High-κ perovskite membranes as insulators for two-dimensional transistors.

The scaling of silicon metal-oxide-semiconductor field-effect transistors has followed Moore's law for decades, but the physical thinning of silicon at sub-ten-nanometre technology nodes introduces issues such as leakage currents1. Two-dimensional (2D) layered semiconductors, with an atomic thickness that allows superior gate-field penetration, are of interest as channel materials for future transistors2,3. However, the integration of high-dielectric-constant (κ) materials with 2D materials, while scaling their capacitance equivalent thickness (CET), has proved challenging. Here we explore transferrable ultrahigh-κ single-crystalline perovskite strontium-titanium-oxide membranes as a gate dielectric for 2D field-effect transistors. Our perovskite membranes exhibit a desirable sub-one-nanometre CET with a low leakage current (less than 10-2 amperes per square centimetre at 2.5 megavolts per centimetre). We find that the van der Waals gap between strontium-titanium-oxide dielectrics and 2D semiconductors mitigates the unfavourable fringing-induced barrier-lowering effect resulting from the use of ultrahigh-κ dielectrics4. Typical short-channel transistors made of scalable molybdenum-disulfide films by chemical vapour deposition and strontium-titanium-oxide dielectrics exhibit steep subthreshold swings down to about 70 millivolts per decade and on/off current ratios up to 107, which matches the low-power specifications suggested by the latest International Roadmap for Devices and Systems5.

Verification of using virtual reality to evaluate deficiencies in cognitive function among patients with schizophrenia in the remission stage: a cross-sectional study.

BACKGROUND: Schizophrenia is associated with widespread cognitive impairment. The MATRICS Consensus Cognitive Battery (MCCB) is most frequently used to assess cognitive function. However, the MCCB test is time consuming for the clinician. Virtual reality (VR) has emerged as an adjunctive tool to overcome this limitation and provides a new means to assess cognitive function. METHODS: The present study examined the validity and safety of using VR technology to assess cognitive function in Han Chinese patients with schizophrenia (SZs). The VR cognition training system (VRCTS) was used to simulate real-life supermarkets and assess cognitive function. Thirty-two SZs and 25 healthy controls (HCs) underwent VRCTS and MCCB assessments. An auxiliary diagnosis model was created based on the outcomes of the VRCTS to classify SZs and HCs by cognitive impairment. RESULTS: Significant differences in completion time between the SZs and HCs were detected using the VRCTS. SZs spent more time completing tasks than HCs. The outcome of VRCTS significantly correlated with the MCCB. The auxiliary diagnosis model had a sensitivity of 88.89% and a specificity of 88.89%. CONCLUSIONS: These results support the use of VR technology in the assessment of cognitive impairment in Han Chinese schizophrenia patients. TRIAL REGISTRATION: China Clinical Trial Registry, ChiVTR1800016121. Registered 13 May 2018, http://www.chictr.org.cn/showproj.aspx?proj=27233.

Dopant Diffusion and Activation in Silicon Nanowires Fabricated by ex Situ Doping: A Correlative Study via Atom-Probe Tomography and Scanning Tunneling Spectroscopy.

Dopants play a critical role in modulating the electric properties of semiconducting materials, ranging from bulk to nanoscale semiconductors, nanowires, and quantum dots. The application of traditional doping methods developed for bulk materials involves additional considerations for nanoscale semiconductors because of the influence of surfaces and stochastic fluctuations, which may become significant at the nanometer-scale level. Monolayer doping is an ex situ doping method that permits the post growth doping of nanowires. Herein, using atom-probe tomography (APT) with subnanometer spatial resolution and atomic-ppm detection limit, we study the distributions of boron and phosphorus in ex situ doped silicon nanowires with accurate control. A highly phosphorus doped outer region and a uniformly boron doped interior are observed, which are not predicted by criteria based on bulk silicon. These phenomena are explained by fast interfacial diffusion of phosphorus and enhanced bulk diffusion of boron, respectively. The APT results are compared with scanning tunneling spectroscopy data, which yields information concerning the electrically active dopants. Overall, comparing the information obtained by the two methods permits us to evaluate the diffusivities of each different dopant type at the nanowire oxide, interface, and core regions. The combined data sets permit us to evaluate the electrical activation and compensation of the dopants in different regions of the nanowires and understand the details that lead to the sharp p-i-n junctions formed across the nanowire for the ex situ doping process.

