Enriching<sup>28</sup>Si beyond 99.9998 % for semiconductor quantum computing

Dwyer, Kevin; Pomeroy, Joshua M.; Simons, David S.; Steffens, Kristen L.; Lau, June W.

doi:10.1088/0022-3727/47/34/345105

Cited by 25 publications

(43 citation statements)

References 37 publications

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“…These calculations use Gaussian fits to the mass peaks to determine the overlap of the 29 u peak on the 28 u peak. They give a peak separation of about 11 σ (standard deviations) and a resolving power m /Δ m ≈ 80 for m = 28 u, which yields a lower bound on the fraction of ions at 28 u consisting of 29 Si of roughly 10 −25 , as previously discussed elsewhere 16 . However, this argument neglects gas scattering effects, which would likely be a dominant contributing factor to the contamination compared to this extremely small geometric component.…”

Section: Experimental Methodssupporting

confidence: 56%

“…This system injects commercial, natural abundance SiH 4 source gas into a high vacuum Penning-type ion source generating a Si + ion beam and then mass filters the ions in a magnetic field before depositing them onto heated Si(100) substrates. The mass separation principle and ion beam system used here have been described in more detail elsewhere 16,20 . Previously, we analyzed SiH 4 incorporation in samples deposited at room temperature, but now we examine the temperature dependence of s ( T ) at temperatures required to facilitate epitaxial growth.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Achieving single crystal epitaxial deposition of 28 Si films on Si(100) substrates requires elevated substrate temperatures during deposition. We previously showed that for amorphous room temperature deposition, the 29 Si in the film could be accounted for by 29 SiH 4 incorporation into 28 Si films due to a physical adsorption process which was coincident with the ion beam deposition 16 . Depositing with an elevated substrate temperature is expected to lead to a change in the activation of the 29 Si contamination through a chemical activation process described by a reactive sticking coefficient that is similar in nature to chemical vapor deposition (CVD).…”

Section: Introductionmentioning

confidence: 92%

“…The lack of simply produced, readily available, and consistently highly enriched 28 Si has led us to develop a mass selected ion beam deposition system capable of taking natural abundance silane (SiH 4 ) gas and enriching it in situ to an extremely high level of 28 Si just prior to depositing it epitaxially on a target Si(100) substrate. Using this system, thin films of highly enriched materials including 28 Si have previously been grown amorphously on Si substrates at room temperature 15,16 as well as epitaxially at higher temperatures (this work). Several other groups have also previously demonstrated enriched 28 Si thin film deposition using an ion beam system, though not generally with a focus on high quality material (highly enriched, chemically pure) for QI 17–19 .…”

Section: Introductionmentioning

confidence: 99%

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Temperature-dependent Si29 incorporation during deposition of highly enriched Si28 films

Dwyer

Kim

Simons

et al. 2017

Phys. Rev. Materials

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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 develop the ability 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 in enriched samples deposited from ≈ 250 °C up to 800 °C. The 29Si isotope fraction is found to increase from < 1 × 10−6 at the lower temperatures, up to > 4 × 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 × 10−4 at 500 °C to 2.3 × 10−2 at 800 °C. We determine an activation energy of 1.00(8) 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.

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Section: Experimental Methodssupporting

confidence: 56%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Temperature-dependent Si29 incorporation during deposition of highly enriched Si28 films

Dwyer

Kim

Simons

et al. 2017

Phys. Rev. Materials

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“…The presence of the 29 Si and 30 Si isotopes decreases the phase coherence time of qubits in quantum information systems. Long coherence times are achieved using highly enriched 28 Si [3]. On the other hand, 29 Si is used for studying information on nuclear-spin systems [4].…”

Section: Introductionmentioning

confidence: 99%

Silicon Isotope Separation by two frequency IRMPD

Risaro¹,

D'Accurso²,

Codina³

et al. 2017

Opt. Pura Apl.

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ABSTRACT:InfraRed Multi-Photon Dissociation (IRMPD) is a highly selective laser isotope separation technique. This process consists of a sequential IR photon absorption from the ground vibrational state up to dissociation by a molecule that contains the isotope of interest. High dissociation threshold molecules require large intensity radiation fields. This drawback could be overcome by two-frequency IRMPD. In this technique, a low energy laser resonant with the first energy levels guarantees isotopic selectivity excitation and a second non-resonant large energy laser achieves molecular dissociation. The possibility of obtaining silicon laser isotopic enrichment using SiF4 as working molecule was investigated in this work. Two-frequency IRMPD of SiF4 with two TEA CO2 single transverse mode lasers was studied in a molecular jet. The dissociation process was monitored with a Time-of-Flight mass spectrometer with UV multi-photon ionization. The excitation laser fluence and wavelength dependence of the isotopic dissociation estimator, α, and the enrichment factor estimator, β, were determined and compared to those obtained in single-frequency IRMPD.Key words: isotope separation, laser, silicon, infrared multiphoton dissociation. RESUMEN:La Disociación Multifotónica InfrarRoja (DMFIR) es un método de separación de isótopos con láser altamente selectivo el cual consiste en la absorción secuencial de fotones resonantes con un modo de vibración de la molécula que contiene el isótopo de interés, desde el estado fundamental hasta sobrepasar el umbral de disociación. Las moléculas con umbrales de disociación alto requieren láseres de alta energía. Esta desventaja puede superarse mediante la DMFIR con dos frecuencias. En esta técnica, un láser de baja energía, resonante con los primeros niveles vibracionales garantiza la selectividad isotópica del proceso y otro, menos restrictivo en sintonía, pero de alta fluencia produce la disociación molecular. En este trabajo se investigó la posibilidad de obtener enriquecimiento isotópico utilizando SiF4 como molécula de trabajo. Se estudió la DMFIR de SiF4 con dos frecuencias provenientes de dos láseres de CO2 TEA monomodo transversal en un jet molecular. Como sistema de detección se utilizó un espectrómetro de masas de tiempo de vuelo con ionización multifotónica UV. Se determinó el efecto de la variación de la fluencia y longitud de onda de los láseres de excitación y de disociación sobre los valores de los estimadores α y β asociados a la eficiencia de la disociación y al grado de enriquecimiento isotópico obtenido, respectivamente, y se comparó con los resultados obtenidos en la DMFIR con una sola frecuencia.Palabras clave: separación de isótopos, láser, silicio, disociación multifotónica infrarroja. 413-415 (1997).https://doi.org/10. 1080/18811248.1997.9733683 [12] A. Yokoyama, H. Ohba, M. Hashimoto, K. Katsumata, H. Akagi, T. Ishii, A. Ohya, S. Arai, "Silicon isotope separation utilizing infrared multiphoton dissociation of Si2F6 irradiated with two-frequency CO2 laser ligh...

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