Atomic layer deposition of ferroelectric LiNbO3

The ferroelectric and electro-optical properties of LiNbO3 make it an important material for current and future applications. It has also been suggested as a possible lead-free replacement for present PZT-devices. The atomic layer deposition (ALD) technique offers controlled deposition of films at an industrial scale and thus becomes an interesting tool for growth of LiNbO3. We here report on ALD deposition of LiNbO3 using lithium silylamide and niobium ethoxide as precursors, thereby providing good control of cation stoichiometry and films with low impurity levels of silicon. The deposited films are shown to be ferroelectric and their crystalline orientations can be guided by the choice of substrate. The films are polycrystalline on Si (100) as well as epitaxially oriented on substrates of Al2O3 (012), Al2O3 (001), and LaAlO3 (012). The coercive field of samples deposited on Si (100) was found to be similar to 220 kV cm(-1), with a remanent polarization of similar to 0.4 mu C cm(-2). Deposition of lithium containing materials is traditionally challenging by ALD, and critical issues with such deposition are discussed.