To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Introduction: Although use of point of care ultrasound (PoCUS) protocols for patients with undifferentiated hypotension in the Emergency Department (ED) is widespread, our previously reported SHoC-ED study showed no clear survival or length of stay benefit for patients assessed with PoCUS. In this analysis, we examine if the use of PoCUS changed fluid administration and rates of other emergency interventions between patients with different shock types. The primary comparison was between cardiogenic and non-cardiogenic shock types. Methods: A post-hoc analysis was completed on the database from an RCT of 273 patients who presented to the ED with undifferentiated hypotension (SBP <100 or shock index > 1) and who had been randomized to receive standard care with or without PoCUS in 6 centres in Canada and South Africa. PoCUS-trained physicians performed scans after initial assessment. Shock categories and diagnoses recorded at 60 minutes after ED presentation, were used to allocate patients into subcategories of shock for analysis of treatment. We analyzed actual care delivered including initial IV fluid bolus volumes (mL), rates of inotrope use and major procedures. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: Although there were expected differences in the mean fluid bolus volume between patients with non-cardiogenic and cardiogenic shock, there was no difference in fluid bolus volume between the control and PoCUS groups (non-cardiogenic control 1878 mL (95% CI 1550 – 2206 mL) vs. non-cardiogenic PoCUS 1687 mL (1458 – 1916 mL); and cardiogenic control 768 mL (194 – 1341 mL) vs. cardiogenic PoCUS 981 mL (341 – 1620 mL). Likewise there were no differences in rates of inotrope administration, or major procedures for any of the subcategories of shock between the control group and PoCUS group patients. The most common subcategory of shock was distributive. Conclusion: Despite differences in care delivered by subcategory of shock, we did not find any significant difference in actual care delivered between patients who were examined using PoCUS and those who were not. This may help to explain the previously reported lack of outcome difference between groups.
Introduction: Point of care ultrasound has been reported to improve diagnosis in non-traumatic hypotensive ED patients. We compared diagnostic performance of physicians with and without PoCUS in undifferentiated hypotensive patients as part of an international prospective randomized controlled study. The primary outcome was diagnostic performance of PoCUS for cardiogenic vs. non-cardiogenic shock. Methods: SHoC-ED recruited hypotensive patients (SBP < 100 mmHg or shock index > 1) in 6 centres in Canada and South Africa. We describe previously unreported secondary outcomes relating to diagnostic accuracy. Patients were randomized to standard clinical assessment (No PoCUS) or PoCUS groups. PoCUS-trained physicians performed scans after initial assessment. Demographics, clinical details and findings were collected prospectively. Initial and secondary diagnoses including shock category were recorded at 0 and 60 minutes. Final diagnosis was determined by independent blinded chart review. Standard statistical tests were employed. Sample size was powered at 0.80 (α:0.05) for a moderate difference. Results: 273 patients were enrolled with follow-up for primary outcome completed for 270. Baseline demographics and perceived category of shock were similar between groups. 11% of patients were determined to have cardiogenic shock. PoCUS had a sensitivity of 80.0% (95% CI 54.8 to 93.0%), specificity 95.5% (90.0 to 98.1%), LR+ve 17.9 (7.34 to 43.8), LR-ve 0.21 (0.08 to 0.58), Diagnostic OR 85.6 (18.2 to 403.6) and accuracy 93.7% (88.0 to 97.2%) for cardiogenic shock. Standard assessment without PoCUS had a sensitivity of 91.7% (64.6 to 98.5%), specificity 93.8% (87.8 to 97.0%), LR+ve 14.8 (7.1 to 30.9), LR- of 0.09 (0.01 to 0.58), Diagnostic OR 166.6 (18.7 to 1481) and accuracy of 93.6% (87.8 to 97.2%). There was no significant difference in sensitivity (-11.7% (-37.8 to 18.3%)) or specificity (1.73% (-4.67 to 8.29%)). Diagnostic performance was also similar between other shock subcategories. Conclusion: As reported in other studies, PoCUS based assessment performed well diagnostically in undifferentiated hypotensive patients, especially as a rule-in test. However performance was similar to standard (non-PoCUS) assessment, which was excellent in this study.
