Initial stages of epitaxial growth of Y-stabilized ZrO2 thin films on a-SiOx/Si(001) substrates

Abstract

The initial stages of crystallization and growth of epitaxial Y-stabilized ZrO2 (YSZ) thin films on Si (001) substrates covered with amorphous native oxide were investigated by transmission electron microscopy (TEM) and reflection high-energy electron diffraction (RHEED). The YSZ crystallizes by solid-phase epitaxy with an initial thickness of 1 nm. The crystallization is initially incomplete, yielding both epitaxial and disordered regions of the YSZ film. In situ RHEED measurements showed the lattice parameter of the YSZ gradually decreased during growth, reaching the bulk value at a film thickness of 5–7 nm. For a larger thickness, the film is fully elastically relaxed. TEM revealed misfit dislocations at the YSZ/Si interface. The average spacing between misfit dislocations with Burgers vector b=1/2 〈110〉 was measured as 8.3 nm, showing epitaxial misfit strain to be fully accommodated by misfit dislocations. Thermal strain introduced during cooldown from the deposition temperature is fully elastically accommodated. For YSZ thicknesses below 7 nm, the thickness of the regrown layer of silicon oxide at the YSZ/Si interface is 0–0.5 nm.

Growth of (001) oriented La0.5Sr0.5CoO3 films directly on SiO2/Si substrate by pulsed laser deposition

“…Nano-crystals of LSCO layer are formed on the early stage of crystallization and growth, which may lead to the orientation growth of the LSCO films. The behaviors are similar to the case which observed in the growth of Ca 3 Co 4 O 9 [13] and YSZ [14] thin films on SiO 2 /Si substrate. Electron back-scattering Diffraction measurement was used to investigate the in-plane alignment.…”

In situ growth of c-axis-oriented Ca3Co4O9 thin films on Si (100)

“…A behavior bearing some similarity to this case was observed in the growth of YSZ thin film on a SiO x /Si͑001͒ substrate at the very early stages of crystallization and growth. 11 However, the disordered regions ͑SiO x and YSZ amorphous layer͒ disappeared when the YSZ film was thicker than 6.5 nm. Figure 3 shows the temperature dependence of the resistivity for Ca 3 Co 4 O 9 films grown on Si ͑100͒ substrate.…”

CoFe2O4/buffer layer ultrathin heterostructures on Si(001)

“…Inhomogeneous YSZ crystallization on Si(001) had been earlier reported. 16 In contrast, the homogeneous crystallization reported here results in ultrathin YSZ films that are atomically flat and epitaxial from thickness of about 1.5 nm as detected by in situ RHEED.…”

“…It is concluded that a minimum amount of Y and Zr atoms has to be deposited on SiO x to reduce it and then to form a crystalline YSZ epilayer on the bare Si(001) surface. 16 The time dependence of the RHEED line profiles plotted in Fig. 1(e) reflects these stages.…”

“…16,17 However, it had been found that in ultrathin YSZ films islands are formed in the early growth stages, and although coalescence and flattening were observed for thicker YSZ films, 16 the roughness at the initial stage is a severe limitation that prevents the use of YSZ as a buffer for applications requiring an ultrathin buffer.…”