@article{zhu_stevie_griffis_2008, title={Model study of electron beam charge compensation for positive secondary ion mass spectrometry using a positive primary ion beam}, volume={254}, DOI={10.1016/j.apsusc.2007.10.008}, abstractNote={A new modeling approach has been developed to assist in the SIMS analysis of insulating samples. This approach provides information on the charging phenomena occurring when electron and positive primary ion beams impact a low conductivity material held at a high positive potential. The concept of effective leakage resistance aids in the understanding of the dynamic electrical properties of an insulating sample under dynamic analysis conditions. Modeling of steady state electron beam charge compensation involves investigation of electron injection and charge drift. Using a Monte Carlo program to simulate electron injection and dc conduction calculations to predict charge drift, detailed information regarding charging phenomena can be determined.}, number={9}, journal={Applied Surface Science}, author={Zhu, Z. M. and Stevie, F. A. and Griffis, D. P.}, year={2008}, pages={2708–2711} }
 @article{harton_zhu_stevie_aoyama_ade_2007, title={Carbon-13 labeling for quantitative analysis of molecular movement in heterogeneous organic materials using secondary ion mass spectrometry}, volume={79}, ISSN={["1520-6882"]}, DOI={10.1021/ac070437q}, abstractNote={Secondary ion mass spectrometry (SIMS) is used to probe the movement of macromolecules in heterogeneous organic systems. Using 13C tracer labeling and two model systems, polystyrene/poly(2-vinylpyridine) (PS/P2VP) and polystyrene/poly(4-bromostyrene) (PS/P4BrS), the diffusion of 13C-labeled PS has been investigated near the respective heterogeneous interfaces using a CAMECA-IMS-6F magnetic sector mass spectrometer. 13C labeling has been shown to greatly minimize matrix effects (i.e., changes in secondary ion yields due to changing chemical environment) in heterogeneous systems. P2VP is a nitrogen-rich polymer (C7H7N monomer composition), making it an excellent model polymer for exploration of this technique for potential future use in biological applications, and probing the PS/P4BrS interface demonstrates the versatility of this technique for analysis of various heteroatom-containing materials. Results confirm that the 13C-labeling method does indeed allow for quantitative analysis of molecular movement in heterogeneous organic systems containing matrix-enhancing heteroatoms such as nitrogen. Therefore, extension of this method to more complicated biological systems involving multiple heteroatoms (oxygen, nitrogen, etc.), layers, and heterogeneous interfaces, as well as two- and three-dimensional profiling and imaging using SIMS, can be envisaged.}, number={14}, journal={ANALYTICAL CHEMISTRY}, author={Harton, Shane E. and Zhu, Zhengmao and Stevie, Frederick A. and Aoyama, Yoko and Ade, Harald}, year={2007}, month={Jul}, pages={5358–5363} }
 @article{harton_zhu_stevie_griffis_ade_2007, title={Mass fractionation of carbon and hydrogen secondary ions upon Cs+ and O-2(+) bombardment of organic materials}, volume={25}, ISSN={["1520-8559"]}, DOI={10.1116/1.2718957}, abstractNote={A phenomenon known as mass fractionation has been probed in organic materials using secondary ion mass spectrometry (SIMS). Mass fractionation occurs because two isotopes of a particular species (i.e., identical number of protons, but different number of neutrons) do not have identical secondary ion yields in a constant chemical environment. Two primary ion probes, Cs+ and O2+, have been utilized with detection of negative and positive secondary ions, respectively, using a magnetic sector mass spectrometer. These two analysis conditions have been found to yield considerably different mass fractionation effects as a result of different sputtering and ionization mechanisms. Also, as determined previously with SIMS analysis of inorganic materials, the lower molecular weight species carbon and hydrogen are particularly susceptible to mass fractionation effects. Because organic materials are primarily composed of carbon and hydrogen, and because isotopic labeling is often utilized to accurately analyze such materials, knowledge of these effects in organic materials is essential for quantitative SIMS analysis.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Harton, Shane E. and Zhu, Zhengmao and Stevie, Frederick A. and Griffis, Dieter P. and Ade, Harald}, year={2007}, pages={480–484} }
