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Notes: Summary Immunohistochemical staining of epidermal growth factor receptor (EGF-R) with a monoclonal antibody was performed in 43 biopsies of cervical tissue. The distribution of the receptors in normal cervical tissue differs from that of cervical intraepithelial neoplasia (CIN) and squamous cell carcinoma of the cervix. Whereas the staining reaction in normal squamous epithelium was confined to the basal and deep parabasal cell layer, in all cervical intraepithelial neoplasias, with or without human papilloma virus association, a homogeneous EGF-R staining reaction could be observed throughout the entire lesion. This means that the dysplasia cells of a CIN I-III, like the tumor cells of a squamous cell carcinoma, have a raised EGF-R content, which in the normal squamous epithelium is usually only found in the basal and deep parabasal cells that are capable of dividing. No EGF-R staining reaction could be detected in the higher, differentiated cell layers of the normal squamous epithelium of the cervix.

Notes: Beam-induced broadening effects in SIMS depth profiling have been studied for eight impurities (Li through Al) implanted in amorphized silicon at energies between 1 and 15 keV. Depth profiling was performed under Ar+ (≤2.5 keV) or O2+ (≤3 keV) impact. In selected cases (Li, N) the effect of the probe energy has also been investigated. The measured profiles show exponential tails. The decay length γ characterizing these tails exhibits strong oscillations when plotted as a function of the atomic number of the dopant. Maxima are seen for N and O (γ ≃ 7 nm) as well as for Mg (γ ≃ 13 nm), minima for B and Na (γ ≃ 2 nm). The results suggest that the observed effects are due to a yet unpredictable combination of collisional mixing, defect-assisted diffusion and selective sputtering.

Notes: Depth profile analyses by secondary ion mass spectrometry (SIMS) are often carried out using oxygen bombardment at near-normal beam incidence. During the initial stages of oxygen incorporation in the sample the secondary ion yield and the sputtering yield change significantly, notably in silicon, and stabilize only after a transition layer of thickness ztr has been eroded. In SIMS depth analyses these transient effects give rise to a depth scale offset zdU0 and an associated profile shift zsh. A simple model is presented that provides means for determining zdU0 and ztr from the difference between the initial and the final sputtering yield, the oxygen retention coefficient and the thickness of the oxide, wSiO2, established under stationary bombardment of silicon. The results derived from the model are shown to be in good agreement with apparent shifts observed in depth profiling of boron implantation distributions, in which case zdU0∽zsh. The profile shift increases almost linearly with the oxygen energy E: zsh(nm)∽1.8E (keV per O atom). The same number is derived from measurements on boron delta doping layers, provided that the centroid of the measured profile is used to quantify the shift. The transition depth ztr amounts to ∽2zdU0 and roughly equals the sum of the mean oxygen range 〈z〉 and range straggling σ, or ∽80% of the oxide thickness. This is much larger than the previously advocated value of ztr≤〈z〉. With clean samples and at impact energies between 0.5 and 5 keV atom-1 the model predicts surface recession from the beginning of bombardment, but with a very small initial recession rate. The extrapolated zero-fluence surface position or apparent crater offset zsU0 is estimated to be negative (‘swelling’) but rather small: zsU0∽-0.15wSiO2. This is in accordance with most of the previously reported crater depth measurements, which suggested that the surface recedes directly proportional to the bombardment fluence with an undetectably small crater offset. With dirty or otherwise ill-defined surfaces an initial swelling and a significantly enlarged negative crater offset might be observed.

Notes: Recent progress in materials characterization by sputter profiling is discussed, with particular emphasis on a critical evaluation of the parameters that determine the depth resolution. The net effect of beam-induced material transport and sputtering can be studied in a straightforward manner using abrupt doping distributions embedded in the matrix of interest, parallel to its flat surface. It is shown that the quality of the data that can be obtained with modern instruments is sufficient to identify lack of sample quality in terms of either surface flatness or abruptness of the doping distributions. Except for the presence of special artefacts, the depth resolution is always improved by using as low a bombardment energy as possible. The optimum angle of beam incidence depends on the crystalline structure of the sample as well as on the chemical identity of the primary ions. With oxygen primary ions a rather complex situation is encountered. Compared to inert gas ions, an improvement or a degradation in depth resolution may be achieved, depending on the impurity-matrix system under study. The merits of sample rotation are also discussed.

