Tailoring Lattice Strain and Ferroelectric Polarization of Epitaxial BaTiO3 Thin Films on Si(001)

Abstract

Ferroelectric BaTiO3 films with large polarization have been integrated with Si(001) by pulsed laser deposition. High quality c-oriented epitaxial films are obtained in a substrate temperature range of about 300 °C wide. The deposition temperature critically affects the growth kinetics and thermodynamics balance, resulting on a high impact in the strain of the BaTiO3 polar axis, which can exceed 2% in films thicker than 100 nm. The ferroelectric polarization scales with the strain and therefore deposition temperature can be used as an efficient tool to tailor ferroelectric polarization. The developed strategy overcomes the main limitations of the conventional strain engineering methodologies based on substrate selection: it can be applied to films on specific substrates including Si(001) and perovskites, and it is not restricted to ultrathin films.

Control of Polar Orientation and Lattice Strain in Epitaxial BaTiO3 Films on Silicon

“…The crystal lattice of films deposited on a particular substrate, for example silicon, can be tuned using deposition parameters. For instance, growth rate and deposition temperature in pulsed laser deposition (PLD) of SrTiO 3 (STO) films 13 and ferroelectric BTO/STO superlattices 14 and BTO films 15 have been shown to permit control lattice strain.…”

Selectable texture in epitaxial ferroelectric BaTiO3 films integrated with silicon

“…5,6 The BTO(101)/(100) film LNO/CeO 2 /YSZ/Si(111) ( Figure 3b) presents similar morphology of small grains, being the roughness very low (rms = 0.44 nm) and the surface very homogeneous in spite of the coexistence of the two crystalline orientations. The BTO(101) film on LNO(110)/CTO(110)/YSZ(001)/Si(001) (Figure 3c) shows dense morphology of large grains (a few hundred of nm wide), with some grain boundaries (see two examples marked with white dotted lines) oriented along BTO [1][2][3][4][5][6][7][8][9][10] and BTO[001] directions. The grains are very flat (see the corresponding height profile) and the overall roughness very low (rms = 0.53 A/cm 2 at 45 kV/cm), whereas in the BTO(101) film on CTO(110)/YSZ(001)/Si(001) is similar to the BTO(001) sample (8x10 -8 A/cm 2 at 45 kV/cm).…”

“…The deposition conditions used for the other buffer layers and BTO are reported elsewhere. [4][5] Crystal orientation, epitaxial relationships and lattice parameters were determined by X-ray diffraction (XRD) using CuK α radiation. Topographic images were recorded by atomic force microscopy (AFM).…”

“…Epitaxial ferroelectric oxides on Si(001) are generally (001) or (100) oriented and rarely present different texture. [3][4][5][6][7][8][9] Exceptions include (110)-oriented PZT 10 (Figure 1a, left panel). The first route ( Figure 1a, right panel) involves the use of the alternative LNO/CaTiO 3 (CTO)/YSZ buffer layer on Si(001).…”

Влияние Разряда На Температуру Подложки При Напылении Пленки

“…Основным фактором, влияющим на свойства пленки, является вынужденная деформация (misfit strain) [2], появляющаяся из-за несоответствия величин теплового расширения пленки и подложки. Абсолютная величина вынужденной деформации в рамках линейной теории упругости пропорциональна разности между температурой напыления и температурой измерения свойств [3,4]. Поэтому температура подложки при напылении является важным фактором, влияющим на свойства пленки.…”