Using a quartz crystal microbalance for low energy ion beam etching studies

Doemling, M. F.; Lin, Bo-Yang; Rueger, N. R.; Oehrlein, G. S.; Haring, R.A.; Lee, Y. H.

doi:10.1116/1.582139

Cited by 12 publications

(12 citation statements)

References 10 publications

(8 reference statements)

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“…If only a section of the surface is influenced by the ion bombardment, the spatial sensitivity of the induced frequency change becomes important. It is well known that the latter is described in good approximation by a Gaussian° [35],° [36] ⌬f ϭ ⌬f 0 exp ͩ Ϫa r 2 r 0 2ͪ ,…”

Section: Quartz Crystal Microbalancementioning

confidence: 99%

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Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

Sun

Szakal

Winograd

et al. 2005

J. Am. Soc. Mass Spectrom.

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The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C 60 ϩ cluster projectiles compared with Ga ϩ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C 60 ϩ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga ϩ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. T he elucidation of the mechanism of interaction of energetic polyatomic or cluster ions with surfaces is of current interest since these projectiles are now being extensively employed as desorption probes in secondary ion mass spectrometry (SIMS) experiments [1,2]. Because of their propensity to produce higher molecular ion signals than corresponding atomic ions and the emergence of commercially available C 60 ϩ [3,4] and Au 3 ϩ [5, 6] ion guns, applications have expanded dramatically. For example, these sources can be focused onto the sample with a probe size about 1 micron, allowing greatly improved molecule-specific imaging experiments. The high secondary ion yield associated with the cluster/solid interaction also allows for molecular depth profiling studies without the accompanying damage accumulation normally associated with atomic bombardment [7][8][9][10][11][12][13][14][15][16][17].The mechanisms associated with the observed secondary ion yield enhancement are not yet clear, although details are emerging quickly. A basic question that must be resolved is to determine whether the yield enhancement occurs as a consequence of increased ionization efficiency, or is due to more effective sputtering in the neutral desorption channel. There is mixed information about this point. For In and Ag surfaces, for example, it has been shown that the enhanced secondary ion yield under SF m ϩ bombardment (m ϭ 1-5) largely arises from the enhanced ionization efficiency attributable to implanted F atoms [18]. For organic systems, however, very high removal rates of neutral species have been reported [2], obviating the need to invoke enhancement of the secondary ionization probability. Most recently, yields and velocity distributions were measured for In and In 2 sputtered from In surfaces bombarded with Au ϩ , Au 2 ϩ , and Au 3 ϩ [19]. Although these experiments do not ad...

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Section: Quartz Crystal Microbalancementioning

confidence: 99%

“…Assuming, for simplicity, a radially symmetric beam profile of radius R centered on the surface, the resulting value D R is determined°by° [36] …”

Section: Quartz Crystal Microbalancementioning

confidence: 99%

Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

Sun

Szakal

Winograd

et al. 2005

J. Am. Soc. Mass Spectrom.

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“…The measured displacements of the beams relative to the quartz crystal center, δ , were typically a few tenths of a millimeter and did not exceed 0.5 mm. Since the impact areas of the beams were significantly smaller than the microbalance sensor active area, the microbalance response depended sensitively on both A and δ [ Doemling et al ., ; Kelly et al ., ; Martin and Hager , ; Yao , ].…”

Section: Experimental Approachmentioning

confidence: 98%

“…The literature [ Doemling et al ., ; Kelly et al ., ; Martin and Hager , ; Yao , ] shows that the QCM response is strongly dependent on the beam spot position on the quartz crystal. The mass sensitivity, S , is a radially symmetric function of the distance from the sensor center and can be described to very good approximation by a Gaussian,

S = S_{0} e^{prefix- \frac{true}{r^{2}}},

where S 0 is the peak sensitivity and r 0 is a shape constant.…”

Section: Experimental Approachmentioning

confidence: 98%

“…For our sensor geometry, the coefficient r 0 was experimentally determined to be 1.03 mm [ Yao , ]. The total sputtering yield, Y , is given by the following [ Doemling et al ., ; Kelly et al ., ; Martin and Hager , ; Yao , ; Oliva‐Florio et al ., ; Neidhart et al ., ]:

Y = D_{R} A \frac{normalΔ f}{N_{incident}} \frac{N_{A}}{M} + \frac{((), 1 - R) m_{p}}{M},

where Δ f is the frequency change, A is the measured beam area, M is the atomic mass in (amu) of the target material (i.e., anorthite), and N A is Avogadro's number. In the second term, which is a correction for the target mass increase due to projectile implantation, R is the projectile reflection coefficient (as determined using Stopping and Range of Ions in Matter (SRIM) [ Ziegler et al ., ]), and m p is the projectile mass in amu.…”

Section: Experimental Approachmentioning

confidence: 98%

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Anorthite sputtering by H⁺ and Ar^q+ (q = 1–9) at solar wind velocities

et al. 2014

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We report sputtering measurements of anorthite-like material, taken to be representative of soils found in the lunar highlands, impacted by singly and multicharged ions representative of the solar wind. The ions investigated include protons, as well as singly and multicharged Ar ions (as proxies for the nonreactive heavy solar wind constituents), in the charge state range +1 to +9, at fixed solar wind-relevant impact velocities of 165 and 310 km/s (0.25 keV/amu and 0.5 keV/amu). A quartz microbalance approach (QCM) for determination of total sputtering yields was used. The goal of the measurements was to determine the sputtering contribution of the heavy, multicharged minority solar wind constituents in comparison to that due to the dominant H + fraction. The QCM results show a yield increase of a factor of about 80 for Ar + versus H + sputtering and an enhancement by a factor of 1.67 between Ar 9+ and Ar + , which is a clear indication of a potential sputtering effect.

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