We are investigating well-ordered highly crystalline thin films made using organic molecular beam deposition (OMBD) since it is important to control the formation mechanism at the initial growth process. Then, we developed a new in situ technique of energy dispersive grazing incidence X-ray diffraction utilized within an ultrahigh vacuum system. This technique (in situ ED-GID) makes it possible to examine the crystal structure, orientation and morphology of organic thin films during deposition without any damage to the film. In the present review, we examined the growth process of thin films of functional organic dyes, fullerene (C60) and p-sexiphenyl (6P) by using this in situ ED-GID. The crystal strucutre and molecular orientation in epitaxially-grown thin films were confirmed during the initial stages of growth. Also, the morphology of C60 thin films was examined during the deposition. As a result, it was confirmed that the decay curves of X-ray fluorescence indicate different island growth in C60 thin films.

Selective etch of SiO2/poly Si in a high density CF4+D2 plasma generated by ECR (Electron Cyclotron Resonance) system was studied. The end point detection of the SiO2 sidewall spacer etch was monitored using optical emission spectroscopy and mass spectrometer. SEM cross sectional analysis was conducted to confirm the end point detection and spacer formation.

An experimental apparatus which exploits synchrotron white beam X-ray diffraction topography has been developed to perform real time in situ observation of deformation processes of single crystals. The apparatus consists of a fully automated and remotely controlled mini-tensile device and a CCD based X-ray imaging detector with associated video system. Both tensile data and X-ray topographic images are recorded simultaneously. The materials under study include single crystals of Si, and single crystals or bicrystals of the refractory metals W and Mo. The deformation processes of these crystals have been studied by monitoring a selected transmission Laue spot while the specimen is mechanically cycled by loading and unloading. The X-ray images have been captured by a frame grabber and recorded via a VCR. Several phenomena have been observed, including bending contours, strain concentrations, reversible anelastic effect and microyielding. The observed stress relaxations are correlated to microstructural variations shown by X-ray topography. The stability of low angle grain boundaries in bicrystals; and the effect of high strength and toughness coatings on the deformation of single crystal substrates was investigated.

Various position sensitive microchannel-plate (MCP) detector systems for ion, electron and photon detection are presented. We have also developed a complete set of electronics to operate the detectors and software to analyze the incoming data. The detectors provide two-dimensional position as well as excellent timing information, e.g. for time-of-flight measurements. All data can be stored in single event mode. These MCP-detectors were used for electron and ion analyzers, which provide a three-dimensional imaging of the momentum space of all detected particles.

Atomic Oxygen (AO) and ultraviolet (UV) radiation contribute (including synergistically) to degradation of spacecraft materials in Low Earth Orbit (LEO). NASA is, therefore, interested in determining what effects the harsh LEO environment has on materials exposed to it, as well as develop materials that are more AO and UV resistant. The present work involves the study of AO and UV effects on polyarylene ether benzimidazole (PAEBI) with in situ and ex situ spectroscopic ellipsometry. PAEBI is a polymer proposed for space applications due to its reported ability to form a protective phosphorous oxide on the surface when exposed to AO. In our experiments PAEBI was exposed to UV radiation from a xenon lamp while in situ ellipsometry data were acquired. The effects of UV radiation were modeled as an exponentially graded layer on the surface of bulk PAEBI. The change in UV absorption spectra, depth profile of the index of refraction, and growth trends of the UV irradiated PAEBI were all studied in these experiments. In addition, PAEBI was exposed to an oxygen plasma to simulate the synergistic effects of AO and UV. Ellipsometry data were acquired in-line with both a UV-Visible ellipsometer and an infrared ellipsometer. The change in UV absorption bands and index of refraction due to synergistic AO/UV, as well as the growth trends of the oxide layer were studied.