Introduction: Point of care ultrasonography (PoCUS) is an established tool in the initial management of hypotensive patients in the emergency department (ED). It has been shown rule out certain shock etiologies, and improve diagnostic certainty, however evidence on benefit in the management of hypotensive patients is limited. We report the findings from our international multicenter RCT assessing the impact of a PoCUS protocol on diagnostic accuracy, as well as other key outcomes including mortality, which are reported elsewhere. Methods: Recruitment occurred at 4 North American and 3 Southern African sites. Screening at triage identified patients (SBP<100 mmHg or shock index >1) who were randomized to either PoCUS or control groups. Scans were performed by PoCUS-trained physicians. Demographics, clinical details and findings were collected prospectively. Initial and secondary diagnoses were recorded at 0 and 60 minutes, with ultrasound performed in the PoCUS group prior to secondary assessment. Final chart review was blinded to initial impressions and PoCUS findings. Categorical data was analyzed using Fishers two-tailed test. Our sample size was powered at 0.80 (α:0.05) for a moderate effect size. Results: 258 patients were enrolled with follow-up fully completed. Baseline comparisons confirmed effective randomization. The perceived shock category changed more frequently in the PoCUS group 20/127 (15.7%) vs. control 7/125 (5.6%); RR 2.81 (95% CI 1.23 to 6.42; p=0.0134). There was no significant difference in change of diagnostic impression between groups PoCUS 39/123 (31.7%) vs control 34/124 (27.4%); RR 1.16 (95% CI 0.786 to 1.70; p=0.4879). There was no significant difference in the rate of correct category of shock between PoCUS (118/127; 93%) and control (113/122; 93%); RR 1.00 (95% CI 0.936 to 1.08; p=1.00), or for correct diagnosis; PoCUS 90/127 (70%) vs control 86/122 (70%); RR 0.987 (95% CI 0.671 to 1.45; p=1.00). Conclusion: This is the first RCT to compare PoCUS to standard care for undifferentiated hypotensive ED patients. We found that the use of PoCUS did change physicians’ perceived shock category. PoCUS did not improve diagnostic accuracy for category of shock or diagnosis.
Introduction: Point of care ultrasound (PoCUS) is an established tool in the initial management of patients with undifferentiated hypotension in the emergency department (ED). While PoCUS protocols have been shown to improve early diagnostic accuracy, there is little published evidence for any mortality benefit. We report the findings from our international multicenter randomized controlled trial, assessing the impact of a PoCUS protocol on survival and key clinical outcomes. Methods: Recruitment occurred at 7 centres in North America (4) and South Africa (3). Scans were performed by PoCUS-trained physicians. Screening at triage identified patients (SBP<100 or shock index>1), randomized to PoCUS or control (standard care and no PoCUS) groups. Demographics, clinical details and study findings were collected prospectively. Initial and secondary diagnoses were recorded at 0 and 60 minutes, with ultrasound performed in the PoCUS group prior to secondary assessment. The primary outcome measure was 30-day/discharge mortality. Secondary outcome measures included diagnostic accuracy, changes in vital signs, acid-base status, and length of stay. Categorical data was analyzed using Fishers test, and continuous data by Student T test and multi-level log-regression testing. (GraphPad/SPSS) Final chart review was blinded to initial impressions and PoCUS findings. Results: 258 patients were enrolled with follow-up fully completed. Baseline comparisons confirmed effective randomization. There was no difference between groups for the primary outcome of mortality; PoCUS 32/129 (24.8%; 95% CI 14.3-35.3%) vs. Control 32/129 (24.8%; 95% CI 14.3-35.3%); RR 1.00 (95% CI 0.869 to 1.15; p=1.00). There were no differences in the secondary outcomes; ICU and total length of stay. Our sample size has a power of 0.80 (α:0.05) for a moderate effect size. Other secondary outcomes are reported separately. Conclusion: This is the first RCT to compare PoCUS to standard care for undifferentiated hypotensive ED patients. We did not find any mortality or length of stay benefits with the use of a PoCUS protocol, though a larger study is required to confirm these findings. While PoCUS may have diagnostic benefits, these may not translate into a survival benefit effect.
