Search

Author(s): Takahiro Shinada (corresponding author) [1]; Shintaro Okamoto [2]; Takahiro Kobayashi [2]; Iwao Ohdomari [1, 2] As the size of semiconductor devices continues to shrink, the normally random distribution of [...]

Special point defects in semiconductors have been envisioned as suitable components for quantum‐information technology. The identification of new deep centers in silicon that can be easily activated and controlled is a main target of the research in the field. Vacancy‐related complexes are suitable to provide deep electronic levels but they are hard to control spatially. With the spirit of investigating solid state devices with intentional vacancy‐related defects at controlled position, the functionalization of silicon vacancies is reported on here by implanting Ge atoms through single‐ion implantation, producing Ge‐vacancy (GeV) complexes. The quantum transport through an array of GeV complexes in a silicon‐based transistor is investigated. By exploiting a model based on an extended Hubbard Hamiltonian derived from ab initio results, anomalous activation energy values of the thermally activated conductance of both quasi‐localized and delocalized many‐body states are obtained, compared to conventional dopants. Such states are identified, forming the upper Hubbard band, as responsible for the experimental sub‐threshold transport across the transistor. The combination of the model with the single‐ion implantation method enables future research for the engineering of GeV complexes toward the creation of spatially controllable individual defects in silicon for applications in quantum information technology. [ABSTRACT FROM AUTHOR]

Dopant atoms are used to control the properties of semiconductors in most electronic devices. Recent advances such as single-ion implantation have allowed the precise positioning of single dopants in semiconductors as well as the fabrication of single-atom transistors, representing steps forward in the realization of quantum circuits. However, the interactions between dopant atoms have only been studied in systems containing large numbers of dopants, so it has not been possible to explore fundamental phenomena such as the Anderson-Mott transition between conduction by sequential tunnelling through isolated dopant atoms, and conduction through thermally activated impurity Hubbard bands. Here, we observe the Anderson-Mott transition at low temperatures in silicon transistors containing arrays of two, four or six arsenic dopant atoms that have been deterministically implanted along the channel of the device. The transition is induced by controlling the spacing between dopant atoms. Furthermore, at the critical density between tunnelling and band transport regimes, we are able to change the phase of the electron system from a frozen Wigner-like phase to a Fermi glass by increasing the temperature. Our results open up new approaches for the investigation of coherent transport, band engineering and strongly correlated systems in condensed-matter physics. [ABSTRACT FROM AUTHOR]

Single‐nitrogen‐vacancy (NV) centers in diamond are highly promising quantum nuclear magnetic resonance (NMR) sensors. However, their exposure to many sources of noise, such as surface impurities, shot noise from avalanche photodiode overlaps, and spin‐state projection errors inherent in quantum systems, limits their usefulness. Often, long measurement durations are required to accumulate sufficient data for NMR signal detection via fast Fourier transform spectrometry. For practical reasons, methods to shorten the necessary accumulation time for NMR signal detection are greatly desired. In this article, an on‐line formulation of maximum likelihood estimation (MLE) signal processing for quantum heterodyne NMR measurements is presented as a step toward this goal. This MLE method reduces the required data accumulation time by orders of magnitude and provides good estimates of target frequency locales in real time. These results are significant to practitioners of NMR detection with single‐NV centers in diamond who require a quick litmus test for potential signals when probing a wide area. [ABSTRACT FROM AUTHOR]

Ge-vacancy complex, Hubbard model, point defects, quantum transport, single-ion implantation Keywords: Ge-vacancy complex; Hubbard model; point defects; quantum transport; single-ion implantation EN Ge-vacancy complex Hubbard model point defects quantum transport single-ion implantation 1 1 1 05/26/21 20210521 NES 210521 In article number, 2011175, Simona Achilli, Enrico Prati, and co-workers report on the controlled creation of individual vacancies in silicon by implanting Ge atoms via single ion implantation, the quantum transport model of a disordered 1D array of Ge-V complexes, and its experimental characterization. Single-Ion Implantation: Position-Controlled Functionalization of Vacancies in Silicon by Single-Ion Implanted Germanium Atoms (Adv. Funct. [Extracted from the article]

As semiconductor device dimensions decrease, the individual impurity atom position becomes a critical factor in determining device performance. We fabricated transistors with ordered and random dopant distributions on one side of the channel and evaluated the transconductance to investigate the impact of discrete dopant positions on the electron transport properties. The largest transconductance was observed when dopants were placed on the drain side in an ordered distribution; this was attributed to the suppression of injection velocity degradation on the source side and the uniformity of the electrostatic potential. Thus, the control of discrete dopant positions could enhance the device performance. [ABSTRACT FROM AUTHOR]

