Single Ion Implantation of Bismuth

Abstract

Herein, the results from a focused ion beam instrument, designed to implant single ions with a view to the fabrication of qubits for quantum technologies, are presented. The difficulty of single ion implantation is accurately counting the ion impacts. This is achieved here through the detection of secondary electrons generated upon each ion impact. The implantation of single bismuth ions with different charge states into Si, Ge, Cu, and Au substrates is reported, and the counting detection efficiency for single ion implants and the factors that affect such detection efficiencies are determined. It is found that for 50 keV implants of Bi++ ions into silicon an 89% detection efficiency can be achieved, which is the first quantitative detection efficiency measurement for single ion implants into silicon without implanting through a thick SiO2 film. This level of counting accuracy provides implantation of single impurity ions with a success rate significantly exceeding that achievable by random (Poissonian) implantation.

The multi-photon induced Fano effect

“…2), and even recovery times that are comparable with the inverse of the typical microwave spin qubit Larmor frequencies (e.g., X-band at 10 GHz), and much faster than consequent Bloch rotation times [36][37][38][39][40] . For concreteness we give a specific example for Si:Bi, a popular qubit choice [44][45][46] , which displays large zero-field spin splitting (originating from hyperfine interaction) visible in the small-signal absorption shown on Fig. 4.…”

Error Rates in Deterministic Ion Implantation for Qubit Arrays

“…An alternative method for determining η is to collect the number of negatives for a fixed, large number of pulses, m , and then use and Equation (12), as in Cassidy et al [ 18 ] It may be shown that for small λ , . Note that just as for the stopping time experiment in the previous paragraph, small λ is not beneficial for such calibration experiments, and ideally just as before, so there is no statistical advantage in either experiment.…”

“…Note that just as for the stopping time experiment in the previous paragraph, small λ is not beneficial for such calibration experiments, and ideally just as before, so there is no statistical advantage in either experiment. See Cassidy et al [ 18 ] for a treatment of the uncertainty in η if it is determined from a graph of versus λ rather than a single setting of λ . Other experimenters [ 11 ] have investigated the number of positives as a proportion of the number of pulses containing ions, and this fraction has been called the detection efficiency, .…”

“…The Surrey University machine has been used for bismuth implants into different hosts: silicon, germanium, and gold. [ 18 ] For this machine, the detection of secondary electrons used a channeltron detector. The dark count rate was determined simply by several long asynchronous acquisitions over a time scale much longer than any other time scale in the system, and was found to be counts μs −1 .…”

“…[7][8][9] Post-implant determinism detects the impacts using prefabricated transistors in the substrate or in a contactless way detecting the secondary electrons produced by ion impacts. [10][11][12][13][14][15][16][17][18][19] As one of the main motivations of such effort is to make large arrays for quantum technologies, it is important to consider the error rates. In this work, we investigate the importance of the different sources of error in post-implant determinism to help guide engineering effort.…”