Interface formation

Figure 7 HREELS vibrational spectra of the interface formation between a polyimida film and evaporated aluminum (a) ciean polyimida surface (b) with 1/10 layer of Al (c) withi /2 layer of Al. ...

Horizontal vessels as cylinders are generally more suitable for diameters up to about 8 feet than other shapes, or vertical, due in part to the increased interfacial area for interface formation. For a horizontal drum (See Figure 4-12) ... 

The systems discussed in this chapter give some examples using different theoretical models for the interpretation of, primarily, UPS valence band data, both for pristine and doped systems as well as for the initial stages of interface formation between metals and conjugated systems. Among the various methods used in the examples are the following semiempirical Hartree-Fock methods such as the Modified Neglect of Diatomic Overlap (MNDO) [31, 32) and Austin Model 1 (AMI) [33] the non-empirical Valence Effective Hamiltonian (VEH) pseudopotential method [3, 34J and ab initio Hartree-Fock techniques. 

In the many reports on photoelectron spectroscopy, studies on the interface formation between PPVs and metals, focus mainly on the two most commonly used top electrode metals in polymer light emitting device structures, namely aluminum [55-62] and calcium [62-67]. Other metals studied include chromium [55, 68], gold [69], nickel [69], sodium [70, 71], and rubidium [72], For the cases of nickel, gold, and chromium deposited on top of the polymer surfaces, interactions with the polymers are reported [55, 68]. In the case of the interface between PPV on top of metallic chromium, however, no interaction with the polymer was detected [55]. The results concerning the interaction between chromium and PPV indicates two different effects, namely the polymer-on-metal versus the metal-on-polymer interface formation. Next, the PPV interface formation with aluminum and calcium will be discussed in more detail. 

Finally, the investigation of noble metal bonding on semiconductor surfaces provides evidence that at moderate temperatures Cu diffuses easily into the Si surface whereas the penetration barrier for Ag is almost as large as its binding energy. The theoretical results help in the understanding of an important catalytic process in the synthesis of silicone polymers and shed light on the Cu/Si and Ag/Si interface formation. 

Janssen FJJ, van Uzendoom LJ, van der Gon AWD, de Voigt MJA, Brongersma HH. 2004. Interface formation between metal and poly-dialkoxy-p-phenylene vinylene. Phys Rev B 70 165425. 

Polarization modulation can be done by rotating the polarizer, as is done in rotating-element ellipsometers [339], or by using photoelastic devices [337]. Data acquisition nowadays is fast, which makes real-time measurements of film and interface formation possible a full spectrum ranging from 1.5 to 5 eV can be measured in less than a second [340-342]. 

C. Monteux, C.E. WiUiams, J. Meunier, O. Anthony, and V. Bergeron Adsorption of Oppositely Charged Polyelectrolyte/Surfactant Complexes at the Air/Water Interface Formation of Interfacial Gels. Langmuir 20, 57 (2004). 

Structural information on the atomic arrangements at the early stage of formation of metal-metal, metal-semiconductor interfaces and semiconductor-semiconductor heterojunctions is needed along with the determination of the structure of the electron states in order to put on a complete experimental ground the discussion of the formation of solid-solid junctions. Amongst the structural tools that have been applied to the interface formation problem Surface-EXAFS is probably the best... 

A surface sensitive version of the EXAFS technique has been attempted ten years ago, and has proven to be successful in a large variety of surface chemisorption and interface formation problems. In the following we recall very briefly what makes SEXAFS different from EXAFS and what is the specific information that can be withdrawn from the SEXAFS data, and address the problems of metal-metal interface formation, and metal-semiconductor interface formation with detailed examples. 

Examples. Combined experimental—theoretical studies lead to information at a level not easily obtainable from either approach separately15. Several detailed examples are provided in chapter 7 to illustrate this point, and to provide the basis for the conclusions drawn on relevant polymer surfaces and the early stages of metal-polymer interface formation. This portion of the book is for the reader who wants to become familiar with details upon which certain conclusions, in the final chapter, have been drawn. 

X-ray photoelectron spectroscopy of atomic core levels (XPS or ESCA) is a very powerful tool for characterization of the chemical surrounding of atoms in molecules. In particular, since the method is very surface sensitive, it is possible to monitor the first stages of the interface formation, i.e., in our case the interaction between individual metal atoms and the polymer. Standard core level bonding energies are well known for common materials. However, in our case, we are studying new combinations of atoms and new types of structures for which there are no reference data available. In order to interpret the experimental chemical shifts it is useful to compare with theoretical estimates of the shifts. 

Here we survey a series of possible surface-sensitive measurements which in principle can be used to study the surfaces of conjugated polymers and the early stages of metal interface formation. We then motivate the use of photoelectron spectroscopy. 

First, satellite structure on the high binding energy side of, for example, an XPS core-level line (or peak ) corresponds to so-called shake-up (referred to below as s.u. ) and shake-ofF2S-29 effects, the former of which is illustrated, by M+, in Fig. 3.1. Shake-off is just shake-up to the continuum rather than to an unoccupied molecular state. Considerations of (1) are important in comparisons with the results of model calculations while (2) is of use as an indication of the electronic transitions in the molecules under study, an example of which is found in studies of the early stages of interface formation, i.e., the interactions of reactive metal atoms with conjugated polymer surfaces. Since use will be made of these effects in subsequent chapters, they are outlined briefly below. 

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