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Irreversible investments made with incomplete information are the mainstay of the petroleum industry. Sequential, non-repetitive investment decisions with alternative pathways associated with exploration through full-field development are common. We demonstrate a policy development approach that combines the Bellman equation for dynamic programming with a real options valuation algorithm. This represents the first demonstration of the mathematical union of the two techniques for branching decision pathways, producing a generalized policy development framework that provides risk management of investments. Production expansion investment decisions for a Central Asian gas condensate field are analyzed using the framework.

Electron beam irradiation was utilized to fabricate planar Josephson junctions in Y 1 Ba 2 Cu 3 O 7 thin films. After the micron-size bridges had been fabricated by way of standard optical lithography, they were modified using a well focused nanometer STEM probe with beam energy within the range of 80 – 120 keV. Modified junctions exhibit a two-step normal/superconductor transition. We attribute the lower transition temperature, which is of the order of 77 K, to the transition of the damaged region. Shapiro steps under applied microwave radiation of the frequency 10–15 GHz, as well as oscillation of the critical current in a magnetic field were observed up to 70 K. A comparison with the RSJ model is made and a possible damage mechanism is discussed.

The properties of YBa 2 Cu 3 O 7− x grain boundary Josephson junctions have been reproducibly modified by a focused electron beam irradiation. The original junctions were fabricated by using the biepitaxial technique on (110) SrTiO 3 substrates. The technique utilizes the property of YBa 2 Cu 3 O 7− x film to grow (103)-oriented on the bare substrate and (001)-oriented on the part of the substrate with the MgO seed layer, providing Josephson junctions of good quality and excellent reproducibility. The junction parameters can be adjusted controllably by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions I C and increased the normal state specific resistivity. The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed. Isothermal annealing partly restores the original junction properties. We also speculate that some aspects of the nature of the grain boundary barriers can be better understood from the study of the transport properties of irradiated junctions. PACS: 74.50+r, 74.72Bk, 74.76Bz, 85.25Cp

The properties of the Y 1 Ba 2 Cu 3 O 7-x biepitaxial Josephson junctions were reproducibly modified by a focused electron beam irradiation of the interface region. The original structures are based on 45° a-axis tilt grain boundaries. The junction parameters can be controllably adjusted by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions and increased the normal state specific resistivity The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed. Isothermal annealing partly restores the original junction properties. Some aspects of the nature of the grain boundary barriers can be better understood from the study of the properties of irradiated junctions.

Electron-beam irradiation has been used to induce controllable variations in the properties of YBa2Cu3O72x biepitaxial grain-boundary Josephson junctions. A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. These results give evidence of the role of the oxygen content and the dielectric constant of the interface region in transport phenomena. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. @S0163-1829~98!51322-2#

A description is given of the fabrication method and Josephson properties of high temperature superconducting junctions produced by focused electron beam writing. The nature of a weak link, I-V characteristics, transition to flux flow, and magnetic field modulation are discussed in some detail. The materials aspects such as the mechanism of e-beam damage to HTS, threshold energy, junction stability, and some technological issues such as reproducibility and uniformity are also addressed. >

Electron beam irradiation has been used to induce controllable variations in the properties of YBa2Cu3O7, biepitaxial grain boundary Josephson junctions. Electron irradiation decreased the critical current of the junctions Ic and increased the normal state specific resistivities. The junction parameters can be adjusted controllably by applying an appropriate dose. The original properties of the junctions could be partly restored by isothermal annealing A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. The experiment also demonstrates frequency tunability in a resonant soliton oscillator. Preliminar results of irradiation on (103) YBCO films have been given demonstrating differences from data on c-axis films, as partly expected from the anisotropy of these materials.

The properties of YBa2Cu3O7-x grain boundary Josephson junctions have been reproducibly modified by a focused electron beam irradiation. The original junctions were fabricated by using the property of YBa2Cu3O7-x film to grow (103)-oriented on the bare (110) SrTiO3 substrate and (001)-oriented on the part of the substrate with the MgO seed layer. The junction parameters can be adjusted controllably by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions Ic and increased the normal state specific resistivity. The shift of the voltage position of the Fiske steps was also observed. Isothermal annealing partly restores the original junction properties. A correlation between the transport properties and the microstructure was obtained by determining the ratio of a barrier thickness to the dielectric constant of the junctions with different barriers. These results give evidence of the role of the oxygen content and the dielectric constant of the interface region in transport phenomena. The experiment also demonstrates frequency tunability in a resonant soliton oscillator.

