<i>In situ</i> monitoring of molecular beam epitaxy using specularly scattered ion beam current oscillations

Labanda, J. G. C.; Barnett, Scott A.

doi:10.1063/1.119020

Cited by 13 publications

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References 14 publications

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“…The change in growth mode is readily monitored by growth oscillations. In the present experiments, we have used SICM oscillations [11], which are similar to reflection high-energy electron diffraction (RHEED) oscillations [16].…”

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confidence: 99%

“…The substrates were semiinsulating, double-polished vicinal GaAs(001) wafers misoriented by 2.5 ± 6 0.5 ± towards ͑110͒. The chamber contained a specular ion current measurement (SICM) system that has been described elsewhere [8][9][10][11]. A 3-4 keV Ar ion beam, incident at f 3 ± relative to the nominal substrate surface plane, was used both for monitoring and modifying growth.…”

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Glancing-Angle Ion Enhanced Surface Diffusion on GaAs(001) during Molecular Beam Epitaxy

2001

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We describe the effects of glancing incidence 3-4 keV Ar ion bombardment on homoepitaxial growth on vicinal GaAs(001). The average adatom lifetime on surface terraces, measured during growth using specular ion scattering, decreased monotonically with increasing ion current density. The results indicated that surface diffusivity was increased by the ions. The ion beam also suppressed growth oscillations and decreased the film surface roughness. This indicates a change from two-dimensional island nucleation to step-flow growth due to increased adatom surface diffusivity. A simple model, involving direct momentum transfer from ions to adatoms, is shown to be consistent with the measured enhanced diffusion.

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Glancing-Angle Ion Enhanced Surface Diffusion on GaAs(001) during Molecular Beam Epitaxy

2001

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“…An interesting alternative to RHEED is scattering of fast atoms or ions instead of fast electrons. [6][7][8][9][10] This technique is similar to RHEED, however, it bears the advantage that the projectile trajectories can be described classically in terms of pure kinematical concepts. 11 For growth of thin semiconductor and metal films, grazing scattering of keV ions has been proven to be a powerful tool to study details on growth mode, island densities, critical island size, etc.…”

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“…11 For growth of thin semiconductor and metal films, grazing scattering of keV ions has been proven to be a powerful tool to study details on growth mode, island densities, critical island size, etc. [6][7][8][9][10][11][12] As an example, we mention studies on growth of ultrathin Co films on Cu͑001͒, where a deviation from a monotonic Arrhenius type of dependence for the island density as a function of inverse growth temperature is observed. 13 This unusual behavior of film growth is attributed to intermixing of film and substrate atoms at elevated temperatures as predicted from density-functional theory ͑DFT͒ calculations and kinetic theory.…”

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Monitoring growth of ultrathin films via ion-induced electron emission

Bernhard

Winter

2005

Phys. Rev. B

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H + , He + , and N + ions with energy of 25 keV are scattered under a grazing angle of incidence from a clean and flat Cu͑001͒ surface during deposition of ultrathin Co films. Making use of the ion-induced emission of electrons allows us to monitor growth of thin films via simple measurements of target current or from energy spectra of emitted electrons. The method provides excellent signals and is also applicable in the regime of poor layer growth.The physics of ultrathin films plays an important role in fundamental research as well as technological applications. As a prominent recent example, we mention the "giant magneto resistance" ͑GMR͒ effect 1,2 present in ultrathin films showing antiferromagnetic couplings. This effect is the basis for the function of reading heads used in modern magnetic hard disk drives or in sensor technology. 3 In particular for fundamental research, the preparation of defined ultrathin films in the monolayer ͑ML͒ regime is crucial. An established method is epitaxial growth of thin films via "molecular-beam epitaxy" ͑MBE͒ ͑Ref. 4͒, where atoms from an evaporator source are deposited on monocrystalline substrates.In the characterization of films, monitoring of growth plays an essential role, since thickness and growth mode determine decisively the structure and the functioning of the system. A widely used technique to inspect growth of thin films in the monolayer regime is "reflection high-energy electron diffraction" ͑RHEED͒ ͑Ref. 5͒, where keV electrons are scattered from the surface of the film under a grazing angle of incidence. In a simple picture, the intensity of reflected electrons depends on the "smoothness" of the film surface. Then, e.g., for "layer-by-layer growth" the morphology changes periodically with coverage, and intensity oscillations for reflected electrons are observed. Aside from the powerful features of RHEED, diffraction phenomena make the general interpretation of data a nontrivial problem.As alternative probes for monitoring film growth, scattering experiments with other microscopic particles are feasible which show a dependence of the backscattered yield on the morphology of the film surface. An interesting alternative to RHEED is scattering of fast atoms or ions instead of fast electrons. 6-10 This technique is similar to RHEED, however, it bears the advantage that the projectile trajectories can be described classically in terms of pure kinematical concepts. 11 For growth of thin semiconductor and metal films, grazing scattering of keV ions has been proven to be a powerful tool to study details on growth mode, island densities, critical island size, etc. 6-12 As an example, we mention studies on growth of ultrathin Co films on Cu͑001͒, where a deviation from a monotonic Arrhenius type of dependence for the island density as a function of inverse growth temperature is observed. 13 This unusual behavior of film growth is attributed to intermixing of film and substrate atoms at elevated temperatures as predicted from density-functional theory ͑DFT͒ calculation...

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“…The values obtained were = 29, 25, and 21 nm for 630, 570, and 520~ respectively (see Ref. 26 for details). This decrease in step spacing with decreasing T s reflects the expected decrease in two-dimensional island size.…”

Section: Specular Beam Current Oscillationsmentioning

confidence: 99%

Glancing-angle ion bombardment for modification and monitoring of semiconductor surfaces

Labanda

Barnett

1997

Journal of Elec Materi

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Using glancing-angle ion bombardment for surface modification rather than conventional near-normalincidence ions has the advantages of reducing damage and implantation projected ranges, reducing channeling, reducing sputtering, and preferentially removing surface asperities leading to flat surfaces. The effects of bombardment conditions on the surface morphology and perfection of GaAs (001), InP (001), and Si (001) surfaces are reported. Air-exposed surfaces were cleaned and smoothened to near atomic flatness without damage under optimal conditions. Sputtering yield, measured using film thicknesses and changes in reflection high-energy electron diffraction oscillations, decreased with decreasing incidence angle. The low sputtering yield and minimal damage make a glancing-angle geometry ideal for real-time characterization by ion scattering spectroscopy. Surface composition measurements on single monolayers of InAs on GaAs showed that the glancing-angle Ar beam did not measurably change the In coverage over relatively long times. A new ion beam monitoring technique was also developed that utilizes the advantages of glancing-angle ions. Specular scattering of 3 keV He ions was observed for incidence angles of 2-6 ~ from GaAs (001). Oscillation in the specularly scattered ion current during GaAs growth were observed with periods corresponding to monolayer growth times. The oscillations allow a simple quantitative interpretation based on scattering by adatoms and step edges.

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In situ monitoring of molecular beam epitaxy using specularly scattered ion beam current oscillations

Cited by 13 publications

References 14 publications

Glancing-Angle Ion Enhanced Surface Diffusion on GaAs(001) during Molecular Beam Epitaxy

Glancing-Angle Ion Enhanced Surface Diffusion on GaAs(001) during Molecular Beam Epitaxy

Monitoring growth of ultrathin films via ion-induced electron emission

Glancing-angle ion bombardment for modification and monitoring of semiconductor surfaces

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