Electro-Optic Materials by Solid Source MOCVD

Abstract

The solid source MOCVD technique1,2, employing a single powder vaporization source composed of mixed beta-diketonate metalorganic compounds, has been used to grow thin films of a variety of electro-optic materials, including lithium niobate, strontium barium niobate, and potassium niobate. Results for potassium niobate films are quite preliminary, but indicate that a volatile potassium organometallic source can be synthesized which is useful for growing potassium niobate by MOCVD. High quality single phase (001) oriented strontium barium niobate films have been deposited which exhibit waveguiding behavior. The most extensive work has been done on lithium niobate, which has been deposited epitaxially on a variety of substrates. Oriented z-axis (001) films have been grown on c-axis sapphire with and without a (111) oriented platinum base electrode and on a bulk grown lithium niobate substrate. Films grown directly on c-axis sapphire at 700 C exhibit x-ray rocking curve linewidths as low as.044 degrees, nearly perfect in-plane orientation as determined by x-ray phi scans, and peak-to-peak surface roughness less than 40 Å. Optical waveguiding has been demonstrated by a single prism coupling technique on similar films 1175 – 2000 Å thick grown at 500 C, with optical losses of approximately 2 db/cm at 632.8 nm measured over 3.5 cm long films. Polarization vs. electric field measurements on 1100 Å thick films grown on platinum show a hysteresis loop indicating ferroelectric behavior.

LiNbO 3 thin film growth on (0001)-GaN

“…The growth of c+ (that is, with the spontaneous polarization vector of the films pointing from the substrate to the surface of the films 14 ) on sapphire has been reported for both sputter deposited 14 and MOCVD grown films. 16 It has been well established that the c− face of LiNbO 3 etches much faster in HF and HF: HNO 3 than the c+ face. 14,16,17 The outgrowths of sputter deposited LiNbO 3 films on sapphire were shown to be c− grains in a c+ matrix by etching in HF.…”

“…16 It has been well established that the c− face of LiNbO 3 etches much faster in HF and HF: HNO 3 than the c+ face. 14,16,17 The outgrowths of sputter deposited LiNbO 3 films on sapphire were shown to be c− grains in a c+ matrix by etching in HF. 14 To investigate the polarity of our films, the samples were etched in HF: HNO 3 and investigated with AFM following etching.…”

“…7,8 It has been reported that homoepitaxial MOCVD grown LiNbO 3 films have a c+ orientation regardless of the polarity of the LiNbO 3 substrate. 16 To investigate whether or not the substrate polarity affected the LiNbO 3 film polarity, homoepitaxial LiNbO 3 films were sputtered on substrates with c+ and c− orientations and CBED images were taken. The polarity of the films followed the polarity of the substrate, indicating that the orientation of the films was not an artifact of the deposition method.…”

MOCVD of KNbO3 Ferroelectric Films and their Characterization

“…[15±18] An attempt to grow KNbO 3 films by single-source MOCVD was undertaken earlier, [19] but the films were of low quality. The major problem that makes separate evaporation necessary is the difference in melting points of commonly used precursors: potassium 2,2,6,6-tetramethylheptanedionate-3,5 (K(thd) T melt = 185 C) and niobium alkoxides (commonly used Nb(OEt) 5 T melt = 6 C), as well as their tendency to cross-exchange ligands.…”

The Growth of Optical Quality LiNbo3 Thin Films On Sapphire and LiTao3 Substrates Using Solid-Source Mocvd

“…A number of thin film fabrication techniques have been used for the growth of LiNbO 3 thin films including liquid phase epitaxy (LPE) [3,4], epitaxial growth from melts [5], sol-gel processing [6], sputtering [7,8], laser ablation [9], molecular beam epitaxy (MBE) [10], and metalorganic chemical vapor deposition (MOCVD) [ 11,12]. Sapphire has been used most often as the substrate material because of its low optical index and chemical inertness.…”