Enhancing Carrier Mobility in Monolayer MoS2 Transistors with Process-Induced Strain.

Two-dimensional electronic materials are a promising candidate for beyond-silicon electronics due to their favorable size scaling of electronic performance. However, a major challenge is the heterogeneous integration of 2D materials with CMOS processes while maintaining their excellent properties. In particular, there is a knowledge gap in how thin film deposition and processes interact with 2D materials to alter their strain and doping, both of which have a drastic impact on device properties. In this study, we demonstrate how to utilize process-induced strain, a common technique extensively applied in the semiconductor industry, to enhance the carrier mobility in 2D material transistors. We systematically varied the tensile strain in monolayer MoS2 transistors by iteratively depositing thin layers of high-stress MgOx stressor. At each thickness, we combined Raman spectroscopy and transport measurements to unravel and correlate the changes in strain and doping within each transistor with their performance. The transistors displayed uniform strain distributions across their channels for tensile strains of up to 0.48 ± 0.05%, at 150 nm of stressor thickness. At higher thicknesses, mechanical instability occurred, leading to nonuniform strains. The transport characteristics systematically varied with strain, with enhancement in electron mobility at a rate of 130 ± 40% per % strain and enhancement of the channel saturation current density of 52 ± 20%. This work showcases how established CMOS technologies can be leveraged to tailor the transport in 2D transistors, accelerating the integration of 2D electronics into a future computing infrastructure.

Stretchable Thin-Film Transistors Based on Wrinkled Graphene and MoS2 Heterostructures.

Two-dimensional (2D) materials are outstanding candidates for stretchable electronics, but a significant challenge is their heterogeneous integration into stretchable geometries on soft substrates. Here, we demonstrate a strategy for stretchable thin film transistors (2D S-TFT) based on wrinkled heterostructures on elastomer substrates where 2D materials formed the gate, source, drain, and channel and characterized them with Raman spectroscopy and transport measurements. The 2D S-TFTs had initial mobility of 4.9 ± 0.7 cm2/(V s). The wrinkling reduced the strain transferred into the 2D materials by a factor of 50, allowing a substrate stretch of up to 23% that could be cycled thousands of times without electrical degradation. The stretch did not alter the mobility but did lead to strain-induced threshold voltage shifts by ΔVT = -1.9 V. These 2D S-TFTs form the foundation for stretchable integrated circuits and enable investigations of the impact of heterogeneous strain on electron transport.

[Epidemiology of unpleasant experiences in conscious critically ill patients during intensive care unit stay].

OBJECTIVE: To survey the incidences of psychological and physiological unpleasant experiences in conscious critically ill patients during their intensive care unit (ICU) stay, and investigate the inducing factors. METHODS: A two-month consecutive nationwide investigation was prospectively performed in 31 academic hospital ICUs. An in-person questionnaire interview to each conscious patient was performed by specific trained staff from RMC-ROMIT Healthcare Consulting Company within 2 days after the patient was transferred from ICU. RESULTS: Two hundred and thirty-four cases were interviewed in this survey. One hundred and sixty-three of the 234 patients (69.6%) appeared psychological unpleasant experience. The ratio of patients with physiological unpleasant experience was as high as 97.0%, and 74.8% of whom were with serious physiological unpleasant experiences. The incidence of serious physiological unpleasant experiences was markedly higher in patients with than without psychological unpleasant experience (46.5% vs. 86.5%). The difference was shown to be statistical significant (P < 0.01). The percentage of patients complained of ICU noise and medical or nursing manipulations not tolerable was 65.8% and 74.8%, respectively. Compared with the tolerable cases, the incidences of psychological and physiological unpleasant experiences were significantly increased in those patients (P < 0.05 or P < 0.01). Acute physiology and chronic health evaluation II (APACHE II) score was the independent high risk factor inducing psychological unpleasant experience through multiple factor analysis [odds ratio (OR) = 1.070, 95% confidence interval (CI) = 1.020-1.130, P < 0.05]. Age was the high risk factor inducing physiological unpleasant experience (OR = 0.936, 95% CI = 0.879-0.998, P < 0.05). In addition, adequate sedation significantly reduced the incidence of the psychological and physiological unpleasant experiences. CONCLUSION: A high incidence of unpleasant experience is found in conscious critically ill patients during their ICU stay. Patients with psychological unpleasant experiences are with higher possibility of occurring physiological unpleasant experiences. The data show that APACHE II score is the independent high risk factor inducing psychological unpleasant experiences. ICU environment, noise for instance, and medical or nursing manipulations are closely related with the incidence of psychological and physiological unpleasant experiences. Meanwhile, adequate sedation is one of the effective methods to reduce the incidences of them.

[Prospective, multi-center investigation on safety of critical patients in intensive care units].

OBJECTIVE: To perform a prospective, multi-center investigation of the incidence and causes of medical errors happened in intensive care unit (ICU). METHODS: This investigation was performed in eight ICUs in level A, grade 3 teaching hospitals from October 23 to December 23, 2006. One attending physician and the head nurse in each center were entrusted with the responsibility for this project. Medical errors were identified as (1) type of errors (happened in diagnosis, medication, caring procedures or monitoring etc.); (2)characteristics of errors (related to complications, emergency intervention, low ability or carelessness of care givers and others); (3) consequence of errors (resulted in non-serious influence, vital signs fluctuation, alternation of respiratory or circulatory function, organ injury or death). Besides the medical errors, data included ICU beds, numbers of doctors or nurses, numbers of critical patients receiving intensive care during the investigation period and their acute physiology and chronic health evaluation II (APACHE II) scores, the academic degree and title and years of ICU working experience of doctors or nurses who made medical errors. RESULTS: Data from three of eight centers were excluded due to lack of objectivity. A total number of 232 critical patients were surveyed in 1 319 ICU patient x days. Two hundred and ninety-six ICU errors were found. One error occurred in average of 4.46 patient x days. Medical errors happened in 157 patients (67.6%). The percentage of error related to nursing (74.3%) was significantly higher than that made by doctor's caring (25.7%). Two hundred and twelve errors (71.6%) were devoid of serious effects to patients. However, Eighty-two errors were followed by vital signs instability. Medical errors occurred more frequently in patients with the higher (greater than 20) than the lower (less than 20) APACHE II score. The frequency of nursing oriented errors was closely positively correlated with the rates of shortage of working force, low educational level and working years less than 3 years respectively. CONCLUSION: Our survey indicates that critical patients are facing high medical error risk in the higher level Chinese teaching hospitals. There is a close relationship between ICU errors and severity of patient's disease, inadequate training and less working experience.