An erbium-doped silicon transistor prepared by ion implantation and co-doped with oxygen is investigated by photocurrent generation in the telecommunication range. The photocurrent is explored at room temperature as a function of the wavelength by using a supercontinuum laser source working in the μW range. The 1-μm2 transistor is tuned to involve in the transport only those electrons lying in the Er-O states. The spectrally resolved photocurrent is characterized by the typical absorption line of erbium and the linear dependence of the signal over the impinging power demonstrates that the Er-doped transistor is operating far from saturation. The relatively small number of estimated photoexcited atoms (≈ 4 × 10 4 ) makes Er-dpoed silicon potentially suitable for designing resonance-based frequency selective single photon detectors at 1550 nm. [ABSTRACT FROM AUTHOR]

Single-photon emitters with stable and uniform photoluminescence properties are important for quantum technology. However, in many cases, colour centres in diamond exhibit spectral diffusion and photoluminescence intensity fluctuation. It is therefore essential to investigate the dynamics of colour centres at the single defect level in order to enable the on-demand manipulation and improved applications in quantum technology. Here we report the polarization switching, intensity jumps and spectral shifting observed on a negatively charged single silicon-vacancy colour centre in diamond. The observed phenomena elucidate the single emitter dynamics induced by photoionization of nearby electron donors in the diamond. [ABSTRACT FROM AUTHOR]

To investigate the impact of only the dopant position on threshold voltage (Vth) in nanoscale field-effect transistors, we fabricated transistors with ordered dopant arrays and conventional random channel doping. Electrical measurements revealed that device performance could be enhanced by controlling the dopant position alone, despite varying dopant number according to a Poisson distribution. Furthermore, device-to-device fluctuations in Vth could be suppressed by implanting a heavier ion such as arsenic owing to the reduction of the projected ion struggling. The results of our study highlight potential improvements in device performance by controlling individual dopant positions. [ABSTRACT FROM AUTHOR]

A single-ion implantation technique that enables us to implant dopant ions one-by-one into semiconductors until the desired number is reached has been developed. The key to controlling the ion number is to detect secondary electrons (SEs) emitted from a target upon ion incidence. The SE detection efficiency currently achieved is 90% due to the low probability of SE emission, but has been enhanced to almost 100% by increasing the number of SEs by controlling the substrate bias voltage. This improvement has accelerated the prospects for realizing single-dopant devices, which are necessary for the ultimate control of the ion number. [ABSTRACT FROM AUTHOR]

The demand for single photon emitters at λ=1.54  μm, which follows from the consistent development of quantum networks based on optical fiber technologies, makes Er:O x centers in Si a viable resource, thanks to the I 13/2 4→I4 15/2 optical transition of Er 3+ . While its implementation in high-power applications is hindered by the extremely low emission rate, the study of such systems in the low concentration regime remains relevant for quantum technologies. In this Letter, we explore the room-temperature photoluminescence at the telecomm wavelength from very low implantation doses of Er:O x in Si. The lower-bound number of optically active Er atoms detected is of the order of 10 2 , corresponding to a higher-bound value for the emission rate per individual ion of about 10 4   s -1 .

Single photon sources (SPS) are crucial for quantum key distribution. Here we demonstrate a stable triggered SPS at 738 nm with linewidth less than 5 nm at room temperature based on a negatively charged single silicon vacancy color center. Thanks to the short photon duration of about 1.3-1.7 ns, by using high repetition pulsed excitation at 30 MHz, the triggered single photon source generates 16.6 kcounts/s. And we discuss the feasibility of this triggered SPS in the application of quantum key distribution.

We demonstrate a novel application of TiO2 photocatalysis for modifying the cell affinity of a scaffold surface in a cell-culture environment. An as-deposited octadecyltrichlorosilane self-assembled monolayer (OTS SAM) on TiO2 was found to be hydrophobic and stably adsorbed serum albumins that blocked subsequent adsorption of other proteins and cells. Upon irradiation of ultraviolet (UV) light, OTS molecules were decomposed and became permissive to the adhesion of PC12 cells via adsorption of an extracellular matrix protein, collagen. Optimal UV dose was 200 J cm(-2) for OTS SAM on TiO2. The amount of collagen adsorption decreased when excessive UV light was irradiated, most likely due to the surface being too hydrophilic to support its adsorption. This UV-induced modification required TiO2 to be present under the SAM and hence is a result of TiO2 photocatalysis. The UV irradiation for surface modification can be performed before cell plating or during cell culture. We also demonstrate that poly(ethylene glycol) SAM can also be patterned with this method, indicating that it is applicable to both hydrophobic and hydrophilic SAMs. This method provides a unique tool for fabricating cell microarrays and studying dynamical properties of living cells.