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ABSTRACT: 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.
Nature Nanotechnology 07/2012; 7(7):443-7. · 27.27 Impact Factor
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Enrico Prati,
Marco De Michielis,
Matteo Belli,
Simone Cocco,
Marco Fanciulli,
Dharmraj Kotekar-Patil,
Matthias Ruoff,
Dieter P Kern,
David A Wharam,
Jan Verduijn,
Giuseppe C Tettamanzi,
Sven Rogge,
Benoit Roche,
Romain Wacquez,
Xavier Jehl,
Maud Vinet,
Marc Sanquer
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ABSTRACT: We report the electronic transport on n-type silicon single electron transistors (SETs) fabricated in complementary metal oxide semiconductor (CMOS) technology. The n-type metal oxide silicon SETs (n-MOSSETs) are built within a pre-industrial fully depleted silicon on insulator (FDSOI) technology with a silicon thickness down to 10 nm on 200 mm wafers. The nominal channel size of 20 × 20 nm(2) is obtained by employing electron beam lithography for active and gate level patterning. The Coulomb blockade stability diagram is precisely resolved at 4.2 K and it exhibits large addition energies of tens of meV. The confinement of the electrons in the quantum dot has been modeled by using a current spin density functional theory (CS-DFT) method. CMOS technology enables massive production of SETs for ultimate nanoelectronic and quantum variable based devices.
Nanotechnology 05/2012; 23(21):215204. · 3.98 Impact Factor
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ABSTRACT: We charge an individual donor with electrons stored in a quantum dot in its proximity. A Silicon quantum device containing a single Arsenic donor and an electrostatic quantum dot in parallel is realized in a nanometric field effect transistor. The different coupling capacitances of the donor and the quantum dot with the control and the back gates are exploited to generate a relative rigid shift of their energy spectrum as a function of the back gate voltage, causing the crossing of the energy levels. We observe the sequential tunneling through the $D^{2-}$ and the $D^{3-}$ energy levels of the donor hybridized at the oxide interface at 4.2 K. Their respective states form an honeycomb pattern with the quantum dot states. It is therefore possible to control the exchange coupling of an electron of the quantum dot with the electrons bound to the donor, thus realizing a physical qubit for quantum information processing applications. Comment: 12 pages, 5 figures
05/2010;
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ABSTRACT: We review the effects of microwave irradiation on low dimensional electron systems in Silicon nanostructures. Depending on the temperature and the energy scales involved, different effects may be observed on the transition probabilities of elastic and inelastic processes. In particular two cases of 0 dimensional confinement are analyzed, i.e., the trapping of a single electron in point defects close to a two dimensional electron system, and in single donor atoms trapped in the channel of a nanoMOSFET. Microwave dependent capture and emission phenomena and photon assisted tunneling are described in such kind of systems. Consequences on the single spin resonance detection and on the spin manipulation are discussed.
Journal of Nanoscience and Nanotechnology 04/2010; 10(4):2650-5. · 1.56 Impact Factor
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ABSTRACT: We measure the temperature of a mesoscopic system consisting of an ultra-dilute two dimensional electron gas at the $Si/SiO_2$ interface in a metal-oxide-semiconductor field effect transistor (MOSFET) quantum dot by means of the capture and emission of an electron in a point defect close to the interface. Contrarily to previous reports, we show that the capture and emission by point defects in Si n-MOSFETs can be temperature dependent down to 800 mK. As the finite quantum grand canonical ensemble model applies, the time domain charge fluctuation in the defect is used to determine the temperature of the few electron gas in the channel. Comment: 4 Figures (color)
01/2010;
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Enrico Prati
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ABSTRACT: I present a theoretical model of a quantum statistical ensemble for which, unlike in conventional physics, the total number of particles is extremely small. The thermodynamical quantities are calculated by taking a small $N$ by virtue of the orthodicity of canonical ensemble. The finite quantum grand partition function of a Fermi-Dirac system is calculated. The model is applied to a quantum dot coupled with a small two dimensional electron system. Such system consists of an alternatively single and double occupied electron system confined in a quantum dot, which exhanges one electron with a small $N$ two dimensional electron reservoir. The analytic determination of the temperature of a $(1\leftrightarrow 2)$ electron system and the role of ergodicity are discussed. The generalized temperature expression in the small $N$ regime recovers the usual temperature expression by taking the limit of $N\to\infty$ of the electron bath. Comment: 1 Figure
01/2010;
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ABSTRACT: Single donors in semiconductor nanostructures represent a key element to develop spin related quantum functionalities in atomic scale devices. Quantum transport through a single Arsenic donor in the channel of a Silicon nano-field effect transistor under microwave irradiation is investigated. The device is characterized at mK temperatures in the regime of Coulomb-blockade. Photon assisted tunneling and microwave induced electron pumping regimes are revealed respectively at low and high microwave power. At sufficiently high power, the microwave irradiation induces tunneling through the first excited energy level of the $D_0$ energy of the donor. Such microwave assisted transport at zero bias enhances the resolution in the spectroscopy of the energy levels of the donor. Comment: 8 Figures
07/2008;
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ABSTRACT: We report on the current fluctuations of random telegraph signal experimentally observed at cryogenic temperatures in ordinary submicron Si / Si O <sub>2</sub> metal-oxide-semiconductor field-effect transistors (MOSFETs). A giant drain current fluctuation ΔI/I up to 55% is observed at sub-Kelvin temperature in samples with a large channel width. The current variation is compatible with predictions for decanano MOSFETs at room temperature. The similarity suggests the formation of a quasi-one-dimensional conduction channel at gate voltages sufficiently close to the threshold voltage.
