Showing papers by "David P. Norton published in 2004"

Measuring the Strategic Readiness of Intangible Assets

Abstract: Measuring the value of intangible assets such as company culture, knowledge management systems, and employees' skills is the holy grail of accounting. Executives know that these intangibles, being hard to imitate, are powerful sources of sustainable competitive advantage. If managers could measure them, they could manage the company's competitive position more easily and accurately. In one sense, the challenge is impossible. Intangible assets are unlike financial and physical resources in that their value depends on how well they serve the organizations that own them. But while this prevents an independent valuation of intangible assets, it also points to an altogether different approach for assessing their worth. In this article, the creators of the Balanced Scorecard draw on its tools and framework--in particular, a tool called the strategy map--to present a step-by-step way to determine "strategic readiness," which refers to the alignment of an organization's human, information, and organization capital with its strategy. In the method the authors describe, the firm identifies the processes most critical to creating and delivering its value proposition and determines the human, information, and organization capital the processes require. Some managers shy away from measuring intangible assets because they seem so subjective. But by using the systematic approaches set out in this article, companies can now measure what they want, rather than wanting only what they can currently measure.

Recent advances in processing of ZnO

Abstract: A review is given of recent results in developing improved fabrication processes for ZnO devices with the possible application to UV light emitters, spin functional devices, gas sensors, transparent electronics, and surface acoustic wave devices. There is also interest in integrating ZnO with other wide band-gap semiconductors, such as the AlInGaN system. In this article, we summarize recent progress in controlling n- and p-type doping, materials processing methods, such as ion implantation for doping or isolation, Ohmic and Schottky contact formation, plasma etching, the role of hydrogen in the background n-type conductivity of many ZnO films, and finally, the recent achievement of room-temperature ferromagnetism in transition-metal (Mn or Co)-doped ZnO. This may lead to another class of spintronic devices, in which the spin of the carriers is exploited rather than the charge as in more conventional structures.

ZnO nanowire growth and devices

Abstract: The large surface area of ZnO nanorods makes them attractive for gas and chemical sensing, and the ability to control their nucleation sites makes them candidates for micro-lasers or memory arrays. In addition, they might be doped with transition metal (TM) ions to make spin-polarized light sources. To date, most of the work on ZnO nanostructures has focused on the synthesis methods and there have been only a few reports of the electrical characteristics. We review fabrication methods for obtaining device functionality from single ZnO nanorods. A key aspect is the use of sonication to facilitate transfer of the nanorods from the initial substrate on which they are grown to another substrate for device fabrication. Examples of devices fabricated using this method are briefly described, including metal-oxide semiconductor field effect depletion-mode transistors with good saturation behavior, a threshold voltage of ∼−3 V and a maximum transconductance of order 0.3 mS/mm and Pt Schottky diodes with excellent ideality factors of 1.1 at 25 °C and very low (1.5 × 10 −10 A, equivalent to 2.35 A cm −2 , at −10 V) reverse currents. The photoresponse showed only a minor component with long decay times (tens of seconds) thought to originate from surface states. These results show the ability to manipulate the electron transport in nanoscale ZnO devices.

Dilute magnetic semiconducting oxides

Abstract: A review of recent results on transition metal doping of electronic oxides such as ZnO, TiO2, SnO2, BaTiO3, Cu2O, SrTiO3 and KTaO3 is presented. There is interest in achieving ferromagnetism with Curie temperatures above room temperature in such materials for applications in the field of spintronic devices, in which the spin of the carriers is exploited. The incorporation of several atomic per cent of the transition metals without creation of second phases appears possible under optimized synthesis conditions, leading to ferromagnetism. Pulsed laser deposition, reactive sputtering, molecular beam epitaxy and ion implantation have all been used to produce the oxide-based dilute magnetic materials. The mechanism is still under debate, with carrier-induced, double-exchange and bound magnetic polaron formation all potentially playing a role depending on the conductivity type and level in the material.