The properties of the Y1Ba2Cu3O7-x biepitaxial Josephson junctions a ere reproducibly modified by a focused electron beam irradiation of the interface region. The original structures are based on 45 degrees a-axis tilt rain boundaries The junction parameters can be controllably adjusted by applying an appropriate irradiation dose Electron irradiation reduced the critical current of the junctions and increased the normal stare specific resistivity. The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed Isothermal annealing partly restores the original junction properties Some aspects of the nature of the grain boundary barriers can be better understood from the study of the properties of irradiated junctions.

The properties of the Y1Ba2Cu3O7−x biepitaxial Josephson junctions were reproducibly modified by a focused electron beam irradiation of the interface region. The junctions were fabricated by depositing Y1Ba2Cu3O7−x thin film by cylindrical magnetron sputtering technique on the (110) SrTiO3 substrate, partially covered by a pregrown MgO seed layer. The junction parameters can be adjusted controllably by applying an appropriate dose. Electron irradiation decreased the critical current of the junctions IC and increased the normal state resistance times area to values of the order of 1(μ Ω cm2). Some other effects, such as the disappearance of the excess current, were also observed. The original properties of the junctions could be partly restored by isothermal annealing. We also speculate that some aspects of the nature of the grain boundary barriers can be better understood from the study of the properties of irradiated junctions.

We have investigated dc superconducting quantum interference devices (SQUIDs) with loop areas 8 and 64 μm2 made by direct electron beam writing in YBa2Cu3O7−x films with thickness 25 and 50 nm. The SQUIDs have maximum peak‐to‐peak voltage modulation of about 20 μV, which corresponds to the transfer factor dV/dΦ0∼50–60 μV/Φ0 at 30–40 K. By measuring the mutual inductance of the SQUID signal line as a function of temperature and comparing the data with the numerical calculations and the two‐fluid model, we extracted the values of the London penetration depth for YBa2Cu3O7−x thin films.

We have implemented a simple circuit of the rapid single‐flux‐quantum (RSFQ) logic family using a single‐layer YBa2Cu3O7−x thin‐film structure with 14 in‐plane Josephson junctions formed by direct electron beam writing. The circuit includes two dc/SFQ converters, two Josephson transmission lines, a complete RS SFQ flip‐flop, and an SFQ/dc converter (readout SQUID). Low‐frequency testing has shown that the dc‐current‐biased circuit operates correctly and reliably at T∼30 K, a few degrees below the effective critical temperature of the junctions. Prospects for a further increase of the operation temperature and implementation of more complex RSFQ circuits are discussed in brief.

High‐Tc Josephson junctions have been fabricated by direct electron beam writing over YBa2Cu3O7 thin‐film microbridges, using scanning transmission electron microscope (STEM) with an accelerating voltage of 80–120 kV. Annealing at 330–380 K increases Tc and Ic of the junctions and makes them more stable. In the operating range of a few degrees below Tc, the junctions show 100% magnetic field modulation of the critical current, microwave‐induced Shapiro steps oscillating according to the resistively shunted junction (RSJ) model, and RSJ current‐voltage characteristics with IcRn product up to 0.5–0.6 mV at 75 K and 0.3 mV at 77 K.

We present the results of detailed chemical and structural characterization of the VO2/Al/Si(100) thin film heterostructures fabricated by chemical vapor deposition and physical vapor deposition methods. The presence of the thermochromic behavior in the VO2 layer around 68°C and its correlation with the layer composition and structure are discussed. The study compares the structural and chemical properties of the two types of thin VO2 layers: one which exhibits a metal-insulator phase transition around 68°C, and another which fails to undergo the temperature-induced transition. The study of interfaces was carried out by transmission electron microscopy, and showed the existence of an aluminum oxide interfacial layer between VO2 and Al for the samples with the metal-insulator phase transition. The smooth VO2/Al interface and the presence of more than one VO2 monoclinic polytypes were observed for the CVD films exhibiting no phase transition.

The properties of YBa2Cu3O7-x grain boundary Josephson junctions have been reproducibly modified by a focused electron beam irradiation. The original junctions were fabricated by using the biepitaxial technique on (110) SrTiO3, substrates. The technique utilizes the property of YBa2Cu3O7-x film to grow (103)-oriented on the bare substrate and (001)-oriented on the part of the substrate with the MgO seed layer, providing Josephson junctions of good quality and excellent reproducibility. The junction parameters can be adjusted controllably by applying an appropriate irradiation dose. Electron irradiation reduced the critical current of the junctions I-C and increased the normal state specific resistivity. The disappearance of the excess current and the shift of the voltage position of the Fiske steps were also observed. Isothermal annealing partly restores the original junction properties. We also speculate that some aspects of the nature of the grain boundary barriers can be better understood from the study of the transport properties of irradiated junctions.