Atomic-scale interfacial band mapping across vertically phased-separated polymer/fullerene hybrid solar cells.

Using cross-sectional scanning tunneling microscope (XSTM) with samples cleaved in situ in an ultrahigh vacuum chamber, this study demonstrates the direct visualization of high-resolution interfacial band mapping images across the film thickness in an optimized bulk heterojunction polymer solar cell consisting of nanoscale phase segregated blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). We were able to achieve the direct observation of the interfacial band alignments at the donor (P3HT)-acceptor (PCBM) interfaces and at the interfaces between the photoactive P3HT:PCBM blends and the poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) anode modification layer with an atomic-scale spatial resolution. The unique advantage of using XSTM to characterize polymer/fullerene bulk heterojunction solar cells allows us to explore simultaneously the quantitative link between the vertical morphologies and their corresponding local electronic properties. This provides an atomic insight of interfacial band alignments between the two opposite electrodes, which will be crucial for improving the efficiencies of the charge generation, transport, and collection and the corresponding device performance of polymer solar cells.

Nonvolatile Modulation of Bi2O2Se/Pb(Zr,Ti)O3 Heteroepitaxy.

The pursuit of high-performance electronic devices has driven the research focus toward 2D semiconductors with high electron mobility and suitable band gaps. Previous studies have demonstrated that quasi-2D Bi2O2Se (BOSe) has remarkable physical properties and is a promising candidate for further exploration. Building upon this foundation, the present work introduces a novel concept for achieving nonvolatile and reversible control of BOSe's electronic properties. The approach involves the epitaxial integration of a ferroelectric PbZr0.2Ti0.8O3 (PZT) layer to modify BOSe's band alignment. Within the BOSe/PZT heteroepitaxy, through two opposite ferroelectric polarization states of the PZT layer, we can tune the Fermi level in the BOSe layer. Consequently, this controlled modulation of the electronic structure provides a pathway to manipulate the electrical properties of the BOSe layer and the corresponding devices.

Effect of 40 Hz light flicker on cognitive impairment and transcriptome of hippocampus in right unilateral common carotid artery occlusion mice.

Vascular cognitive impairment caused by chronic cerebral hypoperfusion (CCH) seriously affects the quality of life of elderly patients. However, there is no effective treatment to control this disease. This study investigated the potential neuroprotective effect of the 40 Hz light flicker in a mouse model of CCH. CCH was induced in male C57 mice by right unilateral common carotid artery occlusion (rUCCAO), leading to chronic brain injury. The mice underwent 40 Hz light flicker stimulation for 30 days after surgery. The results showed that 40 Hz light flicker treatment ameliorated memory deficits after rUCCAO and alleviated the damage to neurons in the frontal lobe and hippocampus. Light flicker administration at 40 Hz decreased IL-1ß and TNF-α levels in the frontal lobe and hippocampus, but immunohistochemistry showed that it did not induce angiogenesis in mice with rUCCAO. Gene expression profiling revealed that the induction of genes was mainly enriched in inflammatory-related pathways. Our findings demonstrate that 40 Hz light flicker can suppress cognitive impairment caused by rUCCAO and that this effect may be involved in the attenuation of neuroinflammation.

Mapping band alignment across complex oxide heterointerfaces.

In this study, direct observation of the evolution of electronic structures across complex oxide interfaces has been revealed in the LaAlO(3)/SrTiO(3) model system using cross-sectional scanning tunneling microscopy and spectroscopy. The conduction and valence band structures across the LaAlO(3)/SrTiO(3) interface are spatially resolved at the atomic level by measuring the local density of states. This study directly maps out the electronic reconstructions and a built-in electric field in the polar LaAlO(3) layer. Results also clearly reveal the band bending and the notched band structure in the SrTiO(3) adjacent to the interface.

Increased Hypocretin (Orexin) Plasma Level in Depression, Bipolar Disorder Patients.

