Interference-aided spectrum fitting method for accurately film thickness   determination
  A new approach was proposed to accurately determine the thickness of film, especially for ultra-thin film, through spectrum fitting with the assistance of interference layer. The determination limit can reach even less than 1 nm. Its accuracy is far better than traditional methods. This determination method is verified by experiments and the determination limit is at least 3.5 nm compared with the results of AFM. Furthermore, double-interference-aided spectra fitting method is proposed to reduce the requirements of determination instruments, which allow one to determine the film thickness with a low precision common spectrometer and largely lower the cost. It is a very high precision determination method for on-site and in-situ applications, especially for ultra-thin films. 
Xingxing Liu, Shao-Wei Wang, Hui Xia, Xutao Zhang, Ruonan Ji, Tianxin   Li and Wei Lu
physics.optics