XPS and ToF-SIMS Characterization of a BiTeSe Write Layer for Permanent Optical Tape Storage Hao Wang, 1 Anubhav Diwan, 1 Barry M. Lunt, 2 Robert C. Davis, 3 Matthew R. Linford 1 1 Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602 2 Department of Information Technology, Brigham Young University, Provo, UT 84602 3 Deparment of Physics and Astronomy, Brigham Young University, Provo, UT 84602 1. Introduction Magnetic tape is widely used to back up the data of large organizations. [1] However, it is not believed to last more than ca. 30 years and data migration often begins sooner. We recently proposed that a write layer similar to that in an archival DVD (the M-Disc TM , see www.mdisc.com) could be deposited onto Mylar to create a flexible optical storage medium that might show similar permanency to the M-Disc TM (1000+ years) and perhaps be a replacement for magnetic tape. [2] This write layer consists of a Bi-Te-Se (BTS) alloy that is sandwiched between two reactively sputtered carbon films. [3] The composition of the BTS film was confirmed by Rutherford backscattering (RBS) and it could be marked with a laser to yield 2 – 3 µm spots. [3] A previous study also showed that the film should be readily manufacturable and that it does not delaminate. [4] Here we describe characterization of this layer using X- ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS and ToF-SIMS suggest that the BTS film is stable over the time period in which it was analyzed (ca. 3 months). Fig. 1. XPS survey spectrum (A), and narrow scans of Bi, Te, and Se (B)—(D) from a BTS thin film. 2. Experimental BTS thin films were deposited onto Si(100) substrates by co-sputtering Bi and Te-Se targets. [3] The BTS film thicknesses for this study were ca. 42 nm, as determined by tapping mode AFM. The chemical composition of the BTS layer was probed by XPS (SSX-100 system, Al Kα X-rays) and ToF-SIMS (ION-TOF IV system, Ga + primary ions). Longevity tests of the films were performed by regularly repeating XPS and SIMS measurements on the same sample over a period of weeks. 3. Results & discussion Figure 1A is an XPS survey spectrum of the BTS thin film. Signals attributable to Bi, Te, and O are obvious. The Se 3d signal is relatively weak. Figure 1B—1D shows XPS narrow scans of Bi, Te, and Se. The Bi narrow scan shows the expected Bi 4f 5/2 (164 eV) and 4f 7/2 (159 eV) peaks. The presence of these two signals, and no others, suggests that the Bi is in a single oxidation state although the signals are shifted ca. +2 eV from those of metallic Bi.