Thin-film deposition infrared spectroscopy

Infrared spectroscopy, including Fourier-transform infrared (FTIR) spectroscopy, is one of the oldest techniques used for surface analysis. ATR has been used for many years to probe the surface composition of polymers that have been surface-modified by an etching process or by deposition of a film. RAIR has been widely used to characterize thin films on the surfaces of specular reflecting substrates. FTIR has numerous characteristics that make it an appropriate technique for... 

Gonzalez-Elipe, A.R. (2000 a) Iron oxide thin films prepared by ion beam induced chemical vapour depositions. Structural characterization by infrared spectroscopy. J. Vac. 

Many investigations of the molecular structure of thin films formed by y-APS deposited onto inorganic substrates from aqueous solutions have been carried out. Ondrus and Boerio [2] used reflection-absorption infrared spectroscopy (RAIR) to determine the structure of y-APS films deposited on iron, 1100 aluminum, 2024 aluminum, and copper substrates from aqueous solutions at pH 10.4. They found that the as-formed films absorbed carbon dioxide and water vapor to form amine bicarbonate salts which were characterized by absorption bands near 1330, 1470, 1570, and 1640 cm-1. y-APS films had to be heated to temperatures above about 90°C in order to dissociate the bicarbonates, presumably to free amine, carbon dioxide, and water. Since the amine bicarbonates failed to react with epoxies, the strength of adhesive joints prepared... 

A typical surface profile is shown on the video display. Vertical resolution of 5 A and horizontal resolution of 400 A is claimed. As long as the deposited film can be etched off the substrate without etching the substrate, this technique can be used for any thin film. Its primary utility is for R D studies, as it is clearly not a production technique. The only film for which it is not suited is an epi silicon film on a single-crystal silicon substrate. A technique for measuring the thickness of these films will be described in the section on Infrared Spectroscopy. 

Conversion of the as-deposited film into the crystalline state has been carried out by a variety of methods. The most typical approach is a two-step heat treatment process involving separate low-temperature pyrolysis ( 300 to 350°C) and high-temperature ( 550 to 750°C) crystallization anneals. The times and temperatures utilized depend upon precursor chemistry, film composition, and layer thickness. At the laboratory scale, the pyrolysis step is most often carried out by simply placing the film on a hot plate that has been preset to the desired temperature. Nearly always, pyrolysis conditions are chosen based on the thermal decomposition behavior of powders derived from the same solution chemistry. Thermal gravimetric analysis (TGA) is normally employed for these studies, and while this approach seems less than ideal, it has proved reasonably effective. A few investigators have studied organic pyrolysis in thin films by Fourier transform infrared spectroscopy (FTIR) using reflectance techniques. - This approach allows for an in situ determination of film pyrolysis behavior. 

Attention in this chapter will be mainly focused on che reaction of tecrahydrofuran (THF) with thin lithium films vapor-deposited in UHV on clean polycrystalline Ag substrates. The techniques employed in this study included TPD, XPS and AES. A parallel study of THF adsorption on Li layers deposited on Au substrates is currently being pursued by Ms. Guorong Zhuang using FTIRRAS (Fourier Transform Reflection Absorption Infrared Spectroscopy) in this laboratory. 

This paper describes ongoing studies of the electrodeposition thin films of the compound semiconductors CdTe and InAs, using the method of electrochemical atomic layer epitaxy (ALE). Surface limited electrochemical reactions are used to form the individual atomic layers of the component elements. An automated electrochemical flow deposition system is used to form the atomic layers in a cycle. Studies of the conditions needed to optimize the deposition processes are underway. The deposits were characterized using X-ray diffraction, scanning probe microscopy, electron probe microanalysis and optical/infrared absorption spectroscopy. 

The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism pla dng a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed. 

The characterization of the resultant film by VC was carried out by various methods. The CH = CHOCO Li was detected by infrared reflection absorption spectroscopy (IRRAS). It also was speculated that the formation of polymers having -OCOjLi group affords good adhesiveness and flexibility to the passivation film. The deposition process by VC reduction, which started from 1.3 V vs. LP/Li, was monitored by in-situ atomic force microscopy (AFM) and the film thickness down to 0.8 V was about 10 nm. Ex-situ AFM also revealed an ultra-thin film (less than 1 nm) on the terrace of the basal plane of a highly oriented pyrolytic graphite (HOPG)... 

Chen et al. [95], very recently, prepared Au thin-film electrodes made by electroless deposition for in situ electrochemical attenuated total-reflection surface-enhanced infrared adsorption spectroscopy (ATR-SEIRAS) which consisted of 46 nm Au nanoparticles deposited on a Si infrared window. Very interestingly, they observed that a square-wave treatment of the Au film led to a much enhanced ORR activity (02-saturated 0.1 M HCIO4) as a consequence of the surface reconstruction of the nanoparticle film. Thus, whereas the ORR activity of the initial Au... 

Characterization of the Unmodified and PLL-g-PEG-Modified Surfaces. 3.2.1. RAIRS Measurements of the PLL(20)-g[3.5]-PEG(2) Monolayer. Reflection-absorption infrared spectroscopy (RAIRS) is well suited to study adsorbates on metallic surfaces, which are highly reflective. It relies on reflecting an infrared beam at near-grazing incidence from the metallic surface on which the thin film of interest has been deposited. Only the component of the vibrational transition dipole moments perpendicular to the surface plane contributes to the absorption spectra. The intensity of an absorption band is proportional to the squared cosine of the angle between the transition dipole moment and the surface normal. Therefore, RAIRS provides information not only on fimctional groups but also on orientation and conformation of adsorbed molecules or molecular entities. Metal oxides... 

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