AVS 46th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM-WeP

Paper EM-WeP5
Nanoscale Silicon Features Produced by Slow Highly Charged Ions

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: M.W. Newman, Lawrence Livermore National Laboratory
Authors: M.W. Newman, Lawrence Livermore National Laboratory
A.V. Hamza, Lawrence Livermore National Laboratory
H. Lee, Lawrence Livermore National Laboratory
A.V. Barnes, Lawrence Livermore National Laboratory
T. Schenkel, Lawrence Livermore National Laboratory
J.W. McDonald, Lawrence Livermore National Laboratory
G.A. Machicoane, Lawrence Livermore National Laboratory
T. Niedermayr, Lawrence Livermore National Laboratory
D.H. Schnieder, Lawrence Livermore National Laboratory
Correspondent: Click to Email
Phase transformations induced by intense, ultrafast electronic excitation from slow highly charged ions from the Lawrence Livermore National Laboratory (LLNL) Electron Beam Ion Trap(EBIT) have been studied. A 308 keV beam of Xe@super 44+@ (~51 keV of potential energy) was used to irradiate a 3 mm spot of clean float zone (FZ) silicon (100) (2X1) for a total dose of ~5x10@super 11@ ions. Due to the indirect nature of its band gap, bulk silicon is typically a poor photon emitter upon external excitation. However, as the crystal size approaches nanometer scales, the band gap widens due to quantum confinement and becomes direct allowing for more efficient photon emission. Ex-situ room temperature photoluminescence (PL) spectra were measured using a high resolution grating spectrometer with an excitation wavelength of 379 nm from a Titanium-Sapphire laser. PL spectra from areas exposed to SHCI bombardment show a broad emission centered at 504 nm. This is consistent with emission observed from 1-2 nm silicon nanocrystals. No PL is observed from similarly prepared FZ Silicon samples exposed to beams of 308 keV Xe@super 27+@ (~10 keV of potential energy) and 5 keV Xe@super 1+@ with comparable doses. A series of sharp lines at 548 nm, 534 nm, and 530 nm are also present in the PL spectrum from areas exposed to Xe@super 44+@ which is characteristic of an excitonic series in nanometer size direct band gap materials. The deposition of potential energy from Xe@super 44+@ produces a phase transition in silicon surfaces at nanometer size level that is not produced from normal ion bombardment. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No, W-74505-ENG-48.