Silicon Surface Deoxidation Using Strontium Oxide Deposited with the Pulsed Laser Deposition Technique

Abstract

The epitaxial growth of functional oxides on silicon substrates requires atomically defined surfaces, which are most effectively prepared using Sr-induced deoxidation. The manipulation of metallic Sr is nevertheless very delicate and requires alternative buffer materials. In the present study the applicability of the chemically much more stable SrO in the process of native-oxide removal and silicon-surface stabilization was investigated using the pulsed-laser deposition technique (PLD), while the as-derived surfaces were analyzed in situ using reflection high-energy electron diffraction and ex situ using X-ray photoelectron spectroscopy, X-ray reflectivity, and atomic force microscopy. After the deposition of the SrO over Si/SiO2, in a vacuum, different annealing conditions, with the temperature ranging up to 850 °C, were applied. Because the deposition took place in a vacuum, a multilayer composed of SrO, Sr-silicate, modified Si, and Si as a substrate was initially formed. During the subsequent annealing the topmost layer epitaxially orders in the form of islands, while a further increase in the annealing temperature induced rapid desorption and surface deoxidation, leading to a 2 × 1 Sr-reconstructed silicon surface. However, the process is accompanied by distinctive surface roughening, and therefore the experimental conditions must be carefully optimized to minimize the effect. The results of the study revealed, for the first time, an effective pathway for the preparation of a SrO-induced buffer layer on a silicon substrate using PLD, which can be subsequently utilized for the epitaxial growth of functional oxides.

Effects of annealing on structure and composition of LSMO thin films

“…The Sr/La, Mn/La, and O/La ratios are increasing from 973 to 1023 K, which can be attributed to the crystallization of LSMO, as discussed in the XRD and AFM results. The Sr/La ratio has almost no change from 1023 to 1073 K but decreases linearly from 1073 to 1173 K, indicating that desorption and deoxidation processes of the segragated SrO are occurring [41]. The O/La ratios increase from 1023 to 1073 K due to the formation of SrO from segregated strontium [31].…”

Integration of Single Oriented Oxide Superlattices on Silicon Using Various Template Techniques

“…In particular, it has been demonstrated that STO grown on a graphene buffer layer on silicon has a dominant (00 l ) orientation, but coexisting with a small portion of (110)-, (111)-, and (211)-oriented grains. 26 In this work, we employ SrO to deoxidize the uncovered Si surface before STO deposition, 33 which plays a key role in inducing (001) single oriented growth of STO on rGO. The details will be presented in a separate publication.…”

“…To deoxidize the Si surface uncovered by rGO and achieve a (001) single oriented growth of STO, 15 pulses of SrO were first deposited using a laser fluence of 2 J/cm 2 and a frequency of 0.1 Hz. 33 After flash annealing at 840 °C for 2 min, the sample was cooled down to 760 °C and 40 nm STO was deposited in high vacuum with a laser fluence of 2 J/cm 2 and a frequency of 3 Hz. RHEED patterns recorded during the growth of SrO and STO can be found in Figure S3 of the Supporting Information.…”

The importance of annealing and stages coverage on the epitaxial growth of complex oxides on silicon by pulsed laser deposition

“…This model assumes, aside from STO and interface layers, an additional Si layer with less density than the substrate, in order to simulate possible ion implantation due to the energetic nature of the PLD deposition. 3 For the interface layer, strontium silicates (SrSiO 3 and Sr 2 SiO 4 ) and silicon oxides were tested: the best results were obtained using a strontium silicate, with no denite improvements found when one of them was used over the other. A model without this interface layer was also tested, but the ttings quality decreased noticeably.…”