Notes: The experimental conditions required for charge compensation in depth profiling of polymer foils have been investigated with reference to the analysis of negative secondary ions. Low energy (≤500 eV) electron beams were employed in combination with 8 keV Xe+ ion beams. The minimum electron current required for the appearance of a stable SIMS signal was found to be equal to the ion current. Optimum SIMS signals were achieved by sufficiently overcompensating the primary ion current. Signals due to electron stimulated desorption could be suppressed by appropriate adjustment of the target bias. Reproducible depth profiles were obtained without major difficulties.

Notes: Secondary ion yields are known to be strongly enhanced by the presence of oxygen in the analysed sample. The magnitude of the yield enhancement is often significantly different for impurity and matrix ion species. This kind of SIMS matrix effect severely aggravates concentration calibration in depth profiling through regions of transiently varying oxygen concentration. To eliminate the matrix effect, a procedure has been developed that allows the differences in yield enhancement to be corrected in a quantitative manner. The procedure will ultimately be required to calibrate profiles extending through native surface oxide layers. The calibration exercise was carried out for boron in silicon. The dependence of the B+/Si+ sensitivity ratio, RB,Si, on the oxygen content of the sample was explored in situ by implanting 1.9 keV O2+ ions at O° (normal incidence) into a uniformly B-doped reference sample, followed by sputter profiling through the synthesized oxide with the same beam incident at 75°. All measurements were performed at base pressure. During oxygen build-up after initial sputter cleaning the Si+ and SiO+ yields increased by factors of 200 and 500, respectively, whereas for B+ the yield increased only 40 times. Almost inverse yield changes were observed during oxide removal. Bombardment-induced mixing caused a broadening of the oxide/Si interface and some relocation of B atoms. Under internally consistent assumptions the relatively small boron mixing effect could be separated from the oxygen-induced B+ yield enhancement effect. The normalized SiO+ signal ĨSiO+, was used as a measure of the oxygen content of the samples bombarded at the two different impact angles. The B+ yields and the sensitivity ratios RB,Si(ĨSiO+) could be fitted very well by polynomial functions. The polynomials were employed to quantify the depth profiles of 0.5 and 2 keV 11B implanted in Si test samples covered with 6 nm layers of thermal SiO2 (i.e. thinner than the synthesized oxide layer that can be produced by the 1.9 keV O2+ beam at O°). The compositional changes encountered in passing from the thermal oxide into the Si substrate had be taken into account, not only for time-to-depth conversion but also for concentration calibration based on the measured sensitivity ratios. The changes in erosion rate and Si density around the interface were modelled by error functions. Direct evidence is presented that, for accurate calibration, density and sensitivity changes must be treated separately. Even though the through-oxide variations of RB,Si are quite different for O° and 75°, the calibrated 2 keV 11B profiles derived from measurements at these two vastly different impact angles agree very well, even at the interface. This implies that the large matrix effect occurring in through-oxide profiling at 75° can be eliminated using the new calibration procedure. Minor differences (〈10%) between the calibrated 2 keV 11B profiles from measurements at 0° and 75° can be attributed to differences in bombardment-induced relocation. The mixing effect is particularly severe for the profiles of the very narrow and shallow 0.5 keV 11B implantation distributions, which turned out to be heavily distorted at depths below 10 nm, both at 0° and 75°. Hence it is mandatory, for reasonably accurate profile measurements, to use O2+ energies that are significantly (∽50%) lower than the implantation energy, both for normal and oblique incidence of the probing beam. © 1998 John Wiley & Sons, Ltd.