Improvement of laser molecular beam epitaxy grown SrTiO3 thin film properties by temperature gradient modulation growth

Abstract

Oxygen diffusion at the SrTiO 3 / Si interface was analyzed. A method called temperature gradient modulation growth was introduced to control oxygen diffusion at the interface of SrTiO 3 / Si. Nanoscale multilayers were grown at different temperatures at the initial growing stage of films. Continuous growth of SrTiO 3 films was followed to deposit on the grown sacrificial layers. The interface and crystallinity of SrTiO 3 / Si were investigated by in situ reflection high energy electron diffraction and x-ray diffraction measurements. It has been shown that the modulated multilayers may help suppress the interfacial diffusion, and therefore improve SrTiO 3 thin film properties. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2790074͔Many efforts have been devoted to the study of crystalline oxide thin films on silicon ͑Si͒ since the unique properties of those oxides may be combined with Si-based integrated circuits. 1,2 SrTiO 3 ͑STO͒ is a cubic perovskite structure and has a lattice constant closely matched to a large number of other perovskite oxides. Thus, the STO/Si system can be used as a growth substrate for the preparation of many functional oxides. However, the union of oxides and Si presents potentially the significant challenge to the basic study of growth, due to serious complications concerning reactivity between the oxide and Si as well as bonding changes from covalent bond in Si to ionic in the oxide. 3 The main problem is the formation of an amorphous oxide over Si surface due to oxygen diffusion, which may prevent STO film from crystal growth. Therefore, those STO films grown directly on Si were usually polycrystalline with randomly oriented grains. [4][5][6] Extensive research has been carried out on the finding of a solution to the problem. Up to know, the study mainly focuses on the introduction of additional materials, i.e., various single or double buffer layers between Typical work includes the growth of SrSi 2 submonolayer as a buffer layer by molecular beam epitaxy ͑MBE͒, which was reported by McKee et al. 10 There are a few reports on the growth of STO directly on Si. 11,12 In this letter, we have grown ͑100͒-oriented STO thin films on silicon without any buffer layer by controlling oxygen diffusion at the STO/Si interface by laser MBE. The growth mode and structure of STO/Si were verified using a variety of measurements.STO thin films were deposited directly on p-type Si substrates by laser MBE. The laser used in this study was KrF ͑ = 248 nm͒ excimer laser. The laser energy density was 6 J/cm 2 in a repetition rate of 3 Hz. A single crystal target of STO was employed in the experiments. The ͑100͒-oriented Si substrates were first chemically cleaned, then dipped into a buffered solution with 4% HF for 60 s to remove the amorphous SiO 2 layer from the surface of the Si, leaving a hydrogen-terminated surface. The substrates were mounted on a commonly used resistive heater block made of heating wire. During the film growth, the in situ reflection high energy electron diffraction ͑RHE...

Low‐Temperature Epitaxy of Perovskite WO3 Thin Films under Atmospheric Conditions

“…Large-scale epitaxial growth of perovskite oxides typically requires vacuum and high temperatures (>500 °C), making it difficult to implement large-area, high-throughput deposition. [6] Success in deposition of uniform SrTiO 3 films on Si [7,8] and the recent advancement in depositing large-scale films allow for wider integration of oxide materials in the future. [9] Such an oxide layer on Si can serve as a buffer/epitaxial template for subsequent oxide deposition, making complementary metaloxide-semiconductor (CMOS)-compatible processing of oxides on large areas relevant.Recent advances in oxide deposition techniques have enabled low-temperature epitaxy using atomic layer deposition (ALD), chemical vapor deposition (CVD), pulsed laser deposition (PLD), and molecular beam epitaxy (MBE).…”