Hafnium oxide (HfO2) is one of the most promising high-k materials to replace SiO2 as a gate dielectric. Here we report material and electrical characterization of atomic layer deposition (ALD) ...hafnium oxide and the correlations between the results. The HfO2 films were deposited at 200, 300, or 370DGC and annealed in a nitrogen ambient at 550, 800, and 900DGC. Results indicate that deposition temperature controls both the material and the electrical properties. Materials and electrical properties of films deposited at 200DGC are most affected by annealing conditions compared to films deposited at higher temperatures. These films are amorphous as deposited and become polycrystalline after 800DGC anneals. Voids are observed after a 900DGC anneal for the 200DGC deposited films. The 200DGC deposited films have charge trapping and high leakage current following anneals at 900DGC. The 300DGC deposited films have lower chlorine content and remain void-free following high-temperature anneals. These films show a thickness-dependent crystal structure. Annealing the films reduces leakage current by four orders of magnitude. Finally, films deposited at 370DGC have the highest density, contain the least amount of impurities, and contain more of the monoclinic phase of HfO2 than those deposited at 300 and 200DGC. The best electrical performance was obtained for films deposited at 370DGC.
The factors that control carbon nanotube (CNT) adsorption onto aminopropyl siloxane (APS)-derivatized surfaces were investigated using two distinct types of well-characterized films with significant ...differences in their detailed structures. Both types of APS films showed a marked increase in CNT adsorption relative to untreated SiO2 surfaces but differed in the amount of CNTs adsorbed. To gain insight into the factors governing adsorption, the surface coverage of the CNTs was monitored as a function of the pH during the deposition, the surfactant used to suspend the CNTs, and the type and amount of salt added to the deposition solution. The adsorption is shown to be governed by electrostatic and VDW forces. In the case of complimentarily charged surfaces, the adsorption is proposed to occur through an ion exchange mechanism.
Synchrotron radiation based total reflection X-ray fluorescence (TXRF) has been shown to meet the critical needs of the semiconductor industry for the analysis of transition metal impurities on ...silicon wafer surfaces. The current best detection limit achieved at the Stanford Synchrotron Radiation Laboratory (SSRL) for Ni is 8×10
7 atoms/cm
2 which is a factor of 50 better than what can be achieved using laboratory-based sources. SSRL has established a TXRF facility which meets the cleanliness and stability requirements of the semiconductor industry. This has enabled both industrial and academic researchers to address industrially relevant problems. In addition research is being carried out for the analysis of light elements such as Al and Na.
Having established detection limits for transition elements exceeding current requirements of the semiconductor industry, our recent efforts at the Stanford Synchrotron Radiation Laboratory (SSRL) ...have focused on the improvement of the detection sensitivity for light elements such as Al. Data analysis is particularly challenging for Al, due to the presence of the neighboring Si signal from the substrate. Detection limits can be significantly improved by tuning the excitation energy below the Si–K absorption edge. For conventional TXRF systems this can be done by using a W–Mα fluorescence line (1.78 keV) for excitation. At a synchrotron radiation facility energy tunability is available. However, in both cases this results in a substantial increase in background due to resonant X-ray Raman scattering. This scattering dominates the background under the Al Kα fluorescence line, and consequently limits the achievable sensitivity for the detection of Al surface contaminants. In particular, we find that for a precise determination of the achievable sensitivity, the specific shape of the continuous Raman background must be taken into account in the data analysis. The data deconvolution presented here opens a new perspective for conventional TXRF systems to mitigate this background limitation. This results in a minimum detection limit of 2.4×10
9 atoms/cm
2 for Al. Based on these results it will also be demonstrated that by improving the detector resolution, the minimum detection limit can be improved significantly. For a detector resolution of 15 eV as predicted for novel superconducting tunnel junction detectors, an improvement in minimum detection limit of approximately a factor of 3 can be estimated.
