Nanoscale growth twins in sputtered metal films

Abstract

Vol. 60 No. 9 • JOM 75 www.tms.org/jom.html Overview Twinning in Nano-metals? This article reviews recent studies on the mechanical properties of sputtered copper and 330 stainless-steel fi lms with {111} nanoscale growth twins preferentially oriented perpendicular to growth direction. The mechanisms of formation of growth twins during sputtering, unusually high strengths, and excellent thermal stability of nanotwinned structures are highlighted.

Preferential void formation at crystallographically ordered grain boundaries in nanotwinned copper thin films

“…1A and B). Being low energy, a high density of CTBs and triple junctions (TJ) composed of low angle boundaries (LAGB, angular misorientation <15°) and CTBs can limit thermal coarsening in nanocrystalline materials [15,16], but the sink efficiency of such microstructures is poor. Conversely, a mixture of random HAGB and CTBs is prone to destabilization if the majority of the TJs have only one low energy component (out of three), with incoherent twin boundary (ITB) segments readily nucleating and causing the hitherto low mobility interfaces to migrate at a faster rate [13].…”

In-situ TEM study of dislocation-twin boundaries interaction in nanotwinned Cu films

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] For example, while retaining the same electrical conductivity as conventional coarse-grained Cu, nanotwinned Cu has the strength about 10 times higher. 3 Both experiments and molecular dynamics (MD) simulations reveal that coherent twin boundaries (CTBs) can act as strong barriers for dislocation slip transmission due to the discontinuity of slip systems across TBs.…”

“…3 Both experiments and molecular dynamics (MD) simulations reveal that coherent twin boundaries (CTBs) can act as strong barriers for dislocation slip transmission due to the discontinuity of slip systems across TBs. [12][13][14][15][16][17][18] By applying high enough stresses, the transmission of a dislocation across a CTB takes place, and the corresponding reaction mechanisms vary with the character of dislocations and the local stress states. [19][20][21][22][23][24][25] Apart from CTBs, S3{112} incoherent twin boundaries (ITBs) are generally observed to be bounded with nanotwins [26][27][28][29] and they exert a crucial role in the mechanical deformation.…”

Vacancies, twins, and the thermal stability of ultrafine-grained copper

“…Observations of thermal stability in nano-scale growth twins have elsewhere been attributed to the low free energy of the coherent twin, which is a fraction ($0.03) of that of a general high angle grain boundary (HAGB). 1,11 While this reasoning might be applied in the present study, the structures of deformation twins can vary from those of growth twins due to interactions with defects that alter the interface and elevate free energy. In this regard, twin boundary energy likely increases with strain, as increased deformation levels promote the generation of a greater number of defects.…”