Formation of High-Mass Cluster Ions from Compound Semiconductors Using Time-of-Flight Secondary Ion Mass Spectrometry with Cluster Primary Ions (original) (raw)
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Applied Surface Science, 1999
Secondary ion mass spectrometry (SIMS) provides direct methods to characterize the chemical composition of III-V materials at major, minor and trace level concentrations as a function of layer depth. SIMS employs keV primary ions to sputter the surface and sensitive mass spectrometry techniques to mass analyze and detect sputtered secondary ions which are characteristic of the sample composition. In-depth compositional analysis of these materials by SIMS relies on a number of its unique features including: (1) keV primary ion sputtering yielding nanometer depth resolutions, (2) the use of MCs+ detection techniques for quantifying major and minor constituents, and (3) ion implant standards for quantifying trace constituents like dopants and impurities. Nanometer depth resolution in SIMS sputtering provides accurate detection of diffusion of dopants, impurities and major constituents. MCs+ refers to the detection of "molecular" ions of an element (M) and the Cs+ primary beam. MCs÷ minimizes SIMS matrix effects in analysis for major and minor constituents, thus providing good quantification. This paper presents a SIMS study of AlxGal.xAs structures with three different x values. MCs' (M=A1 or Ga) data are presented for the accurate determination of major and minor components. Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD) data were crosscorrelated with the MCs+ results. Three specimens with different x values were ion implanted with H, C, 0, Mg, Si, Zn and Se to study quantification of trace levels. SIMS data acquired on a double focusing instrument (CAMECA IMS-4f) and a quadrupole instrument (PHI ADEPT 1010) are also compared. Lastly, we discuss our efforts to improve the analysis precision for pand n-type dopants in AIGaAs which currently is + 3% (1 sigma).
Surface and Interface Analysis, 1994
This paper reports results of the second SIMS round-robin study on GaAs impurity analysis in which 16 laboratories participated. Three different types of SIMS instruments, including Cameca IMS3F or IMS4F, Atomika ADIDA-3000 and Hitachi IMA-3, were used for this study. The specimens were cut from identical multielementdoped GaAs crystals and distributed as common standards for the quantitative impurity analyses. The interlaboratory deviations in quantitative results based on the common standards were found to be 10-20%, except for some lowconcentration specimens and the results for zinc. This was approximately half of the corresponding results produced from standard specimens provided by the laboratories themselves. The interlaboratory deviations of relative ion intensity between impurity and matrix were < 50% for those laboratories employing instruments of the same type, except for lowconcentration specimens. These results show that quantitative analysis to an accuracy of 50% can be performed without standard specimens by utilizing relative sensitivity factors for each type of instrument.
Isomers of gallium arsenide cluster ions
Chemical Physics Letters, 1992
Gallium arsenide duster ions were generated by laser vaporization in a supersonic nozzle, trapped in a Fourier transform ioncyclotron resonance mass spectrometer, and allowed to react with NH3 forming addition complexes with the cluster cations. With excess NH3, GaxAsy(NH3)~ + with the same GaAs composition (x+y) was observed with several values ofz. This observation of different numbers of chemisorbed NH3 molecules at completion is explained in terms of the existence of multiple isomers of positive GaAs clusters. Negative GaxAsy clusters were found to be inert toward NH3.
Secondary ion mass spectrometry with gas cluster ion beams
Applied Surface Science, 2003
Secondary ion mass spectrometry (SIMS) with gas cluster ion beams was studied with experiments and molecular dynamics (MD) simulations to achieve a high-resolution depth profiling. For this purpose, it is important to prevent both ion mixing and the surface roughening due to energetic ions. As the Ar cluster ion beams shows high secondary ion yield and surface smoothing effects in the low-energy regime, it is suitable for the primary ion beam of SIMS. From MD simulations of Ar cluster ion impact on Si, ion mixing is heavier than than those for Ar monomer ions at the same energy per atom, because the energy density at the impact point is extremely high. However, the sputtering yields with Ar cluster ions are one or two orders of magnitude higher than that with Ar monomer ions at the same energy per atom. Comparing at the ion energy where the ion-mixing depths are the same by both Ar cluster and Ar monomer ions, cluster ions show almost 10 times higher sputtering yield than by Ar monomer ions. A preliminary experiment of SIMS with Ar cluster ion was performed and a mass resolution of several nm was achieved for a Ta film. Ó 2002 Published by Elsevier Science B.V.
An Introduction to Cluster Secondary Ion Mass Spectrometry (Cluster SIMS)
Principles and Applications, 2013
Cluster secondary ion mass spectrometry (SIMS) has had a significant impact on the mass spectrometry and surface analysis communities over the past two decades, with its newfound ability to characterize surface and in-depth compositions of molecular species with minimal damage, excellent spatial (100 nm or less) and depth (5 nm) resolutions, and increased sensitivities for bioimaging applications. With the continual development of new cluster ion beam technologies, we are breaking down barriers once thought to be unbreakable, and entering into new fields once labeled as out of reach. Instrument designs are now advancing to account for these new applications, allowing for further improvements in molecular sensitivities, selectivities, and even high throughput analysis. Although we are * Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States. † Commercial equipment and materials are identified in order to adequately specify certain procedures. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. ‡ This document was prepared as an account of work sponsored by an agency of the US Government.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Experimental and simulated energy distributions of Ga þ and In þ secondary ions produced by 4 keV Ne þ , Ar þ and Kr þ bombardment of the A III B V semiconductors (GaP, GaAs, GaSb, InP, InAs and InSb) are reported. The measurements were carried out for a wide range of initial energy (up to 1000 eV) in a small solid angle along the surface normal, without applying electric field to extract the ions into the mass-energy analyser. It is shown that the energy spectra are complex, with evident high-energy hump, whose relative intensity increases with the mass of the second component (P, As, Sb) of the compound. The Sigmund-Thompson distribution cannot fit reliably these data, and a satisfactory approximation of the measured spectra was obtained with a sum of two decaying exponential functions to describe the contribution of both, the isotropic linear collision cascades and the outward knock-on atoms. The experimental results are compared with simulations based on the MARLOWE computer code.
Electronic structure of small GaAs clusters
The Journal of Chemical Physics, 1991
The electronic structure of small Ga x Asy clusters (x + y< 10) are calculated using the local density method. The calculation shows that even-numbered clusters tend to be singlets, as opposed to odd-numbered clusters which are open shell systems. This is in agreement with the experimental observations of even/odd alternations of the electron affinity and ionization potential. In the larger clusters, the atoms prefer an alternating bond arrangement; charge transfers are observed from Ga sites to As sites. This observation is also in agreement with recent chemisorption studies of ammonia on GaAs clusters. The close agreement between theoretical calculations and experimental results, together with the rich variation of electronic properties of GaAs clusters with composition makes GaAs clusters an ideal prototype system for the study of how electronic structure influences chemical reactivity.