Charging problems

Some disadvantages for SEM measurements, compared with data from mechanical and optical profilers, are that the sample must be inserted into a vacuum system, and charging problems can make the analysis of insulators difficult. SEMs are also much more expensive than profilers. 

Charging problems have limited the UHV work largely to metals and absence of organometallic complex analogs to metals has limited applications of work in this area largely to nonmetals. 

Fig. 45. Top-level organization of malfunction hypotheses for an existing batch polymer reactor with a focus on Step 1 Initial Charge problems.

The technique, although attractive, is experimentally rather complex charging problems can frequently occur, leading to the observation of elevated apparent binding energies, and interpretational difficulties exist. Thus, the X-PES of palladium(II) sulfoxide complexes are difficult to interpret unambiguously as the oxygen Is peak is nearly... 

Polymers. Molecular SIMS is an especially attractive surface analytical technique for the characterization of polymer surfaces because of its high surface sensitivity, molecular specificity over an extended mass range, and versatility in ionization. However, only a few polymer SIMS studies have been reported [104-113] due to the serious sample charging problems that occur with thick insulating films. 

The optimal value for k is k = 1 for / = 0 and k = 2 for l = +oo. On the other hand, numerical simulations on real molecular systems seem to show that, depending on the charge and shape of the system, the optimal value for k is between k = 0 and k= 1/2. The discrepancy between theoretical arguments and numerical results might originate in the escaped charge problem, that is addressed in the following section. 

E. Cances and B. Mennucci, The escaped charge problem in solvation continuum models, J. Chem. Phys., 115 (2001) 6130. 

The semiconducting properties of ZnO have nevertheless proved to be advantageous because they permit the extensive application of modern surface spectroscopies (such as XPS, UPS, EELS, and LEED) for the investigation of the surface structures since the charging problems that are usually encountered with oxides are avoided (393). For this reason, ZnO is one of the most thoroughly investigated oxides. 

There are still a number of surface systems where the structure cannot be determined by LEED for theoretical and experimental reasons. High Miller-index surfaces, such as stepped or kinked surfaces, have layers separated by very small distances normal to the surface. The calculational tools normally used for LEED break down in this case, and no new approach has yet been developed to solve this problem. Experimental difficulties restrict the study of insulator surfaces, because of charging problems, and of molecular crystal surfaces, because of beam damage problems. 

Since the AI2O3, in question, is a surface insulator, the ESCA examination of these systems must consider the aforementioned charging problem. In addition, since there is some question herein as to the distribution of a conductive metal in this insulator, one must also be cognizant of the more difficult feature generally labeled as differential charging (13). 

It also should be noted that we have herein, in effect, turned the charging problem around and made it an auxiliary morphological tool. In order to demonstrate the versatility of this tool, we have employed the aforementioned negative shift with cluster formation not only to study metals dispersions, but also to assist in the study of the integrity of thin film interfaces (16), and metals segregation during alloying corrosion (H). 

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