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We present a scalable strategy to manufacture quantum computer devices, by encoding quantum information in the combined electron-nuclear spin state of individual ion-implanted phosphorus dopant atoms in silicon. Our strategy allows a typical pitch between quantum bits of order 200 nm, and retains compatibility with the standard fabrication processes adopted in classical CMOS nanoelectronic devices. We theoretically predict fast and high-fidelity quantum logic operations, and present preliminary experimental progress towards the realization of a “flip-flop” qubit system.

We describe an approach to quantum computer technology based on engineered single donor atoms implanted into silicon. We exploit quantum superposition and entanglement in potentially scalable nanoscale quantum devices engineered with just a single phosphorus donor atom in a silicon nano-scale complementary metal-oxide-semiconductor device. The devices are sensitive to the variation in the position of the donor atoms and also, when cooled to 100 mK, to the quantum state of single donors. Over the past two years we have fabricated devices incorporating 31P donor atoms implanted 20 nm deep into isotopically enriched 28Si followed by rapid thermal annealing at 1000oC for 5 s to activate the donors and minimise diffusion. Measurement of a single ionized donor gives the 31P nuclear spin (I=1/2) coherence time greater than 30 seconds showing exceptional promise and the robustness of this quantum system despite the influence of the nearby gate oxide and electrode metals. To implant donor atoms in a large-scale device we have developed a deterministic ion implantation method that is cited by the 2011 International Semiconductor Roadmap. We exploit signals arising from the ion induced charge from single implants in the substrate detected by on-chip detector electrodes. We describe our approach to take this technology to the next stage by building deterministic arrays of single atoms with the goal of sub-10 nm positioning precision as a pathway to a large scale device that could form the building block of a future CMOS quantum computer fabricated with the standard tools of the industry.

Silicon has dominated the microelectronics industry for the last 50 years. With its zero nuclear spin isotope (28Si) and low spin orbit coupling, it is believed that silicon can become an excellent host material for an entirely new generation of devices that operate under the laws of quantum mechanics [1}. Semiconductor nanowires however, offer huge potential as the next building blocks of nano-devices due to their one-dimensional structure and properties [2]. We describe a fabrication process to prepare doped vapor-liquid-solid (VLS) grown silicon nanowire samples in a 2- and 4-terminal measurement setup for electrical characterisation., 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2014 Conference

The insulator-to-metal transition (IMT) of vanadium dioxide (VO 2 ) is promising for applications in optoelectronic switching devices. The IMT is reversible, involves dramatic changes in the optical and electrical properties, and can be triggered both optically and electrically. Furthermore, the IMT is extremely fast when excited by ultra-short optical pulses. Using this method, one transition cycle can be accomplished within a picosecond. Combining VO 2 with optically active erbium ions (Er3+) grants an optical-amplification capability to the material. This feature is appealing for research, especially since the luminescence of Er3+ lies at the standard wavelength for fiberoptic communication system. This paper presents a study on the optical spectroscopy of monocrystalline VO 2 :Er and an empirical determination of the Er3+ transition energies in VO 2 .

Nickel germanide formed on amorphous and crystalline germanium is investigated for material and electrical properties. The crystal quality of films formed is poorer for the germanides formed on amorphous germanium with a slight increase in sheet resistance. The grains of NiGe formed on amorphous germanium show a growth that is hexagonal like, extending into the substrate further than germanides grains formed on crystalline germanium. The NiGe formed on crystalline germanium has a much more uniform thickness and uniform grain size and shape. Hollow cone illumination shows that some recrystallisation of the amorphised region of germanium does occur.

Raman scattering is used to investigate the metastable Si phases formed by indentation. The indent strain, phase distribution and the kinetics of the phase transformations are examined.

We show the photo-ionisation of an individual erbium centre in silicon. A single-electron transistor is used as a charge detector to observe the resonant ionization as a function of photon energy. This allows for optical addressing and electrical detection of individual erbium centres with exceptionally narrow line width.

