Low-Temperature Epitaxial Growth of CeO 2(110)/Si(100) Structure by Evaporation under Substrate Bias

Epitaxial growth of CeO2 layers on silicon (100) substrates is studied using electron-beam evaporation under substrate bias application in an ultrahigh vacuum. Both negative and positive biases are proved to be effective for lowering the epitaxial temperature. Sample current characteristics are measured as a function of the bias voltage. Under negative bias condition, as the bias voltage increases, the sample current varies from negative to positive with a transition point at -42 V and then reaches a saturation value of ∼ +4 µA above -60 V. Use of a negative bias of -60 V leads to epitaxial growth temperature lowering of at least 40°C. Under positive bias application, the sample current is negative and increases with the bias voltage, where the sample current components are anions and electrons (46%) as determined by mass separation with magnetic field application. It is experimentally clarified that the degree of enhancement of epitaxial growth is greater than that in the negative bias experiment (epitaxial growth temperature lowering of more than 55°C) and the enhancement is attributed to the electron component. It is found that a negative current of ∼ -0.15 mA flows at zero bias, indicating that even in conventional evaporation, electrons somewhat promote epitaxial growth.