 @article{harton_stevie_zhu_ade_2006, title={Carbon-13 labeled polymers: An alternative tracer for depth profiling of polymer films and multilayers using secondary ion mass spectrometry}, volume={78}, ISSN={["1520-6882"]}, DOI={10.1021/ac060133o}, abstractNote={13C labeling is introduced as a tracer for depth profiling of polymer films and multilayers using secondary ion mass spectrometry (SIMS). Deuterium substitution has traditionally been used in depth profiling of polymers but can affect the phase behavior of the polymer constituents with reported changes in both bulk-phase behavior and surface and interfacial interactions. SIMS can provide contrast by examining various functional groups, chemical moieties, or isotopic labels. 13C-Labeled PS (13C-PS) and unlabeled PS (12C-PS) and PMMA were synthesized using atom-transfer radical polymerization and assembled in several model thin-film systems. Depth profiles were recorded using a Cameca IMS-6f magnetic sector mass spectrometer using both 6.0-keV impact energy Cs+ and 5.5-keV impact energy O2+ primary ion bombardment with detection of negative and positive secondary ions, respectively. Although complete separation of 12C1H from 13C is achieved using both primary ion species, 6.0-keV Cs+ clearly shows improved detection sensitivity and signal-to-noise ratio for detection of 12C, 12C1H, and 13C secondary ions. The use of Cs+ primary ion bombardment results in somewhat anomalous, nonmonotonic changes in the 12C, 12C1H, and 13C secondary ion yields through the PS/PMMA interface; however, it is shown that this behavior is not due to sample charging. Through normalization of the 13C secondary ion yield to the total C (12C + 13C) ion yield, the observed effects through the PS/PMMA interface can be greatly minimized, thereby significantly improving analysis of polymer films and multilayers using SIMS. Mass spectra of 13C-PS and 12C-PS were also analyzed using a PHI TRIFT I time-of-flight mass spectrometer, with 15-keV Ga+ primary ion bombardment and detection of positive secondary ions. The (12)C7(1)H7 ion fragment and its 13C-enriched analogues have significant secondary ion yields with negligible mass interferences, providing an early indication of the potential for future use of this technique for cluster probe depth profiling of high molecular weight 13C-labeled fragments.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Harton, S. E. and Stevie, F. A. and Zhu, Z. and Ade, H.}, year={2006}, month={May}, pages={3452–3460} }
 @article{sivasubramani_lee_kim_kim_gnade_wallace_edge_schlom_stevie_garcia_et al._2006, title={Thermal stability of lanthanum scandate dielectrics on Si(100)}, volume={89}, ISSN={["0003-6951"]}, DOI={10.1063/1.2405418}, abstractNote={The authors have examined the thermal stability of amorphous, molecular beam deposited lanthanum scandate dielectric thin films on top of Si (100) after a 1000°C, 10s rapid thermal anneal. After the anneal, crystallization of LaScO3 is observed. Excellent suppression of lanthanum and scandium diffusion into the substrate silicon is indicated by the back-side secondary ion mass spectrometry (SIMS) analyses. In contrast, front-side SIMS and high-resolution electron energy loss analyses of the amorphous Si∕LaScO3∕Si (100) stack indicated the outdiffusion of lanthanum and scandium into the silicon capping layer during the anneal.}, number={24}, journal={APPLIED PHYSICS LETTERS}, author={Sivasubramani, P. and Lee, T. H. and Kim, M. J. and Kim, J. and Gnade, B. E. and Wallace, R. M. and Edge, L. F. and Schlom, D. G. and Stevie, F. A. and Garcia, R. and et al.}, year={2006}, month={Dec} }