A method of fabricating a double tapered scanning tunneling microscope comprises immersing one end of the tip in {HEAD ~ a bath} of an acidic aqueous etchant solution containing an alkaline earth salt, with the wire positioned substantially perpendicularly to {TAIL ~ the surface} of the solution; and etching the wire at about 25 volts root mean squared alternating current until a double tapered tip is formed thereon 
A method of fabricating a double tapered scanning tunneling microscope comprises immersing one end of the tip in { HEAD ~ a bath } of an acidic aqueous etchant solution containing an alkaline earth salt , with the wire positioned substantially perpendicularly to { TAIL ~ the surface } of the solution ; and etching the wire at about 25 volts root mean squared alternating current until a double tapered tip is formed thereon
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