R.K. Wild

XPS and laser Raman analysis of hydrogenated amorphous carbon films

Abstract Hydrogenated amorphous carbon films were deposited in an RF parallel plate plasma reactor using various values of process pressure (10–50 mTorr) and DC self-bias (0–300 V). The films were then analysed by laser Raman spectroscopy (LRS) at 514.5 nm and X-ray photoelectron spectroscopy (XPS). Values for the ratio of sp 2 :sp 3 bonded carbon in the various films were obtained by suitable fitting of the XPS carbon 1s energy peaks, using a three-curve fitting procedure, which recognises a portion of the peak attributable to CO surface bonding. The sp 3 content was found to depend upon the DC self bias (and hence the ion impact energy) during deposition, peaking at a value of 81% at approximately 150 V. The softer films grown at lower DC bias values still had an sp 3 content of approximately 70%. Microcombustion analysis showed that films deposited with low DC bias contained 7 at.% H compared to less than 2 at.% for films deposited at biases greater than 100 V. This high sp 3 content can be explained by H-termination of dangling bonds, suggesting that sp 3 content alone is not a reliable indication of film properties. Curve-fittings of LRS spectra of the films showed that the Breit–Wigner–Fano lineshape is inappropriate for use with hydrogen containing films. Fitting using a Gaussian profile gave precise values for the FWHM, intensity, and Stokes’ shift of the G and D-peaks. A linear relationship between the intensity ratio of the D to G peaks and the width of the G peak was found for films deposited at high DC bias (with low H content), but not for films deposited at low DC bias. This is consistent with the increased H content of the films causing a change in the elastic constants and/or affecting the stress levels within the films.

Deposition and properties of amorphous carbon phosphide films

a Abstract Radio frequency plasma deposition has been used to deposit phosphorus doped diamond-like carbon (DLC) films on Si and quartz substrates, using a gas mixture consisting of CH with additions of 0-90% PH . XPS studies reveal that the films contain 43

The effect of ion energy on the deposition of amorphous carbon phosphide films

Abstract A detailed study has been performed of diamond-like carbon films containing high concentrations of phosphorus deposited onto a variety of substrates. These ‘amorphous carbon phosphide’ films have been grown using RF plasma CVD at varying ion impact energies by changing the DC self bias on the powered electrode. X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS) have been used to determine changes in the chemical composition and chemical bonding structure of these films. UV/visible absorption spectroscopy employing the Tauc-plot method has determined the band gap change with varying ion energies. Results show the enhancement of CP bonding ratios with deposition under high average ion energies, and also with the dramatic reduction in contaminant elements (O, H).

The effect of the microscale distribution of boron on the yield strength of C-Mn steels subjected to neutron irradiation

Abstract The presence of B as an impurity in C–Mn steel and weld metal can have a significant effect on the mechanical properties of these materials depending upon whether this element is present as the free atomic species or incorporated within particular microstructural features such as grain boundaries, inclusions or precipitates. This is important in the case of the steel plates and weld metals used for the construction of nuclear pressure vessels where irradiation, with a contribution from thermalised neutrons to the fast neutron spectrum, can lead to transmutation of the B. In this work we examine the distribution of B within the microstructure of a range of C–Mn steels and weld metals containing 1 ppm ≤ boron ≤48 ppm using low and high resolution microanalytical techniques. These results are compared with measured tensile and hardness properties. The distribution of the impurity B within the microstructure and the measured changes in the yield strength of these C–Mn steels following neutron irradiation are discussed. The measured changes in the yield strength are addressed using models that describe the displacement damage arising from several sources. In particular the contribution of neutron irradiation damage from B transmutation to the irradiation strengthening is related to the bulk B content and its distribution to inclusions and carbide precipitates in the overall microstructure.

Distribution of boron within the microstructure of a ferritic steel determined using secondary ion mass spectrometry

At low concentrations, boron in ferritic steels can potentially have a significant effect on the mechanical properties. High spatial resolution microanalyses have been undertaken on a normalised C–Mn ferritic steel containing less than 1 wt. ppm boron. Secondary ion mass spectrometry on bulk samples has been used to map the distribution of boron with the overall microstructure. Image analysis has been used to determine the location and concentration of boron within the overall microstructure of the steel. The results are discussed in terms of the microstructure, distribution, detection capability and overall audit of boron.