## 1 Introduction  
Polymer-metal nanocomposites exhibit excellent optical [1; 2; 3; 4; 5; 6; 7; 8], electrical [1; 4], and mechanical properties [9; 10] and have been attracting much attention owing to their various characteristics such as surface hardness [6], bioactivity [11; 12], perfect absorbance, [13; 14; 15], and sensing ability [16]. Polymers with good insulating properties are well suited as host materials for supporting a variety of metal clusters [5; 17]. The excellent properties of polymer-metal nanocomposites depend on the size, quantity, and shape of various metal clusters contained in the polymer matrix; various studies elucidating these properties have been performed [17; 18], with reference to surface antimicrobials and abrasion-resistant coatings, and gas sensor films [19; 20; 21; 22]. As a polymer matrix, polytetrafluoroethylene (PTFE), which is mechanically, thermally, and chemically stable, and has excellent insulation and optical properties, is widely used [1; 3; 6; 9; 11; 19; 23]. Studies using noble metals such as Ag [5; 9; 11; 24; 25; 26], Au [3; 16; 27], and Cu [12; 13; 14] have been carried out, but mostly, Ag and Au have been used. In addition to noble metals, nanocomposites using SiO\({}_{2}\)[6], graphite [10], ZnO [19], Ti [28], Fe-Ni-Co [29], and TiO\({}_{2}\)[30], with PTFE, have also been reported. A nanocomposite can be fabricated by the physical vapor deposition (PVD) method, as PVD allows for control of the dopant, enables uniform coating, and minimizes the reaction with air. The co-sputtering method employing two sputtering cathodes [3; 6; 9; 10; 12; 13; 14; 19; 28] is the most widely used method, and other methods involve the use of an evaporator [9; 25], sputter evaporator, ion beam co-sputtering [16], and pulsed laser deposition [24], to fabricate a polymer-metal nanocomposite. However, the use of two sputtering cathodes or a combination of two deposition methods to fabricate nanocomposites requires precise control for yield matching; moreover, it is difficult to ensure reproducibility of the experimental results owing to the complicated equipment configuration and difficulty in securing uniformity over a large area, which are stumbling blocks toward commercialization. In a previous study, our group found that a plasma polymer fluorocarbon (PPFC) thin film prepared using a carbon nanotube (CNT)/PTFE composite sputtering target exhibited diverse physical properties depending on the content of the CNT. In addition, it has been reported that CNT, when added to a composite target, imparts conductivity; hence, sputtering is also possible using a mid-range frequency (MF) power source [31]. Taking our previous study forward, in this study, a Cu/PTFE composite target for sputtering was first introduced for fabricating a Cu/PPFC nanocomposite thin film by uniformly dispersing Cu metal powder in PTFE powder and pressing at high temperature. Previously, the composite target was prepared by attaching half of the polymer target to half of the metal target, or attaching a metal foil or wire to the surface of the polymer target [1; 6]. However, in those studies, it was challenging to deposit a nanocomposite thin film of uniform composition ratio over a large substrate area and prepare a reproducible target; therefore, practical composite targets have been difficult to achieve thus far. We fabricated noble polymer-metal composite targets with 20, 50, and 80 wt.% Cu in PTFE powder. Thus, the filling ratio of the metal nanoclusters in the nanocomposite thin film can be easily controlled, and the nanocomposite thin film can be prepared by long-duration sputtering with one target in the same manner as the conventional sputtering target, enabling excellent reproducibility. Finally, because of the controllability and simple equipment configuration, large-area sputtering is possible; hence, this method can be employed in a wide variety of polymer-metal nanocomposite technical and commercial applications.