The strategy map: guide to aligning intangible assets

Abstract: Advice to senior management on how to use the balanced scorecard measurement system and the strategy map, a visual representation of the components of an organization’s strategy to leverage a corporation’s intangible assets. These include human capital; databases and information systems; responsive, high‐quality processes; customer relationships and brands; innovation capabilities; and culture. The author’s hypothesis: because an organization’s intangible assets may easily represent more than 75 percent of its value, then its strategy formulation and execution need to explicitly address their mobilization and alignment. The balanced scorecard tool and strategy map offer a framework to measure intangible assets and to describe strategies as a series of cause‐and‐effect linkages among objectives. They provide a language that executive teams can use to discuss the direction and priorities of their enterprises. This article also presents a case study of Crown Castle International, Inc.

Synthesis and properties of epitaxial electronic oxide thin-film materials

Abstract: The growth and properties of electronic oxide thin films are reviewed. In particular, the synthesis and properties of superconducting, insulating, conducting, magnetic, and semiconducting epitaxial oxide structures are discussed. Crystal structures and functional properties common to many oxide materials are briefly reviewed. A description of film-growth techniques follows. Finally, an extensive overview of the epitaxial growth for specific oxide material systems is given. This includes the epitaxial growth of electronic oxide thin films on oxide and non-oxide substrates.

Depletion-mode ZnO nanowire field-effect transistor

Abstract: Single ZnO nanowire metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated using nanowires grown by site selective molecular-beam epitaxy. When measured in the dark at 25°C, he depletion-mode transistors exhibit good saturation behavior, a threshold voltage of ∼−3V, and a maximum transconductance of order 0.3mS∕mm. Under ultraviolet (366nm) illumination, the drain–source current increase by approximately a factor of 5 and the maximum transconductance is ∼5mS∕mm. The channel mobility is estimated to be ∼3cm2∕Vs, which is comparable to that reported for thin film ZnO enhancement mode MOSFETs, and the on∕off ratio was ∼25 in the dark and ∼125 under UV illumination.

p-type behavior in phosphorus-doped (Zn,Mg)O device structures

Abstract: The characteristics of device structures that employ phosphorus-doped (Zn,Mg)O have been examined in a effort to delineate the carrier type behavior in this material. The capacitance–voltage properties of metal/insulator/P-doped (Zn,Mg)O diode structures were measured and found to exhibit a polarity consistent with the P-doped (Zn,Mg)O layer being p type. In addition, thin-film junctions comprising n-type ZnO and P-doped (Zn,Mg)O display asymmetric I–V characteristics that are consistent with the formation of a p–n junction at the interface. Although Hall measurements of the P-doped (Zn,Mg)O thin films yielded an indeterminate Hall sign due to a small carrier mobility, these results are consistent with previous reports that phosphorus can yield an acceptor state and p-type behavior in ZnO materials.

Enhancement-mode thin-film field-effect transistor using phosphorus-doped (Zn,Mg)O channel

Abstract: We report on enhancement-mode ZnO-based field-effect transistors that utilize an acceptor-doped channel. In particular, the active channel is polycrystalline ZnO doped with Mg, to increase the band gap, and P, to decrease the electron carrier concentration. Devices are realized that display an on/off ratio of 103 and a channel mobility on the order of 5 cm2/V s. HfO2 serves as the gate dielectric. Capacitance–voltage properties measured across the gate indicate that the ZnO channel is n type. The use of acceptor doping improves the control of the initial channel conductance while having a minimal impact on channel mobility relative to undoped ZnO polycrystalline channels.

Effects of high-dose Mn implantation into ZnO grown on sapphire

Abstract: ZnO films grown by pulsed-laser deposition on c-plane Al2O3 substrates were annealed at temperatures up to 600 °C to produce n-type carrier concentrations in the range 7.5×1015–1.5×1020 cm−3. After high-dose (3×1016 cm−2) Mn implantation and subsequent annealing at 600 °C, all the films show n-type carrier concentrations in the range 2–5×1020 cm−3 and room temperature hysteresis in magnetization loops. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn, and that factors such as crystalline quality and residual defects play a role.