As hypocretin can markedly affect neurophysiological and behavioural processes in mood disorders. However, few studies have measured changes in hypocretin levels in patients with mood disorders. We estimated the hypocretin-1 plasma levels in mood disorder patients and controls (CON) using an enzyme-linked immunosorbent assay. Results: (i) The hypocretin-1 plasma level was significantly higher in major depressive disorder (MDD) patients [59.04 (35.78-80.12) pg/ml, P < 0.001] and bipolar disorder (BD) patients [65.50 (58.46-74.57) pg/ml, P < 0.001] patients than in CON [49.25 (28.51-80.40) pg/ml]. Moreover, the plasma hypocretin-1 levels in the BD group were significantly higher than those in the MDD group (P < 0.001). (ii). In the MDD group, patients with higher suicidal ideation had higher hypocretin-1 levels [62.09 (38.23-80.12) pg/ml] than those with lower suicidal ideation [59.63 (35.79-77.37) pg/ml), P = 0.032]. (iii). Plasma hypocretin-1 levels were increased in both female and male mood disorder patients compared to CON [male: MDD 60.51 (35.79-80.12) pg/ml; BD 65.40 (58.76-74.14) pg/ml; CON 45.63 (28.51-62.05) pg/ml; all P < 0.016; female: MDD 57.37 (34.59-80.40) pg/ml; BD 65.61 (58.46-74.57) pg/ml; CON 52.92 (38.23-78.89) pg/ml; all P < 0.015]. (iv). In CON, we found a significant negative correlation between plasma hypocretin-1 levels and age (rho = -0.251, P = 0.032), while this negative correlation was absent in the MDD and BD groups. Limitations may partly arise from the relatively small sample size and the medication history of patients participating in our research. We concluded that the clear changes found in plasma hypocretin-1 levels might be applied in the diagnosis of depression and the differential diagnosis of MDD and BD. The clear suicidal-ideation-related change found in hypocretin-1 levels in depression might be taken into account in the prevention of suicidal behaviour and further study of hypocretin-targeted therapies.

Atomically-resolved interlayer charge ordering and its interplay with superconductivity in YBa2Cu3O6.81.

High-temperature superconductive (SC) cuprates exhibit not only a SC phase, but also competing orders, suppressing superconductivity. Charge order (CO) has been recognized as an important competing order, but its microscopic spatial interplay with SC phase as well as the interlayer coupling in CO and SC phases remain elusive, despite being essential for understanding the physical mechanisms of competing orders and hence superconductivity. Here we report the achievement of direct real-space imaging with atomic-scale resolution of cryogenically cleaved YBa2Cu3O6.81 using cross-sectional scanning tunneling microscopy/spectroscopy. CO nanodomains are found embedded in the SC phase with a proximity-like boundary region characterized by mutual suppression of CO and superconductivity. Furthermore, SC coherence as well as CO occur on both CuO chain and plane layers, revealing carrier transport and density of states mixing between layers. The CO antiphase correlation along the c direction suggests a dominance of Coulomb repulsion over Josephson tunneling between adjacent layers.

Discovery of new genetic loci for male sexual orientation in Han population.

Epidemiological studies have demonstrated that the genetic factors partly influence the development of same-sex sexual behavior, but most genetic studies have focused on people of primarily European ancestry, potentially missing important biological insights. Here, we performed a two-stage genome-wide association study (GWAS) with a total sample of 1478 homosexual males and 3313 heterosexual males in Han Chinese populations and identified two genetic loci (rs17320865, Xq27.3, FMR1NB, Pmeta = 8.36 × 10-8, OR = 1.29; rs7259428, 19q12, ZNF536, Pmeta = 7.58 × 10-8, OR = 0.75) showing consistent association with male sexual orientation. A fixed-effect meta-analysis including individuals of Han Chinese (n = 4791) and European ancestries (n = 408,995) revealed 3 genome-wide significant loci of same-sex sexual behavior (rs9677294, 2p22.1, SLC8A1, Pmeta = 1.95 × 10-8; rs2414487, 15q21.3, LOC145783, Pmeta = 4.53 × 10-9; rs2106525, 7q31.1, MDFIC, Pmeta = 6.24 × 10-9). These findings may provide new insights into the genetic basis of male sexual orientation from a wider population scope. Furthermore, we defined the average ZNF536-immunoreactivity (ZNF536-ir) concentration in the suprachiasmatic nucleus (SCN) as lower in homosexual individuals than in heterosexual individuals (0.011 ± 0.001 vs 0.021 ± 0.004, P = 0.013) in a postmortem study. In addition, compared with heterosexuals, the percentage of ZNF536 stained area in the SCN was also smaller in the homosexuals (0.075 ± 0.040 vs 0.137 ± 0.103, P = 0.043). More homosexual preference was observed in FMR1NB-knockout mice and we also found significant differences in the expression of serotonin, dopamine, and inflammation pathways that were reported to be related to sexual orientation when comparing CRISPR-mediated FMR1NB knockout mice to matched wild-type target C57 male mice.

