Si interstitial contribution of F+ implants in crystalline Si

The F effect in crystalline Si is quantified by monitoring defects and B diffusion in samples implanted with 25 keV F+ and/or 40 keV Si+. We estimate that about +0.4 Si interstitials are generated per implanted F+ ion, in agreement with the value resulting from the net separation of Frenkel pairs. For short annealings, B diffusion is lower when F+ is coimplanted with Si+ than when only Si+ is implanted, while for longer annealings, B diffusion is higher. This is consistent with a lower but longer-lasting Si interstitial supersaturation set by the additional defects generated by the F+ implant

Structural and optical properties of Ge islands grown in an industrial chemical vapor deposition reactor

The use of Si based materials for optoelectronic applications is hampered by the indirect nature of the band gap. One possible solution by which to improve the radiative light emission is three-dimensional Stranski-Krastanow growth of Si1-xGex or pure Ge on top of Si. In this article we give a detailed overview about the growth kinetics observed for Ge growth in a standard production oriented chemical vapor deposition system. With increasing deposition time, we observed the usual changeover from monomodal to bimodal island distribution. The island morphology and density can be controlled by varying the growth conditions or by applying a thermal anneal after island growth. Island densities up to 2.3x10(10) cm(-2) have been obtained for depositions at 650 degreesC. A Si cap layer is needed for photoluminescence measurements as well as for some device structures. However, Si capping at 700 degreesC leads to nearly total dissolution of small islands and truncation of bigger dome-shaped islands. This can be prevented by reducing the deposition temperature and by changing the Si gas source. Photoluminescence measurements demonstrate the high layer quality of Si capped islands by the clear separation between the no-phonon line and the transversal optical (TO) replica and the high peak intensities. The spectral range of the island luminescence is between 1.35 (920 meV) and 1.50 mum (828 meV) and depends on the growth conditions. At 20 K, we found up to 70 times higher values for the integrated no-phonon and the TO luminescence from the islands, compared to the integrated intensity from the Si TO peak. Nevertheless, the high photoluminescence intensity can be further enhanced by a thermal treatment in a H-2 plasma. Clear island luminescence up to 200 K has been observed after such thermal treatment, which shows the potential of this material system for optoelectronic device applications. (C) 2001 American Institute of Physics

Diffusion suppression in silicon by substitutional C doping

\u3cp\u3eThe role of C as a suppressor of B, P, and In diffusion is widely known but the mechanisms involved are still poorly understood. This paper presents novel results on the diffusion of C at the nanometer scale, which clearly show that the suppression of diffusion arises from the expulsion of interstitials from the Cdoped region, caused by long-range migration of interstitial C atoms. Fundamental parameters for C diffusion (migration frequency and jump length) are presented and compared with existing data for B diffusion, and the results are placed in the context of a unified model of impurity diffusion.\u3c/p\u3

Experimental study on the mechanism of carbon diffusion in silicon

\u3cp\u3eCVD-grown lightly C-doped superlattices with peak C concentrations of 2.10\u3csup\u3e18\u3c/sup\u3e/cm\u3csup\u3e2\u3c/sup\u3e and 2.10\u3csup\u3e19\u3c/sup\u3e/cm\u3csup\u3e2\u3c/sup\u3e were annealed in NH\u3csub\u3e3\u3c/sub\u3e, N\u3csub\u3e2\u3c/sub\u3e/H\u3csub\u3e2\u3c/sub\u3e, N\u3csub\u3e2\u3c/sub\u3e, and O\u3csub\u3e2\u3c/sub\u3e ambient gases to investigate the influence of a range of point-defect conditions on C diffusion at the nanometer scale. C profiles were measured by Secondary-ion mass spectroscopy. The profiles exhibit exponential-like diffusion consistent with a 'long hop' diffusion process with a characteristic migration length λ (=19 ± 3 nm at 850 °C). Within experimental errors the value of λ is the same for all the ambient gases used, whereas the migration frequency g increases by two orders of magnitude as the ambient gas is changed from NH\u3csub\u3e3\u3c/sub\u3e ambient (interstitial undersaturation) to O\u3csub\u3e2\u3c/sub\u3e ambient (interstitial supersaturation), and decreases as a function of C concentration in the as-grown superlattice. The results confirm that C diffuses predominantly by a kick out mechanism under near-equilibrium diffusion conditions. Initial results support the chemical-pump model for suppression of diffusion in C-doped silicon.\u3c/p\u3

