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High‐resolution secondary ion mass spectrometry depth profiling of nanolayers
Author(s) -
Baryshev Sergey V.,
Zinovev Alexander V.,
Tripa C. Emil,
Pellin Michael J.,
Peng Qing,
Elam Jeffrey W.,
Veryovkin Igor V.
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6344
Subject(s) - chemistry , secondary ion mass spectrometry , ion beam , ion , analytical chemistry (journal) , mass spectrometry , resolution (logic) , static secondary ion mass spectrometry , ion beam deposition , ion source , sputtering , thin film , materials science , nanotechnology , organic chemistry , chromatography , artificial intelligence , computer science
RATIONALE Although the fundamental physical limits for depth resolution of secondary ion mass spectrometry are well understood in theory, the experimental work to achieve and demonstrate them is still ongoing. We report results of high‐resolution TOF SIMS (time‐of‐flight secondary ion mass spectrometry) depth profiling experiments on a nanolayered structure, a stack of 16 alternating MgO and ZnO ~5.5 nm layers grown on a Si substrate by atomic layer deposition. METHODS The measurements were performed using a newly developed approach implementing a low‐energy direct current normally incident Ar + ion beam for ion milling (250 eV and 500 eV energy), in combination with a pulsed 5 keV Ar + ion beam at 60° incidence for TOF SIMS analysis. By this optimized arrangement, a noticeably improved version of the dual‐beam (DB) approach to TOF SIMS depth profiling is introduced, which can be dubbed gentle DB. RESULTS The mixing‐roughness‐information model was applied to detailed analysis of experimental results. It revealed that the gentle DB approach allows ultimate depth resolution by confining the ion beam mixing length to about two monolayers. This corresponds to the escape depth of secondary ions, the fundamental depth resolution limitation in SIMS. Other parameters deduced from the measured depth profiles indicated that a single layer thickness is equal to 6 nm so that the 'flat' layer thickness d is 3 nm and the interfacial roughness σ is 1.5 nm, thus yielding d + 2σ = 6 nm. CONCLUSIONS We have demonstrated that gentle DB TOF SIMS depth profiling with noble gas ion beams is capable of revealing the structural features of a stack of nanolayers, resolving its original surface and estimating the roughness of interlayer interfaces, information which is difficult to obtain by traditional approaches. Copyright © 2012 John Wiley & Sons, Ltd.