Recent advances and perspectives in synchrotron radiation TXRF Baur, K.; Brennan, S.; Werho, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2001, Letnik:
467
Journal Article
Recenzirano
Odprti dostop
Total reflection X-ray fluorescence (TXRF) using Synchrotron Radiation is likely to be the most powerful non-destructive technique for the analysis of trace metal impurities on silicon wafer ...surfaces. Of fundamental importance in TXRF is the achievable sensitivity as characterized by the minimum detection limit. This work describes the progress we achieved recently at the Stanford Synchrotron Radiation Laboratory (SSRL) in minimum detection limits for transition metals and will give an estimate of what can be achieved using a third generation synchrotron radiation source such as SPEAR3.
IMPORTANCE: Extubation failure (EF) after pediatric cardiac surgery is associated with increased morbidity and mortality. OBJECTIVES: We sought to describe the risk factors associated with early (< ...48 hr) and late (48 hr ≤ 168 hr) EF after pediatric cardiac surgery and the clinical implications of these two types of EF. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cohort study using prospectively collected clinical data for the Pediatric Cardiac Critical Care Consortium (PC4) Registry. Pediatric patients undergoing Society of Thoracic Surgeons benchmark operation or heart transplant between 2013 and 2018 available in the PC4 Registry were included. MAIN OUTCOMES AND MEASURES: We analyzed demographics and risk factors associated with EFs (primary outcome) including by type of surgery. We identified potentially modifiable risk factors. Clinical outcomes of mortality and length of stay (LOS) were reported. RESULTS: Overall 18,278 extubations were analyzed. Unplanned extubations were excluded from the analysis. The rate of early EF was 5.2% (948) and late EF was 2.5% (461). Cardiopulmonary bypass time, ventilator duration, airway anomaly, genetic abnormalities, pleural effusion, and diaphragm paralysis contributed to both early and late EF. Extubation during day remote from shift change and nasotracheal route of initial intubation was associated with decreased risk of early EF. Extubation in the operating room was associated with an increased risk of early EF but with decreased risk of late EF. Across all operations except arterial switch, EF portrayed an increased burden of LOS and mortality. CONCLUSION AND RELEVANCE: Both early and late EF are associated with significant increase in LOS and mortality. Study provides potential benchmarking data by type of surgery. Modifiable risk factors such as route of intubation, time of extubation as well as treatment of potential contributors such as diaphragm paralysis or pleural effusion can serve as focus areas for reducing EFs.
Background Stroke is a common complication of extracorporeal membrane oxygenation (ECMO), and pediatric cardiac surgical patients may be at higher risk. Epidemiology and risk factors for stroke in ...these patients are not well characterized. Methods We analyzed pediatric (<18 years) cardiac ECMO cases in the Extracorporeal Life Support Organization Registry from 2002 to 2013. Cardiac surgical patients were identified, and procedures were stratified according to The Society of Thoracic Surgeons morbidity categories. The primary outcome was any stroke (hemorrhagic or infarction) identified by neuroimaging. Risk factors were identified through multivariable logistic regression. Results We analyzed 3,517 cardiac surgical patients; 81% with cyanotic disease, and 57% in high-risk categories from The Society of Thoracic Surgeons (categories 4 and 5). Overall, 12% experienced stroke while receiving ECMO, and those with stroke had greater in-hospital mortality (72% versus 51%; p < 0.0001). In multivariable analysis, neonatal status (adjusted odds ratio, 1.8; 95% confidence interval, 1.3 to 2.4), lower weight-for-age z score (adjusted odds ratio, 1.1 for each 1-point decrease; 95% confidence interval, 1.04 to 1.25), and longer ECMO duration (upper quartile ≥167 hours adjusted odds ratio, 1.4; 95% confidence interval, 1.1 to 1.8) were independently associated with increased stroke risk, whereas cyanotic disease, The Society of Thoracic Surgeons category, and bypass time were not. Conclusions This multicenter analysis demonstrates that pediatric cardiac surgical patients on ECMO are at high risk of stroke; younger or underweight patients and those with longer ECMO duration are at greatest risk, independent of procedural complexity. Future study is necessary to determine how anticoagulation or other clinical practices can be modified to reduce stroke incidence.
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