Electrical transport properties of single ZnO nanorods

Abstract: Single ZnO nanorods with diameters of ∼130nm were grown on Au-coated Al2O3 substrates by catalyst-driven molecular beam epitaxy. Individual nanorods were removed from the substrate and placed between Ohmic contact pads and the current–voltage characteristics measured as a function of temperature and gas ambient. In the temperature range from 25to150°C, the resistivity of nanorods treated in H2 at 400°C prior to measurement showed an activation energy of 0.089±0.02eV and was insensitive to the ambient used (C2H4,N2O,O2 or 10% H2 in N2). By sharp contrast, the conductivity of nanorods not treated in H2 was sensitive to trace concentrations of gases in the measurement ambient even at room temperature, demonstrating their potential as gas sensors.

Pt∕ZnO nanowire Schottky diodes

Abstract: Pt Schottky diodes were formed on single ZnO nanowires grown by site-selective molecular-beam epitaxy and then transferred to SiO2-coated Si substrates. The diodes exhibit excellent ideality factors of 1.1 at 25 °C and very low (1.5×10−10A, equivalent to 2.35Acm−2, at −10V) reverse currents. The nanowire diodes show a strong photoresponse, with the current–voltage characteristics becoming ohmic under ultraviolet illumination (366 nm light). The on-off current ratio of the diodes at 0.15∕−5V was ∼6. These results show the ability to manipulate the electron transport in nanoscale ZnO devices.

Wide bandgap GaN-based semiconductors for spintronics

Abstract: Recent results on achieving ferromagnetism in transition-metal-doped GaN, A1N and related materials are discussed. The field of semiconductor spintronics seeks to exploit the spin of charge carrier ...

How strategy maps frame an organization's objectives: in an excerpt from their new book, two noted authors on corporate management outline how organizations can mobilize and sustain their intangible assets for value-creating internal processes

Abstract: The strategy literature is uncommonly diverse. Scholars and practitioners have very different frameworks for strategy and don't even agree on its definition. While \"strategy maps\"--to be discussed in this article--and Balanced Scorecards can be developed for any strategic approach, we base our approach on the general framework articulated by Michael Porter, a founder and outstanding leader in the strategy field. Porter argues that strategy is about selecting the set of activities in which an organization will excel to create a sustainable difference in the marketplace. The sustainable difference can be to deliver greater value to customers than competitors, or to provide comparable value, but at lower costs than competitors. He states, \"Differentiation arises from both the choice of activities and how they are performed.\

Temperature-dependent characteristics of Pt Schottky contacts on n-type ZnO

Abstract: The Schottky barrier height of Pt contacts on n-type (n∼1016 cm−3) thin film ZnO deposited by pulsed laser deposition was obtained from current–voltage measurements as a function of temperature. The resulting values ranged from 0.61±0.04 eV at 25 °C to 0.46±0.06 eV at 100 °C with saturation current densities of 1.5×10−4 A cm−2 (25 °C) to 6.0×10−2 A cm−2 (100 °C), respectively. The reverse current magnitude was larger than predicted by thermionic emission alone. The measured barrier height for Pt on ZnO is similar to the value reported for both Au and Ag rectifying contacts on this material.

Zn0.9Mg0.1O∕ZnOp–n junctions grown by pulsed-laser deposition

Abstract: The electrical characteristics of Zn0.9Mg0.1O∕ZnOp–n junctions grown by pulsed-laser deposition on bulk, single-crystal ZnO substrates are reported. The forward turn-on voltage of the junctions was in the range 3.6–4V for Pt∕Au metallization used for the p-Ohmic contact on Zn0.9Mg0.1O.The reverse breakdown voltage is as high as 9V, but displays a small negative temperature coefficient of −0.1–0.2VK−1 over the range 30–200°C. The achievement of acceptable rectification in the junctions required growth of an n-type ZnO buffer on the ZnO substrate prior to growth of the p-type, phosphorus-doped Zn0.9mg0.1O.Without this buffer, the junctions showed very high leakage current.

