Sputter-depth profiling for thin-film analysis

Hofmann, S.

doi:10.1098/rsta.2003.1304

Cited by 42 publications

(7 citation statements)

References 84 publications

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“…In particular, Figure reports the profiles obtained in the case of delta layers located at different depth, but all within a distance from the surface comparable or lower than that of the interaction depth of the primary ion (i.e., in the region where D ≠ 0). In each simulated profile, both the broadening and the maximum shift increase for deeper and deeper original position of the layer, in very good agreement with the results reported in the literature. − The case of a thicker layer, initially located at a depth where D ≈ 0 and with a thickness wider than D , is shown in Figure . Again, the results of our simulation are in excellent agreement with previous results. − …”

Section: Resultssupporting

confidence: 88%

“…In each simulated profile, both the broadening and the maximum shift increase for deeper and deeper original position of the layer, in very good agreement with the results reported in the literature. − The case of a thicker layer, initially located at a depth where D ≈ 0 and with a thickness wider than D , is shown in Figure . Again, the results of our simulation are in excellent agreement with previous results. − …”

Section: Resultssupporting

confidence: 88%

“…The so-called mixing-roughness-information depth (MRI) model developed by Hofmann et al is another shining example. In this model, three fundamental parameters control the depth resolution: atomic mixing length, roughness and information depth. − However, all the above methods do not take into account any reaction occurring during sputtering. Recently, Krantzman and Wucher developed the statistical sputtering model (SSM) in order to correlate the information obtained from molecular dynamic simulations to depth profiles .…”

Section: Introductionmentioning

confidence: 99%

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A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

et al. 2016

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The continuum equation is used for modeling erosion rate, ion beam induced mixing, and reactions during the sputtering process involved in secondary ion mass spectrometry experiments. We developed a new approach that is able to incorporate the beam induced reactivity, so leading to a reasonable simulation of depth profiles of polymers and organic solids. The model allows one to include the effects of the reactive gas dosing on sputtering yield and damage accumulation during profiling. Comparison with experimental data confirms the quality of the model and strengthens the proposed approach.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

et al. 2016

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“…The zero depth interface width as a function of the primary ion energy is shown in Figure b. Lower impact energy clearly leads to better depth resolution, a finding that is well-known for inorganic systems . This effect is understandable since the zero depth interface width depends upon the altered layer thickness, which increases with increasing energy.…”

Section: Resultsmentioning

confidence: 64%

Depth Resolution During C₆₀⁺ Profiling of Multilayer Molecular Films

2008

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Time-of-flight secondary ion mass spectrometry is utilized to characterize the response of LangmuirBlodgett (LB) multilayers under the bombardment by buckminsterfullerene primary ions. The LB multilayers are formed by barium arachidate and barium dimyristoyl phosphatidate on a Si substrate. The unique sputtering properties of the C 60 ion beam result in successful molecular depth profiling of both the single component and multilayers of alternating chemical composition. At cryogenic (liquid nitrogen) temperatures, the high mass signals of both molecules remain stable under sputtering, while at room temperature, they gradually decrease with primary ion dose. The low temperature also leads to a higher average sputter yield of molecules. Depth resolution varies from 20 to 50 nm and can be reduced further by lowering the primary ion energy or by using glancing angles of incidence of the primary ion beam.The development of polyatomic projectiles for cluster-based secondary ion mass spectrometry (SIMS) is opening new opportunities for materials characterization. Of special interest is the emergence of molecular depth profiling whereby the projectile removes molecules in nearly a layer-by-layer fashion without the accumulation of chemical damage. [1][2][3][4][5][6][7] This problem has plagued atomic projectiles for many years 8 and has limited sensitivity. When the molecular samples are bombarded with cluster ion sources, the energy is deposited close to the surface and the chemical damage is then removed as fast as it accumulates, leaving subsurface layers relatively intact. [9][10][11][12][13][14][15] The quality of the depth profile has recently been characterized by a cleanup efficiency parameter derived from a simple erosion model for molecular solids. 16 Among all the cluster projectiles, buckminsterfullerene (C 60 + ) generally exhibits the highest cleanup efficiency. 17,18 New fundamental studies of the sputtering process are now required to optimize the experimental parameters for molecular depth profiling. The literature concerning the interactions between energetic cluster ions and molecular solids has grown rapidly, including experimental approaches 16,[19][20][21][22][23][24][25][26] and molecular dynamic (MD) simulations. [11][12][13][27][28][29] While MD simulations have provided insightful understanding, much of the experimental work lacks a quantitative understanding for comparison to the simulation results. Moreover, most of the molecular depth profiling experiments are performed on organic systems either with uniform chemical content or with unknown composition. 3,4,30,31 The analysis of buried organic layers under cluster bombardment has been shown to be feasible, but the degree of beam-induced * To whom correspondence should be addressed. nxw@psu.edu.Supporting Information Available: Representative AFM images of sample roughness ( Figure S1). This is material is available free of charge via the Internet at http://pubs.acs.org. mixing between organic layers is not fully understood. This info...

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“…The improvement is even more dramatic for 40 keV projectiles, where the ejection depth is reduced from ∼14 nm to ∼3 nm when the impact angle is changed from 0° to 60°. This phenomenon is known from studies on inorganic systems and model calculations. , However, the degree of the improvement observed in LB systems could not be anticipated from previous studies of cluster induced sputtering.…”

Section: Resultsmentioning

confidence: 84%

Molecular Dynamics Simulations of Sputtering of Langmuir−Blodgett Multilayers by Kiloelectronvolt C₆₀ Projectiles

et al. 2009

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Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C 60 projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed.The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C 60 bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles.

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Sputter-depth profiling for thin-film analysis

Cited by 42 publications

References 84 publications

A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

Depth Resolution During C₆₀⁺ Profiling of Multilayer Molecular Films

Molecular Dynamics Simulations of Sputtering of Langmuir−Blodgett Multilayers by Kiloelectronvolt C₆₀ Projectiles

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Sputter-depth profiling for thin-film analysis

Cited by 42 publications

References 84 publications

A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

A Transport and Reaction Model for Simulating Cluster Secondary Ion Mass Spectrometry Depth Profiles of Organic Solids

Depth Resolution During C60+ Profiling of Multilayer Molecular Films

Molecular Dynamics Simulations of Sputtering of Langmuir−Blodgett Multilayers by Kiloelectronvolt C60 Projectiles

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Depth Resolution During C₆₀⁺ Profiling of Multilayer Molecular Films

Molecular Dynamics Simulations of Sputtering of Langmuir−Blodgett Multilayers by Kiloelectronvolt C₆₀ Projectiles