Abstract
Li–Nb–O amorphous films were deposited onto Si substrates by the radio-frequency magnetron sputtering method in an Ar environment and an Ar(60%)+O 2 (40%) gas mixture. A positive effective fixed oxide charge Q eff having negative, -Q eff , and positive, +Q eff , components, exists in the as-grown heterostructures. -Q eff is located near the substrate/film interface, whereas + Q eff is determined by a deficit of Li and O (vacancies) in the bulk of Li–Nb–O films. As-grown films crystallized under thermal annealing (TA) at temperatures up to 600 °C and revealed the formation of polycrystalline LiNbO 3 . TA at about 520 °C resulted in the formation of the second phase LiNb 3 O 8 , increasing + Q eff , and compensating -Q eff entirely. The dielectric constants of the as-grown films exhibit two peaks at the annealing temperatures of 450 °C and 550 °C, which are attributed to the total crystallization and recrystallization of the LN films under TA, respectively.
Highlights
Ferroelectric oxides in a thin-film form are essential components in a variety of applications
The amorphous LieNbeO films were deposited onto Si substrates by the Radio-frequency magnetron sputtering (RFMS) process in an Ar reactive gas environment and an Ar þ O2 gas mixture
All as-grown films manifested the net effective oxide charge having two components: a negative -Qeff, dominating in the “thin” (d < 200 nm) LieNbeO films, and a positive þ Qeff, prevailing in the “thick” (d > 200 nm) films. -Qeff is attributed to structural defects near the substrate/film interface, whereas þ Qeff is determined by a deficit of Li and O in the bulk of LieNbeO films
Summary
Ferroelectric oxides in a thin-film form are essential components in a variety of applications. They have been used in various sensor and actuator designs, in optoelectronics and in rf devices for tunable microwave circuits. The practical application requires the formation of LN-based heterostructures (like Si-LN) with specific properties. One of the objectives is to find a ferroelectric material demonstrating little or no degradation of the switchable ferroelectric polarization [3]. This requirement, as well as other features like optical loss, depends on both the LN film properties and the characteristics of the LN film/substrate interface. Sumets et al / Journal of Science: Advanced Materials and Devices 5 (2020) 256e262
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