Introduction: Point of Care Ultrasound (PoCUS) protocols are commonly used to guide resuscitation for emergency department (ED) patients with undifferentiated non-traumatic hypotension. While PoCUS has been shown to improve early diagnosis, there is a minimal evidence for any outcome benefit. We completed an international multicenter randomized controlled trial (RCT) to assess the impact of a PoCUS protocol on key resuscitation markers in this group. We report diagnostic impact and mortality elsewhere. Methods: The SHoC-ED1 study compared the addition of PoCUS to standard care within the first hour in the treatment of adult patients presenting with undifferentiated hypotension (SBP<100 mmHg or a Shock Index >1.0) with a control group that did not receive PoCUS. Scans were performed by PoCUS-trained physicians. 4 North American, and 3 South African sites participated in the study. Resuscitation outcomes analyzed included volume of fluid administered in the ED, changes in shock index (SI), modified early warning score (MEWS), venous acid-base balance, and lactate, at one and four hours. Comparisons utilized a T-test as well as stratified binomial log-regression to assess for any significant improvement in resuscitation amount the outcomes. Our sample size was powered at 0.80 (α:0.05) for a moderate effect size. Results: 258 patients were enrolled with follow-up fully completed. Baseline comparisons confirmed effective randomization. There was no significant difference in mean total volume of fluid received between the control (1658 ml; 95%CI 1365-1950) and PoCUS groups (1609 ml; 1385-1832; p=0.79). Significant improvements were seen in SI, MEWS, lactate and bicarbonate with resuscitation in both the PoCUS and control groups, however there was no difference between groups. Conclusion: SHOC-ED1 is the first RCT to compare PoCUS to standard of care in hypotensive ED patients. No significant difference in fluid used, or markers of resuscitation was found when comparing the use of a PoCUS protocol to that of standard of care in the resuscitation of patients with undifferentiated hypotension.
Introduction: Point of care ultrasound (PoCUS) has become an established tool in the initial management of patients with undifferentiated hypotension in the emergency department (ED). Current established protocols (e.g. RUSH and ACES) were developed by expert user opinion, rather than objective, prospective data. Recently the SHoC Protocol was published, recommending 3 core scans; cardiac, lung, and IVC; plus other scans when indicated clinically. We report the abnormal ultrasound findings from our international multicenter randomized controlled trial, to assess if the recommended 3 core SHoC protocol scans were chosen appropriately for this population. Methods: Recruitment occurred at seven centres in North America (4) and South Africa (3). Screening at triage identified patients (SBP<100 or shock index>1) who were randomized to PoCUS or control (standard care with no PoCUS) groups. All scans were performed by PoCUS-trained physicians within one hour of arrival in the ED. Demographics, clinical details and study findings were collected prospectively. A threshold incidence for positive findings of 10% was established as significant for the purposes of assessing the appropriateness of the core recommendations. Results: 138 patients had a PoCUS screen completed. All patients had cardiac, lung, IVC, aorta, abdominal, and pelvic scans. Reported abnormal findings included hyperdynamic LV function (59; 43%); small collapsing IVC (46; 33%); pericardial effusion (24; 17%); pleural fluid (19; 14%); hypodynamic LV function (15; 11%); large poorly collapsing IVC (13; 9%); peritoneal fluid (13; 9%); and aortic aneurysm (5; 4%). Conclusion: The 3 core SHoC Protocol recommendations included appropriate scans to detect all pathologies recorded at a rate of greater than 10 percent. The 3 most frequent findings were cardiac and IVC abnormalities, followed by lung. It is noted that peritoneal fluid was seen at a rate of 9%. Aortic aneurysms were rare. This data from the first RCT to compare PoCUS to standard care for undifferentiated hypotensive ED patients, supports the use of the prioritized SHoC protocol, though a larger study is required to confirm these findings.
A simple, portable capillary refill time (CRT) simulator is not commercially available. This device would be useful in mass-casualty simulations with multiple volunteers or mannequins depicting a variety of clinical findings and CRTs. The objective of this study was to develop and evaluate a prototype CRT simulator in a disaster simulation context.
A CRT prototype simulator was developed by embedding a pressure-sensitive piezo crystal, and a single red light-emitting diode (LED) light was embedded, within a flesh-toned resin. The LED light was programmed to turn white proportionate to the pressure applied, and gradually to return to red on release. The time to color return was adjustable with an external dial. The prototype was tested for feasibility among two cohorts: emergency medicine physicians in a tabletop exercise and second year medical students within an actual disaster triage drill. The realism of the simulator was compared to video-based CRT, and participants used a Visual Analog Scale (VAS) ranging from “completely artificial” to “as if on a real patient.” The VAS evaluated both the visual realism and the functional (eg, tactile) realism. Accuracy of CRT was evaluated only by the physician cohort. Data were analyzed using parametric and non-parametric statistics, and mean Cohen’s Kappas were used to describe inter-rater reliability.
The CRT simulator was generally well received by the participants. The simulator was perceived to have slightly higher functional realism (P=.06, P=.01) but lower visual realism (P=.002, P=.11) than the video-based CRT. Emergency medicine physicians had higher accuracy on portrayed CRT on the simulator than the videos (92.6% versus 71.1%; P<.001). Inter-rater reliability was higher for the simulator (0.78 versus 0.27; P<.001).
