Sputtering of silicon by multiply charged ions

Zwart, S.T. de; Fried, T.; Boerma, D.O.; Hoekstra, Ronnie; Drentje, A.G.; Boers, A.L.

doi:10.1016/0039-6028(86)90126-3

Cited by 67 publications

(19 citation statements)

References 16 publications

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“…Insulators and thin ͑ϳ10 nm͒ semimetallic conductors react to this intense, ultrafast, and localized electronic excitation by emission of large numbers of neutral particles [5,9] and secondary ions [3,9]. For bulk semiconductors, no increase of ablation rates as a function of projectile charge was observed for Si interacting with Ar q1 , q # 91 [10]. Reports for GaAs are controversial.…”

Section: J C Banks and B L Doylementioning

confidence: 97%

Ablation of GaAs by Intense, Ultrafast Electronic Excitation from Highly Charged Ions

et al. 1998

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We have measured total ablation rates and secondary ion yields from undoped GaAs(100) interacting with slow ͑y 6.6 3 10 5 m͞s͒, very highly charged ions. Ablation rates increase strongly as a function of projectile charge. Some 1400 target atoms are removed when a single Th 701 ion deposits a potential energy of 152.6 keV within a few femtoseconds into a nanometer-sized target volume. We discuss models for ablation of semiconductors by intense, ultrafast electronic excitation.[S0031-9007(98)07165-8] PACS numbers: 79.20.Rf, 34.50.Fa The interaction of slow ͑y , 2 3 10 6 m͞s͒ highly charged ions (SHCI) with surfaces is an active field of research [1,2] with applications in materials analysis [3] and modification [4][5][6][7]. In slow ion-solid collisions, where the projectile velocity is smaller than the Bohr velocity ͑y Bohr 2.19 3 10 6 m͞s͒, most target electrons move faster than the projectile and readily react to the perturbation during a collision. SHCI, such as Xe 441 and U 901 , are extracted from electron beam ion traps (EBIT) [1] while fast ͑y ¿ y Bohr ͒ highly charged ions are formed by charge state equilibration in gaseous or solid targets using heavy ion accelerators. Charge states of SHCI are far in excess of mean equilibrium charge states formed by slow ions when traveling through solids. The latter are ϳ11 at the velocities selected in this study [8]. Consequently, SHCI neutralize and deexcite rapidly when they interact with solid surfaces. Charge state equilibration times are in the order of a few femtoseconds [8]. The potential energy of SHCI, i.e., the sum of the binding energies of electrons removed to form the ion, is deposited during deexcitation. Individual SHCI deposit tens to hundreds of keV of potential energy into a small (nanometer scale) target volume at the surface. Insulators and thin ͑ϳ10 nm͒ semimetallic conductors react to this intense, ultrafast, and localized electronic excitation by emission of large numbers of neutral particles [5,9] and secondary ions [3,9]. For bulk semiconductors, no increase of ablation rates as a function of projectile charge was observed for Si interacting with Ar q1 , q # 91 [10]. Reports for GaAs are controversial. Using Ar q1 , q # 91, Varga et al. [5] found no increase of the sputtering yield with charge. The null result was interpreted in the context of a model of defect-mediated potential sputtering. For the same projectiles, Mochji et al. [7] observed a charge dependent sputter yield increase, and the results were interpreted using a Coulomb explosion model [11]. The ionization probability for secondary ions was not determined in either of these two studies. In this Letter we report on measurements of charge state dependencies of total sputtering and secondary ion yields from GaAs interacting with slow, very highly charged ions up to Th 701 . Using projectiles in much higher charge states than were used in earlier studies [5,7,10], we find results that do not follow predictions of established defect mediated or Coulomb explosion models of electro...

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Section: J C Banks and B L Doylementioning

confidence: 97%

Ablation of GaAs by Intense, Ultrafast Electronic Excitation from Highly Charged Ions

et al. 1998

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“…In conductors, electronic excitation of target atoms can be dissipated more efficiently than in insulators. Consequently, stopping power thresholds for electronic darnage production are found to be higher for metals [9,16,17] than for insulators [18]. In the interaction of slow HCI with solids, electronic excitation of target material is driven by the dissipation of tens to hundreds of keV of ion potential energy into a surface near target volume.…”

Section: Secondary Ion Emissionmentioning

confidence: 99%

“…Coulomb repulsion between ionized target atoms results in an explosive lattice relaxation before charge neutrality can be reestablished. The question of the occurrence of Coulomb explosions in the interaction of HCI (q<16+) with insulators and semi conductors had been controversial for many years [8][9][10]. Evidence for electronic sputtering and damage production by Coulomb explosions was found in studies of secondary ion emission from thin Si02 films and defect formation on mica using slow very highly charged ions with q>35+ [2,11].…”

Section: Introductionmentioning

confidence: 99%

Emission of secondary particles from metals and insulators at impact of slow highly charged ions

Schenkel

Barnes

Briere

et al. 1997

Nuclear Instruments and Methods in Physics Research Section B:

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The emission of secondary electrons and ions from clean Au, GHrAu and Si02 surfaces at impact of slow (v= 0.3 v-) ions has been measured as a finction of incident ion charge for l+3+. Yields of negative secondary ions from Si02 and CHY-AUwere recorded in parallel with electron emission data and exhibit a q", n=l, dependency on incident ion charge. A direct comparison of collisional and electronic contributions to secondary ion production from Si02 films using abeam of charge state equilibrated Xe-(at 2.75 keV/u) shows positive and negative secondary ion yield increases with incident ion charge of >400. Results are dkcussed in relation to key signatures of electronic sputtering by Coulomb explosions.

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“…Similar q-dependence was also observed in the AFM images of mica substrates with Xe q+ impacts [4], where the sizes of blister-like structures increased with q, starting at q = 30. In earlier experiments with Ar q+ ions (q 5 9) [9,10], it was shown that the total sputtering yields of Si were independent of q. However the results from the STM observation implies that in the high q HCI-collision, a larger number of Si atoms are removed with higher q HCI impacts.…”

Section: Resultsmentioning

confidence: 68%

“…It has been reported from experiments with low-q HCIs that the total sputtering yield for Si is independent of q [2,9,10]. To confirm whether this q-independence follows the collision of high q-HCIs, e.g., q = 50, with a Si(1 1 1) surface, we observed the HCI-radiation effects using a scanning tunneling microscope (STM), morphological changes in surface structure, and by time of flight secondary ion mass spectrometry (TOF/SIMS) to measure the emission yield of the sputtered fragment ions.…”

Section: Introductionmentioning

confidence: 98%

Nano-crater formation on a Si(111)-(7×7) surface by slow highly charged ion-impact

et al. 2007

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Sputtering of silicon by multiply charged ions

Cited by 67 publications

References 16 publications

Ablation of GaAs by Intense, Ultrafast Electronic Excitation from Highly Charged Ions

Ablation of GaAs by Intense, Ultrafast Electronic Excitation from Highly Charged Ions

Emission of secondary particles from metals and insulators at impact of slow highly charged ions

Nano-crater formation on a Si(111)-(7×7) surface by slow highly charged ion-impact

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