InAs/GaAs quantum dot laser epitaxially grown on on-axis (001) GaAsOI substrate

Quantum dot (QD) laser as a light source for silicon optical integration has attracted great research attention because of the strategic vision of optical interconnection. In this paper, the communication band InAs QD ridge waveguide lasers were fabricated on GaAs-on-insulator (GaAsOI) substrate by combining ion-slicing technique and molecular beam epitaxy (MBE) growth. On the foundation of optimizing surface treatment processes, the InAs/In0.13Ga0.87As/GaAs dot-in-well (DWELL) lasers monolithically grown on a GaAsOI substrate were realized under pulsed operation at 20 \ub0C. The static device measurements reveal comparable performance in terms of threshold current density, slope efficiency and output power between the QD lasers on GaAsOI and GaAs substrates. This work shows great potential to fabricate highly integrated light source on Si for photonic integrated circuits

Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes

BiFeO3 based MIM structures with Ti-implanted Pt bottom electrodes and Au top electrodes have been fabricated on Sapphire substrates. The resulting metal-insulator-metal (MIM) structures show bipolar resistive switching without an electroforming process. It is evidenced that during the BiFeO3 thin film growth Ti diffuses into the BiFeO3 layer. The diffused Ti effectively traps and releases oxygen vacancies and consequently stabilizes the resistive switching in BiFeO3 MIM structures. Therefore, using Ti implantation of the bottom electrode, the retention performance can be greatly improved with increasing Ti fluence. For the used raster-scanned Ti implantation the lateral Ti distribution is not homogeneous enough and endurance slightly degrades with Ti fluence. The local resistive switching investigated by current sensing atomic force microscopy suggests the capability of down-scaling the resistive switching cell to one BiFeO3 grain size by local Ti implantation of the bottom electrode

Wafer-scale heterogeneous integration InP on trenched Si with a bubble-free interface

Heterogeneous integration of compound semiconductors on a Si platform leads to advanced device applications in the field of Si photonics and high frequency electronics. However, the unavoidable bubbles formed at the bonding interface are detrimental for achieving a high yield of dissimilar semiconductor integration by the direct wafer bonding technology. In this work, lateral outgassing surface trenches (LOTs) are introduced to efficiently inhibit the bubbles. It is found that the chemical reactions in InP-Si bonding are similar to those in Si-Si bonding, and the generated gas can escape via the LOTs. The outgassing efficiency is dominated by LOTs\u27 spacing, and moreover, the relationship between bubble formation and the LOT\u27s structure is well described by a thermodynamic model. With the method explored in this work, a 2-in. bubble-free crystalline InP thin film integrated on the Si substrate with LOTs is obtained by the ion-slicing and wafer bonding technology. The quantum well active region grown on this Si-based InP film shows a superior photoemission efficiency, and it is found to be 65% as compared to its bulk counterpart

Preoperative Hematocrit Levels and Postoperative Mortality in Patients Undergoing Craniotomy for Brain Tumors

BACKGROUND: Abnormal hematocrit values, including anemia and polycythemia, are common in patients undergoing craniotomy, but the extent to which preoperative anemia or polycythemia independently increases the risk of mortality is unclear. This retrospective cohort study aimed to examine the association between preoperative anemia and polycythemia and postoperative mortality in patients who underwent craniotomy for brain tumor resection. METHODS: We retrospectively analyzed data from 12,170 patients diagnosed with a brain tumor who underwent cranial surgery at West China Hospital between January 2011 and March 2021. The preoperative hematocrit value was defined as the last hematocrit value within 7 days before the operation, and patients were grouped according to the severity of their anemia or polycythemia. We assessed the primary outcome of 30-day postoperative mortality using logistic regression analysis adjusted for potential confounding factors. RESULTS: Multivariable logistic regression analysis reported that the 30-day mortality risk was raised with increasing severity of both anemia and polycythemia. Odds ratios for mild, moderate, and severe anemia were 1.12 (95% CI: 0.79-1.60), 1.66 (95% CI: 1.06-2.58), and 2.24 (95% CI: 0.99-5.06), respectively. Odds ratios for mild, moderate, and severe polycythemia were 1.40 (95% CI: 0.95-2.07), 2.81 (95% CI: 1.32-5.99), and 14.32 (95% CI: 3.84-53.44), respectively. CONCLUSIONS: This study demonstrated that moderate to severe anemia and polycythemia are independently associated with increased postoperative mortality in patients undergoing craniotomy for brain tumor resection. These findings underscore the importance of identifying and managing abnormal hematocrit values before craniotomy surgery

