NbN CVD

Niobium nitride (also known as columbium nitride) has three phases Nb2N, Nb4N3, and NbN. The mononitride, NbN, is the most common phase and the only one reviewed here. NbN is an excellent superconductor. It is produced by CVD mostly on an experimental basis. Its characteristics and properties are summarized in Table 10.5. 

K [75a]. NbN can be considered to be a face-centered cubic interstitial compound which adopts the B1 rocksalt structure (Fig. 2-6) with an a-axis spacing of 3.33 to 3.36 A [76] (Table 2-4). The first CVD synthesis of NbN was reported by Powell et al. in 1955 [77]. Only a limited number of papers have been reported subsequently. 

CVD reactors employed for NbN film growth typically consist of quartz tubes or employ fused silica inserts which are stable at the high temperature required for super-... 

Due to lack of research in this area, only limited information on film properties-CVD growth conditions relationships is available. The highest reported for a CVD-de-rived NbN film is 15.7 K (Table 2-4) [76]. The dependence of phase development on substrate temperature and CI2 flow rate will next be discussed. The reaction of NbCls... 

A similar pattern is observed for CVD-derived Nb-N films using NH3 as the N source gas. In this instance, a deposition temperature of 880 °C gives rise to mixed phase Nb2N + NbN development, while deposition temperatures > 900°C give phase-pure NbN films [76]. 

K. Brennfleck, E. Fitzer, G. Schoch, M. Dietrich, CVD of SiC-lnterlayers and Their Interaction with Carbon Fibers and with Multi-Layered NbN Coatings, Proc. 9th Int. Conf. on CVD, Electrochemical Society, Pennington, NJ, 1984, pp. 649-62. 

Niobium carbonitride has comparable properties to NbN, including a relatively high critical temperature [165]. The material has been prepared by the CVD of a mixture of bis(toluene) niobium (21) and hydrazine, NH2-NH2 [254]. 

Ceramic superconducting films are divided into three classes, Bl-type compounds, ternary compounds, and high-temperature oxide superconductors. The Bl-type (NaCl-type structure) compound superconductors consist of nitrides and carbides with 5A, 6A, and 7A transition metals, such as TiN, ZrN, HfN, VN, NbN TaN, MoN, WN, TiC, ZrC, HfC, VC, NbC, TaC, MoC, WC, NbNi tC t, hex-MoN, and hex-MoC. Regarding the thin-film material, it is notable that NbN and NbN] (C ( (x = 0.08 and 0.15) have superconducting critical temperature, T, values of 17.3 and 17.8 K, respectively. The deposition method used is almost always sputtering or CVD. The properties of films deposited by the former method are superior. A highly reliable Josephson device was realized with an NbN film. 

In the chemical vapor deposition (CVD) method, NbN films are fabricated by decomposing NbCls gas in NH3 and Hj gases at a high temperature, about 1000°C. When MgO single crystal is used as a substrate, single-crystal NbN film can be grown (5). 

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