Electron Spin-Lattice Relaxation of Substitutional Nitrogen in Silicon: The Role of Disorder and Motional Effects.

In a previous investigation, the authors proposed nitrogen as a possible candidate for exploiting the donor spin in silicon quantum devices. This system is characterized by a ground state deeper than the other group V impurities in silicon, offering less stringent requirements on the device temperature necessary to access the unionized state. The nitrogen donor is slightly displaced from the substitutional site, and upon heating, the system undergoes a motional transition. In the present article, we show the results from our investigation on the spin-relaxation times in natSi and 28Si substrates and discuss the motional effects on relaxation. The stretched exponential relaxation observed is interpreted as a distribution of spin-lattice relaxation times, whose origin is also discussed. This information greatly contributes to the assessment of a nitrogen-doped silicon system as a potential candidate for quantum devices working at temperatures higher than those required for other group V donors in silicon.

Few electron limit of n-type metal oxide semiconductor single electron transistors.

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.

Li4C60: a polymeric fulleride with a two-dimensional architecture and mixed interfullerene bonding motifs.

All known fullerene polymers have interfullerene connections via either [2 + 2] cycloaddition or single C-C bonds. The high-resolution synchrotron X-ray powder diffraction technique was employed here to determine the crystal structure of the Li4C60 fulleride. We find that the ground state of Li4C60 is a two-dimensional polymer with monoclinic crystal symmetry and an unprecedented architecture, combining both the [2 + 2] cycloaddition and the single C-C bridging motifs. The small size of the Li+ cations is crucial in stabilizing the resulting tightly packed polymeric structure.