Electrophysical Complex on Basis of the Electrostatic Accelerator Esa-2 for Fundamental and Applied Investigations


Electrostatic accelerator ESA-2 is a multy-purpose tool for fundamental and applied research in nuclear and particle physics. Usage of ESA-2 in quality an implanter, and as a source of ions for conducting of investigations of solid-state materials by non-destructive control methods, such as, for example, the Rutherford backscattering (RBS) is discussed. The Rutherford backscattering spectrometer has been designed and assembled. The present paper deals with the interaction of 380 keV H ions with Si surface at glancing angles corresponding to the quasi-channeling regime. The outcomes of the experimental researches of sliding interaction of beams of the accelerated protons with energy from 180 up to 350 keV with a surface of a dielectric capillary are presented. INTERACTION OF FAST HYDROGEN IONS WITH SILICON SURFACE AT GLANCING ANGLES OF INCIDENCE Angular distributions of 380 keV protons reflected from (111) surface of Si monocrystal were measured in the range of projectiles glancing angle from 0.3° up to 0.8°. It is shown that increase of glancing angle causes non-linear change of such distribution parameters as angular width of the front rise, angular width of the distribution, the maximum yield value. Registered energy spectrum of reflected particles for glancing angle of 0.5° consists of several peaks with practically constant angular intervals between them and maxima weakly reducing towards lower energy region. It is experimentally shown that the most energetic peak relates to the reflection from the very surface and the rest ones are caused by successive scattering of ions by inner silicon crystallographic planes [1]. Fig.1 is a scheme of the experimental setup used in Figure 1: Schematic of the experimental setup. the present study. Monoenergetic proton beam, generated by the Van de Graaf accelerator, is collimated by 1 mm circular diaphragms S1 and S2. Twinned diaphragm S3 is used for ion beam monitoring. The exit part of S3 has a diameter of 0.5 mm. One more 0.5 mm collimator S4 is placed in front of the sample to avoid the influence of the particles scattered at the edge of S3. The sample is placed on two-axis goniometer having an accuracy not worse than 10 degree. Silicon surface-barrier detector with an aperture 0.3 mm is placed at a distance of 115 cm from the sample. The detector can move perpendicularly the ion beam axis direction in the range from 0 to 6.9 degrees with the velocity of 2.42·10 degree per second. Measured angle divergence of the ion beam was not worse than ± 2.0·10 degree. The energy of the proton beam was set by calibrated magnetic analyzer with the accuracy of ± 0.1 %. The overall measured energy resolution of the system including the energy spread of the ion beam did not exceed 19 keV. The samples for angular distribution measurements were cut from (111) silicon wafers with epitaxially grown Si film 3.94 μm in thickness and the resistivity of 1 Ω·cm. Strips 20 mm wide and 70 mm long were cut parallel to (110) plane. After cleaning in boiling toluol samples were pasted to the sample holder. Samples were mounted in the goniometer in such a way that the angle between their long side and the beam axis was near 11°, that allowed to avoid the influence of (110) plane on the process of ions scattering at (111) silicon surface. Rutherford backscattering with 1.1 % resolution electrostatic analyzer was used to control crystal structure and surface quality of the samples. The pressure in the vacuum chamber during measurements was 6·10 Pa. Angular distributions of hydrogen ions with the energy of 380 keV reflected from the polished silicon surface for glancing angles 0.3° and 0.5° are shown in fig.2. The difference between the distributions is clearly visible. Maxima position for reflected particles distributions. At glancing angle of 0.3° the maximum yield in the angular distribution is situated at scattering angle of 0.48°, whereas for glancing angle of 0.5° – at 0.90°, i.e. these values are substantially less than those for mirror reflection. The same maximum behaviour was observed at larger glancing angles. E. g., for glancing angle of 0.8° the maximum was situated at 1.4°. Energy spectrum of 380 keV protons reflected by (111) Si crystal plane at glancing angle of 0.5° is given in fig. 3. The angle value of 0.5° was chosen with the aim both to minimize the spectrum background, as in this case projection of the beam cross section lies entirely on the ___________________________________________

6 Figures and Tables

Cite this paper

@inproceedings{Lagutin2006ElectrophysicalCO, title={Electrophysical Complex on Basis of the Electrostatic Accelerator Esa-2 for Fundamental and Applied Investigations}, author={A . E . Lagutin and E . B . Boyko and A . S . Kamyshan and F . F . Komarov}, year={2006} }