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The optical constants of fine-grained diamond layers have been investigated by spectrophotometric means in the near-IR and visible spectral ranges. The layers were deposited by a microwave chemical vapour deposition technique on 〈100〉 and 〈111〉 oriented silicon substrates. For determining the optical parameters, measurements of the directed and diffuse reflectance and transmittance of the layer-on-substrate system have been carried out. The calculation of the optical constants has been accomplished by a curve-fitting procedure. For that purpose, a quadratic error function has been minimized by the method of conjugated gradients. To reduce the multiplicity of solutions, the refractive index has been assumed to increase with increasing wavenumber following a quadratic dispersion law, while the loss coefficient is assumed to increase exponentially with increasing wavenumber. The investigation of experimental spectra has shown that the method works successfully in application to layers with a surface r.m.s. roughness less than approximately 100 nm. For such layers, refractive index values have been obtained which are slightly lower than those of natural diamond, while the loss coefficients are much higher because of surface and bulk scattering.

The preparation of polycrystalline diamond particles and thin diamond films by deposition in the plasma discharge of a hollow cathode arc has been investigated. Although this discharge is known as a very simple and effective system for plasma generation, there has been little information about the growth of diamond by means of this method up to now. This type of discharge combines thermal and plasma dissociation of the reactant gases for diamond deposition. The temperature of the deposition area can be easily controlled by the electron current to the substrate and thus no auxiliary heating system is required, in contrast to many other diamond deposition methods. Furthermore, we assume additional decomposition of the reactant gases at the surface of the substrate due to the strong electron bombardment. As-deposited diamond particles and films were investigated by various electron microscopy methods, Raman spectroscopy and optical methods. They clearly show a polycrystalline structure with good crystallinity and quality. The diamond growth rate reaches about 2 μm h−1 on a deposition area of about 4 cm2.

The optical properties of hard dc plasma deposited amorphous carbon layers have been investigated from the middle IR up to the visible spectral region. Refractive indices and absorption coefficient behaviour have been determined by means of spectral transmittance and reflectance measurements. The layers show a transparency window in the middle IR in the wavenumber range 1700 cm −1 v −1 . The refractive indices in the “window” region are between 2.1 and 2.3 with weak dispersion. IR-absorption losses have been discussed in terms of a dispersion model, considering the absorption detected to be caused by a superposition of Lorentz-lines and an Urbach-part. Planar and transverse conductivities of the layers have been determined at room temperature. In addition, the conductivity of representative samples has been investigated in dependence of the temperature in the range of 80 K up to 350 K. A correlation between the thus-obtained activation energies for thermally-activated hopping in the band tails and the Urbach parameters of the layers could be established.

Imaging spectroscopy is a powerful tool for visualization of plasma phenomena. A novel type of imaging spectrometer based on an acoustic optical tunable filter (AOTF) was used to select several emission lines for imaging from a mercury: rare gas glow discharge driven by direct current (dc) current. Images taken from this discharge show different locations of light origin for different emission lines. The spatial and wavelength resolutions of the spectrometer are evaluated.