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| 2. |
- Andersson, Joakim, et al.
(författare)
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Diamanter blir var mans egendom
- 2003
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Ingår i: Forskning & Framsteg. ; :1, s. 38-41
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
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| 4. |
- Hammersberg, Johan, et al.
(författare)
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Injection dependent long carrier lifetimes in high quality CVD diamond
- 2001
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:3-7, s. 574-579
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report an experimental study of photocurrent mobility x lifetime products and free carrier lifetimes in CVD grown polycrystalline diamond of various qualities. The investigated samples are low impurity samples, nitrogen content similar to 10(15) cm(-3), with an average grain size ranging from 25 mum up to 110 mum. This large difference in average grain size makes it possible to distinguish effects due to Lifetime limiting trapping and recombination defect centers inside the grains from effects caused by defect centers at grain boundaries. At low carrier densities, < 10(13) cm(-3) the effective free carrier lifetime is in the sub-nanosecond to nanosecond range in all samples due to intra-grain trapping and recombination centers. At high carrier densities, > 10(13) cm(-3), the intra-grain centers becomes saturated and the effective lifetime becomes predominately given by carrier diffusion to and recombination at the defects related to the grain boundaries. Hence, the effective lifetime at high carrier densities is strongly related to the average grain size and increases up to several tens of nanoseconds, in samples with a large average grain size, whereas it remains in the nanosecond range for samples with small average grain size. In addition, we observe a lower mobility x lifetime product and decay constant with increasing nitrogen content, clearly showing the negative influence of nitrogen and nitrogen-related defects on these important material parameters.
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| 8. |
- Nilsson, Tore, et al.
(författare)
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Virtual reality for simulation of radiographic projections: validation of projection geometry
- 2004
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Ingår i: Dento-Maxillo-Facial Radiology. - : British Institute of Radiology. - 0250-832X .- 1476-542X. ; 33:1, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To develop a software for virtual reality (VR) simulation of X-ray images based on perspective projections through a patient model derived from data from a CT examination and to evaluate the accuracy in the projection geometry obtained by the software. Methods: A VR software was developed on a personal computer, with models of a patient, an X-ray machine and a detector. The model of the patient was derived from data from a CT examination of a dry skull. Simulated radiographic images of the patient model could be rendered as perspective projections based on the relative positions between the models. The projection geometry of the software was validated by developing an artificial CT data set containing high attenuation points as objects to be imaged. The accuracy in projection geometry was evaluated in a systematic way. The distances between two dots, representing the projected test points in the simulated radiographic images, were measured. They were compared with theoretical calculations of the corresponding distances using traditional mathematical tools. Results: The difference between the simulated and calculated projected distances never exceeded 0.5 mm. The error in simulated projected distances was in most cases within 1%. No systematic errors were revealed. Conclusion: The software, developed for personal computers, can produce simulated X-ray images with high geometric accuracy based on perspective projections through a CT data set. The software can be used for simulation of radiographic examinations.
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| 9. |
- Twitchen, D.J., et al.
(författare)
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High Voltage Single Crystal Diamond Diodes
- 2004
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383 .- 1557-9646. ; 51:5, s. 826-828
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Tidskriftsartikel (refereegranskat)abstract
- Demonstration of a 2.5-kV diamond diode is provided by electrical measurements using a circular gold Schottky contact, with an area > 1 mm(2), on large area freestanding single-crystal diamond consisting of a thin high purity layer (< 1 X 10(13) [B]/cm(3)) on a thicker heavily boron-doped (> 1 X 10(19) [B]/cm(3)) substrate with an ohmic back contact. The diode structures were fabricated using a microwave-assisted chemical vapor deposition process. The forward properties of the diode show a space charge limited current, with a forward-voltage drop of 2 V and a hole mobility of 4100 +/- 400 cm(2) /Vs at room temperature. For temperatures between 300 K < T < 380 K the mobility show T-312 dependence. This is consistent with acoustic phonon scattering, emphasizing the high purity quality of the top layer in which carrier transport is phonon rather than defect limited.
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