## 1 Introduction  
High quality poly-crystalline silicon (poly-Si) is in great demand in the electronics industry, due to its low cost, the need for less semiconductor materials and simpler fabrication compared with monocrystalline Silicon (C-Si). The main applications of poly-Si are electronics (such as thin film transistors (TFTs) used in flat-panel, liquid-crystal displays), optoelectronics (optical Blu-ray discs) and photovoltaic (PV) devices (thin film solar cells) [1; 2; 3; 4]. Poly-Si films may be fabricated by variety methods that result in different crystal sizes and properties. Nowadays, plasma-enhanced chemical vapor deposition (PECVD) is the most widely used method for poly-Si thin film fabrication [5; 6; 7; 8]. However, this technique requires a large volume of SiH\({}_{4}\) gas for the deposition of Si as a raw material; the majority of the SiH\({}_{4}\) gas is screened out by the vacuum system, reducing the Si deposition rate to lower than 10% [9; 10]. In addition, SiH\({}_{4}\) is a highly flammable, toxic and not eco-friendly gas which requires many safety considerations and precautions for its storage, transportation and exhaust from the operational PECVD system. In contrast to PECVD systems, magnetron sputtering (MS), as a physical vapor deposition (PVD) technique, generally uses inert gases such as argon as the reaction gas for the creation of plasma, and solid target materials as the source of the deposited film, making it a much simpler and safer approach than chemical vapor depositions (CVDs). Additionally, the MS technique has a higher raw material utilization (\(\sim\)30%) for Si deposition in comparison to CVD processes. Another important advantage of MS systems is the elimination of the need to use toxic or flammable gases. Furthermore, MS is a scalable deposition technique which is suitable for the fabrication of large-scale devices while maintaining the uniformity of the deposited layer; the technique makes it possible to easily deposit silicon and other semiconductors onto various rigid and/or flexible substrates with different properties such as glass, wafer, metal, polymers, fabrics, etc. Therefore, MS has many advantages and much potential as an eco-friendly, low-cost technique for the mass production of Si thin film solar cells [11; 12; 13; 14]. However, the fabrication of such solar cells by MS has not been widely investigated; just a few research groups have reported successful approaches. There are two main reasons for this: The first is the very short effective diffusion length of the photo-generated carriers in a-Si made by MS (which prevents them from passing the p-n junction of the solar cell and reaching the electrode contacts); the second is the large number of dangling bonds in the sputtered a-Si thin film which act as traps for photo-generated carriers [15; 16]. One effective solution to these problems is the crystallization of a-Si and its conversion to micro- or poly-Si by thermal annealing. This process combines the dangling bonds of a-Si film and forms orderly covalent bonding which reduces the trapping of the photo-generated carriers and increases the short circuit current density in the thin film solar cell. Usually, a pure solid-phase crystallization of a-Si only happens at very high temperatures, which limits the applicability of crystallized a-Si for the fabrication of solar cells on low-cost substrates such as ordinary float glass. Using the metal-induced crystallization (MIC) method can reduce the activation energy and temperature for a-Si crystallization to a much lower percentage of the eutectic point of Si-metal binary systems [17; 18]. Among different metals, aluminum has been widely studied [19; 20; 21], and different methods of aluminum-induced crystallization (AIC) have been proposed [22; 23; 24; 25].