The feasibility of depth profiling was studied by using a 193-nm ArF* excimer laser ablation system (GeoLas, MicroLas, Goettingen, Germany) with a lens array-based beam homogenizer in combination with an ICP-QMS Agilent 7500. Two ablation cells (20 and 1.5 cm3) were compared at the laser repetition rate of 1 Hz, laser beam energy of 135 mJ and the carrier gas flow rate 1.5 L min(-1) He + 0.78 L min(-1) Ar. The ablation cell dimensions are important parameters for signal tailing; however, very small cell volumes (e.g. 1.5 cm3) may cause memory effects, which can be probably explained by dominant inertial losses of aerosol on cell walls with its delayed mobilization. The 20-cm3 ablation cell seems to be appropriate for depth profiling by continuous single-hole drilling. The study of the influence of the pit diameter magnitude on the waning and emerging signals under small crater depth/diameter aspect ratios, which range between 0.75 and 0.0375 for the 3-microm-thick coatings and pit diameters 4-80 microm, revealed that the steady-state signals of pure coating and pure substrate (out of interface) were obtained at crater diameters between 20 and 40 microm. Depth resolution defined by means of slopes of tangents in the layer interface region depend on the pit diameter and has an optimum value between 20 and 40 microm and gives 0.6 microm for the 20-microm pit. In-depth variation of concentration of coating constituent (Ti) was proved to be almost identical with two different laser/ICP systems.
This paper examines the damage created by an electron beam on layered specimens consisting of a (CH2)17 self-assembled monolayer (SAM) deposited on an oxidized Si wafer. Beam effects on both the SAM and substrate were observed. X-ray photoelectron spectroscopy (XPS) measurements indicate that less than 20% of the carbon from the film is lost during the beam damage, ion analysis shows hydrogen emission from the films, and residual gas analysis suggest loss of some CHx (x=2–4) molecules. Consistent with the conversion of some (CH)n chains to ‘‘graphite,’’ the C 1s photopeak is broadened by the electron beam. In addition to the effects on the SAM layer, there are shifts for the O 1s and oxidized-Si2p binding energies due to the electron beam exposure. Studies on SiO2 films formed in a wide variety of ways, without the SAM, show similar effects. These shifts are attributed to changes in potential at the Si–SiO2 interface.
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