Methods for the Evaporation of Solid Materials

The temperature in a Scandinavian source is, for example, around 1000°C. If this is not enough for certain elements, one may use a hollow cathode source which operates at 1500 - 2000°C or even a special high-temperature source using electron bombardment for the vaporization of the material. In that way one may achieve temperatures as high as 3000° 

Another possibility is the sputter ion source. Here inside the source gaseous ions are accelerated to the reflector electrode containing an insert made of the element to be vaporized. Due to the sputtering effect, the material evaporates and is converted into ions. This technique is universal and applicable for all elements. Fig. 17 shows a sketch of a sputter source  

If one does not have the possibility of using different sources for different elements, one may feed the source with compounds more volatile than the elements. Chlorides, fluorides, and oxides, in particular, are useful feed materials. Unfortunately, some compounds, which are otherwise suitable, tend to undergo thermal decomposition in the source and therefore have to be eliminated. Others, such as some chlorides, are extremely sensitive to water and hence converted under normal experimental conditions into their non-volatile oxides. To overcome this difficulty, the CCI4 method was developed. With it the desired element is stored as an oxide in a rather hot zone near the inlet of the ion source. By passing CCI4 over the oxide an in situ chlorination takes place and the resulting chloride is immediately swept in- 

A compilation of evaporation methods for the different elements has been published by Freeman and Sidenius  

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Chemical Effects of Ion Bombardment 3.2,5 Methods for the Evaporation of Solid Materials... 

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