Situ Characterization of Deposition

In Chapter 13 we discussed methods available for the characterization of surfaces and thin films. These were shown to be of practical importance mainly before and/or after the plating process. It is no less important to discuss the methods that are available to characterize, study, understand, and thus control the plating operation in situ that is, while the plating process is taking place. 

As a general observation it may be stated that as far as in situ studies are concerned, the testing methods are derivatives of those discussed in Chapter 13. Experimental setups, however, require special attention. Conditions must be maintained to ensure 

Fundamentals of Electrochemical Deposition, Second Edition. By Milan Paunovic and Mordechay Schlesinger Copyright 2006 John Wiley Sons, Inc. 

It is understood that the x-ray absorption spectrum should be treated as divided into near-edge and extended fine structures. The x-ray absorption near-edge structure 

Briefly, XANES is associated with the excitation process of a core electron to bound and quasibound states, where the bound states interacting with the continuum are located below the ionization threshold (vacuum level) and the quasibound states interacting with the continuum are located above or near the threshold. Thus, XANES contains information about the electronic state of the x-ray absorbing atom and the local surrounding structure. However, as stated above, unhke EXAES, since the excitation process essentially involves multielectron and multiple scattering interactions, interpretation of XANES data is substantially more complicated than that of EXAFS data. 

For in situ X-ray diffraction measurements, the basic construction of an electrochemical cell is a cell-type enclosure of an airtight stainless-steel body. A beryllium window, which has a good X-ray transmission profile, is fixed on an opening in the cell. The cathode material can be deposited directly on the beryllium window, itself acting as a positive-electrode contact. A glass fiber separator soaked in liquid electrolyte is then positioned in contact with the cathode followed by a metal anode (3). A number of variations and improvements have been introduced to protect the beryllium window, which is subject to corrosion when the high-voltage cathode is in direct contact with it. 

We next discuss X-ray absorption studies. To put matters in context, it is useful to understand that conventional studies using Auger electron spectroscopy (AES) and X-ray photoemission spectroscopy (XPS) can be carried out only ex situ in high vacuum after electrochemical treatment since the techniques involve electron detection. X-ray absorption spectroscopy can, in contrast, be used for valence and structural environment studies. As X-rays only are involved, they can be carried out in situ in an electrochemical cell or similar. 

SOLID-STATE STUDIES (CHEMICAL MECHANICAL POLISHING) 

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It is seen from the above that the present book contains a number of different types of material, and it is likely that some readers, on first reading, will want to use some chapters while others may want to use different ones. For this reason the chapters and their different sections have been made independent of each other as far as possible. Certain chapters can be omitted without causing difficulties in reading the following chapters of the book. For example, Chapters 3 (on metals and metal surfaces), 7 (on nucleation and growth models), 14 (on in situ characterization of deposition processes), and 15 (mathematical modeling in electrochemistry) can be omitted on first reading. Thus, the book can be used in a variety of ways to serve the needs of different readers. 

Understanding the dependence of film structure and morphology on system layout and process parameters is a core topic for the further development of ZnO technology. Work is being performed on in situ characterization of deposition processes. Growth processes are simulated using Direct Simulation Monte-Carlo (DSMC) techniques to simulate the gas flow and sputter kinetics simulation and Particle-ln-Cell Monte-Carlo (PICMC) techniques for the plasma simulation [132]. 

Fig. 5.12. Process control techniques for the in situ characterization of film and process properties and closed-loop control strategies for optical film deposition by reactive sputtering...

Fig. 1.5. Experimental setup of the high-frequency laser vaporization cluster ion source driven by a 100-Hz Nd Yag laser for the production of ion clusters, ion optics with a quadrupole deflector, and quadrupole mass Alter for size-selection and deposition the analysis chamber with a mass spectrometer for thermal desorption spectroscopy (TDS), a Fourier transform infrared spectrometer, a spherical electron energy analyzer for Auger electron spectroscopy (AES) for in situ characterization of the clusters [73]...

Ravaghnan, L. Siviero, F. Lenardi, C. Milani, P. Cluster-beam deposition and in situ characterization of carbyn-rich carbon films. Phys. Rev. Lett. 2002, 89, 285506. 

Hot Wall Epitaxy (HWE). HWE is a high vacuum variant of physical vapor deposition with a base pressure of 10 6 mbar [9], In contrast to many other growth techniques it utilizes the near field of the molecular beam by moving the sample close or even into the hot wall tube that holds the film material. The walls of the tube can be heated separately and are held on a higher temperature than the sample and the source. This prevents deposition on the tube wall and helps to create a uniform flux of molecules. The main advantages of HWE are that the films are grown close to the thermodynamic equilibrium. The main drawback is that the position of the sample close to the evaporator makes an in situ characterization of the film growth impossible. 

Small amounts of Ru or Ir were sputter-deposited on Pt-NSTF substrate to determine their stability and OER activity in a fuel cell environment. Ex situ characterization of as-grown material was first performed in order to characterize the morphology and surface state of each OER catalyst. Scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS) were employed to complete this task. Two different OER catalyst loadings were studied, 2 and 10 pg/cm, in order to explore the impact of layer thickness on the catalyst morphology and composition. 

Oran, U., Swaraj, S., Lippitz, A., Unger, W.E.S. (2006) In situ characterization of plasma deposited allylamine films by ToF-SSIMS, XFS and NEXAFS spectroscopy. Plasma Process. Polym., 3,288-298. 

By considering in situ characterization of the deposits, hyphenated techniques can represent very important tools to enrich the picture of the coating when subjected to electrochemical polarization. In this case, the electrochemical stimulus, in terms of either potential or current applied to the system, is coupled to a direct observation of the modification induced. UV-visible and Raman spectroelectrochemistry were and still are infi equently used to simultaneously... 

Anodic Electrochemical Oxidation. The anodic electropolymerization of thiophene presents several distinct advantages such as the absence of catalyst, direct grafting of the doped conducting polymer onto the electrode surface (which is of particular interest for electrochemical applications), easy control of the film thickness by deposition charge, and possibility to perform a first in situ characterization of the growing process or of the polymer by electrochemical and/or spectroscopic techniques. 

Figure 8.13 In situ electrochemical SXS characterization of PtsNi) 11) and Pt(l 11) surfaces (a)XRV measurements forPtsNitlll) at the (0, 0, 2.7) (filled squares) andPt(lll)at (1, 0, 3.6) (open triangles) (b) surface coverage by underpotentially deposited hydrogen (Hupd) and hydroxyl species (OHad) calculated from the cyclic voltammograms (c) segregation profile ascertained from the SXS measurements. (Reprinted with permission from Stamenkovic et al. [2007a]. Copyright 2007. American Association for the Advancement in Science.)...

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Primary clay is also known as residual clay, indicating that they are either the in situ residue of one type of weathered rock or the transported residue of many types of rocks most primary clay deposits occur, however, in situ, at the location where the clay particles were formed. The clay is usually quite pure and colorless or white, but very small relative amounts of minerals mixed with the clay, such as quartz and/or iron oxides, may impart to it a yellow, brown, or green color. Primary clay is also characterized by the extreme fineness of its particles, which usually measure below 2 micrometers (0.002 mm) in diameter. The more than 20 different types of primary clay minerals can be distinguished by their chemical composition, which varies widely, and by their physical properties. Primary clays that have been used for making ceramic objects are listed in Table 55. 

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