A simple, LED-based CRT simulator was well received in both settings. Prior to widespread use for disaster triage training, validation on participants’ ability to accurately triage disaster victims using CRT simulators and video-based CRT simulations should be performed.
ChangTP, SantillanesG, Claudius I, PhamPK, KovedJ, CheyneJ, Gausche-HillM, KajiAH, SrinivasanS, DonofrioJJ, BirC. Use of a Novel, Portable, LED-Based Capillary Refill Time Simulator within a Disaster Triage Context. Prehosp Disaster Med. 2017;32(4):451–456.
Introduction: Point of care ultrasound has become an established tool in the initial management of patients with undifferentiated hypotension. Current established protocols (RUSH, ACES, etc) were developed by expert user opinion, rather than objective, prospective data. We wished to use reported disease incidence to develop an informed approach to PoCUS in hypotension using a “4 F’s” approach: Fluid; Form; Function; Filling. Methods: We summarized the incidence of PoCUS findings from an international multicentre RCT, and using a modified Delphi approach incorporating this data we obtained the input of 24 international experts associated with five professional organizations led by the International Federation of Emergency Medicine. The modified Delphi tool was developed to reach an international consensus on how to integrate PoCUS for hypotensive emergency department patients. Results: Rates of abnormal PoCUS findings from 151 patients with undifferentiated hypotension included left ventricular dynamic changes (43%), IVC abnormalities (27%), pericardial effusion (16%), and pleural fluid (8%). Abdominal pathology was rare (fluid 5%, AAA 2%). After two rounds of the survey, using majority consensus, agreement was reached on a SHoC-hypotension protocol comprising: A. Core: 1. Cardiac views (Sub-xiphoid and parasternal windows for pericardial fluid, cardiac form and ventricular function); 2. Lung views for pleural fluid and B-lines for filling status; and 3. IVC views for filling status; B. Supplementary: Additional cardiac views; and C. Additional views (when indicated) including peritoneal fluid, aorta, pelvic for IUP, and proximal leg veins for DVT. Conclusion: An international consensus process based on prospectively collected disease incidence has led to a proposed SHoC-hypotension PoCUS protocol comprising a stepwise clinical-indication based approach of Core, Supplementary and Additional PoCUS views.
Introduction: Point of care ultrasound (PoCUS) provides invaluable information during resuscitation efforts in cardiac arrest by determining presence/absence of cardiac activity and identifying reversible causes such as pericardial tamponade. There is no agreed guideline on how to safely and effectively incorporate PoCUS into the advanced cardiac life support (ACLS) algorithm. We consider that a consensus-based priority checklist using a “4 F’s” approach (Fluid; Form; Function; Filling), would provide a better algorithm during ACLS. Methods: The ultrasound subcommittee of the Australasian College for Emergency Medicine (ACEM) drafted a checklist incorporating PoCUS into the ACLS algorithm. This was further developed using the input of 24 international experts associated with five professional organizations led by the International Federation of Emergency Medicine. A modified Delphi tool was developed to reach an international consensus on how to integrate ultrasound into cardiac arrest algorithms for emergency department patients. Results: Consensus was reached following 3 rounds. The agreed protocol focuses on the timing of PoCUS as well as the specific clinical questions. Core cardiac windows performed during the rhythm check pause in chest compressions are the sub-xiphoid and parasternal cardiac views. Either view should be used to detect pericardial fluid, as well as examining ventricular form (e.g. right heart strain) and function, (e.g. asystole versus organized cardiac activity). Supplementary views include lung views (for absent lung sliding in pneumothorax and for pleural fluid), and IVC views for filling. Additional ultrasound applications are for endotracheal tube confirmation, proximal leg veins for DVT, or for sources of blood loss (AAA, peritoneal/pelvic fluid). Conclusion: The authors hope that this process will lead to a consensus-based SHoC-cardiac arrest guideline on incorporating PoCUS into the ACLS algorithm.
