Sputtering pulsed mode

Hollow cathode gas flow sputtering operates in the pressure range of 0.1-1 mbar. The particles are thermalized at the substrate. Plasma activation of growth processes can be achieved either by applying a substrate bias or by pulsed mode operation of the discharge. 

GoB, D., Frach, P, Zywitzki, O., Modes, T., Klinkenberg, S. and Gottfried, C. (2005). Photo-catalytic titanium dioxide thin films prepared by reactive pulse magnetron sputtering at low temperature. Surf. Coat. Technol. 200( 1—4), 967-971. 

Laser SNMS requires the operation with properly selected duty cycles that control the delay times between the primary ion pulse, a pulsed extraction voltage for separating the secondary ions from post-ionized neutrals, and the firing of the postionizing laser pulse. Such duty cycles have, in addition, to be synchronized with the stepwise motion of the pulsed primary ion beam across the sample surface in the microprobe mode of laser SNMS. The selection of appropriate duration and decay times of the ion and laser pulses, of the laser intensity, and beam shape is important to make the photoion yields independent on the sputtered particle velocities. The detection volume must be matched to the entrance ion optics of the TOP such that it becomes independent of the individual ionization process. Usually, laser intensities in the range from 10 to lO Wcm are applied. While the particle density in the detection volume is monitored at small laser intensities, the particle flux is measured at high photon densities. 

There also exist different pulse sequences for the analysis and sputter beams during depth profiling. These are referred to as the interlaced or interleaved and the noninterlaced or Phase modes. Both essentially produce the same result on conductive samples when species present in the gas phase are not of interest, i.e. Hydrogen, Carbon, Oxygen, and Nitrogen. When these are of interest, the interlaced mode is preferred. 

With the exception of one variant of the last, all nse a single continuous primary ion beam that can be operated over a large range of primary ion dose values. Time-of-Flight instruments utilizing pulsed primaiy ion beams reqnire a low-dose analysis primary ion beam. To contend with this, a second primaiy ion beam is often employed. This is referred to as the sputter primaiy ion beam. The presence of two primary ion beams introduces further variables dependent on how these are operated, which will enhance either the mass resolntion or the spatial image resolution, but at the expense of the other. Additional modes can, however, be implemented to minimize the loss. 

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