DOE OSTI2014
Tantalum oxide has shown promising electrical switching characteristics for memristor devices. Consequently, a number of reports have investigated the electrical behavior of TaO{sub x} thin films. Some effort has been made to characterize the composition of the TaO{sub x} films and it is known that there must be an optimal stoichiometry of TaO{sub x} where forming and switching behavior are optimized. However, many previous reports lack details on the methodology used for identifying the chemistry of the films. X-ray photoelectron spectroscopy has been the most commonly used technique; however, peak fitting routines vary widely among reports and a native surface oxide of Ta{sub 2}O{sub 5} often confounds the analysis. In this report a series of large area TaO{sub x} films were deposited via sputtering with controlled O{sub 2} partial pressures in the sputtering gas, resulting in tunable oxide compositions. Spectra from numerous samples from each wafer spanning a range of oxide stoichiometries were used to develop a highly constrained peak fitting routine. This procedure allowed for the composition of the TaO{sub x} films to be identified with greater detail than elemental ratios alone. Additionally, the peak fitting routine was used to evaluate uniformity of deposition across individual wafers. The appearance of a greater contribution of Ta{sup 4+} oxidation states in the oxygen starved films are believed to relate to films with optimal forming characteristics.