Phase-stabilization and substrate effects on nucleation and growth of (Ti,V)n+1GeCn thin films

Abstract

and Per Eklund, Phase-stabilization and substrate effects on nucleation and growth of (Ti,V)(n+1)GeC(n) thin films, 2011, Journal of Applied Physics, (110) Phase-pure epitaxial thin films of (Ti,V) 2 GeC have been grown onto Al 2 O 3 (0001) substrates via magnetron sputtering. The c lattice parameter is determined to be 12.59 Å , corresponding to a 50=50 Ti=V solid solution according to Vegard's law, and the overall (Ti,V):Ge:C composition is 2:1:1 as determined by elastic recoil detection analysis. The minimum temperature for the growth of (Ti,V) 2 GeC is 700 C, which is the same as for Ti 2 GeC but higher than that required for V 2 GeC (450 C). Reduced Ge content yields films containing (Ti,V) 3 GeC 2 and (Ti,V) 4 GeC 3 . These results show that the previously unknown phases V 3 GeC 2 and V 4 GeC 3 can be stabilized through alloying with Ti. For films grown on 4H-SiC(0001), (Ti,V) 3 GeC 2 was observed as the dominant phase, showing that the nucleation and growth of (Ti,V) n þ 1 GeC n is affected by the choice of substrate; the proposed underlying physical mechanism is that differences in the local substrate temperature enhance surface diffusion and facilitate the growth of the higher-order phase (Ti,V) 3 GeC 2 compared to (Ti,V) 2 GeC.

Growth and characterization of epitaxial Ti3GeC2 thin films on 4H-SiC(0001)

“…The same trend can be observed for M 2 GeC (M = Ti, V, Cr) where the highest resistivity is reported for Cr 2 GeC films [15,18,19]. In the M-Ge-C system, the influence of M-site solid solutions on material properties has been studied for (Ti,V) n+1 GeC n [20] and (…”

Tailoring of the thermal expansion of Cr2(Alx,Ge1−x)C phases

“…Solid-solution studies have mostly focused on exploring solid solution hardening effects [18,19,20,21,22,23], the evolution of the unit cell structure [24,25] or the possibility to synthesize new MAX phases [26,27,28,29]. Interestingly, with a few possible exceptions [30,31,32], solid solution hardening of the MAX phases does in general not appear to be pronounced.…”

Order and disorder in quaternary atomic laminates from first-principles calculations

“…In particular, solid solutions on the M-site include, e.g., (Ti,M)2AlC where M = V, Nb, Ta, Cr, [8][9][10][11] (V,M)2AlC where M = Nb, Ta, Cr, 9,12 (Cr,Mn)2AC where A = Al, Ga, Ge, 3,[13][14][15][16][17][18][19] (Ti,V)3AC2 where A = Al, Ge, 20,21 and (V,M)4AlC3 where M = Ti, Nb. 20,21 Adding a fourth element has also been demonstrated by realization of TiCr2AlC2, 22,23 V1.5Cr1.5AlC2, 12 TiMo2AlC2, 24,25 and Ti2Mo2AlC3, 24 which all are recent discoveries of chemically ordered quaternary MAX phases, with atomic layers composed of a single element only. This raises the question why certain combinations of M elements form layered chemically ordered MAX phases, while other combinations result in a solid solution.…”