Journal of Applied Physics 07/2008; · 2.17 Impact Factor
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ABSTRACT: Microwave irradiation causes voltage fluctuations in solid state nanodevices. Such an effect is relevant in atomic electronics and nanostructures for quantum information processing, where charge or spin states are controlled by microwave fields and electrically detected. Here, the variation of the characteristic times of the capture and emission of a single electron by an interface defect in submicron metal oxide semiconductor field effect transistor is calculated and measured as a function of the microwave power. In the model, the frequency of the voltage modulation is assumed to be large if compared to the inverse of the characteristic times. The variation of the characteristic times under microwave irradiation is quantitatively predicted from the microwave frequency dependent stationary current generated by the voltage fluctuation itself. The expected values agree with the experimental measurements. The reported effect has to be carefully considered in electrically detected single electron spin resonance experiments. In such experiments, a spurious change of the power of the microwave coupled to the device could be confused with the single spin resonance.
Journal of Applied Physics 06/2008; · 2.17 Impact Factor
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ABSTRACT: Microwave irradiation causes voltage fluctuations in solid state nanodevices. Such an effect is relevant in atomic electronics and nanostructures for quantum information processing, where charge or spin states are controlled by microwave fields and electrically detected. Here the variation of the characteristic times of the multiphonon capture and emission of a single electron by an interface defect in submicron MOSFETs is calculated and measured as a function of the microwave power, whose frequency of the voltage modulation is assumed to be large if compared to the inverse of the characteristic times. The variation of the characteristic times under microwave irradiation is quantitatively predicted from the microwave frequency dependent stationary current generated by the voltage fluctuations itself. The expected values agree with the experimental measurements. The coupling between the microwave field and either one or two terminals of the device is discussed. Some consequences on nanoscale device technology are drawn.
01/2008;
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ABSTRACT: We report on the change of the characteristic times of the random telegraph signal (RTS) in a MOSFET operated under microwave irradiation up to 40 GHz as the microwave field power is raised. The effect is explained by considering the time dependency of the transition probabilities due to a harmonic voltage generated by the microwave field that couples with the wires connecting the MOSFET. From the dc current excited into the MOSFET by the microwave field we determine the corresponding equivalent drain voltage. The RTS experimental data are in agreement with the prediction obtained with the model, making use of the voltage data measured with the independent dc microwave induced current. We conclude that when operating a MOSFET under microwave irradiation, as in single spin resonance detection, one has to pay attention into the effects related to microwave irradiation dependent RTS changes. Comment: 3 pages, 4 figures
09/2006;
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ABSTRACT: We report on the static magnetic field dependence of the random telegraph signal (RTS) in a submicrometer silicon n-metal-oxide-semiconductor field-effect transistor. Using intense magnetic fields and $^{3}$He temperatures, we find that the characteristic time ratio changes by 3 orders of magnitude when the field increases from 0 to 12 T. Similar behaviour is found when the static field is either in-plane or perpendicular to the two dimensional electron gas. The experimental data can be explained by considering a model which includes the triplet state of the trapping center and the polarization of the channel electron gas. Comment: 3.3 pages, 3 figures
12/2005;
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ABSTRACT: We study the random telegraph signal (RTS) due to defects at the Si/SiO2 interface of a MOSFET in a microwave field. We observe the change of the characteristic times of the RTS by monitoring the drain current in such device operated under microwave irradiation and the change of the emission/capture time ratio. The random telegraph signal is examined as a function of the microwave power from the temperature of 1.6K to room temperature. We observe a common trend in the RTS modification for all the investigated traps at all temperatures. The effect of increasing the irradiated power is to decrease the emission and capture times, while their ratio may depend on the temperature. © 2005 American Institute of Physics
AIP Conference Proceedings. 08/2005; 780(1):171-174.
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ABSTRACT: With a view to using microwaves to excite the single-spin resonance of an electron trapped in a defect at the Si/SiO2 interface of a metal-oxide-semiconductor field-effect transistor (MOSFET), we report on the experimental evidence for a stationary current in such devices operated under microwave radiation. The stationary current is examined as a function of the microwave power and of the operating voltage of the MOSFET. The transistor behavior is reproduced by a model exploiting the nonlinearity of the MOSFET channel resistance as a component of the circuit coupled with the electromagnetic field. We conclude that, in operating a MOSFET under microwaves, one has to pay attention to the generation of spurious stationary currents that may alter the likelihood to observe spin-dependent phenomena in the random telegraph signal observed in a MOSFET.
Journal of Applied Physics 08/2005; 98(4):044505-044505-4. · 2.17 Impact Factor
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ABSTRACT: The manipulation and quantification of the effects produced by an rf field in a mesoscopic structure are fundamental issues
in view of developing single-spin-based qubits. Here, we review the experiments on electron transport in quantum dots under
microwave irradiation. The electromagnetic vector potential provides excitation of electrons in the leads and in the quantum
dot, and an electromotive potential at the leads. The combinations of the two effects go under the name of photon-assisted
tunneling. In the present review, the theory of photon-assisted tunneling, based on the Tien–Gordon model applied to the Coulomb-blockade
regime of a quantum dot is outlined. An expression for the dc current flowing through the dot in response to a microwave signal
is calculated. Then, a classification of different experiments, organized following the different processes adopted to create
the dot is presented. Measurements of GaAs split-gate-defined single and double quantum dots as well as lithographically defined
SET based on Si/SiGe technology are considered. Finally, recent experiments on a Si/SiO2 commercial flash memory microwave irradiated up to 40 GHz are illustrated, without and with a static magnetic field up to12 T.
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