# Publication Citation: Enriching 28Si beyond 99.9998 % for semiconductor quantum computing

NIST Authors in Bold

Author(s): Kevin J. Dwyer; Joshua M. Pomeroy; David S. Simons; June W. Lau; Kristen L. Steffens; Enriching 28Si beyond 99.9998 % for semiconductor quantum computing August 05, 2014 Using a laboratory-scale apparatus, we enrich 28Si to 40 times better than previously reported starting from natural abundance silane gas and offer another source for providing these critical materials from the industrial gas centrifuge methods. Recent measurements demonstrating electron and nuclear spin coherence times exceeding seconds and many minutes, respectively, are a direct consequence of the use of highly enriched 28Si in those measurements, underscoring the importance of enriched silicon as a semiconductor vacuum" and the continued benefits of further enrichment. Using a mass spectrometry approach, silicon ions are produced from commercial silane gas and the isotopes are separated in magnetic sector analyzer before deposition onto a Si(100) substrate. Isotope fractions for 29Si and 30Si of < 1 x 10^{-6} are found in the deposited films using secondary ion mass spectrometry (SIMS). Assessment of the deposited films by X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM) are also presented as we work to develop substrates and source material to support the growing silicon quantum computing community. Additionally, the {\em in situ} enrichment method presented here allows for dual enrichment of compound materials like 28Si/74Ge and for heterostructures of enriched materials, which we demonstrate by modulating the 29Si concentration at multiple depths in a deposited film. Journal of Physics D-Applied Physics 47 34 6 pp. quantum information, enriched silicon, isotopic purification, SIMS, TEM, XPS Physics, Quantum Computing/Quantum Computation, Semiconductor Materials http://dx.doi.org/doi:10.1088/0022-3727/47/34/345105  (Note: May link to a non-U.S. Government webpage)