We have utilised ion implantation to fabricate silicon nanocrystal sensitised erbium-doped slot waveguide structures in a Si/SiO2/Si layered configuration and photoluminescence (PL) and Rutherford backscat-tering spectrometry (RBS) to analyse these structures. Slot waveguide structures in which light is confined to a nanometre-scale low-index region between two high-index regions potentially offer significant advantages for realisation of electrically-pumped Si devices with optical gain and possibly quantum optical devices. We are currently investigating an alternative pathway in which high quality thermal oxides are grown on silicon and ion implantation is used to introduce the Er and Si-ncs into the SiO2 layer. This approach provides considerable control over the Er and Si-nc concentrations and depth profiles which is important for exploring the available parameter space and developing optimised structures. RBS is well-suited to compositional analysis of these layered structures. To improve the depth sensitivity we have used a 1 MeV α beam and results indicate that a layered silicon-Er:SiO 2/silicon structure has been fabricated as desired. In this paper structural results will be compared to Er photoluminescence profiles for samples processed under a range of conditions. © Owned by the authors 2012.

In this paper we present our progress towards the opto-electronic characterization of indium phosphide (InP) nanowire transistors at milli-Kelvin (mK) temperatures. First, we have investigated the electronic transport of the InP nanowires by current-voltage (I-V) spectroscopy as a function of temperature from 300 K down to 40 K. Second, we show the successful operation of a red light emitting diode (LED) at liquid-Helium (and base) temperature to be used for opto-electronic device characterization., 2 pages Optoelectronic and Microelectronic Materials & Devices (COMMAD), 2012 Conference

Electrical measurements have been performed on amorphous metal oxide spin-coated thin-film transistors. The conducting layer is amorphous indium zinc oxide (a-IZO) which has been processed at low temperatures. We are looking to improve material and device properties, in particular carrier mobility, using electrical characterisation techniques such as deep-level transient spectroscopy (DLTS) and Hall measurements.

Here we report on the integration of metallic nanorods with the phase-change material Vanadium Dioxide (VO 2 ). The change in its optical constants that accompanies the VO 2 phase transition permits the modulation of the resonant frequencies of these dipoles. This technique will underpin the development of dynamically tunable optical antennas.

The development of processes involving amorphous germanium for electronic and photonic applications is investigated.

We report on the growth of ZnO nanowires using two distinctive methods; sonochemistry and hydrothermal growth. The dimensions of the nanowires were varied by changing the concentration of the solution, growth time and volume of the solution. During growth by sonification, we were also able to alter the power supplied to the solution and the dimensions of the sonicator tip. The nanowires produced were then imaged using Scanning Electron Microscopy (SEM) and optical microscopy. We aim to create nanowires with dimensions suitable for the fabrication of ZnO nanowire transistor.

The effect of intrinsic and applied stress on hydrogen diffusion and trapping are studied by elastic-recoil detection (ERD), Rutherford backscattering and channelling (RBS-C) and transmission electron microscopy (TEM).

The photoluminescence of self-interstitials in silicon produced by ion implantation is investigated. A range of annealing temperatures have been used to follow the evolution of these defects. The effect on the formation of these defects in the presence of B and P dopants is considered. As expected, boron is found to reduce the W-line. Phosphorous also reduces the luminescence but to a lesser extent.

The effect of boron and phosphorous doping and co-doping on the optical properties of silicon nanocrystals formed in fused-silica by ion implantation is being studied. Boron-phosphorus pairs in silicon nanocrystals are of interest for possible applications in optical quantum computing.

The effect of Ni on the kinetics of solid phase epitaxial re-crystallization of amorphous germanium films is investigated with Raman spectroscopy. Both Ni implantation and deposition are employed.

Boron ions will be implanted at 150 keV down the axis of n-type silicon. Deep-level transient spectroscopy will be used to study the range, concentration and species of the created defects. A comparison to crystal-TRIM results will be made in order to refine model parameters.

The development and optimisation of materials and processes used for germanium metal-oxide-semiconductor devices are investigated. The gate oxide and the source-drain are examined using electrical and optical techniques.

