The standard basis vector k\mathbf{k}k in 3D is:
(1,0,0)(1, 0, 0)(1,0,0)
(0,1,0)(0, 1, 0)(0,1,0)
(0,0,1)(0, 0, 1)(0,0,1)
(1,1,1)(1, 1, 1)(1,1,1)