Branched patterns reminiscent of diffusion limited aggregation form around poly(ethylene oxide) dots on Au surfaces in humidity by crystallization of polymer chains in water-assisted diffusion, involving fractal-like structure and dense branching-like morphology (DBM). Higher humidity leads to a slower growth of crystal lamellae. Crystal growth promotes outward diffusion. Fractal-like lamellae are viewed flat-on. Due to the reduction of chain availability in the diffusion field, the fractal-like structure turns into DBM.