Tiling the Silicon for Added Functionality: PLD Growth of Highly Crystalline STO and PZT on Graphene Oxide-Buffered Silicon Surface

Abstract

The application of two-dimensional (2D) materials has alleviated a number of challenges of traditional epitaxy and pushed forward the integration of dissimilar materials. Besides acting as a seed layer for van der Waals epitaxy, the 2D materials� being atom(s) thick�have also enabled wetting transparency in which the potential field of the substrate, although partially screened, is still capable of imposing epitaxial overgrowth. One of the crucial steps in this technology is the preservation of the quality of 2D materials during and after their transfer to a substrate of interest. In the present study, we show that by honing the achievements of traditional epitaxy and wet chemistry a hybrid approach can be devised that offers a unique perspective for the integration of functional oxides with a silicon platform. It is based on SrO-assisted deoxidation and controllable coverage of silicon surface with a layer(s) of spin-coated graphene oxide, thus simultaneously allowing both direct and van der Waals epitaxy of SrTiO 3 (STO). We were able to grow a high-quality STO pseudosubstrate suitable for further overgrowth of functional oxides, such as PbZr 1−x Ti x O 3 (PZT). Given that the quality of the films grown on a reduced graphene oxide-buffer layer was almost identical to that obtained on SiC-derived graphene, we believe that this approach may provide new routes for direct and "remote" epitaxy or layer-transfer techniques of dissimilar material systems.

Robust SrTiO3 Passivation of Silicon Photocathode by Reduced Graphene Oxide for Solar Water Splitting

“…First, it promoted the growth of a single crystalline STO layer since there is a negligible amount of dangling bonds present on the surface of rGO and accordingly the depositing STO material can more easily retain its own crystal structure. Second, rGO effectively mitigated the intermixing reaction between the STO and the Si which was observed in the STO/Si sample, and the deposited STO can grow in the preferred orientation in line with the underlying Si substrate. , Therefore, the degree of epitaxy was significantly improved compared to the case without rGO. Moreover, no other orientations except (00l) were detected, indicating the high quality of the STO film.…”

“…Afterward, GO nanosheets obtained by centrifugation at 1000 rpm and redispersion from the as-received suspension (4 mg mL –1 , Advanced Graphene Products, Poland) to remove agglomerated large particles, were deposited on the surface of piranha-treated Si using a spin-coating technique. The spinning speed was kept at 8000 rpm throughout the coating process while the GO suspension was applied in a dropwise fashion with the duration between each droplet (∼5 μL) of 30 s. 40 μL is required for full coverage of GO on the surface of the Si substrate . Following the spin-coating, the GO-Si sample was glued on the resistive heater by silver paste (Ted Pella, Inc.) and transferred to the UHV PLD chamber (Demcon Twente Solid State Technology, The Netherlands).…”

“…Second, rGO effectively mitigated the intermixing reaction between the STO and the Si which was observed in the STO/ Si sample, and the deposited STO can grow in the preferred orientation in line with the underlying Si substrate. 32,41 Therefore, the degree of epitaxy was significantly improved compared to the case without rGO. Moreover, no other orientations except (00l) were detected, indicating the high quality of the STO film.…”

“…In the present study, we used pulsed laser deposition (PLD) to prepare an STO epitaxial layer on a Si photocathode, where in between the film and the substrate a buffer layer of reduced graphene oxide (rGO) was introduced. In our previous work we demonstrated the necessity of rGO as an epitaxy template guiding the growth of STO along the preferential orientation. , To obtain the best quality of STO layer, an rGO-coated Si substrate with full coverage was adopted as the overgrown template . Moreover, it has been reported that the high electrical conductivity of rGO can accelerate the charge transfer between the semiconductor and the electrolyte and significantly enhance the PEC efficiency. , Herein, the crystal and microstructural properties of the grown STO layer were investigated and discussed using X-ray diffractometry (XRD), in situ reflection high-energy electron diffraction (RHEED), and atomic force microscopy (AFM), in comparison to the polycrystalline film where STO was directly deposited on Si without rGO.…”

Heterogeneous Integration of Graphene and HfO2 Memristors

“…[14,15] Crystalline thin films have also been successfully integrated with Si via the use of a 2D material, such as graphene as a buffer layer. [15][16][17][18] Graphene serves as a diffusion barrier, preventing the interfacial reactions at the high temperatures required for crystallization. [18] Owing to the 2D character of the template and the 3D character of the thin film material, quasi van der Waals (vdW) type of growth is realized.…”