Characterization of Prototype BTeV Silicon Pixel Sensors Before and   After Irradiation
  We report on measurements performed on silicon pixel sensor prototypes exposed to a 200 MeV proton beam at the Indiana University Cyclotron Facility. The sensors are of n+/n/p+ type with multi-guard ring structures on the p+-side and p-stop electrode isolation on the n+-side. Electrical characterization of the devices was performed before and after irradiation up to a proton fluence of 4E14 p/cm2. We tested pixel sensors fabricated from normal and oxygen-enriched silicon wafers and with two different p-stop isolation layouts: common p-stop and individual p-stop. 
Maria R. Coluccia, J. A. Appel, G. Chiodini, D. C. Christian, and S.   Kwan