Influence of flow ratio of N 2 to (N 2 +Ar) mixture on the structure and properties of zirconium nitride films prepared
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Jiukai Liu Jilin Agriculture Engineering Polytechnic College, Siping 136000, China
Bo Liu, Lihong Wang, and Bin Yaoa) Department of Physics, Jilin University, Changchun 130023, China (Received 25 December 2008; accepted 20 March 2009)
Zr–N films were grown on glass and Si (100) substrate by radio-frequency magnetron sputtering using a mixture of high pure nitrogen and argon as sputtering gases. The structure and properties of Zr–N compounds in the films change with N2/(N2+Ar) flow ratio (RN2). At low RN2, a ZrN alloy with the rocksalt structure (denoted as g-ZrNx) is formed. The N concentration x and lattice constant increases with increasing RN2, and x reaches 1 when the RN2 goes up to 20%. As the RN2 exceeds 20%, the film is composed of g-ZrN and Zr3N4 phase with Th3P4 structure (denoted as c-Zr3N4). The relative content decreases for the g-ZrN but increases for the c-Zr3N4 with increasing RN2, and a single phase of c-Zr3N4 was deposited on glass at RN2 of 100%. The c-Zr3N4 behaves with p-type conductivity with a band gap of 2.8 eV. The lattice constant of the c-Zr3N4 was measured to be 0.674 nm. The mechanism of the phase transition from g-ZrN to cZr3N4 with increasing RN2 was suggested. I. INTRODUCTION
Transition metal nitrides have stimulated scientific interest because of their particular properties such as high hardness, good wear, and oxidation resistance that permit using them as a hard coating.1 For the Zr–N compound, a ZrN with a rocksalt structure and a stoichiometric ratio of near 1:1 (denoted as g-ZrN) has been studied widely, because it is the only stable phase in the Zr–N system and has applications in protective coating of cutting tools and decorative coating of materials.2 Many techniques, such as vacuum arc deposition,3 direct current (DC) reactive magnetron sputtering,4 pulse laser deposition,5 and ion beam–assisted deposition,6 were used to grow g-ZrN films. Besides g-ZrN, other metastable Zr–N compounds are also reported to be prepared, such as Zr3N4,6 Zr2N,7 ZrN2,8 and Zr4N3.9 Many experimental results showed that Zr–N compounds, produced in the thermodynamic equilibrium state under atmospheric pressure, are usually poor nitrogen, and the highest N to Zr ratio is 1:1. However, preparation of N-rich Zr–N has proven difficult, and the N-rich Zr–N usually is metastable. Although it is generally difficult to fabria)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0383
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J. Mater. Res., Vol. 24, No. 10, Oct 2009 Downloaded: 25 Mar 2015
cate N-rich Zr–N, study of N-rich Zr–N is interesting in theory and application.10 An N-rich Zr–N compound, Zr3N4, was first discovered by Von et al.11 using ammonolysis of zirconium tetraiodide at 750 C. It is of orthorhombic structure. In 2000, a bulk high-dense Zr3N4 with Th3P4 structure (denoted as c-Zr3N4) was synthesized by Zerr et al.12 using a high-pressure laser-heated diamond anvil cell at a pressure of 15.6–18 GPa and temperature of 2500– 3000 K. It is a superhard mater
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