Interference Phenomena at Transparent Layers in Glow Discharge Optical Emission Spectrometry

Abstract

At the performance of depth profiling by glow discharge optical emission spectroscopy (GD-OES) the intensities of optical emission lines of sample and sputter gas elements are measured in dependence on the time of sputtering. Radio-frequency (rf) sputtering extended the field of application to nonconducting samples including transparent layers. For transparent coatings in the thickness range up to some micrometers, oscillations of measured intensities were observed. This behavior is explained by a thin-film interference effect and discussed for three different materials, i.e., SiO2, TiO2, and BaTiO3. As a result, a new procedure for the determination of either layer thickness or refractive index from GD-OES depth profiles is presented. This effect has to be considered for quantitative GD-OES analysis as well.

Plasma emission controlled multi-target reactive sputtering for in-situ crystallized Pb(Zr,Ti)O3 thin films on 6″ Si-wafers

“…This behavior appears when the film under examination is transparent for the wavelength of the spectral line (here, Ti and Ar spectral lines at wavelengths 365.3 and 415.8 nm, respectively). The detailed analysis of this effect has been reported by V. Hoffmann et al [31]. In the region of oscillation in measured intensities, only the mean value of the concentration ratio should be considered.…”

Electrical measurements at radio frequency glow discharges for spectroscopy

“…For surfaces with a high reflectivity like mirrors or polished silicon the changes can be as large as 100%. The sputtering of transparent layers results in interference effects [46,47]. A simple model has been presented that describes the intensity changes.…”

Radio frequency glow discharge optical emission spectroscopy: a new weapon in the depth profiling arsenal

“…In the case of optical emission monitoring, these devices have been applied in the bulk analyses of copper alloys [27], precious metals [28], and solid and powdered glasses [29,30], as examples. Depthresolved analyses have been reported as well for such applications as hard coatings [31], painted coatings [32], metallic superlattices [19], and thin oxides [33]. In general, comparisons of the plasma characteristics of rf and conventional direct current (DC) devices reveal electron populations of higher energy and far greater temporal stability of the plasma (i.e., analyte signals) for the former [34,35,36].…”