Role of template layer on microstructure, phase formation and polarization behavior of ferroelectric relaxor thin films

Abstract

Articles you may be interested inSignificant enhancement of energy-storage performance of (Pb0.91La0.09)(Zr0.65Ti0.35)O3 relaxor ferroelectric thin films by Mn doping ͑1−x͒Pb͑Mg 1/3 Nb 2/3 ͒O 3 − ͑x͒PbTiO 3 ͑PMNPT͒ a relaxor ferroelectric has gained attention due to its interesting physical properties both in the bulk and thin film forms from a technological and fundamental point of view. The PMNPT solid solution at the morphotropic phase boundary composition has superior properties and is potentially used as an electrostrictive actuator, sensor, and in MEMS applications. Deposition of phase pure PMNPT thin films on bare platinized silicon wafers has been an impossible task so far. In this study the role of the LSCO template on the phase formation and the influence of platinum surface on the same have been studied. It was observed that formation of hillocks in Pt coated silicon wafers is associated with an ATG type of instability while roughening through strain relaxation. The hillocks formation was observed only on the troughs of the strain waves on the surface of Pt. The nucleation and growth of the PMNPT films were analyzed using AFM studies and the nucleation nucleates only at the tips of the hillocks and grows along the same direction with a new nucleus adjacent to the first one. A wavy pattern of PMNPT nuclei was observed and later the lateral growth of the islands takes place to cover the surface and minimizes the roughness to 2 nm. Hence, a template layer with a minimum of 40 nm is required to have a complete coverage with a roughness of less than 2 nm. The chemical states of the PMNPT films grown with and without the template layer were analyzed using x-ray photoelectron spectrum. The XPS spectrum of PMNPT deposited on a Pt surface exhibited a reduced oxidation state of niobium ions and a metallic state of Pb at the initial stage of the growth, which effectively destabilizes the perovskite phase of PMNPT in which the charge states and the ordering of Nb and Mg are more crucial to have a stable perovskite structure.

Tailoring Ferroelectric Properties of 0.37BiScO3–0.63PbTiO3Thin Films Using a Multifunctional LaNiO3Interlayer

“…11 So-called 'buffer layers' between the ferroelectric film and platinized silicon substrate modify the residual stress state 12,13 which has a significant effect on the ferroelectric, piezoelectric and dielectric properties and, along with 'seed-layers', have been used to control film orientation. 14,15 In addition, to the use of buffer and seed layers, it has been known for many years that oxide electrodes used instead of plantinum (Pt on Ti/SiO2/Si) improve performance since they prevent undesired compositional modification and impede charge interdiffusion processes. [16][17][18][19] Table I describes some examples of the effect of interlayers on ferroelectric films.…”

“…So-called “seed layers” are known to control perovskite nucleation, reduce the temperature of phase formation, improve the film crystalline degree, suppress the formation of planar defects, and prevent reaction between films and substrates. − Seed layers have been extensively used on Pt/Ti/SiO 2 /Si bottom electrodes to overcome the detrimental effects of microstructural heterogeneities and variations in the crystalline quality of the films and are known to prevent deterioration of the ferroelectric properties . So-called “buffer layers” between the ferroelectric film and platinized silicon substrate modify the residual stress state , which has a significant effect on the ferroelectric, piezoelectric, and dielectric properties and, along with “seed-layers”, have been used to control film orientation. , In addition to the use of buffer and seed layers, it has been known for many years that oxide electrodes used instead of plantinum (Pt on Ti/SiO 2 /Si) improve performance since they prevent undesired compositional modification and impede charge interdiffusion processes. − Table describes some examples of the effect of interlayers on ferroelectric films.…”

Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer

“…Currently, there are several deposition techniques for fabricating oxide electrodes or buffer layers such as laser ablation, sputtering, and sol-gel [17][18][19]. Tang et al have shown that PCT thin films on LaNiO 3 coated fused quartz and Si substrates maintain good dielectric and ferroelectric properties [20].…”