Carrier concentration dependence of Ti/Al/Pt/Au contact resistance on n-type ZnO

Abstract: Ti/Al/Pt/Au ohmic contacts on n-type ZnO with a range of carrier concentrations (7.5×1015–1.5×1020 cm−3) show as-deposited specific contact resistances in the range from 3×10−4 to 8×10−7 Ω cm2. Temperature-dependent measurements showed that the dominant transport mechanisms were tunneling in the contacts in the most highly doped films and thermionic emission in the more lightly doped films. After annealing at 200 °C, the lowest specific contact resistance achieved was 2.2×10−8 Ω cm2. However, the contacts show evidence of reactions between the Ti and the ZnO film even for this low annealing temperature, suggesting that applications requiring good thermal stability will need metallurgy with better thermal stability.

Improved Pt∕Au and W∕Pt∕Au Schottky contacts on n-type ZnO using ozone cleaning

Abstract: UV-ozone cleaning prior to metal deposition of either e-beam Pt contacts or sputtered W contacts on n-type single-crystal ZnO is found to significantly improve their rectifying characteristics. Pt contacts deposited directly on the as-received ZnO surface are Ohmic but show rectifying behavior with ozone cleaning. The Schottky barrier height of these Pt contacts was 0.70eV, with ideality factor of 1.5 and a saturation current density of 6.2×10−6Acm−2. In contrast, the as-deposited W contacts are Ohmic, independent of the use of ozone cleaning. Postdeposition annealing at 700°C produces rectifying behavior with Schottky barrier heights of 0.45eV for control samples and 0.49eV for those cleaned with ozone exposure. The improvement in rectifying properties of both the Pt and W contacts is related to removal of surface carbon contamination from the ZnO.

Spatial distribution and electronic state of Co in epitaxial anatase CoxTi1−xO2 thin films grown by reactive sputtering

Abstract: The magnetic and phase properties of CoxTi1−xO2 anatase thin films grown epitaxially on (001) LaAlO3 by a reactive rf magnetron cosputter deposition have been examined. CoxTi1−xO2 (x=0.07) thin films exhibit room-temperature ferromagnetism, as evidenced by hysteresis in M–H loop. Chemical mapping indicates segregation of the Co dopant atoms in these films. However, x-ray photoelectron spectroscopy suggests that the segregated Co is not metallic, but in the Co+2 state. These results are consistent with a segregated Ti–Co–O phase being responsible for the ferromagnetic behavior.

Shallow donor formation in phosphorus-doped ZnO thin films

Abstract: ZnO is a direct band gap semiconductor that is attractive for a number of applications, including high-temperature electronics, transparent electronics, and blue to UV optoelectronics. The most significant impediment to the exploitation of ZnO is the difficulty in achieving effective p-type carrier doping. Attractive acceptor-state candidates for ZnO are the group-V elements substituted on the oxygen site. In this paper, the doping behavior of phosphorus in as-deposited ZnO crystalline thin films grown by pulsed-laser deposition is reported. The experimental work reported here indicates that phosphorus doping significantly increases the electron carrier density in as-deposited films, making the material heavily n-type. These results indicate the formation of a shallow donor level associated with the phosphorus impurity, resulting from either substitution on the Zn site or formation of a compensating complex. Based on X-ray photoelectron spectroscopy measurements, the phosphorus-dopant ions in the films occupy multiple sites yielding oxidation states of -3 and +5. This would explain the compensated n-type behavior for group-V doping in the II-VI host material.

Contacts to p-type ZnMgO

Abstract: Ohmic and Schottky contacts to p-type Zn09Mg01O are reported The lowest specific contact resistivity of 3×10−3 Ω cm2 was obtained for Ti/Au annealed at 600 °C for 30 s Ni/Au was less thermally stable and showed severe degradation of contact morphology at this annealing temperature Both Pt and Ti with Au overlayers showed rectifying characteristics on p-ZnMgO, with barrier heights of ∼055–056 eV and ideality factors of ∼19 Comparison of these results with the same metals on n-type ZnO indicates that high surface state densities play a significant role in determining the effective barrier height

Cathodoluminescence from Thin Film Zn2GeO4 : Mn Phosphor Grown by Pulsed Laser Deposition

