| AVS 64th International Symposium & Exhibition | |
| Advanced Ion Microscopy Focus Topic | Wednesday Sessions |
| Session HI-WeA |
| Session: | Emerging Ion Sources and Optics |
| Presenter: | Md Haider Shaim, Old Dominion University |
| Authors: | M. Shaim, Old Dominion University M. Rahman, Old Dominion University O. Balki, Old Dominion University H.E. Elsayed-Ali, Old Dominion University |
| Correspondent: | Click to Email |
Multicharged ions are generated by a Nd:YAG laser (λ = 1064 nm, τ = 7 ns, pulse energy ≤175 mJ ) ablation of aluminum and boron targets in an ultrahigh vacuum. Time-of-flight and electrostatic retarding field ion energy analyzers are used to detect the laser-generated ions. Spark discharge coupling to the laser ion source enhances ion generation along with generating higher charge states than observed with the laser source alone. The spark discharge electrodes are located in front of the target and is triggered by the laser plasma. For an Al target with the laser source alone, the total ion charge delivered to a Faraday cup located 1.4 m away from the source is 1.0 nC with charge state up to Al3+. When the spark amplification stage is used (0.1 μF capacitor charged to 5.0 kV), the total charge increases by a factor of ∼9 with up to Al6+ observed. The spark discharge increases the multicharged ion generation without increasing target ablation, which solely results from the laser pulse. An electrostatic cylindrical ion deflector is used for analysis and selection of charges with a specific energy-to-charge ratio. A three-electrode cylindrical einzel lens is used to focus the ion beam. A minimum ion beam diameter of ~1.5 mm was obtained. A high-voltage pulse applied to a set of two parallel deflecting plates is used for the pickup of ions with different charge states according to their time-of-flight. Fully stripped B ions with 150 eV per charge are obtained with the laser alone. These ions are used for shallow implantation without further acceleration. Al multicharged ion generation from femtosecond laser (λ = 800 nm, τ = 100 fs, pulse energy ≤1 mJ ) ablation is also studied. Production of Al ions up to Al6+ is observed with the laser alone. Compared to nanosecond laser ablation, multicharged ion generation by femtosecond laser ablation require significantly lower laser fluence and generates higher charge states and more energetic ions.