Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Temperature dependent 29Si incorporation during deposition of highly enriched 28Si films



Kevin J. Dwyer, Hyun S. Kim, David S. Simons, Joshua M. Pomeroy


In this study, we examine the mechanisms leading to 29Si incorporation into highly enriched 28Si films deposited by hyperthermal ion beams at elevated temperatures in the dilute presence of natural abundance silane (SiH4) gas. Enriched 28Si is a critical material in the development of quantum information devices because 28Si is free of nuclear spins that cause decoherence in a quantum system. We deposit epitaxial thin films of 28Si enriched in situ beyond 99.99998 % 28Si onto Si(100) using an ion beam deposition system and seek to systematically vary the enrichment and measure the impact on quantum coherence. We use secondary ion mass spectrometry to measure the residual 29Si isotope fraction (amount-of-substance fraction in mol/mol) in enriched samples deposited from ≈ 250 °C up to 800 °C. The 29Si isotope fraction is found to increase from < 1 x 10-6 at the lower temperatures, up to > 4 x 10-6 at around 800 °C. From these data, we estimate the temperature dependence of the incorporation fraction, s, of SiH4, which increases sharply from about 2.9 x 10-4 at 500 °C to 2.3 x 10-2 at 800 °C. We determine an activation energy of 1.00(18) eV associated with the abrupt increase in incorporation and conclude that below 500 °C, a temperature independent mechanism such as activation from ion collisions with adsorbed SiH4 molecules is the primary incorporation mechanism. Direct incorporation from the adsorbed state is found to be minimal.
Physical Review Materials


enriched silicon, quantum information, semiconductor


Dwyer, K. , Kim, H. , Simons, D. and Pomeroy, J. (2017), Temperature dependent 29Si incorporation during deposition of highly enriched 28Si films, Physical Review Materials, [online],, (Accessed May 18, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created November 15, 2017, Updated October 12, 2021