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MICROCOPY RESOLUTION TEST CHART
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67-68
To be published in proceedings of 15th Annual Conf. on Mass Spectrometry
and Allied Topics held in Denver, Colorado, May 14-19, 1967.
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"CoNF 670534-.
INTERACTION OF MONOE!ERGETIC Ar* (.5-8 keV) WITH
A Cu (100) TARGET: SPUTTERING AND ION SCATTERING*
James R. Woodyard"
Solid State Division, Oak Ridge National Laboratory
lini ..! Oak Ridge, Tennessee ,
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AUG 22 1967
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A summary is given of studies of particles emitted from a Cu (100) target when
bombarded by 0.5 to 8 keV Art ions. The target was rotated about a (100) axis and the .
particles emitted at a 90° angle with respect to the incoming beam were analyzed with a
mass spectrometer.2
Sputtered Neutral Particles
Sputtered neutral Cu and Cu2 which were subsequently ionized by electron impact
were studied while bombarding with 2 keV Art. Appearance potential measurements showed
that the sputtered Cu and Cu2 were predominantly in the ground electronic state. The
ratio of the Cu2 and Cu peak heights was 0.2 No Cug was detected; it must be less than
0.02 of the Cu peak height. The Cu and Cu, were sputtered with initial kinetic energies
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Quantitative studies of the neutrals were not conducted because of the large background
signal originating from Cu ions formed at the electrode surfaces,
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Sputtered Ions
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Singly charged copper ions, Cum, with 1sns11 were detected. The peak heights
of the ions alternated, i.e., for n odd,'the Cur peak height was always greater than the
The ratios of the peak heights for 3.5 keV Art measurements were
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Cut
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Cu*:Cu :Curcurcu:Curcu = 1.0:0.40:0.80:0.040:0.14:0.025:0.030
The ratios were constant down to 2.5 keV bombarding ion energy. Below 2.5 keV the ratios
for n > 3 decreased until at .5 keV only Cut, Cuz and Cuž were detected; they were in the
same ratios as at 3.5 kev. The ratios were studied at 2.0 keV as a function of the angle
between the target surface normal and the bombarding ion beam direction, e. The experi-
ments showed that the peak heights varied as tan and that the peaks were broadest for
(110) ejection. The sputtered Cut, Cum and Cuf had energies as large as 130, 60 and 20
eV, respectively. The bombarding ion energy and angular dependence of the peak heights
are not inconsistent with a collision cascade model of sputtering. The alternating peak
heights could be due to the dependence of the dissociation energy and/or ionization po- .
tential on the number of atoms in a particle.
AL
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The Cut peaks were separated into two initial kinetic energy ranges: low
(0-10 eV) and high (10-130 eV). The dependence of the peak heights in these energy
be expected for random sputtering. The high energy component displayed a maximum for
ejection in the (110) direction and may be associated with focussed collisions.
The initial kinetic energy dependence of the ratio of Cu ions to neutrals,
N*/N, at a bombarding energy of 2 keV may be described by the expression
N*/N - 10-4 e+.11 Ei
BLANK PAGE
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Marimentimetri.
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0.02 of the Cu peak height. The Cu and Cu2 were sputtered with initial kinetic energies
as large as 30 and 15 ev, respect (vely. The Cu peaks were broadest for (110) ejection.
Quantitative studies of the neutrals were not conducted because of the large background
signal originating from Cu ions formed at the electrode surfaces
Sputtered Ions
Singly charged copper ions, Cu*, with is ns11 were detected. The peak heights
of the ions alternated, i.e., for n odd,'the Cur peak height was always greater than the
Cut .. The ratios of the k heights for 3.5 keV Art measurements were
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Cu*:cumicum:cucu : cum cum = 1.0:0.40:0.80:0.040:0.14:0.025:0.030
The ratios were constant down to 2.5 keV bombarding ion energy. Below 2.5 keV tie ratios
for n > 3 decreased until at .5 keV only Cut, Cut and Cug were detected; they were in the
same ratios as at 3.5 keV. The ratios were studied at 2.0 keV as a function of the angle
between the target surface normal and the bombarding ion beam direction, o. The experi..
