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Single Ion Implantation and Deterministic Doping

Description: The presence of single atoms, e.g. dopant atoms, in sub-100 nm scale electronic devices can affect the device characteristics, such as the threshold voltage of transistors, or the sub-threshold currents. Fluctuations of the number of dopant atoms thus poses a complication for transistor scaling. In a complementary view, new opportunities emerge when novel functionality can be implemented in devices deterministically doped with single atoms. The grand price of the latter might be a large scale quantum computer, where quantum bits (qubits) are encoded e.g. in the spin states of electrons and nuclei of single dopant atoms in silicon, or in color centers in diamond. Both the possible detrimental effects of dopant fluctuations and single atom device ideas motivate the development of reliable single atom doping techniques which are the subject of this chapter. Single atom doping can be approached with top down and bottom up techniques. Top down refers to the placement of dopant atoms into a more or less structured matrix environment, like a transistor in silicon. Bottom up refers to approaches to introduce single dopant atoms during the growth of the host matrix e.g. by directed self-assembly and scanning probe assisted lithography. Bottom up approaches are discussed in Chapter XYZ. Since the late 1960's, ion implantation has been a widely used technique to introduce dopant atoms into silicon and other materials in order to modify their electronic properties. It works particularly well in silicon since the damage to the crystal lattice that is induced by ion implantation can be repaired by thermal annealing. In addition, the introduced dopant atoms can be incorporated with high efficiency into lattice position in the silicon host crystal which makes them electrically active. This is not the case for e.g. diamond, which makes ion implantation doping to engineer the electrical properties of diamond, ...
Date: June 11, 2010
Creator: Schenkel, Thomas
Partner: UNT Libraries Government Documents Department

Stark Tuning of Donor Electron Spins of Silicon

Description: We report Stark shift measurements for {sup 121}Sb donor electron spins in silicon using pulsed electron spin resonance. Interdigitated metal gates on top of a Sb-implanted {sup 28}Si epi-layer are used to apply electric fields. Two Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also resolved presumably arising from strain.
Date: March 23, 2006
Creator: Bradbury, Forrest R.; Tyryshkin, Alexei M.; Sabouret, Guillaume; Bokor, Jeff; Schenkel, Thomas & Lyon, Stephen A.
Partner: UNT Libraries Government Documents Department

Electron transport through single carbon nanotubes

Description: We report on the transport of energetic electrons through single, well aligned multi-wall carbon nanotubes (CNT). Embedding of CNTs in a protective carbon fiber coating enables the application of focused ion beam based sample preparation techniques for the non-destructive isolation and alignment of individual tubes. Aligned tubes with lengths of 0.7 to 3 mu m allow transport of 300 keV electrons in a transmission electron microscope through their hollow cores at zero degree incident angles and for a misalignment of up to 1 degree.
Date: August 1, 2007
Creator: Schenkel, Thomas; Chai, G.; Heinrich, H.; Chow, L. & Schenkel, T.
Partner: UNT Libraries Government Documents Department

A compact neutron generator using a field ionization source

Description: Field ionization as a means to create ions for compact and rugged neutron sources is pursued. Arrays of carbon nano-#12;bers promise the high #12;eld-enhancement factors required for efficient field ionization. We report on the fabrication of arrays of #12;field emitters with a density up to 10{sup 6} tips/cm{sup 2} and measure their performance characteristics using electron field emission. The critical issue of uniformity is discussed, as are efforts towards coating the nano-fibers to enhance their lifetime and surface properties.
Date: October 31, 2011
Creator: Persaud, Arun; Waldmann, Ole; Kapadia, Rehan; Takei, Kuniharu; Javey, Ali & Schenkel, Thomas
Partner: UNT Libraries Government Documents Department

Chip-Scale Nanofabrication of Single Spins and Spin Arrays in Diamond

Description: We demonstrate a technique to nanofabricate nitrogen vacancy (NV) centers in diamond based on broad-beam nitrogen implantation through apertures in electron beam lithography resist. This method enables high-throughput nanofabrication of single NV centers on sub-100-nm length scales. Secondary ion mass spectroscopy measurements facilitate depth profiling of the implanted nitrogen to provide three-dimensional characterization of the NV center spatial distribution. Measurements of NV center coherence with on-chip coplanar waveguides suggest a pathway for incorporating this scalable nanofabrication technique in future quantum applications.
Date: July 2, 2010
Creator: Toyli, David M.; Weis, Christoph D.; Fuchs, D.; Schenkel, Thomas & Awschalom, David D.
Partner: UNT Libraries Government Documents Department

Using nanoscale transistors to measure single donor spins in semiconductors

Description: We propose a technique for measuring the state of a single donor electron spin usinga field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is faciltated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outlne experimental reqiurements. Our measurement provides a single-shot, projective, and quantum non-demoltion measurement of an electron-encoded qubit state.
Date: December 1, 2008
Creator: Sarovar, M.; Young, K. C.; Whaley, K. B. & Schenkel, Thomas
Partner: UNT Libraries Government Documents Department

In situ optimization of co-implantation and substrate temperature conditions for Nv-center formation in single crystal diamonds

