# Radiation Hardness of Oxide Thin Films Prepared by Magnetron Sputtering Deposition
## 2 Experiment Details  
Amorphous oxide films were prepared by magnetron sputtering deposition on silicon wafers (Si-Mat, P/Bor, (100) orientation) at room temperature and at a base pressure of 4 mTorr. For depositions, we used 3-inch targets of pure SiO\({}_{2}\) ([PERSON], Dresden, Germany, 99.995%), Al\({}_{2}\)O\({}_{3}\) ([PERSON], Dresden, Germany, 99.99%) and MgO (Testbourne, Basingstoke, UK, 99.95%), with copper backing plates. This way, we prepared \(\sim\)150 nm thin films of a-SiO\({}_{2}\), a-Al\({}_{2}\)O\({}_{3}\), and a-MgO. Deposition parameters used in this work are listed in Table 1. After depositions, wafers were cut into \(\sim\)7 \(\times\) 7 mm\({}^{2}\) samples.  
In the next step, samples were irradiated by high-energy heavy ion beams. Irradiations were performed at room temperature and a normal incidence angle. To achieve this, we used a 6 MV EN [PERSON] accelerator (HVEC, Burlington, MA, USA) that provided 23 MeV I, 18 MeV Cu, and 2.5 MeV Cu beams. In addition, the elemental analysis of thick samples was carried out by time-of-flight elastic recoil detection analysis (ToF-ERDA) for which a 23 MeV I beam was used, and in which case ion irradiation was carried out at a 20\({}^{\circ}\) incidence angle. The spectrometer was set to 37.5\({}^{\circ}\) toward the beam direction. The analysis of the TOF-ERDA spectra was performed with the Potku 2.3.0 program [27]. Both high-energy ion irradiation and ERDA analysis were carried out at the ToF-ERDA beamline [28]. Ion irradiation parameters calculated by the SRIM-2013.00 code [29] are listed in Table 2. Since amorphous materials can have densities in a wide range of values, stopping powers are expressed in keV/ug/cm\({}^{2}\) units. It is important to note that 18 MeV Cu has almost the same electronic stopping as 23 MeV I, while 2.5 MeV Cu has almost the same nuclear stopping as a 23 MeV I beam.  
For comparison, one set of samples was irradiated by 1.25 MeV gamma-ray irradiation using a \({}^{60}\)Co panoramic irradiation facility located at RBI [30]. All samples in that set were exposed to the same 6 MGy dose, which accumulated over the course of two months, at  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & **Power (W)** & **Time (s)** &
\begin{tabular}{c} **Nominal** \\ **Thickness (nm)** \\ \end{tabular} \\ \hline SiO\({}_{2}\) & 150 & 6.000 & 150 \\ \hline Al\({}_{2}\)O\({}_{3}\) & 190 & 14.400 & 150 \\ \hline MgO & 140 & 36.000 & 180 \\ \hline SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) & 63 + 190 & 7.200 & 150 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Magnetron sputtering deposition parameters used in this work.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Ion Beam** & \
\begin{tabular}{c} **Electronic Stopping** \\ **(keV/ug/cm\({}^{2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Nuclear Stopping** \\ **(keV/ug/cm\({}^{2}\))** \\ \end{tabular} \\ \hline SiO\({}_{2}\) & 23 MeV I & 23.70 & 1.17 \\  & 18 MeV Cu & 23.53 & 0.28 \\  & 2.5 MeV Cu & 5.74 & 1.19 \\ \hline Al\({}_{2}\)O\({}_{3}\) & 23 MeV I & 22.73 & 1.13 \\  & 18 MeV Cu & 22.73 & 0.27 \\  & 2.5 MeV Cu & 5.58 & 1.16 \\ \hline MgO & 23 MeV I & 23.00 & 1.16 \\  & 18 MeV Cu & 23.54 & 0.28 \\  & 2.5 MeV Cu & 5.74 & 1.18 \\ \hline \hline \end{tabular}
\end{table}
Table 2: High-energy heavy ion irradiation parameters calculated by the SRIM code [29].  
a rate of 3.5 Gy/s. Additionally, one set of samples was annealed at 600 \({}^{\circ}\)C in a vacuum for 1 h.  
For the sample analysis, IR spectroscopy was performed using a PerkinElmer Spectrum GX spectrometer equipped with a DTGS (Deuterated TriGlycineSulfate) detector (PerkinElmer, Springfield, IL, USA). Fourier transform infrared (FTIR) spectra were recorded in the normal transmission mode, averaging 200 scans over the range 370-4000 cm\({}^{-1}\), with a spectral resolution of 4 cm\({}^{-1}\). Before scanning the samples, the background (200 scans; Si wafer in air) was recorded. The background was automatically subtracted from the spectra of all samples.