Preparation and characterization of Pb(Nb,Ti)O3 thin films by metalorganic chemical vapor deposition

Abstract

Lead niobium titanate, Pb(Nb,Ti)O3, thin films were prepared on various substrates by metalorganic chemical vapor deposition from the Pb(C11H19O2)2–Nb(O⋅C2H5)5–Ti(O⋅i-C3H7)4–O2 system. Polycrystalline films with (111) orientation and epitaxially grown films with c-axis orientation were deposited on the (111)Pt/Ti/SiO2(100)Si and PbTiO3/(111)Pt/Ti/SiO2/(100)Si substrates, and (100)SrRuO3//(100)LaAlO3 substrate, respectively, at 620 °C. Nb content in the film can be controlled only by changing the input gas flow rate of Nb(O⋅C2H5)5 under the excess gas flow rate of Pb(C11H19O2)2. The composition of the film was independent of the deposition temperature from 400 to 620 °C. The single phase of Pb(Nb,Ti)O3 was deposited up to the Nb content of about 5 at % and pyrochlore phase was codeposited above this Nb content. Leakage current density decreased with the increasing Nb content in the film up to 6.5 at %. Coercive field (Ec) of the film was about 130 kV/cm and was independent of the Nb content and the kinds of substrates. On the other hand, the remanent polarization (Pr) of the film on the (111)Pt/Ti/SiO2/(100)Si substrate increased from 9 to 29 μC/cm2 with the increasing Nb content from 2.1 to 4.8 at %. Pr of the film on the (100)SrRuO3//(100)LaAlO3 substrate was smaller than those of the (111)Pt/Ti/SiO2/Si and PbTiO3/(111)Pt/Ti/SiO2/Si substrates.

Internal Microstructure and Formation Mechanism of Surface Protrusions in Pb-Ti-Nb-O Thin Films Prepared by MOCVD

“…The apparatus and the procedures for film deposition have been described in a previous paper [8]. We used a tubular, horizontal, cold-wall reactor.…”

“…The investigation into the PZT-family thin films has been extended to a wide composition range, such as Pb(Ti,Nb)-O 3 , [8] (Pb,La)(Ti,Zr)O 3 , [13] (Ba,Sr)TiO 3 , [14] etc. In the first two systems, formation of the perovskite-type, body-centered tetragonal phase is a key consideration in obtaining the desired ferroelectric properties, such as high remnant polarization, low coercive field, high resistance, etc.…”

“…It has been further confirmed that an increased deposition temperature, from the current 400 C to 600 C, gave rise to a complete crystalline state. [8] The low deposition temperature is thus responsible for the formation of amorphous and metastable Pb 2 Ti 2 O 6 phases. Based on the above facts, we suggest a mixed deposition process, which results in both amorphous and crystal phases at 400 C. The difference in the phase constituent among the samples studied was attributed to the different crystallization behaviors of the film-forming precursors in the MOCVD reaction.…”

A General Conductivity Expression for Space-Charge-Limited Conduction in Ferroelectrics and Other Solid Dielectrics

“…Our theoretical investigation of SCLC began with a study of the well-known phenomenon of polarization offsets in compositionally graded ferroelectric films (Bao et al 2000a(Bao et al , 2000b(Bao et al , 2000c(Bao et al , 2001a(Bao et al , 2001bBouregba et al, 2003;Brazier et al, 1998;Chen et al, 1999;Mantese et al, 1997;Matsuzaki & Funakubo, 1999;Schubring et al, 1992). Ferroelectric materials are materials that generally exhibit nonlinear, hysteretic D-E or P-E relations, where D is the electric displacement, P is the polarization and E is the electric field.…”

Polarization Offsets of Non Graded and Graded Ferroelectric Films

“…Many authors have reported shifts of hysteresis loops, so called polarization offsets (P off ), observed on compositionally graded ferroelectric devices (GFD's) prepared with different material systems [1][2][3][4][5][6][7][8][9][10][11]. Offsets were systematically obtained while the devices were "pumped" by an oscillatory field during SawyerTower (S-T) hysteresis measurements [12] and their direction was directly 68 R. Bouregba et al…”