Thin film growth ellipsometry

The first task in any experimental study of low temperature corrosion is to prepare a metal surface free of oxide and adsorbed species. For this the sample must be placed in an ultra- high vacuum (UHV) chamber. One then eliminates the natural oxide layer and adsorbed impurities by ion sputtering. Because ion bombardment disturbs the uppermost atomic layers of the metal (Chapter 3), a thermal treatment is sometimes applied in order to reestablish the original surface structure. Once a clean metal surface is available one introduces a known amount of oxygen into the UHV chamber by setting its partial pressure, and one follows the evolution of the reaction using a suitable method. Surface sensitive methods for the study of adsorption and thin film growth include surface analysis by AES, XPS, SIMS, optical methods, in particular ellipsometry, or mass sensitive methods such as the quartz microbalance. 

Hilfiker, J.N. (2011) In situ spectroscopic ellipsometry (SE) for characterization of thin film growth, in In Situ Characterization of Thin Film Growth (eds G. Koster and G. Rijnders), Woodhead Publishers, Cambridge, pp. 99-151. 

Wronski, and R. Messier, Recent progress in thin film growth analysis by multichannel spectroscopic ellipsometry, Appl. Surf. Sci, 154-155(2000)217-228. 

Applications for ellipsometry range from the simple determination of thin films thicknesses or optical constants, monitoring reactions and film growth [37], study of plasmonic effects in meta-materials [38], to structural and optical analysis of bio-and nano-materials [39, 40]. 

Ellipsometry is an optical monolayer-sensitive interface analysis method for the investigation of various aspects of surface and interfaces, including surface stoichiometry, surface roughness, adsorption, desorption, and surface strain, etc. In combination with the availability of microcomputers, SE has been developed and widely used for studies of thin films in the ambient, where parameters such as film thickness, composition, and interface roughness are determined. SE is now a popular tool for in situ growth control and diagnostics of interfaces. 

Thin layers of electrochemically deposited metals and thin polymer layers deposited on electrode surfaces can be conveniently studied by ellipsometry combined with other electrochemical experiments. Electrocrystallization of nickel was studied by Abyaneh, Visscher, and Barendrecht with ellipsometry and simultaneous amperometric measurements. The initial changes in A and ij/ showed nonlinear variations with the deposition time (Fig. 12), which is apparently abnormal, indicating a marked deviation of the optical properties of the deposited film from the bulk metal properties. The observed trend was explained by theoretical calculations using equations of effective medium theory (see Section IV.4 for effective medium theory) for hemispherical growth of the nucleation centers. The observed ellipsometry data clearly demonstrate that in the initial stage of nonuniform deposition the measured parameters, ij/ in particular, can change in a... 

---