The Vibrio cholerae O1 (VCO1) El Tor biotype appeared during the seventh cholera pandemic starting in 1961, and new variants of this biotype have been identified since the early 1990s. This pandemic has affected Vietnam, and a large outbreak was reported in southern Vietnam in 2010. Pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem-repeat analyses (MLVA) were used to screen 34 VCO1 isolates from the southern Vietnam 2010 outbreak (23 patients, five contact persons, and six environmental isolates) to determine if it was genetically distinct from 18 isolates from outbreaks in southern Vietnam from 1999 to 2004, and two isolates from northern Vietnam (2008). Twenty-seven MLVA types and seven PFGE patterns were identified. Both analyses showed that the 2008 and 2010 isolates were distinctly clustered and separated from the 1999–2004 isolates.
Conflicting reports have been published on the association between Clostridium difficile ribotypes and severe disease outcomes in patients with C. difficile infection (CDI); several so-called hypervirulent ribotypes have been described. We performed a multicenter study to assess severe disease presentation and severe outcomes among CDI patients infected with different ribotypes.
Stool samples that tested positive for C. difficile toxin were collected and cultured from patients who presented to any of 7 different hospitals in Houston, Texas (2011–2013). C. difficile was characterized using a fluorescent PCR ribotyping method. Medical records were reviewed to determine clinical characteristics and ribotype association with severe CDI presentation (ie, leukocytosis and/or hypoalbuminemia) and severe CDI outcomes (ie, ICU admission, ileus, toxic megacolon, colectomy, and/or in-hospital death).
Our study included 715 patients aged 61±18 years (female: 63%; median Charlson comorbidity index: 2.5±2.4; hospital-onset CDI: 45%; severe CDI: 36.7%; severe CDI outcomes: 12.3%). The most common ribotypes were 027, 014-020, FP311, 002, 078-126, and 001. Ribotype 027 was a significant independent predictor of severe disease (adjusted odds ratio [aOR], 2.24; 95% confidence interval [CI], 1.53–3.29; P<.001) and severe CDI outcomes (aOR, 1.71; 95% CI, 1.02–2.85; P=.041) compared with all other ribotypes in aggregate. However, in an analysis using all common ribotypes as individual variables, ribotype 027 was not associated with severe CDI outcomes more often than other ribotypes.
Ribotype 027 showed virulence equal to that of other ribotypes identified in this endemic setting. Clinical severity markers of CDI may be more predictive of severe CDI outcomes than a particular ribotype.
Infect. Control Hosp. Epidemiol. 2015;36(11):1318–1323
Information about viral acute respiratory infections (ARIs) is essential for prevention, diagnosis and treatment, but it is limited in tropical developing countries. This study described the clinical and epidemiological characteristics of ARIs in children hospitalized in Vietnam. Nasopharyngeal samples were collected from children with ARIs at Ho Chi Minh City Children's Hospital 2 between April 2010 and May 2011 in order to detect respiratory viruses by polymerase chain reaction. Viruses were found in 64% of 1082 patients, with 12% being co-infections. The leading detected viruses were human rhinovirus (HRV; 30%), respiratory syncytial virus (RSV; 23·8%), and human bocavirus (HBoV; 7·2%). HRV was detected all year round, while RSV epidemics occurred mainly in the rainy season. Influenza A (FluA) was found in both seasons. The other viruses were predominant in the dry season. HRV was identified in children of all age groups. RSV, parainfluenza virus (PIV) 1, PIV3 and HBoV, and FluA were detected predominantly in children aged <6 months, 6–12 months, 12–24 months, and >24 months, respectively. Significant associations were found between PIV1 with croup (P < 0·005) and RSV with bronchiolitis (P < 0·005). HBoV and HRV were associated with hypoxia (P < 0·05) and RSV with retraction (P < 0·05). HRV, RSV, and HBoV were detected most frequently and they may increase the severity of ARIs in children.
Laryngeal cryptococcosis is a rare condition. In this report, we describe the findings for and treatment of a 58-year-old man with Cryptococcus gattii infection of the right vocal fold.
Case report and review of the relevant English language literature.
The patient presented with persistent hoarseness of voice. Laryngoscopy demonstrated an irregular, red lesion on the right vocal fold. Histopathological examination identified cryptococcus. The patient was treated with oral fluconazole 400 mg/day for eight weeks.
Laryngeal involvement by Cryptococcus gattii can result from prolonged inhaled corticosteroid therapy and proximity to eucalyptus trees. The clinical presentation, laryngoscopic findings and imaging results of laryngeal involvement may mimic a neoplasm. Histopathological examination can demonstrate the causative organism. Management consists of advice from an infectious disease specialist together with adequate treatment by antifungal agents.
