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.