The microstructure of distributed electron cyclotron resonance plasma-deposited hydrogenated amorphous carbon films (a-C:H) was investigated using electron diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. Experimental evidence of the existence of transpolyacetylene (TPA) chains in a-C:H films free of nanocrystalline diamond is presented. The values of the mean bond angles and lengths and first neighbor numbers are consistent with the TPA data. The Raman spectra were fitted using the G and D bands and the bands centered at 1140, 1233, and 1475 cm(-1) assigned to TPA chains modes. The relative intensity of the latter decreases while hydrogen content decreases. A significant sp(2)-CH olefinic mode contribution to the infrared stretching band is observed for the low-density films (similar to1.2 g/cm(3)). TPA chains growth is enhanced when ion current density and energy decrease. (C) 2003 American Institute of Physics. (DOI: 10.1063/1.1538349
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Dose and energy dependence of the E′1 defect density/cm2 created in SiO2 by implantation of Ar ions has been determined by electron paramagnetic resonance. A dose dependent region followed by a saturated, dose independent region is found for all energies studied (50–150 keV). In the low dose limit for 100-keV Ar ions we estimate E1 creation to be 35/implant ion. The defect density/cm2 is found to be a linear function of the longitudinal atomic collisional damage distribution consistent with a picture of overlapping lateral damage distributions. A simple model for defect creation and annihilation gives a good quantitative explanation of the observed energy and dose dependence of the defect density. Isothermal annealing studies have been performed and the results do not follow those expected for a simple exponentially activated process. A model assuming correlated defect/interstitial recovery gives a better description of the experimental results and suggests an activation energy for recovery of approximately 0.85 eV.
The physical properties of plasma-deposited hydrogenated amorphous-carbon films (a-C:H) are investigated and correlations to the competing intrinsic and extrinsic stress fields are established. The (a-C:H) films are grown on single-crystal 〈100〉 silicon substrates in a plasma reactor using acetylene as a precursor. Although constant C2H2 plasma conditions and constant substrate bias and temperature were used during the growth the films display a multilayer structure. The density and the sp3-hybridized carbon fraction are shown to vary during deposition. The microstructure and optoelectronic properties of the (a-C:H) thin film evolve during growth as a result of interaction between the intrinsic tensile stress generated within the growing film and the external stress field existing in the Si substrate. During the initial phase of the growth this external stress field enhances the intrinsic stress. The resulting film is of high density and contains a relatively high fraction of sp3-hybridized carbon atoms. Eventually, when the (a-C:H) layer becomes thick enough, the intrinsic stress compensates the external stress field. Layers grown under balanced stress conditions show an unusual alignment of the graphitic planes. Finally, when the intrinsic stress becomes dominant, the density of the film and the corresponding sp3 fraction decrease, leading to a detectable porosity. The behavior of the optical band gap is shown to reflect the evolution of the (a-C:H) microstructure as it is unambiguously correlated to the evolution of the stress field.
Scanned cw laser beams at different scan velocities from 10 to 400 cm/s have been used to study the interaction of thin metal films of molybdenum deposited by electron beam evaporation with single-crystal silicon substrate. Backscattering technique has been used to investigate the growth mechanism of hexagonal silicide MoSi2 as a function of the number of repetitive laser scans. Silicide layers are found to grow at a rate proportional to the square root of the effective annealing time in the whole range of scan velocities. Effective annealing temperatures are calculated for each laser annealing condition, and from an Arrhenius plot a mean value of activation energy for MoSi2 growth is estimated.
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