AVS 61st International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM1-ThA

Paper EM1-ThA3
28Si Enriched In Situ to 99.9998 % for Quantum Computing Devices

Thursday, November 13, 2014, 3:00 pm, Room 311

Session: Materials for Quantum Computation
Presenter: Kevin Dwyer, University of Maryland, College Park
Authors: K.J. Dwyer, University of Maryland, College Park
J. Pomeroy, National Institute of Standards and Technology (NIST)
D. Simons, National Institute of Standards and Technology (NIST)
Correspondent: Click to Email
We are enriching in situ and depositing epitaxial thin films of 28Si in support of quantum computing devices. Highly enriched 28Si is a critical material for quantum computing as removal of 29Si spins provides a non-interacting “semiconductor vacuum” medium for qubits such as 31P donors which have electron and nuclear coherence (T2) times of seconds and minutes respectively even up to room temperature. 31P donors can also be addressed optically due to hyperfine transitions not normally resolvable in natural Si. Starting with natural abundance silane, we have used mass filtered ion beam deposition to produce 28Si films enriched to > 99.9998 % with a residual 29Si isotope fraction < 1 ppm (40 times less than previously reported 28Si sufficient for optical addressing). Using our ion beam system we have grown crystalline 28Si films and are pursuing characterization of their structural properties using in situ reflection high energy electron diffraction (RHEED), in situ scanning tunneling microscopy (STM), and transmission electron microscopy (TEM). Secondary ion mass spectrometry (SIMS) is used to determine enrichment of crystalline 28Si films. As we move away from silane towards a solid sputtering source, enrichment may be improved even further and the use of additional materials such as Ge can become possible. Numerous experimental systems can take advantage of 28Si as a medium for qubits including STM based hydrogen lithography devices, single donors coupled to single electron transistors, and quantum wells. We have demonstrated the ability to produce isotope heterostructures with applications including fully enriched 28Si/28Si74Ge quantum wells. The importance of 28Si to quantum information systems and the scarcity of such material make clear the critical need for an alternate source of enriched silicon such as the one we demonstrate.