Sputtering methods

The ability to perform mass spectrometry on analytes directly on the (HP)TLC sorbent removes the need to recover them prior to analysis. This greatly reduces the amount of work required to confirm identity. As TLC methods are developed for larger and more nonvolatile sample molecules, the use of sputtering methods will undoubtedly become increasingly important. 

As evident from Scheme 7.13, most modern ionisation techniques have been used for TLC-MS, and no single ionisation method is used exclusively with TLC-MS. Various ionisation methods may be applied that avoid the need to evaporate the sample into an El or Cl source these are based in particular on sputtering (FAB, SIMS) or laser desorption. Several sputtering methods of ionisation do not require the use of a liquid matrix, e.g. TLC-SIMS [797], Recent developments include the use of matrix-assisted laser desorption ionisation (MALDI) and surface-assisted laser desorption ionisation (SALDI). It is obvious that TLC-MS is complemented with TLC-MS11 [800] and TLC-HRMS techniques. Table 7.82 lists the general characteristics of TLC-MS. 

Tanahashi I, Manabe Y, Tohda T, Sasaki S, Nakamura A (1996) Optical nonlinearities of Au/Si02 composite thin films prepared by a sputtering method. J Appl Phys 79 1244-1249... 

K.R. Zhang, F.R. Zhu, C.H.A. Huan, and A.T.S. Wee, Effect of hydrogen partial pressure on optoelectronic properties of indium tin oxide thin films deposited by radio frequency magnetron sputtering method, J. Appl. Phys., 86 974—980, 1999. 

Takahashi M, Tsukigi K, Dorajpalam E, Tokuda Y, Yoko T (2003) Efficient photogeneration in Ti02A/02/Ti02 multilayer thin film electrodes prepared by sputtering method. J Phys Chem B 107 13455-13458... 

Sputtering Method. The high-voltage (around 1000 V) and low-current (microampere) plasma process is called glow discharge. Under this plasma condition (cold plasma), solid materials are sputtered by the bombardment of accelerated positive... 

Fig. 9.4.11 Apparatus for the gas flow-sputtering method. A sputtering gas (mixture of He and 40% H2) was supplied from nozzle A. Produced particles are flowed into the other port B and trapped by a solution trap apparatus cooled at approximately - 50°C. (From Ref. 16.)...

In many cases, particularly with evaporation and sputtering methods, adhesion of the deposited film to the substrate may be inherently poor. It is extremely desirable in such cases to deposit a thin layer of an intermediate material that has better adhesion to the substrate. Examples of appropriate adhesion layers are discussed after presentation of evaporation and sputtering techniques. 

Finally, the carbide phases obtained by reactive sputtering are not the same as those obtained by reaction of the metal film with the gas. In this last case it is indeed possible to be closer to the equilibrium thermodynamic conditions than in the sputtering method. 

Zheng, S. K., Wang, T. M., Xiang, G. and Wang, C. (2001). Photocatalytic activity of nanostruc-tured Ti02 thin films prepared by dc magnetron sputtering method. Vacuum 62(4), 361-366. 

Figure 6.21 shows the AC impedance spectra for the cathodic ORR of the cell electrodes prepared using the conventional method and the sputtering method. It can be seen that the spectra of electrodes 2 and 3 do not indicate mass transport limitation at either potentials. For electrode 1, a low-frequency arc develops, due to polarization caused by water transport in the membrane. It is also observable that the high-frequency arc for the porous electrode is significantly depressed from the typical semicircular shape. Nevertheless, the real-axis component of the arc roughly represents the effective charge-transfer resistance, which is a function of both the real surface area of the electrode and the surface concentrations of the species involved in the electrode reaction. 

Figure 6.21. AC impedance spectra for the cathodic ORR of the cell incorporating electrodes prepared by a the conventional method (electrode 1), b the sputtering method with 50 A rate (electrode 2), and c the sputtering method with 100 A rate (electrode 3) [21]. (Reproduced by permission of ECS—The Electrochemical Society, from Cha SY, Lee WM. Performance of proton exchange membrane fuel cell electrodes prepared by direct deposition of ultrathin platinum on the membrane surface.)...

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