Association of Anemia With Mortality in Young Adult Patients With Intracerebral Hemorrhage

This study aimed to examine the association of hemoglobin concentration with a 90-day mortality of young adult patients with ICH in a large retrospective cohort. A retrospective observational study was conducted between December 2013 and June 2019 in two tertiary academic medical centers in China. We defined patients with hemoglobin concentration \u3c 80 g/L as severe anemia and 80-120/130 g/L as mild to moderate anemia. We also defined patients with hemoglobin concentration \u3e 160 g/L as high hemoglobin. Associations of hemoglobin and outcomes were evaluated in multivariable regression analyses. The primary outcome was mortality at 90 days. We identified 4098 patients with ICH who met the inclusion criteria. After adjusting primary confounding variables, the 90-day mortality rate was significantly higher in young patients with severe anemia (OR, 39.65; 95% CI 15.42-101.97), moderate anemia (OR, 2.49; 95% CI 1.24-5.00), mild anemia (OR, 1.89; 95% CI 1.20-2.98), and high hemoglobin (OR, 2.03; 95% CI 1.26-3.26) group than in young patients of the normal group. The younger age was associated with a higher risk of death from anemia in patients with ICH (P for interaction = 0.01). In young adult patients with ICH, hemoglobin concentration was associated with 90-day mortality, and even mild to moderate anemia correlated with higher mortality. We also found that in ICH patients with anemia, younger age was associated with higher risk

Association Between Intraoperative Steroid and Postoperative Mortality in Patients Undergoing Craniotomy for Brain Tumor

BACKGROUND: Despite the widespread use of intraoperative steroids in various neurological surgeries to reduce cerebral edema and other adverse symptoms, there is sparse evidence in the literature for the optimal and safe usage of intraoperative steroid administration in patients undergoing craniotomy for brain tumors. We aimed to investigate the effects of intraoperative steroid administration on postoperative 30-day mortality in patients undergoing craniotomy for brain tumors. METHODS: Adult patients who underwent craniotomy for brain tumors between January 2011 to January 2020 were included at West China Hospital, Sichuan University in this retrospective cohort study. Stratified analysis based on the type of brain tumor was conducted to explore the potential interaction. RESULTS: This study included 8,663 patients undergoing craniotomy for brain tumors. In patients with benign brain tumors, intraoperative administration of steroids was associated with a higher risk of postoperative 30-day mortality (adjusted OR 1.98, 95% CI 1.09-3.57). However, in patients with malignant brain tumors, no significant association was found between intraoperative steroid administration and postoperative 30-day mortality (adjusted OR 0.86, 95% CI 0.55-1.35). Additionally, administration of intraoperative steroids was not associated with acute kidney injury (adjusted OR 1.11, 95% CI 0.71-1.73), pneumonia (adjusted OR 0.89, 95% CI 0.74-1.07), surgical site infection (adjusted OR 0.78, 95% CI 0.50-1.22) within 30 days, and stress hyperglycemia (adjusted OR 1.05, 95% CI 0.81-1.38) within 24 h after craniotomy for brain tumor. CONCLUSION: In patients undergoing craniotomy for benign brain tumors, intraoperative steroids were associated with 30-day mortality, but this association was not significant in patients with malignant brain tumors

Resistive switching in BiFeO3-based thin films and reconfigurable logic applications

