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- Kassamakova, L, et al.
(author)
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Temperature stable Pd ohmic contacts to p-type 4H-SiC formed at low temperatures
- 1999
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In: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 46:3, s. 605-611
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Journal article (peer-reviewed)abstract
- The formation of low resistivity Pd-based ohmic contacts to p-type 4H-SiC below 750 degrees C are reported herein, The electrical properties of the contacts were examined using I-V measurements and the transmission-line model (TLM) technique. Contact resistivity as a function of annealing was investigated over the temperature range of 600 degrees C-700 degrees C, The lowest contact resistivity (5.5 x 10(-5) Ohm cm(2)) was obtained after annealing at 700 degrees C for 5 min, Atomic force microscopy of the as-deposited Pd layer showed a root-mean square roughness of similar to 8 nm, while after annealing at 700 degrees C, agglomeration occurred, increasing the roughness to 111 nm, Auger electron spectroscopy depth profiles revealed that with annealing, interdiffusion had resulted in the formation of Pd-rich silicides. However, X-ray diffraction and Rutherford backscattering showed that the majority of the film was still (unreacted) Pd. The thermal stability and reliability of the Pd contacts were examined by aging and temperature dependence electrical tests, The contacts annealed at 700 OC were stable at prolonged heating at a constant temperature of 500 degrees C and they showed thermal stability in air at operating temperatures up to 450 degrees C, This stability was not found for contacts formed at lower temperatures of 600 degrees C or 650 degrees C.
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- Carlsson, JRA, et al.
(author)
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A new silicon phosphide, Si12P5 : Formation conditions, structure, and properties
- 1997
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In: Journal of Vacuum Science and Technology A. - : American Vacuum Society. - 0734-2101. ; 15:2, s. 394-401
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Journal article (peer-reviewed)abstract
- The formation conditions, structure, and properties of the recently discovered phosphide, Si12P5 (initially assigned Si7P3), have been studied using x-ray diffraction, high-resolution transmission electron microscopy, photospectrometry, and a four-point probe. The phosphide formed in amorphous Si-P alloy thin films with 30, 35 and 44 at. % P after annealing at 1000°C for 30 min. During annealing at 1100°C, the phosphide dissociated through P evaporation. The Si12P5 phase is proposed to have rhombohedral symmetry with a P31m space group and a C5W12 structure. The hexagonal lattice parameters measured were a = 6.16±0.05 Å and c = 13.17±0.01 Å. The optical band gap and the electrical resistivity of the phosphide were determined to be 1.55 eV and 5 mΩ cm, respectively. The Gibbs free energy diagram for the Si-P system was modified to include this new Si12P5 phase.
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- Kaastad, T S, et al.
(author)
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Effect of intensive training on lower leg structural strength: an in vivo study in ovariectomized rats
- 1997
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In: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 7:4, s. 220-225
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the effect of training on the in vivo tibial structural strength during the development of post-ovariectomy osteoporosis. Seventeen mature Wistar rats (215 g) were ovariectomized and randomized into two groups. The sedentary control group was kept cage confined, while 3 days postoperatively the trained group started treadmill running with high intensity for 1 h 5 days a week. All were given a low calcium diet (Ca 0.01%). After 8 weeks the animals were anaesthetized and the right lower legs fractured during muscle contraction in three-point ventral bending. The left legs were fractured at the same level after removal of all soft tissues. Histomorphometry of the meta- and diaphysis of the distal tibiae was performed. Weight-gain was higher in sedentary (108 g) than in trained (61 g) rats (P<0.0001). There were no significant differences in mechanical results between the groups at in vivo or in vitro fracture. Correcting for weight-gain differences did not change these results. Histomorphometry showed no differences between the groups. Corticosterone was higher in trained than in sedentary rats (P<0.02), and corticosterone may have had a negative influence both on muscle and bone. The study could not show an effect of high intensity training in the early phase after ovariectomy on in vivo or in vitro fracture strength.
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- Kaastad, T S, et al.
(author)
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Effects of clodronate on cortical and trabecular bone in ovariectomized rats on a low calcium diet
- 1997
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In: Calcified Tissue International. - : Springer Science and Business Media LLC. - 1432-0827 .- 0171-967X. ; 61:2, s. 158-164
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate the contribution of a low calcium diet to the cortical and trabecular osteoporosis seen in ovariectomized rats after 7 weeks on a low calcium diet and to investigate the effects of the bisphosphonate clodronate on this development of osteoporosis. Thirty-six mature, female Wistar rats were randomized into four groups: Ovx-B (bisphosphonate) and Ovx-C (control) were ovariectomized, and Sham-Ca (low calcium) and Sham+Ca (normal calcium) were sham operated. The first three groups were fed a low calcium diet (0.01%) and Sham+Ca normal rat chow (Ca 1.1%). The Ovx-B received 10 mg/kg s.c. clodronate daily for nine weeks, and Ovx-C, Sham-Ca, and Sham+Ca received the same volumes of saline. Bone mineral turnover measured as 85Sr-uptake was increased in all low calcium groups compared to Sham+Ca. The Sham+Ca femora had higher dry weight and ash weight than the other groups, and Ovx-C had higher dry weight compared with Ovx-B and Sham-Ca. Calcium content was lower in both Ovx groups compared to both Sham groups. Magnesium was lower in all groups compared to Sham+Ca and higher in Ovx-B compared with Ovx-C. In the femoral shaft, Sham+Ca had significantly higher ultimate bending moment, energy absorption, and deflection compared to the other three groups. Ultimate bending moment was higher in Sham-Ca than in Ovx-C. Stiffness was increased in both Sham+Ca and Ovx-B compared to Ovx-C. The maximum stress in the femoral midshaft was higher in Sham+Ca than in the other groups, and higher in Ovx-B than in Ovx-C. Histomorphometry showed increased medullary area in all low calcium groups compared to Sham+Ca and larger cortical area in Sham+Ca and Ovx-B compared to Ovx-C. Compared to Sham+Ca the trabecular bone volume was decreased to 30% in Sham-Ca and to 9% in Ovx-C, but was unchanged in Ovx-B. The low calcium diet generally increased bone mineral turnover and reduced the tibial bone volume. Femoral changes led to a reduction of cortical fracture strength and maximal stress. Ovariectomy in addition to a low calcium diet reduced femoral strength even more. Daily injections of clodronate to ovariectomized rats on a low calcium diet increased femoral shaft stiffness and maximum stress, and clodronate preserved both trabecular and cortical tibial bone volume completely.
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