Advancements and challenges in strained group-IV-based optoelectronic materials stressed by ion beam treatment

In this perspective article, we discuss the application of ion implantation to manipulate strain (by either neutralizing or inducing compressive or tensile states) in suspended thin films. Emphasizing the pressing need for a high-mobility silicon-compatible transistor or a direct bandgap group-IV semiconductor that is compatible with complementary metal–oxide–semiconductor technology, we underscore the distinctive features of different methods of ion beam-induced alteration of material morphology. The article examines the precautions needed during experimental procedures and data analysis and explores routes for potential scalable adoption by the semiconductor industry. Finally, we briefly discuss how this highly controllable strain-inducing technique can facilitate enhanced manipulation of impurity-based spin quantum bits (qubits)

以書付奉伺候（十五軒程当時相休居候、旅籠取立云々）

Superposition of orbital eigenstates is crucial to quantum technology utilizing atoms, such as atomic clocks and quantum computers, and control over the interaction between atoms and their neighbours is an essential ingredient for both gating and readout. The simplest coherent wavefunction control uses a two-eigenstate admixture, but more control over the spatial distribution of the wavefunction can be obtained by increasing the number of states in the wavepacket. Here we demonstrate THz laser pulse control of Si:P orbitals using multiple orbital state admixtures, observing beat patterns produced by Zeeman splitting. The beats are an observable signature of the ability to control the path of the electron, which implies we can now control the strength and duration of the interaction of the atom with different neighbours. This could simplify surface code networks which require spatially controlled interaction between atoms, and we propose an architecture that might take advantage of this

Magneto-optical and non-linear optical spectroscopy of semiconductors

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Using non-homogeneous point process statistics to find multi-species event clusters in an implanted semiconductor

The Poisson distribution of event-to-ith-nearest-event radial distances is well known for homogeneous processes that do not depend on location or time. Here we investigate the case of a non-homogeneous point process where the event probability (and hence the neighbour configuration) depends on location within the event space. The particular non-homogeneous scenario of interest to us is ion implantation into a semiconductor for the purposes of studying interactions between the implanted impurities. We calculate the probability of a simple cluster based on nearest neighbour distances, and specialise to a particular two-species cluster of interest for qubit gates. We show that if the two species are implanted at different depths there is a maximum in the cluster probability and an optimum density profile

Giant non-linear susceptibility of hydrogenic donors in silicon and germanium

Implicit summation is a technique for the conversion of sums over intermediate states in multiphoton absorption and the high-order susceptibility in hydrogen into simple integrals. Here, we derive the equivalent technique for hydrogenic impurities in multi-valley semiconductors. While the absorption has useful applications, it is primarily a loss process; conversely, the non-linear susceptibility is a crucial parameter for active photonic devices. For Si:P, we predict the hyperpolarizability ranges from Chi((3))/ n(3D) = 2.9 to 580 x 10(-38) m(5)/V-2 depending on the frequency, even while avoiding resonance. Using samples of a reasonable density, n(3D), and thickness, L, to produce thirdharmonic generation at 9 THz, a frequency that is difficult to produce with existing solid-state sources, we predict that Chi((3)) should exceed that of bulk InSb and Chi((3)) L should exceed that of graphene and resonantly enhanced quantum wells

Weak probe readout of coherent impurity orbital superpositions in silicon

Pump-probe spectroscopy is the most common time-resolved technique for investigation of electronic dynamics, and the results provide the incoherent population decay time T1. Here we use a modified pump-probe experiment to investigate coherent dynamics, and we demonstrate this with a measurement of the inhomogeneous dephasing time T2* for phosphorus impurities in silicon. The pulse sequence produces the same information as previous coherent all-optical (photon-echo-based) techniques but is simpler. The probe signal strength is first order in pulse area but its effect on the target state is only second order, meaning that it does not demolish the quantum information. We propose simple extensions to the technique to measure the homogeneous dephasing time T2, or to perform tomography of the target qubit

Excited states of defect linear arrays in silicon: A first-principles study based on hydrogen cluster analogues

Excited states of a single donor in bulk silicon have previously been studied extensively based on effective mass theory. However, proper theoretical descriptions of the excited states of a donor cluster are still scarce. Here we study the excitations of lines of defects within a single-valley spherical band approximation, thus mapping the problem to a scaled hydrogen atom array. A series of detailed full configuration-interaction, time-dependent Hartree-Fock and time-dependent hybrid density-functional theory calculations have been performed to understand linear clusters of up to 10 donors. Our studies illustrate the generic features of their excited states, addressing the competition between formation of inter-donor ionic states and intra-donor atomic excited states. At short interdonor distances, excited states of donor molecules are dominant, at intermediate distances ionic states play an important role, and at long distances the intra-donor excitations are predominant as expected. The calculations presented here emphasise the importance of correlations between donor electrons, and are thus complementary to other recent approaches that include effective mass anisotropy and multi-valley effects. The exchange splittings between relevant excited states have also been estimated for a donor pair and for three-donor arrays; the splittings are much larger than those in the ground state in the range of donor separations between 10 and 20 nm. This establishes a solid theoretical basis for the use of excited-state exchange interactions for controllable quantum gate operations in silicon

Single Ion Implantation of Bismuth

The data contained in this spreadsheet has been used to produce the 'Single Ion Implantation of Bismuth' paper DOI: 10.1002/pssa.202000237 We present the results from a focused ion beam instrument designed to implant single ions with a view to the fabrication of qubits for quantum technologies. The difficulty of single ion implantation is accurately counting the ion impacts. This has been achieved here through the detection of secondary electrons generated upon each ion impact. We report implantation of single bismuth ions with different charge states into Si, Ge, Cu and Au substrates, and we determine the counting detection efficiency for single ion implants and the factors which affect such detection efficiencies. We found that for 50 keV implants of Bi++ ions into silicon we can achieve a 89% detection efficiency, 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 reader of the paper should be able to recreate any calculation and plots found in the paper, using the data contained within this sheet