Room Temperature Vulcanized (RTV) materials, such as silicone adhesives, are commonly used to bond components of
communication satellites and other types of spacecraft. The elevated satellite operating temperature causes the unused
catalyst material in the RTV to volatize, which can then re-deposit or condense onto other spacecraft surfaces. In the
presence of sunlight, this Volatile Condensable Material (VCM) can photo-chemically deposit onto optically-sensitive
spacecraft surfaces and significantly alter their original, beginning-of-life (BOL) optical properties, such as solar
absorptance and emittance, causing unintended performance loss of the spacecraft. Knowledge of the optical impact of
photo-chemically-deposited VCM's is therefore a major concern of spacecraft designers and spacecraft-contamination
engineers. In view of this we have employed in-situ spectroscopic ellipsometry to monitor in real time the optical
constants of the condensed effluent of RTV CV-566 as well as its photofixed effluent. This technique is sensitive to nm
thick layers and can be used to extract n and k as a function of wavelength. We will present the optical constants, n and
k, for both condensed unexposed and the photofixed film.
Steam laser cleaning of alumina and titanium carbide nanoparticles from silicon substrates is presented. A KrF excimer laser with a wavelength of 248 nm was used to irradiate the substrates in laser cleaning. A water layer of micrometer thickness was deposited on silicon substrates to improve the cleaning process. Cleaning efficiency was measured for different laser fluences ranging from 50 to 250 mJ/cm2 and pulse numbers from 1 to 100. Research work was carried out to address the factors governing steam laser cleaning, during which thickness of water thin film and lift-off velocities of water films from Si substrate surfaces were monitored. In addition, one-dimensional simulations were employed to estimate the temperature increase on the material surfaces upon laser irradiation. Water layer thickness was measured using Fourier Transform Infrared Spectroscopy. Monitoring of both lift-off velocities and water thin film removal time were carried out by optical probing approaches using He-Ne laser of 632.8 nm wavelength.
Ellipsometry is well known for its extreme sensitivity to the presence and properties of ultra-thin films. In the infrared, resonance response to chemical bonds allows chemical identification in monolayer-thick biological films. In this paper we show results of attachment repeatability for successive layers of monosialoganglioside, cholera toxin, and related antibodies using in situ visible spectroscopic ellipsometry. Several factors contributing to difficulty in obtaining reproducible results are discussed. Soecifically, these include freshness of reagents; surface type, cleaning, and preparation; temperature; birefringence of liquid cell windows; and cell design. Sensitivity and signal noise considerations for infrared spectra of molecular monolayers are discussed.
Spectroscopic ellipsometry is used to determine optical constants, layer thicknesses in multilayer stacks, and microstructure (voids, alloy fraction, or mixed phase composition), and is a well-developed technique for analysis of optical thin films. Ellipsometers now cover from 140 nm (≈ 9 eV) in the vacuum-ultraviolet to 200 microns (50cm-1) in the far infrared. Generalized anisotropy and depolarization are measurable using rotating compensator ellipsometers or controlled retarders for partial Mueller Matrix analysis. Rotating compensator ellipsometers allow accurate and rapid in situ diagnostics, including window birefringence calibration. Steady progress has been made in both ex situ and in situ ellipsometry hardware, software, and applications. These advances are reviewed and examples given.
Pulsed laser deposition is a technique commonly used to deposit high quality thin films of high temperature superconductors. This paper discusses the results obtained when this technique is applied to the deposition of Tl-Ca-Ba-Cu-O thin films using a frequency doubled Nd:YAG laser operating at 532 nm and an excimer laser operating at 248 nm. Films with onset temperatures of 125 K and zero resistance temperatures of 110 K deposited on (100) oriented MgO from a composite Tl2Ca2Ba2Cu3Ox target were obtained at both wavelengths upon appropriate post deposition annealing. Films deposited at 532 nm exhibit a rough surface, while those deposited at 248 nm are smooth and homogeneous. Upon annealing, films deposited at both wavelengths are single phase Tl2Ca2Ba2Cu3Ox.
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