Growth Temperature and Oxygen Ambient Dependency of SrTiO 3 /Si(100) InterfaceStructures
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Growth Temperature and Oxygen Ambient Dependency of SrTiO3/Si(100) Interface Structures Parhat Ahmet1, Takashi Koida2, Mamoru Yoshimoto3, Hideomi Koinuma2,3,1, , Toyohiro Chikyow1 1 National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan 2 Frontier Collaborative Research Center, Tokyo Institute of Technology, 4259 Nagatsuda, Yokohama, Kanagawa, 226-8503, Japan. 3 Ceramic Materials and Structure Laboratory, Tokyo Institute of Technology, 4259 Nagatsuda, Yokohama, Kanagawa, 226-8503, Japan. ABSTRACT A systematical growth temperature and oxygen ambient dependency of SrTiO3/Si interface structures were investigated using a growth temperature gradient pulse laser deposition (PLD) system and cross sectional high resolution transmission electron microscopy (HRTEM). A SiO2 interfacial layer and an amorphized SrTiO3 layer were observed at the interface for the thin films grown on Si (100) at growth temperatures above 600°C. Our results show that at growth temperatures higher than 600°C, the formation of the amorphized SrTiO3 layer is strongly growth temperature and also oxygen partial pressure dependent. INTRODUCTION Due to the increasing number of transistors on Large Scale Integrated Circuit (LSI), the SiO2 based Field Effect Transistor (FET) is closing to its physical scaling limitation where the direct tunneling leakage currents became unacceptably high. To replace SiO2 to other innovative materials having higher dielectric property, a lot of candidates have been proposed and some of them are examined for practical device applications [1-8]. Among the reported high dielectric materials, perovskite type SrTiO3 (STO) is one of the most attractive candidate material for an alternative gate oxide with desirable structural property, an epitaxial STO thin films on Si can be expected. For device applications, high quality epitaxial STO thin films are expected to offer better uniformity, lower leakage, higher reliability and also higher dielectric constant than amorphous and polycrystalline ones. An epitaxial STO thin film also serves as an ideal buffer layer for heteroepitaxy of various functional oxides including high-Tc superconductor thin films [9] on Si substrate. An oxygen atmosphere is necessary for preventing oxygen deficiency while depositing a S3.4.1
oxide thin film. But, in an oxygen atmosphere, an amorphous silicon oxide layer can be easily formed on the silicon substrate surface. The easily formed amorphous silicon oxide layer makes it difficult to grow epitaxial STO on silicon. Although, there are some reports of successful epitaxial growth of STO on Si [10-11], but the stability of interface structures are still an argumentative problem from the viewpoints of thermal reaction and related diffusion [12, 11]. In this paper, we report the results of our systematical growth temperature and oxygen ambient dependency studies on the SrTiO3/Si interface structures. A combinatorial PLD with growth temperature gradient system was employed to grow STO on Si (100) with systematical variatio
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