Method for producing a beryllium oxide film

A method for preparing a film of beryllium oxide comprising:

• heating metallic beryllium in a closed crucible having at least one injection nozzle, thereby vaporizing said beryllium metal;
• injecting said vapor through said nozzle into an evacuated chamber, whereby a stream of beryllium atoms is produced, while simultaneously injecting oxygen into said chamber around said stream to provide an atmosphere of oxygen having a pressure not greater than 10.sup.-2 of the vapor pressure in said crucible;
• ionizing at least part of said vapor stream by irradiating said vapor stream with electron beams whereby a vapor stream containing ionized and unionized atoms is produced;
• and
• permitting said vapor stream containing ionized and unionized atoms to impinge on a substrate surface together with said oxygen thereby forming a film of beryllium oxide on said substrate.