NbN CVD Precursors and Reaction Schemes

Two general precursor approaches to superconducting NbN films have been described. In each instance, NbCls (g), albeit in powder form or produced via reaction of Nb(s) with CbCg), acts as the Nb precursor. However, either Ni or NH3 have been reportedly employed as N source reagents [76, 78]. The use of ammonia gas as the N source allows superconducting NbN formation at lower temperatures than when nitrogen gas is employed 900°C versus 1350°C, respectively. Nb-N phase development as a function of growth temperature has been documented in each instance (see below). 

In an attempt to find low temperature CVD routes to nitride films, Gordon et al. have recently reported the CVD growth of Nb-N films using a novel homoleptic niobium amido Nb(NR2)n/NH,3 precursor system (R = CH3, /i = 5 R = C2H5, n = 4) [80]. Nb-N films grown at 200°C were amorphous by electron diffraction, and smooth and featureless by SEM. An unusual stoichiometry of Nb3N4 was determined for these amorphous films. 

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