Extremely stable field emission and photo-sensitive field emission from single crystalline CdS nanowires

Field emission and photo-sensitive field emission characteristics of single crystalline CdS nanowires have been investigated. The turn-on field for the emission current density of ~ 0.1μA/cm² is found to be ~ 1.4 V/μm, which is much lower than reported values for various CdS nanostructures. Extremely stable field emission current is observed from CdS nanowires for the duration of 24 hrs with current fluctuations within ± 9 % of the average current. The photo-sensitive field emission current shows a reproducible photo-switching behavior with rise in current level nearly four times that of its initial preset value (~ 1 μA) which is found to be very remarkable. Quite reproducible photo-switching properties are seen for different preset values of emission current. Possible mechanism of photo-sensitive field emission is discussed. Similar photo-sensitive field emission experiment was also carried out for other CdS nanoforms such as nanocombs and nanobelts. The high photo-sensitivity, better enhancement in the emission current and fast response in the visible region along with highly stable emission current indicates that CdS nanowires can be used as photo-field emitter switch in various optoelectronic devices and also in pulsed electron beam technology.