The downscaling of transistors is assumed to come to an end within the next years, and the semiconductor nonvolatile memories are facing the same physical downscaling challenge. Therefore, it is necessary to consider new computing paradigms and new memory concepts. Resistive switching devices (also referred to as memristive switches) are two-terminal passive device, which offer a nonvolatile switching behavior by applying short bias pulses. They have been considered as one of the most promising candidates for next generation memory and nonvolatile logic applications. They provide the possibility to carry out the information processing and storage simultaneously using the same resistive switching device. This dissertation focuses on the fabrication and characterization of BiFeO3 (BFO)-based metal-insulator-metal (MIM) devices in order to exploit the potential applications in nonvolatile memory and nonvolatile reconfigurable logics. Electroforming-free bipolar resistive switching was observed in MIM structures with BFO single layer thin film. The resistive switching mechanism is understood by a model of a tunable bottom Schottky barrier. The oxygen vacancies act as the mobile donors which can be redistributed under the writing bias to change the bottom Schottky barrier height and consequently change the resistance of the MIM structures. The Ti atoms diffusing from the bottom electrode act as the fixed donors which can effectively trap and release oxygen vacancies and consequently stabilize the resistive switching characteristics. The resistive switching behavior can be engineered by Ti implantation of the bottom electrodes. MIM structures with BiFeO3/Ti:BiFeO3 (BFO/BFTO) bilayer thin films show nonvolatile resistive switching behavior in both positive and negative bias range without electroforming process. The resistance state of BFO/BFTO bilayer structures depends not only on the writing bias, but also on the polarity of reading bias. For reconfigurable logic applications, the polarity of the reading bias can be used as an additional logic variable, which makes it feasible to program and store all 16 Boolean logic functions simultaneously into the same single cell of BFO/BFTO bilayer MIM structure in three logic cycles.Die Herunterskalierung von Transistoren für die Informationsverarbeitung in der Halbleiterindustrie wird in den nächsten Jahren zu einem Ende kommen. Auch die Herunterskalierung von nichtflüchtigen Speichern für die Informationsspeicherung sieht ähnlichen Herausforderungen entgegen. Es ist daher notwendig, neue IT-Paradigmen und neue Speicherkonzepte zu entwickeln. Das Widerstandsschaltbauelement ist ein elektrisches passives Bauelement, in dem ein der Widerstand mittels elektrischer Spannungspulse geändert wird. Solche Widerstandsschaltbauelemente zählen zu den aussichtsreichsten Kandidaten für die nächste Generation von nichtflüchtigen Speichern sowie für eine rekonfigurierbare Logik. Sie bieten die Möglichkeit zur gleichzeitigen Informationsverarbeitung und -speicherung. Der Fokus der vorliegenden Arbeit liegt bei der Herstellung und der Charakterisierung von BiFeO 3 (BFO)-basierenden Metal-insulator-Metall (MIM) Strukturen, um zukünftig deren Anwendung in nichtflüchtigen Speichern und in rekonfigurierbaren Logikschaltungen zu ermöglichen. Das Widerstandsschalten wurde in MIM-Strukturen mit einer BFO-Einzelschicht untersucht. Ein besonderes Merkmal von BFO-basierten MIM-Strukturen ist es, dass keine elektrische Formierung notwendig ist. Der Widerstandsschaltmechnismus wird durch das Modell einer variierten Schottky-Barriere erklärt. Dabei dienen Sauerstoff-Vakanzen im BFO als beweglichen Donatoren, die unter der Wirkung eines elektrischen Schreibspannungspulses nichtflüchtig umverteilt werden und die Schottky-Barriere des Bottom-Metallkontaktes ändern. Dabei spielen die während der Herstellung von BFO substitutionell eingebaute Ti-Donatoren in der Nähe des Bottom-Metallkontaktes eine wesentliche Rolle. Die Ti-Donatoren fangen Sauerstoff-Vakanzen beim Anlegen eines positiven elektrischen Schreibspannungspulses ein oder lassen diese beim Anlegen eines negativen elektrischen Schreibspannungspules wieder frei. Es wurde gezeigt, dass die Ti-Donatoren auch durch Ti-Implantation der Bottom-Elektrode in das System eingebracht werden können. MIM-Strukturen mit BiFeO 3 /Ti:BiFeO 3 (BFO/BFTO) Zweischichten weisen substitutionell eingebaute Ti-Donatoren sowohl nahe der Bottom-Elektrode als auch nahe der Top-Elektrode auf. Sie zeigen nichtflüchtiges, komplementäres Widerstandsschalten mit einer komplementär variierbaren Schottky-Barriere an der Bottom-Elektrode und an der Top-Elektrode ohne elektrische Formierung. Der Widerstand der BFO/BFTO-MIM-Strukturen hängt nicht nur von der Schreibspannung, sondern auch von der Polarität der Lesespannung ab. Für die rekonfigurierbaren logischen Anwendungen kann die Polarität der Lesespannung als zusätzliche Logikvariable verwendet werden. Damit gelingt die Programmierung und Speicherung aller 16 Booleschen Logik-Funktionen mit drei logischen Zyklen in dieselbe BFTO/BFO MIM-Struktur