Fourier-transform infrared spectroscopy (FTIR) MOCVD MgF2 PECVD PVD coatings Q-factor RF-PECVD Raman spectroscopy Technology: general issues VI/III ratio X-ray diffraction X-ray diffraction spectroscopy (XRD) Young's modulus adhesion aluminum coating annealing atomic layer deposition brittle cracking color center absorption crystal frequency density diamond coatings dual functional-metalens e-beam physical vapor deposition flat film extrusion fluoropolymer focusing foil quality fracture toughness initiated chemical vapor deposition (iCVD)