Laser doping of chromium as a double acceptor in silicon carbide with reduced crystalline damage and nearly all dopants in activated state

Chromium, a p-type dopant, has been incorporated into silicon carbide by laser doping. Secondary ion mass spectrometric data revealed enhanced solid solubility (2.29 × 1019 cm?3 in 6H–SiC and 1.42 × 1919 cm?3 in 4H–SiC), exceeding the equilibrium limit (3 × 1017 cm?3 in 6H–SiC above 2500 °C). The roughness, surface chemistry and crystalline integrity of the doped sample were examined by optical interferometry, energy dispersive X-ray spectrometry and transmission electron microscopy, respectively, and showed no crystalline disorder due to laser heating. Deep-level transient spectroscopy confirmed Cr as a deep-level acceptor with activation energies Ev + 0.80 eV in 4H–SiC and Ev + 0.45 eV in 6H–SiC. The Hall effect measurements showed that the hole concentration (1.942 × 1019 cm?3) is almost twice the average Cr concentration (1 × 1019 cm?3), confirming that almost all of the Cr atoms were completely activated to the double acceptor state by the laser-doping process without requiring any additional annealing step.

Sachin Beta?Nathaniel Quickb?Aravinda Kara Email:akar@creol.ucf.edu
[a]Laser-Aided Manufacturing, Materials; Micro-processing Laboratory [LAMMMP], College of Optics; Photonics, Center for Research; Education in Optics; Lasers [CREOL], MMAE, University of Central Florida, Orlando, FL 32816-2700, USA;[b]Applicote Associates, LLC, 1445 Dolgner Pl., Ste. 23, Sanford, FL 32771, USA

Low temperature, pressure-assisted sintering of nanoparticulate silver films

The laser ablation of microparticle aerosol (LAMA) process was used to direct-write nanostructured, patterned films of silver with thicknesses in the range 20–200 ?m at room temperature. A critical difference between the LAMA process and conventional processes for depositing patterned, thick films is that the LAMA process does not require surfactants that can interfere with post-deposition sintering. Thus, LAMA-produced films allow the intrinsic sintering of nanoparticulate films to be studied directly. Post-deposition sintering was conducted over a range of temperatures (100–175 °C) and compression loads (25–600 N) and the strength and electrical resistivity of the sintered samples were measured. The samples were characterized using optical microscopy, profilometry, SEM, and XRD and the density of the deposits were determined from the grain size, resistivity and known relationships between these parameters and density. LAMA-produced films were found to sinter to produce high strength, high conductivity films at temperatures 50–100 °C lower than conventional processes that use organic additives. Mechanisms for the low-temperature sintering of the nanostructured films are discussed and compared with established theory for pressure-assisted sintering.

Andre D. Alberta?Michael F. Beckerb?John W. Ketoc?Desiderio Kovard Email:dkovar@mail.utexas.edu
[a]Materials Science; Engineering Program, Center for Nano; Molecular Science; Technology; Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA;[b]Department of Electrical; Computer Engineering, Center for Nano; Molecular Science; Technology, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA;[c]Department of Physics, Center for Nano; Molecular Science; Technology, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA;[d]Department of Mechanical Engineering, Center for Nano; Molecular Science; Technology, Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA

Leaves in turbidite sands: The main source of oil and gas in the deep-water Kutei Basin, Indonesia: Reply

We are glad that Shanmugan has taken time to read and think about our recent article in the AAPG Bulletin. However, the discussion that he has written seems more oriented toward presenting his own sedimentologic ideas than debating whether leaves in deep-water sands can produce viable source rocks, which was the purpose of our article. Nevertheless, we will address some of his questions below.

Arthur Sailer?John Dunham?Rui Lin
Chevron ETC, 1500 Louisiana, Houston, Texas 77002; Chevron Thailand Exploration and Production, Tower III, SCB Park Plaza, 19 Ratchadapisek Road, Chatuchak, Bangkok 10900, Thailand

LEARNING HIGH.TECH @THE BENCH

U.S. District Judge Thomas Penfield Jackson (at right) was quickly thrust into the digital age when the Microsoft case landed before him. Jackson, it turns out, was a quick study. As more high-tech cases flood the courts, there are growing questions about whether other judges will fare as well.

Debra Baker

LOCKED UP TIGHT

Some 3,000 immigrants are lost in the legal limbo known as indefinite detention. They don’t qualify for entry into this country, but there is nowhere else to send them. Critics blame the Immigration and Naturalization Service and a 1996 law for the catch-22. Some legislators say it’s time to revisit the issue.

Margaret Graham Tebo

Learning about economic development from Africa

This article reviews the author’s acquaintance with the literature of economic development, with particular reference to Africa, over the last 50 years. The belief that this development is propelled by the supply of capital, effectively of international aid, is criticized, and emphasis put instead on the effective demand for capital. This demand has been low in Africa; hence much capital investment has been of low or no productivity, and aid has generally failed to fulfil expectations. Aid continues nonetheless, since it serves donor as well as recipient interests and political opposition to it is weak. Continue reading “Learning about economic development from Africa”

Leaves in turbidite sands:The main source of oil and gas in the deep-water Kutei Basin,Indonesia:Reply

We are glad that Shanmugan has taken time to read and think about our recent article in the AAPG Bulletin. However, the discussion that he has written seems more oriented toward presenting his own sedimentologic ideas than debating whether leaves in deep-water sands can produce viable source rocks, which was the purpose of our article. Nevertheless, we will address some of his questions below. Continue reading “Leaves in turbidite sands:The main source of oil and gas in the deep-water Kutei Basin,Indonesia:Reply”

Leaves in turbidite sands: The main source of oil and gas in the deep-water Kutei Basin,Indonesia:Discussion

Sailer et al. (2006) have concluded that leaves in the upper Miocene turbidite sands were the main source of oil and gas in the deep-water Kutei Basin, East Kalimantan (Borneo), Indonesia. They have reported that oils from the Kutei Basin have high (4-7) pristane/phytane ratios, suggesting a coaly organic source. Continue reading “Leaves in turbidite sands: The main source of oil and gas in the deep-water Kutei Basin,Indonesia:Discussion”