Efficient Positron Moderation with A Commercial 4H-Sic Epitaxial Layer

We have studied the properties of a commercially available 4H-SiC epitaxial layer and evaluated its potential application as an efficient positron remoderator. A remoderation efficiency of more than 65% has been measured for incident positrons with 1 keV energy. We have determined the work function and the energy distribution of the emitted slow positrons, a property which is essential for practical applications. Comparison of the positron moderation properties of the epitaxial layer with results from a n-type 4H-SiC single crystal, indicate that the epitaxially grown layer is a superior secondary moderator than its substrate counterpart.