Surface analysis system

Figure A3.10.il Side view of a combined high-pressnre cell and UFIV surface analysis system [37].

Szanyi J and Goodman D W 1993 Combined elevated pressure reactor and ultrahigh vacuum surface analysis system Rev. Sc/. Instrum. 64 2350... 

A Pilot Plant Reactor-Surface Analysis System for Catalyst Studies... 

Sample Introduction and Transfer System. The sample Introduction and sample transfer system is a lengthened version of the PHI Model 15-720B Introduction system which consists of a polymer bellows-covered heating and cooling probe, a transferable sample holder, an eight-port dual-axis cross, and the mlnlreactor Interface port and transfer probe (Figure 2). There Is also a transfer vessel port with the necessary transfer probe for Introduction of air sensitive samples. They are not part of the reactor/surface analysis system. The dual cross and attached hardware are supported by the probe drive mechanism which floats on a block driven vertically and transversely by two micrometers. These micrometers plus the probe drive mechanism allow X-Y-2... 

Figure 1. Block diagram showing the subsystems of the combined reactor and surface analysis system.

A study of a methanol synthesis catalyst Is used to demonstrate the usefulness of the new pilot plant/mlnlreactor/surface analysis system. This work Is described In more detail elsewhere (7). Industrial methanol synthesis catalysts are based on Cu0/Zn0/Al20s or Cu0/Zn0/Cr203 compositions. 

A unique pilot plant/minlreactor/surface analysis system has been designed and put Into operation. This system represents the closest encounter reported In the literature to date between "real world" catalysis and-surface analytical techniques. It allows In depth studies of reaction kinetics and reaction mechanisms and their correlation with catalyst surface properties. 

XPS Analysis. The ultrahigh vacuum (OHV) catalyst treatment-surface analysis system employed to characterize and treat the cobalt catalysts has been described previously ( 1, 2 The catalyst treatment and data analysis procedures have also been described (JJ. Briefly, the samples were treated in quartz reactors and then transferred under UHV into a modified Hewlett-Packard 5950A BSCA spectrometer for emalysis. Peak areas were normalized with theoretical cross-sections (Z) to obtain relative atomic compositions. 

Some of the modern surface analysis methods have been used to study the surface chemistry of both plasma etched surfaces and plasma polymerized thin films. Much of this work has involved exposure of these surfaces to air as the samples are transferred from the plasma system to the surface analysis system. However, in a few cases surface analysis has been performed in the plasma system after the plasma gas has been pumped away. This work will be discussed in more detail later in this chapter. 

If a surface-sensitive solid is processed in one site and needs to be transported to the analysis site without exposure to the atmosphere, a vacuum briefcase or special transportation module needs to be used. This would consist of a small portable vacuum chamber that is capable of attaching and transferring samples between processing and analysis stations. Understandably, designs of such instruments are system specific and often complicated. Most manufacturers of vacuum and surface analysis systems can offer customized options for specific systems. 

The sample preparation chamber on a surface analysis system (AES, XPS) is fitted with an ion gun for depth profiling (see diagram). The gun can be differentially pumped to maintain the required pressure difference between the ion source and the preparation chamber, which is initially fitted with a TMP with 5eff = 50 L s 1. 

The evacuated spectrometer (p < 10 mbar) was attached to a small UHV chamber using calcium-fluoride windows. The small UHV chamber was part of a larger surface analysis system. The polymer films were produced in the vacuum system by vapor deposition and analyzed in ultra-high vacuum without exposure to air. 

To combine optical SFG spectroscopy with the more traditional surface analysis methods (e.g., LEED, AES, TPD, XPS), the basic requirement is to simply add IR-transparent windows (e.g., CaF2 or BaF2) to a UHV chamber. However, if SFG spectroscopy is to be carried out at high pressure or during catalytic reactions, instruments combining a EIHV surface analysis system with an SFG-compatible... 

It is important to consider the connection between the two types of studies. One often refers to the "pressure gap" that separates vacuum studies of chemisorption and catalysis from commercial catalytic reactions, which generally run above —often well above — atmospheric pressure. There is simply no way to properly simulate high pressure conditions in a surface analysis system. Reactions can be run in an attached reaction chamber, which is then pumped out and the sample transferred, under vacuum, into an analysis system equipped for electron, ion and photon spectroscopies. However, except for some optical and x-ray methods that can be performed in situ, the surface analytical tools are not measuring the system under reaction conditions. This gap is well recognized, and both the low- and high-pressure communities keep it in mind when comparing their results. 

Figure 6. Schematic of UHV surface analysis system equipped with sample isolation cell for high pressure (1-20 atm)...

Schematic drawing of the VG ESCALAB 220i-XL surface analysis system, which consists of an analysis chamber, a multiport carousel chamber, an evaporation chamber, and a sample load lock chamber.

The static contact angle was measured for each membrane before and after carbonization using the VCA optima surface analysis system (AST Products, Inc., Billerica, MA). For each membrane the contact angle was measured at five different spots and the values were averaged. 

Examination of the surface roughness and homogeneity by optical microscopy or by SEM (usually available with SAM in most surface analysis systems), followed by selection of a flat area for analysis. 

Commercial surface analysis systems have been available since around 1970 (1). Most of the early instruments were dedicated to longer-term fundamental research, even if they were located at industrial research centers. However. since the latter part of the 1980s, the most popular surface analytical techniques. Auger electron spectroscopy (AES), secondary-ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS), have gained a greater level of acceptance in industry due to their improved reliability. Surface analysis is now routinely used to solve complex industrial problem.s in both research and quality assurance environments. It has been specifically the move toward the use of these techniques in quality-assurance-type applications that has started to force the development of national/international documentary standards in order to formalize the methods of application of the techniques. 

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