ments showed that the peak heights varied as tan 0 and that the peaks were broadest for
(110) ejection. The sputtered Cut, Cum and Cu had energies as large as 130, 60 and 20
eV, respectively. The bombarding ion énergy and angular dependence of the peak heights
are not inconsistent with a collision cascade model of sputtering. The alternating peak
heights could be due to the dependence of the dissociation energy and/or ionization po- .
tential on the number of atoms in a particle.
let him that
one thing
The Cut peaks were separated into two initial kinetic energy ranges: low
(n-10 ey) and high" (10-130 eV). The dependence of the peak heights in these energy
ranges was studied using 2 keV Art. The low energy component varied as tan O as would
be expected for random sputtering. The high energy component displayed a maximum for
ejection in the (110) direction and may be associattu with focussed collisions.
iminto or more
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ressen. Minulla on
The initial kinetic energy dependence of the ratio of Cu ions to neutrals,
N/N, at a bombarding energy of 2 keV may be described by the expression
Clatite obranima i han fet
N*IN - 10-4 e*.11 Ei
55 E = 20 ev
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DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED
where E, is the initial kinetic energy.
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Research sponsored by the U. S. Atomic Energy Commission under contract with the
Union Carbide Corporation.
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"U. S. Atomic Energy Commission Postdoctoral Fellow under appointment from the Oak
Ridge Associated Universities.

Ions Formed at Electrode Surfaces
In addition to the ions formed at the target surface, an appreciable ion.
current was attributable to sputtered neutral particles which were subsequently ionized
. at electrode surfaces in the vicinity of the target. While bombarding with 2 keV Ar*,
ions of Na, K, Cr, Cu, Cuz, Cugna and a number of unidentified species formed by this
process were observed. For ions of the same species, the surface ion peak heights we
within an order of magnitude of the ions originating at the target surface. Most of the
surface ions were formed with kinetic energies less than 0.5 eV; a small fraction of the
Cu surface ions had energies as large as 40 eV. An analysis of the results suggests that
the neutral particles were emitted from the target in merastable states and surface. ion-
ized by resonance transitions.
Fast Scattered Ions
Fast scattered "'Ar* were detected for bombarding ion energies of 1-8. kev.
Peaks resulting from atomic scattering through 90° by a single collision and two
sequential single collisions were identified. Initial studies of the angular depend-
ence of the single collision peak showed it to be essentially insensitive to the rela
tive orientation of the target and ion beam. This observation points to the surface
nature of scattering by a single collision in this energy range.
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The energy spectra also showed two other peaks which have been tentatively
identified as fast Cut. The Cu* are believed to result from the scattering of the
fast recoils generated by hard collisions of the bombarding ions with Cu surface atoms.
References
1. A detailed report of these investigations will be submitted to the J. Appl. Phys.
i for publication.
2.
A. J. Smith, D. J. Marshall, L. A. Cambey and J. Michael, Vacuum 14, 263 (1964). .
A. J. Smith, L. A. Cambey and D. J. Marshall, J. Appl. Phys. 34, 2489 (1963.
A. L. Southern, Twelfth Annual Conferer.ce on Mass Spectrometry, Montreal, 1964. ..
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LEGAL NOTICE
This report was propered as an account of Government sponsored work. Neither the United
Sutes, por the Commission, nor any person acting on behalf of the Commissico:
1. Makes day warruniy or representadon, expressed or implied, with respect w the accu-
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of any information, apparatus, metbod, or process disclosed in this report may not infringo
prinately owned rights; or
B. Assumos any liabilities with rospect to the use of, or for damage resulting from the
UK of any laformation, apparatus, method, or process dsclosed in this roport.
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such employee or contractor of the Commission, or employee of such contractor prepares,
disseminater, or provides access to, any information purmat to be employment or coctrict
wu. the Compassion, or die employment with such contractor.
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DATE FILMED
9 / 29 /67
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