The properties of traps at SiO2/Si and Si3N4/Si interfaces were examined and compared using deep level transient spectroscopy (DLTS). Small pulse DLTS was used to determine the effective electron capture cross-section of the interface states. Similar trends are found for both systems with the capture cross-section decreasing rapidly towards the band edge. The effective capture cross-section and energy level is also given for the Si≡Si3 defect at the Si3N4/Si interface.

Preliminary findings from a photoluminescence (PL) study of 30 keV boron implanted and furnace annealed silicon are presented. When different laser excitation wavelengths were used: namely, 1064 nm, and 532 nm; the observed PL emission yield changed substantially. Since the excitation volumes of these two wavelengths are significantly different in silicon due to sample absorption, they provide a means of probing defect related luminescence as a function of the excitation depth. An additional advantage of using the 1064 nm excitation is the inclusion of the phononic silicon (Raman) band which overlaps with the PL spectrum allowing it to be used as a scattering quantum counter. This provides a means of normalising the luminescence yield for samples prepared under different conditions.

We have studied changes to the surface potential of thermally grown oxides on silicon implanted with 15 keV P or Si using Kelvin-probe force microscopy (KFM). Oxides of 15 nm thickness were implanted through photoresist masks to create disk like islands of 3 μm diameter in the underlying silicon substrate with fluences up to 1×1014 cm-2. Atomic force microscopy shows no change to the topology of the sample except for the case of samples implanted at high fluence (1×1014 P/cm2) and flux (4.7×1010 cm-2s-1), which lead to observable depressions in the oxide. Results from KFM measurements show that there is a change in the surface potential of implanted areas for all samples however. Phosphorus implanted samples show a larger change in potential compared with preliminary results from silicon implanted samples. This increased change may be due to a flux dependence on defect generation but chemical effects associated with phosphorus or the effect of ionised phosphorus cannot be ruled out. Results from samples that have the implanted P activated by rapid thermally annealing at 1000°C for 5 seconds show the surface potential of implanted areas to be reduced but not eliminated. The residual difference may be due to the change in the substrate workfunction due to activated P donors. The measured change in surface potential has also been found to depend on the imaging height

Constant capacitance deep-level transient spectroscopy (CC-DLTS) has been used to study bulk traps and interface states in Si metal-oxide semiconductor (MOS) capacitors with 50 nm thick thermally-grown oxides on an n-type substrate. Both as-grown and P-implanted samples were studied. The P implants were performed at 50 keV to a dose of 1 × 10 10 cm-2. Thermal anneals in the temperature range 200-400°C were performed on implanted and as-grown samples to examine the dynamics of trap annealing

Ion channeling and Raman spectroscopy techniques were used to investigate ion-beam damage created by implantation of 245 keV and 5.5 MeV Si/sup +/ into Si(100). The two techniques employed in this work are compared and are shown to be complimentary with Raman scattering being more sensitive to low damage concentrations. The spatial correlation model is also discussed.

The effect of implantation angle on the profile of vacancy-related defects, represented by the divacancy and vacancy-phosphorus centres, in n-type Cz-Si implanted with 450 keV P or 600 keV Si ions to a dose of 2 /spl times/ 10/sup -9/ ions/spl middot/cm/sup -2/ , has been examined using deep level transient spectroscopy depth profiling. Implants were performed with samples aligned with 10/spl deg/ twists from the [110] planar direction and various tilts from the axis. The peak depth of the VP/V/sub 2/ profile exhibits a systematic variation with the implantation angle: shifting towards the surface, narrowing and increasing in peak concentration as the implantation angle is progressively varied from the aligned direction. For well-channeled 450 keV P ions, the peak in the defect profile is approximately 0.9 microns deeper than the peak in the vacancy profile predicted using the binary collision codes MARLOWE and Crystal-TCAS. The effect of the surface proximity on defect concentrations has been considered by comparing those profiles obtained for 450 keV P implanted samples with those of 600 keV Si implanted samples.