Deposition parameter effects on the composition and the crystalline state of reactively sputtered molybdenum nitride

Nitride or Oxynitride? Elucidating the Composition–Activity Relationships in Molybdenum Nitride Electrocatalysts for the Oxygen Reduction Reaction

“…[40][41][42][43][44] For these applications, precise control of crystal structure and mechanical and electrical properties is desired, and thus the synthesis mechanism has been wellexplored and described. 45,46 A variety of structures, including crystalline rocksalt (face-centered cubic lattice, fcc) γ-Mo2N, tetragonal β-Mo2N, and hexagonal (hex) δ-MoN as well as amorphous and mixed phase films, have been obtained by modification of substrate temperature, nitrogen partial pressure, and target power during sputtering. [47][48][49][50] Further tuning of lattice parameters, N vacancies, and grain size has also been achieved through variation of O partial pressure and total pressure in the sputter chamber due to the strong relationship between composition and formation energy.…”

“…In addition to catalysis, reactively sputtered molybdenum nitride thin films have been extensively studied for various applications, including as hard coatings, superconductors, and diffusion barriers for electronic devices. − For these applications, precise control of crystal structure and mechanical and electrical properties is desired, and thus the synthesis mechanism has been well-explored and described. , A variety of structures, including crystalline rocksalt (face-centered cubic lattice, fcc) γ-Mo 2 N, tetragonal β-Mo 2 N, and hexagonal (hex) δ-MoN as well as amorphous and mixed phase films, have been obtained by modification of substrate temperature, nitrogen partial pressure, and target power during sputtering. − Further tuning of lattice parameters, N vacancies, and grain size has also been achieved through variation of O partial pressure and total pressure in the sputter chamber due to the strong relationship between composition and formation energy . However, within a compositional range, similar formation energies and the presence of vacancies allows for the stabilization of several different phases simultaneously within a sample.…”

Cation and anion vacancies in cubic molybdenum nitride

“…The Mo-N system has been reported to crystallize in various phases, with the most common being (i) BCC Mo with a possible small amount of dissolved nitrogen, (ii) facecentered cubic γ-Mo 2 N x , (iii) body-centered tetragonal β-Mo 2 N x , and (iv) hexagonal δ-MoN [23][24][25][26][27]. Interestingly, the β and γ phases have nominally the same composition range, with some experiments reporting the γ and β phase forming below and above a critical temperature of 775 °C [28], in apparent contradiction to the reported Mo-N phase diagram which suggests γ to be the high-temperature phase and β the low-temperature phase [29].…”

“…MoN x layers have been deposited using a range of methods and processing parameters, leading to different compositions and phases. More specifically, reactive DC sputtering [23][24][25]28,[31][32][33][34][35][36][37][38][39] yields MoN x with x = 1.08 in the γ phase (with a small amount of possible δ phase) using 60 sccm of N 2 gas flow and 55 sccm of Ar gas flow as well as a -50 V substrate bias [31], x = 0-0.54 in the γ phase using 0-26% of N 2 process gas [33] and also from 0-0.35 in the γ phase with varying N 2 / (Ar + N 2 ) gas ratio [37]. RF sputtering [40][41][42] results in x = 0.49-0.67 in the γ phase [41], x = 0.55-0.9 in the γ phase and x = 0.9-1.02 in the δ phase [40], and x = 0.9-1.8 in the B1-MoN phase, which can be described as a cubic variant of the γ phase [42].…”

Magnetic Properties in Mn-Doped δ-MoN: A Systematic Density Functional Theory Study

“…Furthermore, their multiple transport properties (including the metallic and magnetic properties [ 24 , 25 ] and, especially, the high T C superconductivity [ 26 , 27 ]), also support the potential applications in electronic devices. Molybdenum nitrides can crystallize in different phases, including a stoichiometric structure, hexagonal δ -MoN, and two nonstoichiometric structures, cubic γ -Mo 2 N and tetragonal β -Mo 2 N [ 27 , 28 , 29 , 30 ]. In particular, hexagonal δ -MoN is considered the hardest superconducting metal nitride [ 1 ], whose bulk modulus is measured to be 345 GPa [ 20 ] and T C is up to 12–15 K [ 31 , 32 ].…”