Local structural studies of Sr-buffered Si surface prepared with pulsed laser deposition

author: Tjaša Parkelj, Advanced Materials Department, Jožef Stefan Institute
published: May 23, 2017,   recorded: April 2017,   views: 21


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A successful integration of functional oxides with silicon could lead to the design of a wide variety of novel electronic devices with sensing, logic and energy-harvesting capabilities. However, the silicon surface is highly reactive, and needs to be passivated by an appropriate buffer layer that is chemically stable as well as structurally compatible with the overgrown oxide layer. A buffer layer based on ½ monolayer (ML) of Sr on Si(001) has been shown to fulfil both requirements [1,2]. While this surface has been conventionally prepared by Molecular Beam Epitaxy (MBE), one of the most promising techniques for overcoming its numerous shortcomings is Pulsed Laser Deposition (PLD). Plenty of studies for MBE-derived surfaces can be found in the literature, but to the best of our knowledge, there have been no local structural studies of such a surface when prepared by PLD. Nevertheless, a local study of the buffer layer structure is needed to assure a highly-ordered surface, required for a successful integration of oxide materials.

In this contribution, the results of Scanning Tunneling Microscopy (STM) analysis of ½ ML of Sr/Si(001) surfaces prepared by PLD will be presented. The samples were prepared following a procedure previously developed by our group [3], and transferred using an ultra-high vacuum suitcase, in order to ensure an adsorbate free surface necessary for the STM measurements. Large-scale STM images confirm the (2×1) reconstructed Sr/Si(001) surface detected by in-situ reflective high-energy electron diffraction measurements. This reconstruction covers the surface area entirely, and exhibits two equivalent 90°-rotated domains on the neighbouring terraces. High resolution images reveal chain-like structures running along the [011] and [01̅1] directions with a lateral distance of 0.78. Apart from the well-ordered chains, an abundance of various defects can be distinguished. However, the quality of the surface is still comparable to the MBE prepared surfaces. This study represents the first local structural analysis of a PLD prepared Sr-buffered Si surface and confirms that PLD can be used for the preparation of a high quality buffer layer necessary for achieving epitaxial growth of complex oxides on silicon using this technique.

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