L. Hoffmann

Si-H stretch modes of hydrogen-vacancy defects in silicon

Abstract The Si H stretch modes in proton-implanted crystalline silicon have been studied by FTIR spectroscopy. From the annealing behaviour and dose dependence of the stretch-mode intensities, it is found that one complex gives rise to modes at 2121 and 2144 cm −1 , a second to modes at 2166 and 2191 cm −1 , and a third to a single mode at 2222 cm −1 . The isotope shifts of these centres have been obtained from measurements on samples implanted with protons and deuterons. Moreover, the symmetries of the centres have been determined from uniaxial stress measurements. We assign the 2121 and 2144 cm −1 modes to VH 2 , the 2166 and 2191 cm −1 modes to VH 3 , and the 2222 cm −1 mode to VH 4 . Another mode at 2068 cm −1 is tentatively ascribed to VH. The Si H and Si D stretch modes of VH n D m ( n + m ≤ 4) have been calculated with a simple model which has been used to fit all the experimental frequencies. The agreement between fitted and observed frequcies is excellent.

C-H complex in Si observed at low temperatures

Abstract Local vibrational modes of a carbon–hydrogen complex have been identified with infrared absorption spectroscopy. After implantation of protons or deuterons at ≈20 K a carbon mode at 596 cm−1 and a hydrogen mode at 1884 cm−1 are observed in the sample annealed at 180 K. The two modes originate from the same defect, which is tentatively identified as bond centred hydrogen in the vicinity of a nearby substitutional carbon atom.

Inter-tester reproducibility of tumour change in small cell lung cancer patients undergoing chemoradiotherapy

Abstract Background. Tumour volume change during delivery of chemoradiotherapy is observed in small cell lung cancer (SCLC) patients. In this study, we have compared tumour volume and anatomical changes, e.g. atelectasis or pleural effusions determined by three different methods. Method. A total of 37 SCLC patients undergoing thoracic radiotherapy during 2010–2011 were included. The patients were treated based on a daily three-dimensional (3D) cone beam computed tomography (CBCT) bony anatomy registration. The CBCT scans were retrospectively reviewed visually by a radiation therapist (Visual-RTT) in order to register tumour volume changes. Furthermore, the tumour volume changes were obtained by either deformable image registration (DIR) or delineation by a radiation oncologist (RO). Kappa (κ) statistics and paired t-tests were used for evaluation of the inter-tester agreement. Results. The tumour volume change between the Visual-RTT, the DIR and the RO assessments obtained 84–97% agreement (κ = 0.68–0.95). Furthermore, there was no statistically significant difference between the tumour change assessment of the RO (mean 13.6 ml) and the DIR (mean 14.5 ml), p = 0.59. Tumour shrinkage was observed in 15 (41%) patients and anatomical changes in seven (19%) patients. Conclusion. The inter-tester reproducibility of tumour volume change between the three methods is excellent. Visual-RTT on-line inspection may be used to determine tumour shrinkage and anatomical changes as atelectasis or pleural effusions during the radiotherapy course by use of daily CBCT scans.

Local vibrational modes of a dicarbon–hydrogen center in crystalline silicon

Carbon-doped silicon irradiated with electrons at room temperature and subsequently implanted with protons has been studied by infrared absorption spectroscopy. Isochronal annealing in the temperat ...

Raman Investigation of the Localized Vibrational Mode of Carbon in Strain-Relaxed Si1-xGex:C

The localized vibrational mode (LVM) of carbon in strain-relaxed Si1-xGex:C samples with x=0, 0.05, 0.35, and 0.5 have been investigated by Raman spectroscopy at room- and liquid-nitrogen-temperatures. The position of the Raman peaks due to LVM of carbon shifts linearly to lower frequencies with increasing x from 0 to 0.5. The LVM frequencies of carbon obtained by Raman measurement agree very well with those determined by Hoffmann et al. in infrared (IR) absorption recently.