P. Streubel

Hard amorphous CSixNy thin films deposited by RF nitrogen plasma assisted pulsed laser ablation of mixed graphite/Si3N4-targets

Abstract Carbon–silicon–nitride thin films were grown on (100) oriented silicon substrates by pulsed laser deposition (PLD) assisted by a RF nitrogen plasma source. Up to about 30 at% nitrogen and up to 20 at% silicon were found in the hard amorphous thin films by RBS, XPS, and SNMS in dependence on the composition of the mixed graphite/Si3N4–PLD target. Due to incorporation of 10% Si3N4 to the PLD graphite target the CSixNy films show slightly increased universal hardness value of 23 GPa (at 0.1 mN load force, reference value for silicon substrate 14 GPa), increased plastic hardness (67 instead of 61 GPa), but strongly decreased elastic modulus (from 464 to 229 GPa) compared to the corresponding carbon nitride film without silicon. The internal compressive stress of the CSixNy films showed a maximum of 5.5 GPa at a film thickness below 50 nm and decreased down to about 1.5 GPa for film thickness exceeding 100 nm. X-ray photoelectron spectroscopy (XPS) of CSixNy film surfaces shows clear correlation of binding energy and intensity of fitted features of N 1s, C 1s, and Si 2p peaks to composition of the graphite/Si3N4 target and to nitrogen flow through the plasma source, indicating soft changes of binding structure of the thin films due to variation of PLD parameters. Increasing carbon double and triple bonding of the CSixNy films in dependence on the deposition process as identified by FTIR and Raman spectroscopy correlates with decreasing nanohardness. The results demonstrate the capability of the plasma assisted PLD process to deposit hard amorphous CSixNy films with variable chemical binding structure and corresponding mechanical properties.

Influence of nondipolar parameters on the XPS intensities in solids

Abstract The influence of nondipolar parameters on the XPS intensities in solids was investigated experimentally for the first time. Two spectrometers were used with different angles (75 and 125°) between the directions of the X-ray flux and the photoelectrons. The intensities of XPS lines have been normalized using Auger transitions with approximately the same kinetic energy as the corresponding XPS line under investigation. The experimental relative intensities of N 1s, O 1s and F 1s lines for two different angles are in reasonable agreement with the theoretical values, if nondipolar parameters are taken into account.

Angular distribution of photoelectrons from solids with account for elastic scattering and non-dipolar transitions up to the second order corrections: the linearly polarized excitation

Abstract Using the transport theory approach, equations are derived for the angular dependence of X-ray photoelectron spectroscopy intensities from semi-infinite solids taking into account elastic scattering of photoelectrons and non-dipolar transitions up the second order corrections. The linearly polarized source is considered. The elastic scattering presented by the main term smeared the non-dipolar contribution in complete analogy with smearing of dipole contribution. Some additional terms are shown to be negligible small in comparison with the main term for complete sets of emission and azimuth angles, angles between out going photoelectron and polarization vector, two representative single scattering albedo values and five representative sets of the second order non-dipolar parameters. The Monte–Carlo calculations are in agreement with the transport theory approach. The discussed transitions have a strong dependence on the azimuth angle and should be taken into account while performing photoelectron diffraction study.

Soft X-ray photoelectron spectroscopy studies of the initial oxidation of AlxGa1−xAs(100) surfaces

Core level shifts and intensity ratios of the spectra of Zr Mζ excited photoelectrons were used to describe the oxide growth on AlxGa1−xAs(100) surfaces with different x values. The chemisorption of oxygen at exposures up to 109 L was studied at room temperature. In highly surface sensitive experiments (λ ⋍ 0.6 nm) we could show that oxygen interacts first with the aluminium atoms. During the further oxidation an outdiffusion of aluminium takes place leading to the formation of a surface aluminium oxide layer which hinders the oxidation of the other semiconductor elements.

Extended Fenske-Hall LCAO MO calculations of core-level shifts in solid P compounds

Abstract Extended Fenske-Hall LCAO-MO ΔSCF calculations on solids modelled as H-pseudoatom saturated clusters are reported. The computational results verify the experimentally obtained initial-state (effective atomic charges, Madelung potential) and relaxation-energy contributions to the XPS phosphorus core-level binding energy shifts measured in Na 3 PO 3 S, Na 3 PO 4 , Na 2 PO 3 F and NH 4 PF 6 in reference to red phosphorus. It is shown that the different initial-state contributions observed in the studied phosphates are determined by local and nonlocal terms while the relaxation-energy contributions are mainly dependent on the nature of the nearest neighbors of the phosphorus atom.

Mechanical and Chemical Properties of CB x N y and CSi x N y Thin Films Grown by N*-Plasma Assisted Pulsed Laser Deposition

Carbon silicon nitride (CSi x N y ), and carbon boron nitride (CB x N y ) thin films have been grown by pulsed laser deposition (PLD) of various carbon (silicon/boron) (nitride) targets using an additional nitrogen RF plasma source on [100] oriented silicon substrates without additional heating. The CSi x N y and CB x N y thin films were amorphous and showed nano hardness up to 23 GPa compared to 14 GPa for silicon and maximum nitrogen content of 30 at%. The maximum nanohardness was achieved for 10% Si and 10% B content in the films. The lower hardness of this films compared to the nanohardness of 30-50 GPa of DLC films indicates a lower amount of covalent carbon-nitrogen bonding in the films. However, in contrast to DLC films, the CSi x N y and CB x N y films can be grown to thickness above 3 μm due to lower internal compressive stress. XPS of CSi x N y and CB x N y film surfaces shows clear correlation of binding energy and intensity of N ls, C ls, and Si 2p peaks to composition of the PLD-targets and to nitrogen flow through plasma source, indicating soft changes of binding structure due to variation of PLD parameters. The results demonstrate the capability of the plasma assisted PLD process to deposit hard amorphous CSi x N y , and CB x N y thin films with adjustable properties.