Saved in:
| Main Author: | |
|---|---|
| Format: | Recurso digital |
| Language: | |
| Published: |
Zenodo
2024
|
| Online Access: | https://doi.org/10.5281/zenodo.17434986 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Table of Contents:
- <p>For this investigation, a calibration target was prepared and analyzed by 2.0 MeV helium RBS analysis. It consists of a Si substrate (300 μm thick) with three different covering thin films deposited by physical vapor deposition (PVD) in high vacuum. Starting from the surface, the triple film is composed of 130 nm Au thin film, deposited on 98 nm Ag thin film, deposited on 55 nm Cu thin film, and deposited on the Si bulk substrate. The Ortec detector (A series) was a partially depleted silicon surface barrier with 25 mm 2 surface area, polarized at 50 V, with 1000 μm active depth [6]. Its leakage reverse current was about 10–20 nA. The Si detector was placed at an 89 mm distance from the target and at a 165 ◦ backscattering angle, covering a solid angle of 3.16 mstr, The SiC Schottky detector, realized as a prototype some years ago at ST-microelectronics, in collaboration with CNR-IMM of Catania, Italy, was used reversely polarized at 200 V bias, at which the leakage current was 0.1 nA, as measured with a Keythely instrumentation at room temperature and in high vacuum (10 -6 mbar). It uses 4H-SiC epitaxial layers, 80 μm thick, with 10 14 cm -3 dopant concentration onto an n-type heavily doped substrate. Ohmic contacts on the sample<br>back side were formed by sputtering a 200 nm thick nickel film. The front contacts were obtained by sputtering deposition of a Ni thick film and performing a rapid thermal processing at 700 ◦ C producing the formation of Ni 2 Si 200 nm thick. The active surface was 3 mm × 3 mm, characterized by the 200 nm Ni 2 Si layers having a density of 7.4 g/cm 3 . The SiC detector was placed at a 65 mm distance from the target and at a 165 ◦ backscattering angle, covering a solid angle of 2.13 mstr. The low detection solid angles used in the experiment and the low carbon ion current avoid any pile-up effect in the acquired RBS spectra. The detection efficiency curves are agreed with the literature and indicate that carbon ions can be detected from about 400 keV, due to the energy loss in the surface metallization, up to about 400 MeV, due to the limited depletion layer of 80 microns. Both detectors have been employed using a preamplifier (Ortec mod. 142 A), followed by a linear amplifier (Ortec mod. 672) with 0.1 μs shaping time and a very compact digital Multi-Channel Analyzer (MCA, Amptek MCA-8000D) to digitize the analogical input signal and to acquire the RBS spectra on PC. RBS analyses performed using 2–10 MeV carbon beams were performed by considering the kinematic backscattering factor depending on the target element, the backscattering detection angle, the energy of the backscattered particle with respect to that of the incident one, and by considering the differential scattering Rutherford cross sections in the laboratory system. The SIMNRA code was employed to simulate the RBS spectra analysis and to evaluate qualitatively and quantitatively the amount of the elements detected in the analyzed target.</p>