We use single-spin resonant spectroscopy to study the spin structure in the orbital excited state of a diamond nitrogen-vacancy (N-V) center at room temperature. The data show that the excited-state spin levels have a zero-field splitting that is approximately half of the value of the ground state levels, a g factor similar to the ground state value, and a hyperfine splitting approximately 20x larger than in the ground state. In addition, the width of the resonances reflects the electronic lifetime in the excited state. We also show that the spin level splitting can significantly differ between N-V centers, likely due to the effects of local strain, which provides a pathway to control over the spin Hamiltonian and may be useful for quantum-information processing.

[7]. Donor electron and nuclear spins are promising candidates for implementation of quantum bits in silicon [7]. The detection of low energy single ion impacts for device integration has been accomplished via detection of secondary electrons [2,4,9], or by collection of electron holepairs in optimized diodes [3]. It is also well known that high energy (MeV) single ion impacts can upset device currents [10], and an extension of this approach to low energy ions was recently outlined in Ref. 11. Also, random telegraph noise due to switching occupancies of single Coulomb scattering centers [12] has long been observed in sub-micron transistors, and it can thus be expected that the impact of lower energy (<100 keV) single ions, which is accompanied by the generation of multiple charged defects, can also be sensed in FETs.In this letter we report on the detection of low energy (50 to 70 keV) antimony and xenon ion impacts in FETs with channel areas of 4 μm 2 at room temperature. FETs were formed for development of single donor spin readout techniques, and spin dependent neutral donor scattering was recently observed in transport studies with similar devices used here [13]. Single ions change transistor channel mobilities through formation of defects upon impact, enabling precision placement of defined numbers of dopants into transistor channels. Upon further reduction of the beam current to ~0.1 ions/s, pulses contain mostly no ions, and current steps from single ion hits are recorded (Figure 2 c)). The probability for multiple ion hits in one pulse under these conditions of reduced beam current was less then 3%.During exposures with ions of different impact energies and charge states we found that the sensitivity to ion impacts, i. e. the magnitude of current steps, was gradually reduced with increasing implant dose. Further, variations in step heights at the given noise level did not allow us to confidently discriminate multiple hits from single ion hits based on the step heights. Due to the degrading sensitivity, it was also difficult to investigate charge state effects on the single ion induced current step height. It can be expected that the localized deposition of potential energy of multiply and highly charged ions [21] contributes significantly to the formation of defects in the gate oxide and at the Si-SiO 2 interface, and future work aims at quantifying this effect.Following a series of exposures with an accumulated dose of ~10 11 cm -2 , devices were annealed for damage repair and dopant activation. Rapid thermal annealing (RTA) was performed in an AGA Heatpulse at 900º C for 20 s in Argon, followed by another 30 min. N 2 /H 2 -forming gas anneal at 400º C. In figure 3, we show a series of I-V curves of a pristine A-FET 5 (Fig. 3 a) and NMOS-FET (Fig. 3 b), after FIB processing and forming gas anneal, and then after monitored implantation with noble gas and Sb ions and the consecutive anneals, demonstrating that devices were functional transistors after the full process sequence. The threshold voltages, V...

The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species, and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in single atoms, such as proposed quantum computers. The authors describe a single atom injector, in which the imaging and alignment capabilities of a scanning force microscope ͑SFM͒ are integrated with ion beams from a series of ion sources and with sensitive detection of current transients induced by incident ions. Ion beams are collimated by a small hole in the SFM tip and current changes induced by single ion impacts in transistor channels enable reliable detection of single ion hits. They discuss resolution limiting factors in ion placement and processing and paths to single atom ͑and color center͒ array formation for systematic testing of quantum computer architectures in silicon and diamond.

a b s t r a c tWe report on progress in ion placement into silicon devices with scanning probe alignment. The device is imaged with a scanning force microscope (SFM) and an aligned argon beam (20 keV, 36 keV) is scanned over the transistor surface. Holes in the lever of the SFM tip collimate the argon beam to sizes of 1.6 lm and 100 nm in diameter. Ion impacts upset the channel current due to formation of positive charges in the oxide areas. The induced changes in the source-drain current are recorded in dependence of the ion beam position with respect to the FinFET. Maps of local areas responding to the ion beam are obtained.

The interaction between slow highly-charged ions (SHCI) of different charge states from an electron-beam ion trap and highlyoriented pyrolytic graphite (HOPG) surfaces is studied in terms of modification of electronic states at single-ion impact nanosize areas. Results are presented from AFM/STM analysis of the induced-surface topological features combined with Raman spectroscopy. I-V characteristics for a number of different impact regions were measured with STM and the results argue for possible formation of diamond-like nanoscale structures at the impact sites.