A buffer layer formed by depositing a 1 monolayer of Sr on Si(001) is known to passivate the Si surface, while its surface structure constitutes a suitable template for the integration of various functional oxides with the existing Si platform. We used Pulsed Laser Deposition (PLD) to prepare a Sr/Si(001)(1×2) surface and analysed it using in-situ Reflection High-Energy Diffraction (RHEED) in combination with low-temperature Scanning Tunneling Microscopy (STM). The STM images reveal an atomically ordered surface with terraces composed of one-dimensional (1D) chains running along perpendicular directions on neighbouring terraces. The 1D chains are separated by 0.78 nm and exhibit a low-amplitude corrugation with a period of 0.39 nm. The measured values agree well with the size of the (1×2) unit cell observed for similar MBE-grown surfaces, while the density of the surface defects is somewhat higher in the presented case. According to simulated STM images based on DFT calculations, two types of surface defects were identified and explored: arrays of Sr vacancies and Sr adatoms. These results show that PLD can offer precise control for the preparation of high-quality Sr-buffered Si(001) surfaces.
COBISS.SI-ID: 31943975
Sub-monolayer control over the growth at silicon–oxide interfaces is a prerequisite for epitaxial integration of complex oxides with the Si platform, enriching it with a variety of functionalities. However, the control over this integration is hindered by the intense reaction of the constituents. The most suitable buffer material for Si passivation is metallic strontium. When it is overgrown with a layer of SrTiO3 (STO) it can serve as a pseudo-substrate for the integration with functional oxides. In our study we determined a mechanism for epitaxial integration of STO with a (1×2) + (2×1) reconstructed Sr(1/2 ML)/Si(001) surface using all-pulsed laser deposition (PLD) technology. A detailed analysis of the initial deposition parameters was performed, which enabled us to develop a complete protocol for integration, taking into account the peculiarities of the PLD growth, STO critical thickness, and process thermal budget, in order to kinetically trap the reaction between STO and Si and thus to minimize the thickness of the interface layer. The as-prepared oxide layer exhibits STO(001)|| Si(001) out-of-plane and STO[110]||Si[100] in-plane orientation and together with recent advances in large-scale PLD tools these results represent a new technological solution for the implementation of oxide electronics on demand.
COBISS.SI-ID: 32836647
The integration of oxides on Si remains challenging, which largely hampers the practical applications of oxidebased electronic devices with superior performance. Recently, LaMnO3/SrTiO3 (LMO/STO) heterostructures have gained renewed interest for the debating origin of the ferromagnetic-insulating ground state as well as for their spin-filter applications. Here we report on the structural and magnetic properties of high-quality LMO/STO heterostructures grown on silicon. The chemical abruptness across the interface was investigated by atomic-resolution scanning transmission electron microscopy. The difference in the thermal expansion coefficients between LMO and Si imposed a large biaxial tensile strain to the LMO film, resulting in a tetragonal structure with c/a ~ 0.983. Consequently, we observed a significantly suppressed ferromagnetism along with an enhanced coercive field, as compared to the less distorted LMO film (c/a ~ 1.004) grown on STO single crystal. The results are discussed in terms of tensile-strain enhanced antiferromagnetic instabilities. Our results demonstrate that the growth of oxide films on Si can be a promising way to study the tensile-strain effects in correlated oxides.
COBISS.SI-ID: 14858499