Si interstitial contribution of F+ implants in crystalline Si

The F effect in crystalline Si is quantified by monitoring defects and B diffusion in samples implanted with 25 keV F+ and/or 40 keV Si+. We estimate that about +0.4 Si interstitials are generated per implanted F+ ion, in agreement with the value resulting from the net separation of Frenkel pairs. For short annealings, B diffusion is lower when F+ is coimplanted with Si+ than when only Si+ is implanted, while for longer annealings, B diffusion is higher. This is consistent with a lower but longer-lasting Si interstitial supersaturation set by the additional defects generated by the F+ implant

Evolution of fluorine and boron profiles during annealing in crystalline Si

In this work the authors study the interaction of F with point defects and the influence of F on B diffusion in crystalline Si. The authors perform 25 and 100 keV F+ implants and combine them with a 40 keV Si+ implant. The appearance of peaks in the F profile during annealing supports the idea of the formation of F complexes with vacancies and Si interstitials. In all samples implanted with F+ analyzed in this work, B diffusion is higher than in equilibrium conditions indicating that F+ implants in crystalline Si produce a Si interstitial supersaturation. However, B diffusion is reduced when F+ is coimplanted with Si, compared to only Si implants. This effect is more evident when B is located in the region where the F+ implant generates an excess of vacancies, but it also appears in the Si interstitial-rich region. The results indicate that the effect of F on B diffusion in crystalline Si is time dependent

Quantitative prediction of junction leakage in bulk-technology CMOS devised

Junction leakage becomes more significant as metal-oxide-semiconductor (MOS) technologies scale down in bulk-silicon. In this work we quantify the four key elements to junction leakage generation through a combination of experiment and device simulation. These elements are: (i) ultra-shallow junction steepness, (ii) channel and pocket concentrations, (iii) junction curvature, and (iv) the presence of residual defects. We first characterize n+/p and p+/n diodes to quantify how changes in doping profiles affect reverse bias leakage. Diodes with end-of-range (EOR) silicon defects intentionally located in the junction depletion region are also characterized to quantify their contribution. This feeds into a device simulation study to gain insight in the experimental results and in the capabilities of available physical models. Thereafter simulation is used to predict leakage in future generation bulk-silicon MOS devices. In summary, band-to-band tunneling (BBT) due to aggressively scaled doping profiles and trap-assisted tunneling (TAT) due to the increased presence of defects make off-state low-standby-power leakage targets difficult to meet. With the increase of junction leakage from aggressively scaled ultra-shallow junctions, the assumption that the subthreshold leakage component dominates off-state current is no longer valid

Impact of a Postintensive Care Unit Multidisciplinary Follow-up on the Quality of Life (SUIVI-REA): Protocol for a Multicenter Randomized Controlled Trial

International audienceBackground: Critically ill patients are at risk of developing a postintensive care syndrome (PICS), which is characterized by physical, psychological, and cognitive impairments and which dramatically impacts the patient's quality of life (QoL). No intervention has been shown to improve QoL. We hypothesized that a medical, psychological, and social follow-up would improve QoL by mitigating the PICS. Objective: This multicenter, randomized controlled trial (SUIVI-REA) aims to compare a multidisciplinary follow-up with a standard postintensive care unit (ICU) follow-up. Methods: Patients were randomized to the control or intervention arm. In the intervention arm, multidisciplinary follow-up involved medical, psychological, and social evaluation at ICU discharge and at 3, 6, and 12 months thereafter. In the placebo group, patients were seen only at 12 months by the multidisciplinary team. Baseline characteristics at ICU discharge were collected for all patients. The primary outcome was QoL at 1 year, assessed using the Euro Quality of Life-5 dimensions (EQ5D). Secondary outcomes were mortality, cognitive, psychological, and functional status; social and professional reintegration; and the rate of rehospitalization and outpatient consultations at 1 year. Results: The study was funded by the Ministry of Health in June 2010. It was approved by the Ethics Committee on July 8, 2011. The first and last patient were randomized on December 20, 2012, and September 1, 2017, respectively. A total of 546 patients were enrolled across 11 ICUs. At present, data management is ongoing, and all parties involved in the trial remain blinded. Conclusions: The SUVI-REA multicenter randomized controlled trial aims to assess whether a post-ICU multidisciplinary follow-up improves QoL at 1 year