US EPA

4845915 

Journal Article 

A reduction-nitridation process of molybdenum films in expanding microwave plasma: Crystal structure of molybdenum nitrides 

Jauberteau, I; Mayet, R; Cornette, J; Bessaudou, A; Carles, P; Jauberteau, JL; Merle-Mejean, T 

2015 

1 

Surface and Coatings Technology
ISSN: 0257-8972 

270 

77-85 

10.1016/j.surfcoat.2015.03.018 

WOS:000354149400010 

This work reports the structure of molybdenum nitride phases crystallizing in molybdenum films coated on Si (100) substrates, and exposed to (Ar-N-2-H-2) gas mixtures with various gas contents in an expanding microwave plasma reactor. Compared with the numerous data found in literature, the formation of beta Mo2N and gamma Mo2N phases strongly oriented in the [204] and [220] crystalline directions, respectively is unexpected. The beta Mo2N phase is synthesized in molybdenum films exposed to pure N-2 plasma for 1 h whereas the molybdenum films exposed to (Ar-33%N-2-1%H-2) plasma for only 30 min consists almost entirely of gamma Mo2N phase. The Mo2N crystallites about 30 nm wide display a columnar morphology in the growth direction after processing in (Ar-33%N-2-1%H-2) plasma. In contrast with most processes where energetic ions improve the nitrogen transfer into the surface layers of the metal film, the expanding plasma process promotes the chemical reactions on the surface of the material. The remaining oxides are reduced by hydrogen species such as NHx radicals produced in (Ar-N-2-H-2) plasma. The reactions are exothermic and could involve the formation of intermediates such as hydrogen molybdenum bronze HxMoO3 that would promote the crystallization of the high temperature gamma Mo2N phase to the detriment of the low temperature beta Mo2N phase during the reduction-nitridation process. (C) 2015 Elsevier B.V. All rights reserved. 

Expanding plasma; Molybdenum film; Molybdenum nitride phases; Molybdenum oxides; X-ray diffraction