Abstract: Low voltage cathodoluminescent (CL) characteristics of Zn 2 GeO 4 : Mn thin-film phosphors grown by pulsed laser deposition were investigated. The effects of substrate heating (600-750°C) and substrate type (MgO, Si, and yttria-stabilized zirconia) on the cathodoluminescent properties were studied. A characteristic green emission peak at 540 nm was observed at substrate temperatures of 650, 700, or 750°C. However, the emission was red shifted to 650 nm for a substrate temperature of 600°C. The red shift in emission wavelengths from 540 to 650 nm was attributed to a change in ionic state of the activator from Mn 2+ to Mn 4+ . While the spectral position was independent of substrate type, the relative intensities of the cathodoluminescent emission peak varied with both substrate type as well as substrate temperature. At a substrate temperature of 600°C, the crystal structure of the film was mixed polycrystalline and amorphous. However, at substrate temperatures ranging from 650-750°C, the films were only polycrystalline with varying degrees of crystallinity that correlated with the CL intensity.

Sensitivity of Pt/ZnO Schottky diode characteristics to hydrogen

Abstract: Pt/ZnO Schottky diodes show changes in forward current of 0.3 mA at a forward bias of 0.5 V or alternatively a change of 50 mV bias at a fixed forward current of 8 mA when 5 ppm of H2 is introduced into a N2 ambient at 25 °C. The rectifying current–voltage (I–V) characteristic shows a nonreversible collapse to Ohmic behavior when as little as 50 ppm of H2 is present in the N2 ambient. At higher temperatures, the recovery is thermally activated with an activation energy of ∼0.25 eV. This suggests that introduction of hydrogen shallow donors into the ZnO is a contributor to the change in current of the diodes.

Sensitivity of Pt/ZnO schottky diode characteristics to hydrogen

Abstract: Pt/ ZnO Schottky diodes show changes in forward current of 0.3 mA at a forward bias of 0.5V or alternatively a change of 50 mV bias at a fixed forward current of 8 mA when 5 ppm of H 2 is introduced into a N 2 ambient at 25°C.The rectifying current-voltage(I-V) characteristic shows a non-reversible collapse to Ohmic behavior when as little as 50 ppm of H 2 is present in the N 2 ambient. At higher temperatures, the recovery is thermally activated with an activation energy of ∼0.25 eV. This suggests that introduction of hydrogen shallow donors into the ZnO is a contributor to the change in current of the diodes.

Thermal degradation of electrical properties and morphology of bulk single-crystal ZnO surfaces

Abstract: Bulk ZnO substrates were rapid thermal annealed in either air or N2 at temperatures up to 500°C. The root-mean-square roughness of the surface as measured by atomic force microscopy begins to increase even after 200°C anneals in N2 or 300°C in air. The Schottky barrier height, ΦB, obtained from Pt∕Au diodes fabricated on these surfaces shows a decrease in effective barrier height upon annealing from 0.35eV in control samples to ∼0.30eV in those annealed at 400°C and an increase in the saturation current density (from 4Acm−2 in the control samples to 17–37Acm−2 in the annealed samples). These results show that the ZnO surface is degraded by quite low annealing temperatures and care must be exercised in designing the thermal budget for processing of ZnO devices. At much higher annealing temperatures (1000°C), the surface completely decomposes to leave metallic Zn droplets.

Method of producing biaxially textured buffer layers and related articles, devices and systems

Abstract: A superconductor article (10) includes a substrate (12) and a first buffer film (14) disposed on the substrate (12). The first buffer film (14) has a uniaxial crystal texture characterized (i) texture in a first crystallographic direction that extends out-of-plane of the first buffer film (14) with no significant texture in a second direction that extends in-plane of the first buffer film (14), or (ii) texture in a first crystallographic direction that extends in-plane of the first buffer film (14) with no significant texture in a second direction that extends out-of-plane of the first buffer film (14). A second buffer film (16) is disposed on the first buffer film, the second buffer film having a biaxial crystal texture. A superconductor layer (18) can be disposed on the second buffer film (16). Ion-beam assisted deposition (IBAD) can be used to deposit the second buffer film (16).