Non-typhoidal Salmonella are an important but poorly characterized cause of paediatric diarrhoea in developing countries. We conducted a hospital-based case-control study in children aged <5 years in Ho Chi Minh City to define the epidemiology and examine risk factors associated with Salmonella diarrhoeal infections. From 1419 diarrhoea cases and 571 controls enrolled between 2009 and 2010, 77 (5·4%) diarrhoea cases were stool culture-positive for non-typhoidal Salmonella. Salmonella patients were more likely to be younger than controls (median age 10 and 12 months, respectively) [odds ratio (OR) 0·97; 95% confidence interval (CI) 0·94–0·99], to report a recent diarrhoeal contact (8·1% cases, 1·8% controls; OR 5·98, 95% CI 1·8–20·4) and to live in a household with >2 children (cases 20·8%, controls 10·2%; OR 2·32, 95% CI 1·2–4·7). Our findings indicate that Salmonella are an important cause of paediatric gastroenteritis in this setting and we suggest that transmission may occur through direct human contact in the home.
An egg mass of Loligo forbesi was observed in the field for the first time while conducting a remotely operated vehicle dive at a depth of 370 m, off the São Jorge Island (Azores, north-east Atlantic). This observation allowed the confirmation of two hypotheses previously suggested for the reproduction of this species: (i) that in the Azores this species spawns deeper than the previously recorded 144 m; and that (ii) it is likely that this species prefers to spawn within cavities. The way the observed egg strings suspended from the roof of a cavity, underneath a rocky block, surrounded by sediment, is a feature that interestingly seems to be shared between L. forbesi (in the Azores, all the previous naturally-laid egg masses were recovered from within cavities) and L. vulgaris that inhabit shallower waters off the Madeira archipelago.
Pt/Pb(Zr0.4Ti0.6)O3 (PZT)/Pt capacitors were prepared by the sol-gel technique and their electric properties were analyzed. The asymmetry of polarization-electric field (P-E) and capacitor-voltage (C-V) curves exhibits existence of an interface layer (dead-layer) between top Pt electrode and PZT thin film. By conducting temperature dependant measurement, the Pt/PZT/Pt capacitor was confirmed to be Schottky emission conduction. In addition, barrier height of PZT contact calculated 0.67eV. On basic a series capacitors model and Schottky contact of Pt/PZT interface, the thickness and the dielectric constant of this dead-layer were estimated to be 6.4 nm and 170, respectively. Moreover, the dielectric constant of 900 was obtained for the real PZT ferroelectric layer. The existence of the dead-layer was also confirmed by the high resolution transmission electron microscopy (HR-TEM) observation and the energy dispersive X-ray (EDX) analysis on PZT ferroelectric layer in the Pt/PZT/Pt structure. Based on EDX analysis result, a 10-nm layer at Pt/PZT contact was suggested to be the dead-layer.
We report on the use of La2O3 (LO) as a capping layer for ferroelectric-gate thin-film transistors (FGTs) with solution-processed indium-tin-oxide (ITO) channel and Pb(Zr,Ti)O3 (PZT) gate insulator. The fabricated FGT exhibited excellent performance with a high “ON/OFF” current ratio (ION/IOFF) and a large memory window (∆Vth) of about 108 and 3.5 V, respectively. Additionally, a significantly improved data retention time (more than 16 hours) as compared to the ITO/PZT structure was also obtained as a result of good interface properties between the ITO channel and LO/PZT stacked gate insulator. We suggest that the LO capping layer acts as a barrier to prevent the interdiffusion and provides atomically flat ITO/LO/PZT interface. This all-oxide FGT device is very promising for future ferroelectric memories.
The perovskite CaTiO3 is one of the major phases of the Synroc titanate mineral assemblage. Its chemical durability in an aqueous environment, which is relevant to the Synroc concept, has been investigated by solution analysis, surface analysis and electron microscopy. In general it has been found that dissolution due to base catalyzed hydrolysis is the most significant mechanism of attack; the results suggest that an ion exchange mechanism is confined to the first monolayer. Below 90°C the extent of attack, and release of Ca into solution, is limited by the formation of a titanaceous amorphous layer (” 100A thickness) which imposes a reaction constraint at the film-solid interface. Dissolution may also be constrained by the pH and Ca2+concentration in the bulk liquid. Above 90°C dissolution is relatively less constrained due to instability of the amorphous layer which is replaced by nucleation and epitaxial growth of TiO2 on the dissolving substrate. Thermodynamic stability of CaTiO3 for T< 90°C can easily be engineered into the waste repository, while hydrothermal stability (T > 90°C) is more difficult to achieve.