# Investigation of a Possible Material-Saving Approach of
## 2 Materials and Methods  
To find a solution for the main MS process issues, a new recovering shield was designed and proposed in this work. The idea behind such a new shield design was to confine in a controlled volume the plasma generated. To achieve the goal of a replacement of the standard ground shield, the intended design of the new configuration must meet the requirements of the sputtering process: (1) provide a low outgassing rate, which will lead to the proper vacuum level and (2) give the access for free gas circulation to sustain the working pressure inside the close volume. To reach such requirements, it was planned to create an additional six tunnels (\(\mathcal{O}\) 4 mm), indicated in Figure 1a, in the base plate of the recovering shield, perpendicularly to the shield wall. The diameter of the cylinder was chosen according to the target size, which was, in our case, 2 inches. The length of the cylinder was chosen based upon the requirement that the deposition must occur as close as possible to the sputtering target, as presented in Figure 1b. Possibly, such a decision would lead to some known difficulties with mechanical stresses induced on the film, thus reducing the possible sample holder size. However, from the material-saving point of view, it may help to prove a better target material utilization, thus improving the material recovery stage. The recovering shield, shown in Figure 2a, is made of stainless steel (AISI 316). The shield construction is a combination of a flat plate (repeating the function of a standard ground shield) and a cylinder (now made of SS but with the possibility to realize it in insulating material, such as SiO\({}_{2}\) or Al\({}_{2}\)O\({}_{3}\) for special applications), as a collector for the sputtered material, usually deposited on the vacuum chamber walls. The sample holder (SH) was designed for the assembling of four quartz samples (10 \(\times\) 10 mm). The SH assembly, shown in Figure 2b, consists of a stainless steel (AISI 316)  
Figure 1: Design of a recovering shield (**a**); sample holder inside the recovering shield with the variable working distance range 2-5 cm (**b**). Figure 2: New recovering shield mounted on the 2 inches magnetron source (**a**); sample holder with quartz samples (**b**). base and top discs, four screws, nuts and rod with a proper length, all designed in SS. The effective surface left free for the SH is just 5%. All mechanical parts were properly cleaned by applying the following procedures: ultrasound bath (1) with deionized water, with the addition of 5 mL of Rodaclean(r) (NGL Cleaning Technology SA, Nyon, Switzerland) soap for 20 min at 40 \({}^{\circ}\)C; (2) ultrasound bath with deionized water during 20 min at 40 \({}^{\circ}\)C; (3) rinsing with ethanol 96%; and (4) packaging in aluminum foil before assembling into the system. The cleaning process of the quartz samples follows the same protocol, except for the storage in ethanol in a plastic box. Just before the assembling of quartz samples to the SH, they were dried with N\({}_{2}\) gas (oil-free system). As for the target material, Cu (99.99% purity) was used. Such targets were prepared by the LNL mechanical workshop. The cleaning procedure followed for Cu targets has been the same used for the standard cleaning protocol adopted, although with a different detergent agent, the GP 17.40 SUP soap (NGL Cleaning Technology SA, Nyon, Switzerland). The sputtering process was held in the stainless steel cylindrical vacuum chamber with the volume 12.3 dm\({}^{3}\). Depositions were carried out by both DC magnetron and diode sputtering (DS) techniques. The base vacuum level was created by a primary and turbo molecular pump (the Edwards nXDS6i of 100 L/min and Pfeiffer turbo molecular pump of 60 L/s, respectively) with a base pressure always lower than 5 \(\times\) 10\({}^{-4}\) Pa without any additional baking procedure. The duration of the MS process deposition was set at 390 min, with a sputtering current of 1 A.