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- Dick Thelander, Kimberly, et al.
(author)
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Growth of GaP nanotree structures by sequential seeding of 1D nanowires
- 2004
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 272:1-4, s. 131-137
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Journal article (peer-reviewed)abstract
- Complex nanostructures are becoming increasingly important for the development of nanoscale devices and functional nanomaterials. Precise control of size and morphology of these structures is critical to their fabrication and exploitation. We have developed a method for stepwise growth of tree-like nanostructures via the vapour liquid-solid (VLS) growth mode, demonstrated for III-V semiconductor materials. This method uses the initial seeding of nanowires by catalytic aerosol nanoparticles to form the trunk, followed by sequential seeding of branching structures. Here we present a detailed study of the growth of these complex structures using Gap. Diameter of each level of nanowires is directly determined by seed particle diameters, and number of branches is determined by seed particle density. Growth rate is shown to increase with temperature to a maximum corresponding to the temperature of complete decomposition of the Group-III precursor material, and subsequently decrease due to competition with bulk growth. Growth rate also depends on flow of the Group-III precursor, but not on the Group-V precursor. Finally, there is a relationship between the number of branches and their growth rate, suggesting that material diffusion plays a role in nanowire branch growth. (C) 2004 Elsevier B.V. All rights reserved.
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- Seifert, Werner, et al.
(author)
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Growth of one-dimensional nanostructures in MOVPE
- 2004
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 272:1-4, s. 211-220
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Journal article (peer-reviewed)abstract
- The use of metal organic vapor-phase epitaxy (MOVPE) for growth of one-dimensional nanostructures in the material systems GaAs, GaP, InAs and InP is investigated. Some kinetic effects are discussed, especially the general finding that in MOVPE thinner whiskers grow faster than thicker whiskers. Effects of growth temperature on growth rate and shape of the whiskers, the effects of different growth directions on the perfection of the materials and the possibilities to grow heterostructures in axial and lateral directions are reported. Ways to overcome the randomness in whisker growth by controlled seeding of the Au particles and by using lithography for site control are demonstrated.
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- Fritzell, Peter, et al.
(author)
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Cost-effectiveness of lumbar fusion and nonsurgical treatment for chronic low back pain in the Swedish lumbar spine study : A multicenter, randomized, controlled trial from the Swedish Lumbar Spine Study Group
- 2004
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In: Spine. - : Lippincott Williams & Wilkins. - 0362-2436 .- 1528-1159. ; 29:4, s. 421-434
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Journal article (peer-reviewed)abstract
- Study Design. A cost-effectiveness study was performed from the societal and health care perspectives. Objective. To evaluate the costs-effectiveness of lumbar fusion for chronic low back pain (CLBP) during a 2-year follow-up. Summary of Background Data. A full economic evaluation comparing costs related to treatment effects in patients with CLBP is lacking. Patients and Methods. A total of 284 of 294 patients with CLBP for at least 2 years were randomized to either lumbar fusion or a nonsurgical control group. Costs for the health care sector ( direct costs), and costs associated with production losses ( indirect costs) were calculated. Societal total costs were identified as the sum of direct and indirect costs. Treatment effects were measured using patient global assessment of improvement, back pain ( VAS), functional disability (Owestry), and return to work. Results. The societal total cost per patient ( standard deviations) in the surgical group was significantly higher than in the nonsurgical group: Swedish kroner (SEK) 704,000 ( 254,000) vs. SEK 636,000 ( 208,000). The cost per patient for the health care sector was significantly higher for the surgical group, SEK 123,000 ( 60,100) vs. 65,200 ( 38,400) for the control group. All treatment effects were significantly better after surgery. The incremental cost-effectiveness ratio ( ICER), illustrating the extra cost per extra effect unit gained by using fusion instead of nonsurgical treatment, were for improvement: SEK 2,600 ( 600 - 5,900), for back pain: SEK 5,200 ( 1,100 - 11,500), for Oswestry: SEK 11,300 ( 1,200 - 48,000), and for return to work: SEK 4,100 ( 100 21,400). Conclusion. For both the society and the health care sectors, the 2-year costs for lumbar fusion was significantly higher compared with nonsurgical treatment but all treatment effects were significantly in favor of surgery. The probability of lumbar fusion being cost-effective increased with the value put on extra effect units gained by using surgery.
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