  We present an enhancement of spin properties of the shallow (<5nm) NV centers
by using ALD to deposit titanium oxide layer on the diamond surface. With the
oxide layer of an appropriate thickness, increases about 2 up to 3.5 times of
both relaxation time and evolution time were achieved and the shallow NV center
charge states stabilized as well. Moreover, the coherence time kept almost
unchanged. This surface coating technique could produce a protective coating
layer of controllable thickness without any damages to the solid quantum system
surface, making it possible to prolong T1 time and T2* time, which would be a
possible approach to the further packaging technique for the applicating solid
quantum devices.
