  We present nanoscale NMR measurements performed with nitrogen-vacancy (NV)
centers located down to about 2 nm from the diamond surface. NV centers were
created by shallow ion implantation followed by a slow, nanometer-by-nanometer
removal of diamond material using oxidative etching in air. The close proximity
of NV centers to the surface yielded large 1H NMR signals of up to 3.4 uT-rms,
corresponding to ~330 statistically polarized or ~10 fully polarized proton
spins in a ~(1.8 nm)^3 detection volume.
