This review describes recent groundbreaking results in Si, Si/SiGe and dopant-based quantum dots, and it highlights the remarkable advances in Si-based quantum physics that have occurred in the past few years. This progress has been possible thanks to materials development of Si quantum devices, and the physical understanding of quantum effects in silicon. Recent critical steps include the isolation of single electrons, the observation of spin blockade and single-shot read-out of individual electron spins in both dopants and gated quantum dots in Si. Each of these results has come with physics that was not anticipated from previous work in other material systems. These advances underline the significant progress towards the realization of spin quantum bits in a material with a long spin coherence time, crucial for quantum computation and spintronics.

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We report on spectroscopy of a single dopant atom in silicon by resonant tunneling between source and drain of a gated nanowire etched from silicon on insulator. The electronic states of this dopant isolated in the channel appear as resonances in the low temperature conductance at energies below the conduction band edge. We observe the two possible charge states successively occupied by spin-up and spin-down electrons under magnetic field. The first resonance is consistent with the binding energy of the neutral D 0 state of an arsenic donor. The second resonance shows a reduced charging energy due to the electrostatic coupling of the charged D ÿ state with electrodes. Excited states and Zeeman splitting under magnetic field present large energies potentially useful to build atomic scale devices. DOI: 10.1103/PhysRevLett.97.206805 PACS numbers: 73.21.ÿb, 61.72.Vv Dopant atoms are essential in semiconductor technology since they provide extrinsic charges necessary to create devices such as diodes and transistors. Nowadays the size of these electronic devices can be made so small than the discreteness of doping can influence their electrical properties [1]. On the other hand, it may be an important breakthrough if a dopant could be used as the functional part of a device instead of just providing charges. As an example, dopant-based spin qubits in silicon are possible candidates for quantum computation [2,3] thanks to their longer spin coherence time [4] as compared to twodimensional quantum dots defined by top gates in III=V heterostructures [5,6]. Although dopants are well known in bulk semiconductors, specific questions arise in the context of nanoscale devices like the reduced lifetime of the twoelectron state under electric field involved by readout schemes of spin qubits [7]. The aim of this work is to study the electronic states of single dopants in gated silicon nanostructures to bring information useful for these issues.Electron tunneling through isolated impurities has been observed previously in two-terminal devices such as GaAs= Al; Ga As double barrier heterostructures [8,9]. Here we present experimental results on electron transport through the localized states of individual n-type dopants in silicon nanowires. In contrast to previous studies, our devices have a three-terminal configuration with source, drain, and gate electrodes allowing a detailed investigation of charge, orbital, and spin states. In particular, we observe both the neutral D 0 and negatively charged D ÿ states, and compare their binding energy with the case of bulk dopants. This work provides a quantitative description of the electronic properties of a single dopant connected to electrodes in a gated nanostructure. This is the first transport experiment measuring the charge states of a real atomic system with a 1=r attracting Coulomb potential, thus very different from quantum dots with harmonic potentials.Our devices are 60 nm tall crystalline silicon wires (fins) with large contacts patterned by 193 nm optical lithography and ...