Description: We present first results from in situ characterization of NV-formation in single crystal diamonds following implantation of low energy nitrogen ions (7.7 keV), co-implantation of hydrogen, helium and carbon ions and in situ annealing. Diamond samples were implanted at room temperature or at a temperature of 780{degree} C during the implantation steps. We find that dynamic annealing during co-implantation enhances NV-center formation by up to 25%.
Date: February 1, 2011
Creator: Schwartz, Julian; Michaelides, Philip; Weis, Christoph D. & Schenkel, Thomas
Partner: UNT Libraries Government Documents Department

Development of a compact neutron source based on field ionization processes

Description: The authors report on the use of carbon nanofiber nanoemitters to ionize deuterium atoms for the generation of neutrons in a deuterium-deuterium reaction in a preloaded target. Acceleration voltages in the range of 50-80 kV are used. Field emission of electrons is investigated to characterize the emitters. The experimental setup and sample preparation are described and first data of neutron production are presented. Ongoing experiments to increase neutron production yields by optimizing the field emitter geometry and surface conditions are discussed.
Date: November 25, 2010
Creator: Persaud, Arun; Allen, Ian; Dickinson, Michael R.; Schenkel, Thomas; Kapadia, Rehan; Takei, Kuniharu et al.
Partner: UNT Libraries Government Documents Department

Evaluation of Non-Nuclear Techniques for Well Logging: Technology Evaluation

Description: This report presents an initial review of the state-of-the-art nuclear and non-nuclear well logging methods and seeks to understand the technical and economic issues if AmBe, and potentially other isotope sources, are reduced or even eliminated in the oil-field services industry. Prior to considering alternative logging technologies, there is a definite need to open up discussions with industry regarding the feasibility and acceptability of source replacement. Industry views appear to range from those who see AmBe as vital and irreplaceable to those who believe that, with research and investment, it may be possible to transition to electronic neutron sources and employ combinations of non-nuclear technologies to acquire the desired petro-physical parameters. In one sense, the simple answer to the question as to whether petro-physical parameters can be sensed with technologies other than AmBe is probably "Yes". The challenges come when attention turns to record interpretation. The many decades of existing records form a very valuable proprietary resource, and the interpretation of subtle features contained in these records are of significant value to the oil-gas exploration community to correctly characterize a well. The demonstration of equivalence and correspondence/correlation between established and any new sensing modality, and correlations with historic records is critical to ensuring accurate data interpretation. Establishing the technical basis for such a demonstration represents a significant effort.
Date: November 1, 2010
Creator: Bond, Leonard J.; Denslow, Kayte M.; Griffin, Jeffrey W.; Dale, Gregory E.; Harris, Robert V.; Moran, Traci L. et al.
Partner: UNT Libraries Government Documents Department

Single ion implantation for solid state quantum computer development

Description: Several solid state quantum computer schemes are based on the manipulation of electron and nuclear spins of single donor atoms in a solid matrix. The fabrication of qubit arrays requires the placement of individual atoms with nanometer precision and high efficiency. In this article we describe first results from low dose, low energy implantations and our development of a low energy (<10 keV), single ion implantation scheme for {sup 31}P{sup q+} ions. When {sup 31}P{sup q+} ions impinge on a wafer surface, their potential energy (9.3 keV for P{sup 15+}) is released, and about 20 secondary electrons are emitted. The emission of multiple secondary electrons allows detection of each ion impact with 100% efficiency. The beam spot on target is controlled by beam focusing and collimation. Exactly one ion is implanted into a selected area avoiding a Poissonian distribution of implanted ions.
Date: December 18, 2001
Creator: Schenkel, Thomas; Meijers, Jan; Persaud, Arun; McDonald, Joseph W.; Holder, Joseph P. & Schneider, Dieter H.
Partner: UNT Libraries Government Documents Department

Low-temperature charge transport in Ga-acceptor nanowires implanted by focused-ion beams

Description: Ga-acceptor nanowires were embedded in crystalline Si using focused-ion beams. The dc current-voltage characteristics of these wires after annealing are highly nonlinear at low temperatures, and a threshold voltage of less than 50 mV is observed independent of Ga+ dosage and implant beam overlap. These features suggest a Coulomb blockade transport mechanism presumably caused by a network of Ga precipitates in the substrate. This granular scenario is further supported by measurements of gated nanowires. Nanowires with metallic conductance at low temperatures could be achieved by reducing the current density of the focused-ion beams.
Date: July 31, 2007
Creator: Schenkel, Thomas; Robinson, S.J.; Perkins, C.L.; Tucker, J.R.; Schenkel, T.; Wang, X.W. et al.
Partner: UNT Libraries Government Documents Department

Device fabrication and transport measurements of FinFETs built with 28Si SOI wafers towards donor qubits in silicon

Description: We report fabrication of transistors in a FinFET geometry using isotopically purified silicon-28 -on-insulator (28-SOI) substrates. Donor electron spin coherence in natural silicon is limited by spectral diffusion due to the residual 29Si nuclear spin bath, making isotopically enriched nuclear spin-free 28Si substrates a promising candidate for forming spin quantum bit devices. The FinFET architecture is fully compatible with single-ion implant detection for donor-based qubits, and the donor spin-state readout through electrical detection of spin resonance. We describe device processing steps and discuss results on electrical transport measurements at 0.3 K.
Date: June 10, 2009
Creator: Lo, Cheuk Chi; Persaud, Arun; Dhuey, Scott; Olynick, Deirdre; Borondics, Ferenc; Martin, Michael C. et al.
Partner: UNT Libraries Government Documents Department