Carbon　solid　solubility　in　metals　is　an　important　factor　affecting　uniform　graphene　growth　by　chemical　vapor　deposition　(CVD)　at　high　temperatures.　At　low　temperatures,　however,　it　was　found　that　the　carbon　diffusion　rate　(CDR)　on　the　metal　catalyst　surface　has　a　greater　impact　on　the　number　and　uniformity　of　graphene　layers　compared　with　that　of　the　carbon　solid　solubility.　The　CDR　decreases　rapidly　with　decreasing　temperatures,　resulting　in　inhomogeneous　and　multilayer　graphene.　In　the　present　work,　a　Ni-Cu　alloy　sacrificial　layer　was　used　as　the　catalyst　based　on　the　following　properties.　Cu　was　selected　to　increase　the　CDR,　while　Ni　was　used　to　provide　high　catalytic　activity.　By　plasma-enhanced　CVD,　graphene　was　grown　on　the　surface　of　Ni-Cu　alloy　under　low　pressure　using　methane　as　the　carbon　source.　The　optimal　composition　of　the　Ni-Cu　alloy,　1:2,　was　selected　through　experiments.　In　addition,　the　plasma　power　was　optimized　to　improve　the　graphene　quality.　On　the　basis　of　the　parameter　optimization,　together　with　our　previously-reported,　in-situ,　sacrificial　metal-layer　etching　technique,　relatively　homogeneous　wafer-size　patterned　graphene　was　obtained　directly　on　a　2-inch　SiO2/Si　substrate　at　a　low　temperature　(similar　to　600　degrees　C).