Table 1
Parameters used in each step of the annular milling process to fabricate GaAs needles with a reduced diameter along a large range
Step	Inner diameter (nm)	Outer diameter (nm)	Current (pA)	Voltage (kV)
1	1,000	1,500	100	30
2	800	1,400	81	20
3	700	1,200	23	20
4	600	1,000	23	20
5	500	850	23	20
6	400	700	4	20
7	300	600	4	20
8	150	400	4	20
9	-	-	70	5

The last step is to clean the amorphous layer around the needle.

Hernández-Saz et al. Nanoscale Research Letters 2012 7:681   doi:10.1186/1556-276X-7-681