Atomic layer deposition of ferroelectric LiNbO3

Erik Østreng,Henrik H Sønsteby,Timo Sajavaara,Helmer Fjellvåg,Ola Nilsen

doi:10.1039/c3tc30271g

Erik Østreng, Henrik H Sønsteby + Show 3 more

Open Access

https://doi.org/10.1039/c3tc30271g

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Abstract

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 ∼220 kV cm−1, with a remanent polarization of ∼0.4 μC cm−2. Deposition of lithium containing materials is traditionally challenging by ALD, and critical issues with such deposition are discussed.

Highlights

Lithium niobate, LiNbO3, has been the centre of attention for a range of optical applications since the discovery of its ferroelectric properties in 1949.1 The non-centrosymmetric trigonal structure of LiNbO3 was described in detail by Nassau in 1966.2 The strength of LiNbO3 is its relatively large physical coefficients for piezoelectric,[3] pyroelectric[4] and photoelastic[5] effects
Lithium phosphate and lithium silicate have been grown using lithium silylamide (LiN(SiMe3)[2] or LiHMDS) as a precursor by Hamalainen et al.[26,28] and we have recently reported the growth of lithium nitride and carbonate by the same precursor.[30]
The current paper describes the epitaxial growth of ferroelectric LiNbO3 by atomic layer deposition (ALD)

Summary

Introduction

LiNbO3, has been the centre of attention for a range of optical applications since the discovery of its ferroelectric properties in 1949.1 The non-centrosymmetric trigonal structure of LiNbO3 was described in detail by Nassau in 1966.2 The strength of LiNbO3 is its relatively large physical coefficients for piezoelectric,[3] pyroelectric[4] and photoelastic[5] effects. Time of ight elastic recoil detection analysis (TOF-ERDA) measurements were performed at the University of Jyvaskyla using a 8.515 MeV 35Cl4+ beam from the 1.7 MV Pelletron accelerator With this technique all the sample elements, including impurities above 0.1 at% concentration could be quanti ed. Measurements of ferroelectric properties are made with an Aixact TF2000 analyzer at 1 kHz

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