A
laser stimulated
atom probe for
atom probe imaging of
dielectric and low
conductivity semiconductor materials is disclosed. The
laser stimulated
atom probe comprises a conventional atom probe providing a field emission tip and
ion detector arrangement, a
laser system providing a laser short laser pulse and synchronous electronic timing
signal to the atom probe, and an optical
system for delivery of the laser beam onto the field emitting tip apex. The conventional atom probe is employed in a manner similar to that used for investigation of
high conductivity materials. However, the
electric field is held static while the laser is pulsed to provide pulsing of the
ion emission rate. The laser pulsing is accomplished in a manner similar to prior implementations of
pulsed laser atom probe
spectroscopy. The laser pulses provide a trigger
signal to enable recording the
time of flight in the atom probe. The laser operates at a
wavelength in the UV in order to enhance the optical absorption in
semiconductor or
dielectric field emission tips. The increased optical absorption allows efficient thermal pumping of the field
evaporation rate. The tip apex field is also used to
redshift the
optical absorption spectra of the
dielectric or semiconducting material under investigation, further enhancing the optical absorption. Due to the
enhanced absorption, it is also possible to realize a
photo ionization mechanism, wherein the laser stimulates electronic transitions from the more extended surface atoms, thereby ionizing the surface atom. The
laser source is collimated by a collimation lens, reflected using dielectric mirrors, directed onto the sample tip using a focusing lens arrangement, collected from the tip using a collection lens, and directed into a beam stop. The laser
beam diameter at focus is approximately 3-30 microns, thus, individual emission tips may be scanned from a field of tips illuminated by the laser pulse.