Influence of interfacial depth on depth resolution during GDOES depth profiling analysis of thin alumina films

Abstract

Factors controlling the depth resolution in radio frequency glow discharge optical emission spectroscopy (rf-GDOES) depth profiling analysis of thin films have been investigated using anodic alumina films of varying thicknesses with delta function marker layers of ∼2 nm width located at various depths from the oxide surface. In rf-GDOES depth profiling analysis, where a relatively large area of ∼4 mm in diameter is analysed, it was found that the depth resolution is determined mainly by the large-scale variation of sputtering rate across the crater. Despite the relatively large area analysed, the uniformity of sputtering rate across the crater was constant to within 1% under the optimum Ar pressure except for near-edge regions of ∼0.4 mm width, where the sputtering rate was ∼6% higher than in the central crater region. Owing to this relatively minor non-uniformity of sputtering rate, the depth resolution degrades approximately linearly with depth. A depth resolution of ∼1.3 nm was realized to depths of∼25 nm, where the degradation of depth resolution due to the non-uniformity in sputtering rate is insignificant. The depth resolution is close to the ultimate depth resolution in sputter depth profiling, claimed to be 0.7-1.0 nm, and arises from the minimal atomic mixing associated with film sputtering with Ar + ions of very low energy, ∼50 eV, in rf-GDOES analysis.

Advances in sputter depth profiling using AES

“…3 and GDOES 4,5 in comparison. The developments of AES and SIMS are almost parallel but GDOES is obviously less frequently used and still far from saturation whereas both AES and SIMS are now mature techniques.…”

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

“…In addition, the films can be prepared with metal dopant layers at designated positions and thicknesses. The versatility of these films has led Shimizu and co-workers to propose their use as reference materials for thin film profiling methods [46,47]. Figure 4a is a transmission electron micrograph of a microtomed cross section of an ~180 nm thick BTF that has been treated with sodium chromate solution.…”

Feasibility of depth profiling of Zn-based coatings by laser ablation inductively coupled plasma optical emission and mass spectrometry using infrared Nd:YAG and ArF* lasers

“…The ions of isotopes 68 Zn + , 57 Fe + , 60 Ni + , 27 Al + , and 29 Si + were detected as analytical signals of elements contained in coatings (Zn, Al, Ni, Si) and substrates (Fe). The isotopes were measured by using a 0.010-s integration time per channel.…”

“…Depth resolution of laser ablation depth-profiling technique is defined for a sharp interface as a depth interval Dz, for which the signal of the constituent (element) A in the first (upper) layer diminishes with increasing depth from 84% of its plateau value in the first layer to 16% and the signal of the element B in the second (lower) layer increases from 16% to 84% of its plateau value in the second layer [29,30]. It is supposed that element A is present only in the first layer while element B is present only in the second layer.…”