Hyperthermal epitaxy of enriched $^{28}$Si

In the effort to produce devices suitable for quantum computation, it is necessary to increase as much as possible the T$_{2}$ coherence time of the electron or nuclear spin being used as a qubit. For silicon devices this means using isotopically enriched $^{28}$Si. This is because $^{28}$Si has no net nuclear spin while the spin of $^{29}$Si present in natural Si (4.67{\%}) interacts with the qubit spin and reduces the T$_{2}$ time greatly. Sufficiently long T$_{2}$ times are necessary for successful operation of quantum computers and we will demonstrate a method for producing epitaxial layers of $^{28}$Si on a Si substrate. Ideally, the silicon layers produced must not only be isotopically enriched, but chemically pure and defect free for best performance. These qualities are produced by deposition from a hyperthermal energy beam line using a mass selecting magnet. Depositing silicon epilayers at hyperthermal energies allows for greater manipulation of layer quality. This process is tested and calibrated initially using carbon dioxide. As a preliminary test, isotopically enriched $^{13}$C is implanted into semiconductor grade silicon and analyzed by secondary ion mass spectroscopy as an independent check on estimated levels of isotopic and chemical purity.