The key to grow ZnO on Si by radical source (RS)-MBE is surface nitridation of the Si substrate. Growth of ZnO on Si(1 1 1) has been carried out using NH, plasma nitridation of the Si surface prior to ZnO growth and strongly c-axis-orientated ZnO thin films were obtained. Strong excitonic PL emission around 3.38 eV was observed from ZnO on Si while Hall measurements showed n-type conductivity with an electron concentration of 1.87 x 10(18) cm(-3).