High speed imaging and emission spectroscopy are used to characterize the plumes generated from the ablation of bulk barium strontium titanium oxide material in vacuum and 30–60 mTorr of O2 using a pulsed 248-nm laser with fluences ranging from 5–8 J/cm2. High speed imaging reveals that in vacuum the leading edge of the plume expands normal to the substrate surface with a velocity of 19.7 km/sec. The ratio of distance traveled to the plume's radius is ˜ 2 at the early stages of the expansion and 3.2 at the later stages near the substrate. Similar observations are observed when the plume expands in 30 mTorr of O2 for times less than 2.0 μsec. However, at times greater than 2.0 μsec the plume's expansion is retarded due to collisional momentum transfer and reactions with the background gas. This effect is more pronounced when the plume expands in 60 mTorr of O2. Blast wave theory is used to model these results. Time-resolved emission spectroscopy of Ba(I) lines in the 735–770 nm region reveals that the plume' electron temperatures, Te, in a vacuum expansion range from 18000±2000 K at 0.1 μsec to 15000±1500 K at 2.0 /μsec. In contrast, in 30 mTorr of O2 the values of Te range from 17000±2000 K at 0.1 μsec to 4000±500 K at 8.0 μsec. At 0.1 μsec the plume's electron density is estimated as 1.7±0.4 × 1017 cm−3 in both vacuum and 30 mTorr of O2. We also determine the Stark broadening of the Ba(I) line at 746 nm to be 0.5±0.1 Åat an electron temperature of 1 eV and an electron density of 1017 cm−3.

Atomic absorption spectroscopy with tunable diode lasers has been performed for monitoring and study of the physical vapor deposition process. The combination of the wavelength-modulation spectroscopy with diode lasers and the balanced detection scheme guarantees the high sensitivity and reliability of the system. Direct measurements of atomic flux in e-beam evaporated yttrium and barium, which are components in YBCO superconducting thin films, have been demonstrated. The measured velocities show that the e-beam evaporated atoms are in a non-thermal-equilibrium state, dependent on source conditions, implying that the flux measurement rather than a simple density measurement for rate control is necessary. Comparison with quartz crystal monitors shows that the present scheme, employing two laser beams counterpropagating at an angle to the substrate surface for measuring directly the velocity component normal to the substrate surface, can provide a pressure-independent flux measurement. In yttrium, which has an additional significantly populated metastable level, results show that pressure-independent flux measurement requires measurements at both the ground state and the metastable levels. Efforts have also been made to extend the accessible wavelengths of diode lasers to the UV region by using nonlinear optical frequency doubling techniques for other technologically important elements.

Thin films of La2−xSrxCuO4 (LSCO) and La2CuO4+δ (LCO) were grown by reactive coevaporation. We obtained LSCO thin films on (001) LaSrA104 (LSAO) substrates with Tc(R=0) = 44 K, which is higher than that for bulk samples. A structural analysis indicates that the increase in Tc is due to compressive strain generated by the lattice mismatch. A similar strain effect is suggested from the substrate dependence of Tc for superconducting LCO thin films, for which Tc(R=0) reached 50 K on (001) LSAO substrates. We also succeeded in obtaining high-quality LSCO ultrathin films without any buffer or cap layers on (001) LSAO substrates, but not on substrates of other materials with the larger lattice mismatch with LSCO. These results demonstrate that the lattice mismatch with the substrates is important in thin-film growth of LSCO and LCO.

Several groups have monitored the growth of complex oxides in-situ using Reflection High Energy Electron Diffraction (RHEED). In order to utilize RHEED during growth, films are deposited at low background oxygen pressures. Because of the low oxidation power at low pressures, low substrate temperatures have to be used. This hampers, in general, the film crystallinity. Furthermore, the background pressure in Pulsed Laser Deposition (PLD) is an important parameter, because it influences the shape and size of the plasma and, therefore, the deposition rate and homogeneity of the film.

We have developed a high-pressure RHEED system, which can be used for growth monitoring during the deposition of complex oxides at standard PLD conditions. Clear diffraction patterns are observable up to 50 Pa, due to the minimized scattering losses.

SrTi03 substrate treatments as well as growth studies of Yba2Cu3O7−δ, using atomic layers of SrO or BaO as a buffer-layer, will be discussed in this contribution. It will be shown that monitoring and control of thin film growth by PLD on an atomic level is feasible, even in quite high background pressures.

