Research on ²⁸Si

The US National Institute of Standards and Technology has demonstrated that low-energy (<3 keV) 28Si+ ions could be directly deposited onto the surface of natural Si substrates to produce enriched 28Si layers with 1 ppm residual 29Si, using a purpose-built "hyperthermal" ion beam system.
Ultrahigh-vacuum levels were required to avoid oxidation of the deposited layer, but even then O (and C) concentrations were 1 × 10¹⁹ cm⁻³.

The University of Surrey explored increasing beam energies up to 20 keV where the use of conventional high current ion implanters could be possible.
Si beam transport could be significantly improved and surface layer oxidation avoided by implanting the 28Si into the body of a natural Si substrate.
However, the high Si self-sputtering rate (>1 ²⁸Si atoms/ion) in this energy regime limited the achievable enrichment level, and isobaric ¹⁴N₂⁺ and ¹²C¹⁶O⁺ (and even ⁵⁶Fe₂⁺) mass contamination from the implanter was found to be present./

Compared to enrichment by implantation directly into the substrate, the nature of the layer exchange process has introduced the new problem of Al contamination of the Si. However, it should be anticipated that Al will be present in the Si at its solid solubility level (0.75% at 500 °C), still too high for quantum grade Si which may be difficult to eliminate.

Quantum computing industry annual growth rate

Classification according to quantum computing platform

- Quantum computing platform based on semiconductor quantum dots

: A method of forming an energy well with a gate structure of a semiconductor device similar to a field effect transistor, and using the spin state of particles such as electrons or holes trapped there as the qubit energy level.

: A platform that is rapidly developing with the development of isotope-purified silicon substrates that minimize spin noise.

: In addition to the high coherence time of the spin inside the silicon, single measurement with high fidelity is possible, and the parameters for quantum control of the qubit system can be easily adjusted with the gate voltage.

: It shows the highest compatibility with the Complementary Metal-Oxide Semiconductor (CMOS) process, and has the advantage of being able to use the silicon industrial process that has been developed for over 70 years in the future manufacturing process of large-scale integrated quantum processors.

Quantum computing market map