Preparation chamber

Neff H, Foditsch W and Kdtz R 1984 An electrochemical preparation chamber for the Kratos ES 300 electron spectrometer J. Electron. Spectrosc. Relat. Phenom. 33 171-4... 

Figure 6. Plan of the target preparation facilities consisting of UHV preparation chamber (a), (reactive) ion etching chamber (b), ion etching gun (c), laser (d), photon detector (e), transfer arms (f), Auger system for surface analysis (g), sample manipulator and annealing facility (h), load lock and optical microscope for viewing sample (i), evaporator (j), transmission diffractometer (k), and vacuum tank for main spectrometer (1).

Fig. 8. Electrochemical preparation chamber for a Kratos ES 300 photoelectron spectrometer with fast insertion lock. After [38],...

The best approach is of course a fully UHV compatible set-up with an electrochemical preparation chamber which fulfills UHV standards with respect to cleanliness and pressure control. The electrochemical chamber is filled with argon at atmospheric pressure only during the electrochemical treatment. Afterwards the chamber can be pumped down directly. Such a system was first described by O Grady [39] and was also used by Ross [40], Hubbard [41], Gerischer [42], and Streblow [36]. 

To reduce the exposure to residual gas from the vacuum, our samples are sputtered/annealed in separate preparation chambers attached via valves to the SPM chambers. After the final anneal cycle of the cleaning procedure, the sample is transferred to the SPM chamber within a minute or so where the pressure is lower. 

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 sample is to be bombarded with argon ions at a minimum beam current of 1 pA with the preparation chamber at 1 O 8 mbar. The gun is operating at a current density of 1 mA cm 2 and an electron current of 10 mA. The constant for the gun in 5 mbar 1. 

To maintain 10-8mbar in the preparation chamber pumped with a 50 Ls 1 TMP ... 

At the end of the reactivity measurements the sample is transferred back to the preparation chamber where a carbon film is deposited on the sample. This carbon layer has a double use. First, it protects the clusters against a further evolution (coalescence, restructuring, oxidation during air exposure) and second, in the case of MgO crystals it will serve as a thin support for the metal particles (after floating in acidic solution) for subsequent TEM characterization [12]. 

This experimental assembly is much more complex than the preceding one. The oxide surfaces are ultrathin alumina films grown on NiAl(l 1 0) single crystals, in the preparation chamber following a standard procedure [16]. The alumina films are characterized in situ by AES and LEED. The metal clusters are prepared by vacuum condensation at RT of a metal atoms beam generated by an electron bombardment evaporator calibrated by a quartz microbalance. Metal atoms condense only on the sample through an aperture placed closed to it. After preparation the sample is transferred in the reaction chamber. The characterization of the metal clusters is based on STM observations of deposits performed in the same conditions in another UHV chamber [16]. 

The metal-on-polymer interface has been the most studied Interface as metals can conveniently be deposited by evaporation in situ 1n a controllable fashion in a UHV system (26-33). In the case of polyimide, Cu and Cr have been the most studied metals but other metals including N1, Co, Al, Au, Ag, Ge, Ce, Cs, and Si have been studied. The best experimental arrangement includes a UHV system with a load lock Introduction chamber, a preparation chamber with evaporators, heating capabilities, etc., and a separate analysis chamber. All the chambers are separated by gate valves and the samples are transferred between chambers under vacuum. Alternative metal deposition sources such as organometall1c chemical vapor deposition are promising and such techniques possibly can lead to different interface formation than obtained by metal evaporation(34). 

Apparatus. The experiments were performed in a vacuum system consisting of a preparation chamber and an analysis chamber separated by a gate valve. The preparation chamber was pumped by a 150 1/s turbo pump to a base pressure of lxl0 mbar. A quadrupole residual gas analyzer (RGA) was connected to the pumping line of the chamber. It did not have a direct line-of-sight to the specimen. Gases could be admitted to the chamber as desired through a variable leak valve. In the preparation chamber, the specimen could be mounted in a heatable support where it could be irradiated with an electron gun. A transfer device allowed the specimen to be moved to the analysis chamber without exposure to air. 

The analysis chamber was equipped with diffusion and Ti-sublimation pumps and had a base pressure of 1x10 mbar It was also equipped with an RGA identical to the one on the preparation chamber. In this chamber the specimen could be analyzed by XPS and heated by a resistive element Incorporated in the specimen mount. 

Specimen Conditioning. The sample was first placed in the preparation chamber and heated to 350 C. During this first heating in vacuum, there was normally some evolution of gas. The mass spectrum of the gas closely matched that of the tetrafluorethylene monomer. 

Irradiation. Samples were irradiated with electrons in the preparation chamber. The electron accelerating voltage was 3 keV. The beam current was 0.7 fiA and was measured by directing the beam into a hole in the sample support which was biased 30 volts positive. After the beam current was stable, the specimen was placed on the support and the beam was rastered over an area of 1.3 cm which covered the entire PTFE surface, and an absorbed-current image of the specimen was displayed. 

Heating and Mass Spectroscopy. Specimens were prepared as described above but using a Ni stub which had an attached thermocouple. The specimens were placed on a heatable sample mount in the preparation chamber and irradiated. The sample temperature was then raised at a rate of 20 C/min to 30 C/min from 100 C to 300 C. The RGA continuously recorded the spectral intensities at 19, 24, 31, 50, 69, 81,... 

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