Yba2Cu3OT7−x (Y123) and NdBa2Cu3O7−x (Nd123) thin films were deposited by PLD using a 248 nm wavelength KrF excimer laser. The emission spectra PLD process control techniques developed to grow reproducibly high quality Y123 thin films were also applied to the Nd123 depositions. The time-resolved spectral components of plumes generated from Y123 and Nd123 targets at the same deposition conditions were compared. When the two targets were mounted at the same distance from the substrate heater, the spectral emissions at 327 ± 5 nm (Cu*) were essentially identical for similar laser pulse energies and other deposition conditions (150 mTorr oxygen pressure, 760°C substrate heater temperatures, etc.). High quality Nd 123 films (Tc ˜93 K, Jc > 2x 106 A/cm2) are considerably more difficult to produce than those of Y123. Deposition conditions associated with PLD of high quality Y123 films produce very poor Nd 123 films. This observation is consistent with the belief that the nucleation and growth of Nd 123 are significantly different than that of Y 123.

Real-time, in-situ surface monitoring by reflection high-energy electron diffraction (RHEED) has been the key enabling component of atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) of complex oxides. RHEED patterns contain information on crystallographic arrangements and long range order on the surface; this can be made quantitative with help of numerical simulations. The dynamics of RHEED patterns and intensities reveal a variety of phenomena such as nucleation and dissolution of secondary-phase precipitates, switching between growth modes (layer-by-layer, step-flow), surface phase transitions (surface reconstruction, roughening, and even phase transitions induced by the electron beam itself), etc. Some of these phenomena are illustrated here, using as a case study our recent growth of atomically smooth a-axis oriented DyBa2Cu3O7 films.

Atomic-scale growth analysis of oxide thin films was performed by in situ reflection high energy electron diffraction (RHEED) and coaxial impact collision ion scattering spectroscopy (CAICISS) combined with Laser MBE. On single crystal substrates with atomically flat terrace and step structures, the two-dimensional nucleation followed by molecular layer-by-layer growth was verified by in situ monitoring of RHEED intensity oscillations, as well as ex situ atomic force microscopy (AFM) observation, for the growth of BaTiO3, Al2O3 and BaO thin films. The epitaxial BaTiO3 films grown on SrTiO3(100) and c-axis oriented Bi2Sr2CaCu2Ox (Bi2212) superconducting films were subjected to in situ CAICISS measurements in order to examine the topmost surface structure. The key factors to develop oxide lattice engineering are discussed with respect to not only in situ monitoring of the growth process using RHEED but also the atomic regulation of the substrate surface by AFM and ion scattering spectroscopy. The present work also demonstrates the advanced oxide thin film processing based on the laser MBE to control the growth and surface of films on an atomic scale.

Pulsed Laser and Sputter Deposition are used for the fabrication of complex oxide thin films at relatively high oxygen pressures (up to 0.5 mBar). This high pressure hampers the application of a number of in-situ diagnostic tools. One of the exceptions is ellipsometry. Using this technique we studied in-situ the growth of off-axis sputtered Yba2Cu3O6+x thin films on (001) SrTiO3 as a function of the deposition parameters. Furthermore, the oxidation process from O(6) to O(7) has been studied by performing spectroscopic ellipsometry during isobaric cooling procedures.

Another suitable in-situ monitoring technique for the growth of thin films is Reflection High Energy Electron Diffraction (RHEED). In general this is a (high) vacuum technique. Here, we present an RHEED-system in which we can observe clear diffraction patterns up to a deposition pressure of 0.5 mBar. The system has been used for in-situ monitoring of the heteroepitaxial growth of YBa2Cu3 06+x on SrTiO3 by pulsed laser deposition.

We have successfully implemented RHEED monitoring of growth of complex oxides in a reactive evaporation process with substrate rotation and an oxygen environment. A rotating substrate heater is used with a partial enclosure kept at a 10 mTorr oxygen pressure. This heater allows for simultaneous and uniform deposition of multiple 2-inch wafers. The RHEED beam diffracts from samples as they pass through the high-vacuum zone of the heater. A CCD camera is used for RHEED data acquisition and image capture is synchronized to sample position. In order to achieve good quality diffracted images, rotation of the sample is required to be less than 1 degree for the duration of data capture. With our relatively inexpensive setup images can be acquired for sample rotation speeds up to 1500 RPM. We use this RHEED diagnostic system for study of in-situ growth of high-temperature superconducting thin films.

