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Ion beam deposition and surface characterization of thin multi-component oxide films during growth.

Description: Ion beam deposition of either elemental targets in a chemically active gas such as oxygen or nitrogen, or of the appropriate oxide or nitride target, usually with an additional amount of ambient oxygen or nitrogen present, is an effective means of depositing high quality oxide and nitride films. However, there are a number of phenomena which can occur, especially during the production of multicomponent films such as the ferroelectric perovskites or high temperature superconducting oxides, which make it desirable to monitor the composition and structure of the growing film in situ. These phenomena include thermodynamic (Gibbsian), and oxidation or nitridation-driven segregation, enhanced oxidation or nitridation through production of a highly reactive gas phase species such as atomic oxygen or ozone via interaction of the ion beam with the target, and changes in the film composition due to preferential sputtering of the substrate via primary ion backscattering and secondary sputtering of the film. Ion beam deposition provides a relatively low background pressure of the sputtering gas, but the ambient oxygen or nitrogen required to produce the desired phase, along with the gas burden produced by the ion source, result in a background pressure which is too high by several orders of magnitude to perform in situ surface analysis by conventional means. Similarly, diamond is normally grown in the presence of a hydrogen atmosphere to inhibit the formation of the graphitic phase.
Date: January 13, 1998
Creator: Krauss, A.R.; Im, J.; Smentkowski, V.; Schultz, J.A.; Auciello, O.; Gruen, D.M. et al.
Partner: UNT Libraries Government Documents Department

The use of reactive ion sputtering to produce clean germanium surfaces in a carbon rich environment -- An ion scattering study

Description: The authors have used the ion spectroscopic techniques of direct recoil spectroscopy (DRS) and mass spectroscopy of recoiled ions (MSRI) to demonstrate that low energy reactive ion sputtering of Ge is capable of removing surface impurities such as carbon. The experiments were performed in a vacuum chamber maintained at 3.5 {times} 10{sup {minus}7} Torr. At these pressures, physical sputtering using noble gas is not effective for cleaning Ge surfaces as carbon re-deposits onto the surface. In this paper, the authors demonstrate that reactive sputtering of Ge using 4.0 keV nitrogen at a Ge surface temperature of {approximately} 740 K and above removes surface carbon and deposits nitrogen on the Ge surface. Heating the nitrogen exposed Ge surface to above {approximately} 880 K results in the desorption of nitrogen and generates an atomically clean Ge surface, under poor vacuum conditions.
Date: October 7, 1997
Creator: Smentkowski, V.S.; Krauss, A.R.; Gruen, D.M.; Holecek, J.C. & Schultz, J.A.
Partner: UNT Libraries Government Documents Department

Surface analysis of all elements with isotopic resolution at high ambient pressures using ion spectroscopic techniques

Description: The authors have developed a mass spectrometer capable of surface analysis using the techniques of secondary ion mass spectroscopy (SIMS) and mass spectroscopy of recoiled ions (MSRI). For SIMS, an energetic ion beam creates a collision cascade which results in the ejection of low kinetic energy secondary ions from the surface being analyzed. The low kinetic energy SIMS ions are very susceptible to charge neutralization with the surface, and as a result, the SIMS ion yield varies by orders of magnitude depending on the chemical state of the surface. SIM spectra contain elemental ions, and molecular ions. For MSRI, a pulsed ion beam induces a binary collision with the surface being analyzed and the surface species are recoiled into the forward scattering direction with a large kinetic energy. The violence of the binary collision results in complete molecular decomposition, and only elemental ions are detected. The high kinetic energy MSRI ions are much less susceptible to charge neutralization with the surface than the low kinetic energy SIMS ions. In MSRI, the ion yield typically varies by less than a factor of ten as the chemical state of the surface changes--simplifying quantitative analysis vs. SIMS. In this paper, they authors will demonstrate that the high kinetic energy MSRI ions are able to transverse high pressure paths with only a reduction in peak intensity--making MSRI an ideal tool for real-time, in-situ film growth studies. The use of a single analyzer for both MSRI and SIMS is unique and provides complimentary information.
Date: September 1, 1997
Creator: Smentkowski, V.S.; Krauss, A.R.; Gruen, D.M.; Holecek, J.C. & Schultz, J.A.
Partner: UNT Libraries Government Documents Department

In situ analysis of thin film deposition processes using time-of-flight (TOF) ion beam analysis methods

Description: Non-destructive, in situ methods for characterization of thin film growth phenomena is key to understand thin film growth processes and to develop more reliable deposition procedures, especially for complex layered structures involving multi-phase materials. However, surface characterization methods that use either electrons (e.g. AES or XPS) or low energy ions (SIMS) require an UHV environment and utilize instrumentation which obstructs line of sight access to the substrate and are therefore incompatible with line of sight deposition methods and thin film deposition processes which introduce gas, either part of the deposition or in order to produce the desired phase. We have developed a means of differentially pumping both the ion beam source and detectors of a TOF ion beam surface analysis spectrometer that does not interfere with the deposition process and permits compositional and structural analysis of the growing film in the present system, at pressures up to several mTorr. Higher pressures are feasible with modified source-detector geometry. In order to quantify the sensitivity of Ion Scattering Spectroscopy (ISS) and Direct Recoil Spectroscopy (DRS), we have measured the signal intensity for stabilized clean metals in a variety of gas environments as a function of the ambient gas species and pressure, and ion beam species and kinetic energy. Results are interpreted in terms of collision cross sections which are compared with known gas phase scattering data and provide an apriori basis for the evaluation of time-of-flight ion scattering and recoil spectroscopies (ToF-ISARS) for various industrial processing environments which involve both inert and reactive cases. The cross section data for primary ion-gas molecule and recoiled atom-gas molecule interactions are also provided. from which the maximum operating pressure in any experimental configuration can be obtained.
Date: May 1, 1995
Creator: Im, J.; Krauss, A.R.; Gruen, D.M.; Lin, Y.; Schultz, J.A.; Auciello, O.H. et al.
Partner: UNT Libraries Government Documents Department

Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

Description: Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 {Angstrom}), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 {Angstrom} of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.
Date: November 1, 1992
Creator: Krauss, A. R.; Rangaswamy, M.; Lin, Yuping; Gruen, D. M.; Schultz, J. A.; Schmidt, H. K. et al.
Partner: UNT Libraries Government Documents Department

Pulsed ion beam methods for in situ characterization of diamond film deposition processes

Description: Diamond and diamond-like carbon (DLC) have properties which in principle make them ideally suited to a wide variety of thin-film applications. Their widespread use as thin films, however, has been limited for a number of reasons related largely to the lack of understanding and control of the nucleation and growth processes. Real-time, in situ studies of the surface of the growing diamond film are experimentally difficult because these films are normally grown under a relatively high pressure of hydrogen, and conventional surface analytical methods require an ultrahigh vacuum environment. It is believed, however, that the presence of hydrogen during growth is necessary to stabilize the corrugated diamond surface structure and thereby prevent the formation of the graphitic phase. Pulsed ion beam-based analytical methods with differentially pumped ion sources and particle detectors are able to characterize the uppermost atomic layer of a film during, growth at ambient pressures 5-7 orders of magnitude higher than other surface-specific analytical methods. We describe here a system which has been developed for the purpose of determining the hydrogen concentration and bonding sites on diamond surfaces as a function of sample temperature and ambient hydrogen pressure under hot filament CVD growth conditions. It is demonstrated that as the hydrogen partial pressure increases, the saturation hydrogen coverage of the surface of a CVD diamond film increases, but that the saturation level depends on the atomic hydrogen concentration and substrate temperature.
Date: June 1, 1995
Creator: Krauss, A.R.; Smentkowski, V.S.; Zuiker, C.D.; Gruen, D.M.; Im, J.; Schultz, J.A. et al.
Partner: UNT Libraries Government Documents Department

Ion beam spectroscopy as a means of in-situ monitoring of thin film deposition

Description: Low energy (5--15 keV) pulsed beam Ion Scattering Spectroscopy (ISS) and Direct Recoil Spectroscopy (DRS) are surface analytical tools which possess the ability to provide a remarkably wide range of information directly relevant to the growth of multi-component semiconductor, metal and metal oxide thin films and layered structures. Ion beam methods have not been widely used for this purpose because the design of existing commercial instrumentation is unsuitable in terms of vacuum requirements, data acquisition rate, geometric interference with the deposition equipment, and the magnitude of the ion beam dose and consequent film damage required for the acquisition of spectra with reasonable signal-noise ratios. Users of advanced custom-built Time-of-Flight (TOF) instruments have been largely interested in other problems and for the most part, unaware of some of the unique operational characteristics of TOF DR/ISS as they pertain to thin film growth. We discuss here some of the physical properties which may be measured by DR/ISS and describe a physical implementation of the technique which is suitable as a real-time probe of thin film deposition in terms of very low required beam dose, rapid data acquisition, physical non-interference with the deposition equipment and high ambient pressure operation.
Date: January 1, 1992
Creator: Krauss, A.R.; Rangaswamy, M.; Lamich, G.; Gruen, D.M. (Argonne National Lab., IL (United States)); Schultz, J.A. (Ionwerks, Inc., Houston, TX (United States)) & Schmidt, H. (Schmidt Instruments, Inc., Houston, TX (United States))
Partner: UNT Libraries Government Documents Department

Ion beams as a means of deposition and in-situ characterization of thin films and thin film layered structures

Description: Ion beam-surface interactions produce many effects in thin film deposition which are similar to those encountered in plasma deposition processes. However, because of the lower pressures and higher directionality associated with the ion beam process, it is easier to avoid some sources of film contamination and to provide better control of ion energies and fluxes. Additional effects occur in the ion beam process because of the relatively small degree of thermalization resulting from gas phase collisions with both the ion beam and atoms sputtered from the target. These effects may be either beneficial or detrimental to the film properties, depending on the material and deposition conditions. Ion beam deposition is particularly suited to the deposition of multi-component films and layered structures, and can in principle be extended to a complete device fabrication process. However, complex phenomena occur in the deposition of many materials of high technical interest which make it desirable to monitor the film growth at the monolayer level. It is possible to make use of ion-surface interactions to provide a full suite of surface analytical capabilities in one instrument, and this data may be obtained at ambient pressures which are far too high for conventional surface analysis techniques. Such an instrument is under development and its current performance characteristics and anticipated capabilities are described.
Date: January 1, 1992
Creator: Krauss, A.R.; Rangaswamy, M.; Gruen, D.M. (Argonne National Lab., IL (United States)); Lin, Y.P. (Argonne National Lab., IL (United States) Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science); Schultz, J.A. (Ionwerks, Inc., Houston, TX (United States)); Schmidt, H. (Schmidt Instruments, Inc., Houston, TX (United States)) et al.
Partner: UNT Libraries Government Documents Department