The a-Si1-xCx passivation layer was deposited on 2 × 7-cm glass substrates and 4-inch p-type silicon (100) wafers using an RF magnetron co-sputtering system. Figure shows the schematic diagram of our RF magnetron co-sputtering system. Before the RF plasma process, the substrates were cleaned in trichloroethylene, acetone, methanol, and distilled water for 10 min. For the silicon wafers, an acid treatment was added for 45 s. Pure (99.9%), 4-inch Si and C targets were installed to achieve a high-quality a-Si1-xCx passivation layer. The sputtering chamber was vacuumed up to the base pressure of 1 × 10-5 Torr using a turbomolecular pump. A highly pure (99.9999%) argon environment was established for the deposition with a flow of 40 sccm. Then, the Si and C targets were pre-sputtered to clean the target surface and the chamber for 10 min. The target-to-substrate distance and the substrate rotation speed were fixed for all depositions as 6 cm and 1, 700 rph, respectively. In this work, to check the effect of the Si-to-C ratio on the a-Si1-xCx passivation layers, the RF power of the C target was fixed at 150 W, and several different RF powers (100, 150, 175, and 200 W) of the Si target were applied to. However, the thicknesses of all a-Si1-xCx passivation layers were kept constant at 100 nm by controlling the deposition rate. The deposition rates with the different RF powers of the Si target were summarized in Figure , and the detailed experimental parameters were summarized in Table .
A schematic diagram of the RF magnetron co-sputtering system.
Deposition rate of a-Si1-xCx passivation layer as a function of the Si target's RF power.
Deposition conditions of the a-Si1-xCx passivation layer
The deposited a-Si1-xCx passivation layer's thickness and crystal structure were measured using an FE-SEM (S-4800, Hitachi, Tokyo, Japan) and a transmission electron microscope [TEM] (JEM-2100F, JEOL, Seoul, South Korea), respectively. Optical properties of the transmittance and bandgap were measured by UV-visible spectroscopy (S-3100, Scinco, Seoul, South Korea), the refractive indexes were obtained using an ellipsometer (M2000D, Woollam, Uiwang-si, South Korea), and the electrical performance of the a-Si1-xCx passivation layer was analyzed by carrier lifetime measurement (WCT-120, Sinton Consulting Inc., Boulder, CO, USA).