Spatially Resolved Compositional Analysis of a BCN Thin Film Grown on a Ni Substrate by Chemical Vapor Deposition
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Spatially Resolved Compositional Analysis of a BCN Thin Film Grown on a Ni Substrate by Chemical Vapor Deposition Satoru Suzuki1 and Hiroki Hibino1 1 NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan ABSTRACT A thin film consisting of boron, carbon, and nitrogen (BCN) was grown on a polycrystalline Ni substrate by thermal chemical vapor deposition. The local elemental composition of the BCN film was analyzed by scanning Auger electron spectroscopy. The film is elementally highly inhomogeneous and consists of domains with a typical size of 1-10 Pm and irregular shapes. The domain structure is strongly related to the structure of the grains of the polycrystalline Ni film beneath the domain. A thick domain is often formed on a small Ni grain. On a large and flat Ni grain, the film thickness is relatively small, and both the boron and nitrogen contents are often below the detection limit, indicating that it is a graphene domain. Boron and nitrogen contents are highly correlated, which is consistent with formation of hexagonal boron nitride. However, unbalanced boron and nitrogen contents are observed from thick domains. INTRODUCTION Hexagonal boron nitride (h-BN) has a layer structure similar to that of graphite and is often called white graphene (graphite). Combining graphene, which has no band gap, and h-BN, which has a wide band gap, may lead to a wide variety of electrical and optical device applications. The superior electric properties of a graphene device have been demonstrated when the graphene channel is located on a h-BN film, compared to a conventional device on a SiO2 substrate [1]. Moreover, hybridizing B, C and N would make it possible to tune the band gap in a wide range by controlling the composition and to dope carriers in the system [2]. The thermal chemical vapor deposition (CVD) technique has been used for the growth of large-area graphene [3] and atomically thin h-BN films [4-6]. Li et al. also reported growth of atomically thin BCN films on polycrystalline Cu substrates by the thermal CVD method [7]. Recently, we grew BCN films by CVD on Ni substrates using triisopropylborate and benzylamine as CVD sources [8]. According to conventional x-ray photoelectron spectroscopy (XPS) analyses, macroscopic B and N compositions were close to each other regardless of the fact that B and N were supplied using separate sources. That is, the composition was approximately described as BxC1-2xNx. The B and N atoms mostly formed h-BN domains separated from graphene domains. The separation of graphene and h-BN domains is considered to be more complete than that observed in a previous report [7] using a Cu substrate. Such domain separation is quite reasonable, because C-C and B-N bond formation is energetically favorable compared to B-C and C-N [9]. However, an unbalanced B, N composition (BxC1-x-yNy, xzy) would be important for doping of a BCN system. In this paper, we analyze the local composition of a CVD-grown BCN thin film grown on a polycrystalline Ni substrate. The results sugge
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