AVS 53rd International Symposium
    Electronic Materials and Processing Friday Sessions
       Session EM+TF-FrM

Invited Paper EM+TF-FrM5
Molecular Beam Epitaxy of Multifunctional Materials Using a Chloride Refractory Metal Chemistry

Friday, November 17, 2006, 9:20 am, Room 2003

Session: High-k Dielectric & Multi-Functional Oxide Growth & Processing
Presenter: W.A. Doolittle, Georgia Institute of Technology
Authors: W.A. Doolittle, Georgia Institute of Technology
A.G. Carver, Georgia Institute of Technology
W. Henderson, Georgia Institute of Technology
W. Laws Calley, Georgia Institute of Technology
S.-S. Kim, Georgia Institute of Technology
Correspondent: Click to Email
Multifunctional materials, materials that interact with their environment via differing force mechanisms, including but not limited to electrostatic, magnetic, acoustic, photonic, and chemical, are of great interest for future sensor and actuator applications. Lithium metal oxide multifunctional materials, including LiNbO@sub 2@, LiNbO@sub 3@, LiTaO@sub 2@ and LiTaO@sub 3@ are presented as a promising but challenging materials for multifunctional devices. Example proposed applications will be presented. A chloride based chemistry that bypasses many of the traditional pitfalls of Lithium Niobate (LN) epitaxy including the need for electron beam evaporation of refractory metals, and use of complex metal organic precursors prone to pre-reaction is described. Methods of dealing with the normally corrosive chloride based chemistry in a Molecular Beam Epitaxy (MBE) chamber are detailed. The present state of homoepitaxy and heteroepitaxy of LN on semiconductors is presented. It is shown that LiNbO@sub 2@ is preferentially grown over LiNbO@sub 3@ in the oxygen deficient MBE vacuum environment. However, LiNbO@sub 2@ is shown to be converted to LiNbO@sub 3@ by an ex-situ oxygen anneal. Dramatic changes in optical properties and crystalline lattice structure result and will be detailed. A limited stoichiometry control is demonstrated via use of ion filters on an oxygen plasma source including the ability to partially select between various valences of niobium oxides, NbO, NbO@sub 2@ and Nb@sub 2@O@sub 5@. While the demonstrated metal chloride based epitaxy is shown as a viable candidate for MBE of multifunctional refractory metal oxides, particularly for electronic applications, the possibility for thicker films, and thus impact on optical devices, is currently limited by the available Li source. Efforts to circumvent this difficulty, including a large volume valved Li source, will be described.