The Ti interlayer was deposited via sputtering (Safematic CCU-010) sputter coater with a Ti target (99.98%, Baltic Präparation e.K.). The purge and background gas was Ar. The target was pre-sputtered to remove oxides before opening the shutter for deposition. The deposition current was 100 mA and deposition pressure was 8.0×10 -3 mbar.