan=620°C. The formation of a second Ta silicide was not detected up to Tan=900°C. In the case of the Ta film deposited onto the SiO2 substrate, the metastable β-Ta and the β′-Ta transform completely into the thermodynamically stable cubic α-Ta at Tan=750°C. A marked reaction with the substrate indicated by the formation of Ta2O5 and Ta5Si3 occurs at Tan=1,000°C. [ABSTRACT FROM AUTHOR]

Sponge-like Si nanostructures embedded in SiO2 were fabricated by spinodal decomposition of sputter-deposited silicon-rich oxide with a stoichiometry close to that of silicon monoxide. After thermal treatment a mean feature size of about 3 nm was found in the phase-separated structure. The structure of the Si-SiO2 nanocomposite was investigated by energy-filtered transmission electron microscopy (EFTEM), EFTEM tomography, and atom probe tomography, which revealed a percolated Si morphology. It was shown that the percolation of the Si network in 3D can also be proven on the basis of 2D EFTEM images by comparison with 3D kinetic Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Flash lamp annealing (FLA) is an ultra-short annealing method, which excellently meets the requirements of thin-film processing and microelectronics. Due to the relatively high hole mobility, thin Ge layers are highly interesting as a transistor channel material or generally as a functional layer in CMOS technology and for low-cost electronics. One possibility to realize ohmic contacts with low contact resistance is the use of metal germanides, especially the stoichiometric NiGe phase. In this work, NiGe contacts on thin Ge films were fabricated by magnetron sputtering followed by FLA. The evolution of microstructure was traced by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Electrical measurements focused on the determination of contact resistance by the circular transfer length method. The contacts were fabricated by two different approaches, and the influence of different process steps on the layer morphology and uncertainty of the measurement was studied. Finally, we show that FLA as a thermal treatment with a low thermal budget is able to form NiGe on p-type Ge with a low contact resistance similar to that achieved by other thermal treatments. • NiGe was formed by flash lamp annealing with a specific contact resistance below 10−7 Ω cm2. • The formation process of NiGe on short time scales was studied in detail. • Two different NiGe fabrication process for the circular transfer line method were applied and discussed in detail. [ABSTRACT FROM AUTHOR]

[Display omitted] • The microstructural evolution and phase transformation of Te-hyperdoped Si layers upon isochronal furnace annealing are investigated. • A new Raman peak (at 143.7 ± 1.4 cm−1) emerges for Te-hyperdoped Si layers annealed at 950 °C and above. • Te-rich crystalline clusters with a hexagonal shape are assigned to Si 2 Te 3 via TEM and polarization Raman analysis. • Positron annihilation lifetime spectroscopy suggests the formation of vacancy complexes upon furnace annealing. Si hyperdoped with chalcogens via ion implantation and pulsed laser melting is known to exhibit strong room-temperature sub-bandgap photoresponse. As a thermodynamically metastable system, an impairment of the optoelectronic properties in hyperdoped Si materials occurs upon subsequent high-temperature thermal treatment (>500 °C). The substitutional Te atoms that cause the sub-bandgap absorption are removed from the Si matrix to form Te-related complexes, which are electrically and optically inactive. In this work, we explore the formation of defects in Te-hyperdoped Si layers which leads to the electrical deactivation upon furnace annealing through the analysis of optical and microstructural properties as well as positron annihilation lifetime spectroscopy. Particularly, Te-rich clusters are observed in samples thermally annealed at temperature reaching 950 °C and above. Combined with polarized Raman analysis and transmission electron microscopy, the observed crystalline clusters are suggested to be Si 2 Te 3. [ABSTRACT FROM AUTHOR]