AN ABSTRACT OF THE THESIS OF Fanghui Ren for the degree of Master of Science in Electrical and Computer Engineering presented on June 14, 2012. Title: Radiation Tolerance of Magnetic Tunnel Junctions with MgO Barriers

approved: ______________________________________________________ Albrecht Jander In the next decade, technology trends—smaller dimension, lower voltage, higher operating frequency—introduce new technical considerations and challenges for radiation effects in integrated circuits. Semiconductor based circuits and traditional dynamic random-access memories will malfunction when exposed to extreme environments, such as space and nuclear reactor. The mechanisms for radiation effect are mainly attributed to the radiation-induced charging of the oxide in a CMOS device. Spintronics is an emerging area of nanoscale electronics involving the detection and manipulation of electron spin. The magnetic tunnel junctions (MTJs), based on the intrinsic spin of the electron, can be used as the storage elements in non-volatile magnetoresistive random-access memories (MRAMs). In this effort, we study radiation tolerance of MTJs by exposing the devices in gamma and neutron radiation environment. Theoretical model for the radiation-induced defects is analyzed in this work. Experiments of the MgO-based MTJs under the conditions of preand postradiation are concluded. MTJs were irradiated with gamma ray to a total dose of 10 Mrad. During the neutron irradiation, total epithermal neutron fluence up to 2.9×10 15 /cm 2 was obtained. The experimental results show that neither the electrical nor the magnetic properties of MTJs are affected by the radiation. ©Copyright by Fanghui Ren June, 14, 2012 All Rights Reserved Radiation Tolerance of Magnetic Tunnel Junctions with MgO Barriers