The initial growth of pulsed laser deposited SrCuO2 (SCO) and CaCuO2 (CCO) on SrTiO3 has been studied using high pressure Reflection High Energy Electron Diffraction (RHEED) and Atomic Force Microscopy (AFM). For this, we developed a Pulsed Laser Deposition (PLD)- RHEED system, with the possibility to study the growth and to monitor the growth rates, in situ, at typical PLD pressures (10–50 Pa). In case of depositing oxide materials, high oxygen pressures are desired. Moreover, crystallinity can be improved using higher oxygen pressures and therefore higher temperatures. With this technique we are able to obtain atomically flat films, a first step towards multi-layer structures.

In this paper we present the initial growth studies of SCO and first results incorporating CCO layers in a SCO matrix.

A quadrupole mass spectrometer and a total ion-current measuring device have been utilized to monitor the ion compositions of gas mixtures of CH4/H2 and CH4/H2/O2 during the deposition for quality control and process optimization. An ultra high vacuum system using a 20 cm diameter RF excited (13.56 MIfz) ion gun and a four-axis substrate scanner has been developed for deposition of diamond-like carbon films for electrical, optical, and tribological applications. At a constant RF power of 179W, the mass spectra of gas mixture CH4/H2 (1:2.5) showed the most abundant ion is CH3+. Addition of O2 to the ion source has been found to affect the adhesion, deposition rate, and physical and chemical properties of the DLC films. By use of a mass spectrometer with and without the electron beam, the degree of ionization of CH4 was calculated to be about 10%. As the concentration of O2 was increased, all hydrocarbon ions decreased and H3O+ increased, resulting in a decrease in the film growth rate and an increase in etching of Si and glass substrates. In general, the optical bandgap, adsorption coefficients and refractive index decreased as oxygen concentration increased. Raman spectra showed the G-peak position shifted toward the graphitic peak with narrow peak width as oxygen concentration increased. At ultra high vacuum, the coefficient of friction increased with increased adhesion on substrates as oxygen was increased.

In situ Fourier Transform Infrared Reflection Absorption Spectroscopy (FTIRRAS) has been used to study the adsorbed plasma species on sapphire substrate throughout the nucleation and deposition stages under diamond deposition conditions. The focus of this work has been on one of the most fundamental questions in the area of diamond film synthesis that concerns the gas species (precursors) responsible for diamond nucleation and growth especially on foreign substrates. It is experimentally shown here that the most probable precursor for diamond nucleation in methane-hydrogen plasma are methyl radicals.

Diamond deposition on randomly oriented sapphire substrates has been successfully achieved under low pressure- low temperature deposition conditions using an electron cyclotron resonance microwave plasma assisted chemical vapor deposition (ECR-PACVD) system. The deposited thin films were characterized by Raman spectroscopy, and scanning electron microscopy.

We have measured the steady state concentration of gas phase C2 in Ar/H2/CH4 and Ar/H2/C60 microwave plasmas used for the deposition of nanocrystalline diamond films. High sensitivity white light absorption spectroscopy is used to monitor the C2 density using the d 3 Π ← a3Π (0,0) vibrational band of C2 as chamber pressure, microwave power, substrate temperature and feed gas mixtures are varied in both chemistries. Understanding how these parameters influence the C2 density in the plasma volume provides insight into discharge mechanisms relevant to the deposition of nanocrystalline diamond.

Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) and electron energy-loss spectroscopy (EELS) has been used to characterize the elemental composition and oxidation conditions of various soot samples. The STEM employed in this investigation was the Vacuum Generators HB603, with a microanalytical resolution approaching 1 rnm, that allowed the analysis of individual soot particles and aggregates. The aim of this research is quantification of the EDX spectra which is possible after background and absorption corrections. This information can then be used for comparative studies of different fuels and combustion processes. EELS has been employed to determine the amount of graphitic carbon in a soot particulate, and the detection of trace elements of low atomic number. It has been shown in soot that for Carbon the energy-loss of the p shell electrons increases with the amount of oxidation at high temperatures. Analysis and characterization of gas turbine soot, collected from an engine exhaust duct of a 737-300 aircraft showed an abundance of different elements. Some of these elements originated from the fuel and combustion processes, while other elements were components of the engine itself that combined with the soot particulates during the combustion process. The study showed that soot impurities were found in all discrete sections of aggregates, and that only one or two small soot particulates were necessary to obtain a chemical fingerprint. Other investigations include; coal soot, diesel soot at different engine operating conditions and soot produced from wood burning. The richness of the spectra obtained and the ability to quantify results represents an opportunity to accomplish source identification in a novel, powerful way.