Atomic Layer Deposition of LiF Thin Films from Lithd and TiF4 Precursors

Lithium fluoride (LiF) is an important optical material with a low refractive index and a large band gap. In this study, thin films of LiF are deposited using atomic layer deposition (ALD). Lithd and TiF4 are used as precursors, and they produce crystalline LiF in the temperature range 250–350 °C. The films are studied with UV‐Vis spectrometry, field emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD), atomic force microscopy (AFM) and elastic recoil detection analysis (ERDA). Adhesion of the films is tested by a Scotch tape test. This ALD process results in LiF films with a growth rate of approximately 1 Å per cycle at 325 °C. According to ERDA measurements, the films are pure LiF with only small O, C, and H impurities. A deposition method for lithium fluoride thin films by ALD onto Si substrates is described. The deposited films are analyzed by UV‐Vis spectrometry, FESEM, XRD, AFM, and ERDA. This deposition process produces crystalline LiF films with high purity and a refractive index close to that of bulk LiF. The roughness of the films increases with increasing deposition temperature.