1. Old Dominion University, Norfolk, Virginia 23529, USA
Transport Line Components of a Laser Multicharged Ion Implantation and Deposition System
Md. Haider A. Shaim, Md. Mahmudur Rahman, Oguzhan Balki, and Hani E. Elsayed-Ali
Department of Electrical and Computer Engineering and the Applied Research Center,
Old Dominion University, Norfolk, Virginia 23529, USA
Abstract
10-ns laser pulses are used to ablate an aluminum and carbon target in an ultrahigh vacuum.
An electrostatic time-of-flight spectrometer is used to detect the multicharged ions.
Three electrode cylindrical einzel lens is used to focus multicharged ions.
An electrostatic ion energy analyzer is used for multicharged ions pickup with specific energy-to-charge (E/z) ratio.
A set of two parallel deflecting plates combined with high voltage pulsed power supply are used to ion pickup with different charge state.
Schematic
Ion Selection
MCI Analyzer
Ions
Target holder Vb Vs
100 k
50 
5 µF Vc 1
Mesh
Knife edge
Deflecting plates
Einzel lens
Variable delay
Laser
trigger
HV pulsar
HV power supply
Einzel Lens
Figure. A schematic of the laser multicharged ion source showing the target chamber, Vc is the Faraday cup voltage, Vs is the suppressor voltage, and Vb is the barrier voltage.
Figure. schematic of EIA analyzer and Faraday cup for ion selection with E/z.
- V
Focus electrode
SIMION Simulation
Ion Energy Analyzer
SIMION Simulation
156 mm
(b)
(a)
167 mm
(c) -V +V
(a)
(b)
Figure. (a) Time-of-flight analyzer signal for MCIs generating up to Al4+ for 7 kV accelerating voltage and 82 mJ laser energy, (b) Selection of MCI from Al1+ to Al4+ for deflecting voltage -10 kV with pulse width 1 μs, inset shows the voltage pulse for selecting Al3+.
Figure. Schematic of 3-electrode einzel lens.
Figure. Ion trajectory path for C3+ through the EIA. The applied voltage to the EIA (a) ± 500 V, (b) ± 300 V
Figure. (a) Focused Al1+ to Al4+ charges. Effect on ion trajectory for ion source distribution (b) Gaussian energy distribution, (C) Cylindrical spatial distribution
Conclusion
Components of a transport line for LMCI were constructed and tested.
Ion beam diameter down to ~1.5 mm depending on the ion charge state were observed.
The overall energy resolution of the EIA for carbon MCI is 7 – 9%.
Ion pick up from TOF with variable pulse width allows for selecting an ion charge and a narrow energy distribution of the selected charge if the pick-up pulse is shortened below the ion pulse width.
Figure. (a) Carbon ion signal detected by the Faraday cup placed without (black) and with (red, intensity x 5) the EIA. (b) energy spread of C3+ with varying E/z. ΔE/E is 7% for E/z = 1.7 keV and 8% for E/z = 3.8 keV
Figure. Simulated Time-of-Flight spectrum for C1+, C2+, C3+, and C4+. Applied voltage to electrodes of the EIA is ± 500 V. The number of particles in the ion source was 500 for each charge state.
Reference
M. H. A. Shaim and H. E. Elsayed-Ali, Nucl. Instrum. Meth. 356, (2015).
M. H. A. Shaim and H. E. Elsayed-Ali, Rev. Sci. Instrum. 86, (2015)
Figure. Experimental results of effect of einzel lens voltage on the beam diameter of Al1+ to Al4+ at knife edge, inset shows the focusing of Al3+ and Al4+ in the best focusing region obtained.
Figure. Beam diameter of MCIs measured at 30 cm distance from the Einzel lens