Electron-gun evaporation

Co-condensation of Hf and Zr atoms from an electron-gun evaporation device, with P(Me)3 and arenes at 77K gave good yields of the species [M(arene)2P(Me3)]. Metal vapor synthesis led to Fe(i7 -arene)L2 and Fe(i7 -arene)-(i7 -diene), where L is a phosphorus ligand. In addition, complexes of stoichiometry Fe(T) -diene)L3 (where L is again a... 

The vaporization-cold-substrate condensation process of boron carbide melted by electron-gun heating and plasma torch deposition does not give a well-organized and crystalline B4C-type structure. In CH4 [1.33.10 Pa 1 torr)] an electron-gun evaporation of boron carbide contained in a graphite crucible, followed by a condensation on a water-cooled jacket, gives crystals. Sputtering by H is possible . 

Electron-gun evaporation has the advantage that changes in the desired concentration of the deposited film can be made rather easily. 

Micro-cubes of MgO and prisms of ZnO were obtained by burning a Mg or Zn ribbon in a mixture of pure gases (N2 + O2) at 700 torr. The oxide smokes were collected on microscope grids covered with an amorphous carbon film. Thin films of ZnO (00.1) were produced on a lamellar crystal of mica, from an electron-gun evaporator. MgO single crystals were cleaved in dry air and quickly annealed under ultra-high vacuum (UHV) at 900 °C. 

Herd (1979) and Graczyk (1978) propose that structural inhomogeneities are the source of large positive values and that these inhomogeneities are due to phase separation. The phase separation was assumed by Herd to involve anisotropically shaped Co-rich clusters. They furthermore considered it to be the universal source of in both bias-sputtered films and films obtained by means of electron gun evaporation techniques. Their evidence for this was obtained by means of TEM investigations on samples prepared in different ways. 

Fig. 4. Schematic of an ultrahigh vacuum molecular beam epitaxy (MBE) growth chamber, showing the source ovens from which the Group 111—V elements are evaporated the shutters corresponding to the required elements, such as that ia front of Source 1, which control the composition of the grown layer an electron gun which produces a beam for reflection high energy electron diffraction (rheed) and monitors the crystal stmcture of the growing layer and the substrate holder which rotates to provide more uniformity ia the deposited film. After Ref. 14, see text.

From Fig. 6.14 it becomes clear why one must heat filaments to very high temperatures to see electron emission in electron guns. Only the part of the electron distribution that has obtained energies above 0 can be utilized. The occupation number at the vacuum level can be approximated by e hT leading to the well known Richardson-Dushman formula, which describes the fluxj of electrons evaporating from a surface with work function 0 at temperature T ... 

Both characteristic X-ray line and continuous spectra were used to evaluate the performances of the resists. To determine exposure parameters (i.e. sensitivity and contrast) irradiations were carried gut in this study using the aluminum Kot- 2 emission line at 8.3t A generated by means of a modified Vacuum Generators Limited model EG-2 electron beam evaporation gun. The resist samples were exposed through a mask (A) consisting of a range of aluminum foils of different thicknesses supported on an absorbing nickel frame in order to vary the X-ray flux. 

Table I. Power input and rates of evaporation of metals from a 0.5ml hearth of the positive hearth electron gun furnace...

The electron-beam guns may also be integral parts of several special pieces of equipment. Electron-beam evaporation and the related directed vapour deposition technology are relevant examples. 

Figure 9 shows an arrangement for measuring secondary electron emission. An electron gun with an incandescent tungsten cathode and the electrodes Bi and Bi is situated in the lower part of the cell. The secondary emitting target P carries the catalyst. A layer of the latter can also be evaporated from Ey or Ei, and deposited on P, which can be heated by radiation or electron bombardment from D. The leads FF of a... 

The rotatable reactor can also be used for reactions in fluids having suitably low (< 10"3 Torr) vapor pressure. In this mode, metal atoms are evaporated upwards into the cold liquid, which is spun as a thin band on the inner surface of the flask. Reactions with dissolved polymers can then be studied. Specially designed electron gun sources can be operated, without static discharge, under these potentially high organic vapor pressure conditions (6). Run-to-nin reproducibility is obtained by monitoring the metal atom deposition rate with a quartz crystal mass balance (thickness monitor). 

The operation of an ESEM is made possible through use of a differential pumping system (Figure 7.36) that maintains a UHV environment (10 Torr) required for the electron gun, while allowing the presence of gases in the sample chamber (10-20 Torr). The pressure and temperature of the sample chamber may be strictly controlled, inducing evaporation or condensation events. 

Cathodes of electron guns (W, W-ThOa) for example, for electron beam evaporation. 

A rotatable reactor for synthesis using low temperature cocondensation was introduced by Green and co-workers to provide better separation of the evaporate and substrate vapors in order to reduce pyrolysis of the latter at the furnance.(14) As shown in Figure 4, the electron gun (or some other furnace) is used to deposit a layer of atoms into a pre-deposited layer of substrate on the inner top surface of the rotating flask. In this manner, layer upon layer of solid accumulates. Isolation of the products follows procedures like those developed for the static devices. 

A more reliable and rapid technique for evaporating both shadowing metals and carbon is via electron beam bombardment. This method makes use of a focused flux of high-energy electrons to provide the necessary power for the evaporation of a small metal or carbon source. Generally, this is used to form thin films of Pt/C, W/Ta, and pure C. The platinum films contain some carbon (usually <596) due to the presence of the carbon support rod. The electron beam gun evaporation approach greatly improves throughput and consistency compared to the other approaches. 

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