Efficacy of internet-based integrated intervention on depression and anxiety symptoms in patients with COVID-19.

Public health crises, such as the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) since Dec. 2019, are widely acknowledged as severe traumatic events that impose threats not only because of physical concerns but also because of the psychological distress of infected patients. We designed an internet-based integrated intervention and evaluated its efficacy on depression and anxiety symptoms in patients infected by SARS-CoV-2.

Changes In Plasma NPY, IL-1ß And Hypocretin In People Who Died By Suicide.

PURPOSE: There is growing evidence showing that inflammatory cytokines and neuropeptides may be involved in the pathophysiology of suicidal behavior. However, studies have yielded contradictory data, and no biological markers that help predict suicide have been identified. This study aimed to identify biological patterns, such as NPY, IL-1ß and hypocretin plasma levels, in people who died by suicide. PATIENTS AND METHODS: Twenty-two people who died by suicide compared with 22 controls matched for age and sex were studied. In suicide and control subjects, we estimated the levels of NPY, IL-1ß and hypocretin in plasma using enzyme-linked immunosorbent assay. The data are presented as the median (25th-75th percentile). RESULTS: We found (1) a significant elevation in plasma NPY levels in suicide subjects versus control subjects (suicide: 11.38 (9.380-16.55); controls: 8.95 (7.590-10.93); P=0.013), and plasma NPY concentrations were approximately 62% higher in suicide subjects than those in control subjects; (2) a significant decrease in plasma IL-1ß concentrations between suicide and control subjects (suicide: 121.1 (82.97-143.0); controls: 425.9 (233.1-835.3); P<0.001) as well as a decrease in IL-1ß concentrations by almost 80%; and (3) no significant difference in plasma hypocretin levels between suicide and control subjects (suicide: 16.62 (13.62-25.77); controls: 21.63 (14.97-29.72); P=0.356). CONCLUSION: Our results suggest that plasma NPY and IL-1ß were related with suicide behavior rather than to suicide causes or suicide method. Specific combinations of plasma biomarkers may discriminate between types of suicidal behaviors and indicate increased risk for future suicide attempts.

Photodriven Dipole Reordering: Key to Carrier Separation in Metalorganic Halide Perovskites.

Photodriven dipole reordering of the intercalated organic molecules in halide perovskites has been suggested to be a critical degree of freedom, potentially affecting physical properties, device performance, and stability of hybrid perovskite-based optoelectronic devices. However, thus far a direct atomically resolved dipole mapping under device operation condition, that is, illumination, is lacking. Here, we map simultaneously the molecule dipole orientation pattern and the electrostatic potential with atomic resolution using photoexcited cross-sectional scanning tunneling microscopy and spectroscopy. Our experimental observations demonstrate that a photodriven molecule dipole reordering, initiated by a photoexcited separation of electron-hole pairs in spatially displaced orbitals, leads to a fundamental reshaping of the potential landscape in halide perovskites, creating separate one-dimensional transport channels for holes and electrons. We anticipate that analogous light-induced polarization order transitions occur in bulk and are at the origin of the extraordinary efficiencies of organometal halide perovskite-based solar cells as well as could reconcile apparently contradictory materials' properties.

Atomically Resolved Electronic States and Correlated Magnetic Order at Termination Engineered Complex Oxide Heterointerfaces.

We map electronic states, band gaps, and interface-bound charges at termination-engineered BiFeO3/La0.7Sr0.3MnO3 interfaces using atomically resolved cross-sectional scanning tunneling microscopy. We identify a delicate interplay of different correlated physical effects and relate these to the ferroelectric and magnetic interface properties tuned by engineering the atomic layer stacking sequence at the interfaces. This study highlights the importance of a direct atomically resolved access to electronic interface states for understanding the intriguing interface properties in complex oxides.

A Metal-Insulator Transition of the Buried MnO2 Monolayer in Complex Oxide Heterostructure.

A novel artificially created MnO2 monolayer system is demonstrated in atomically controlled epitaxial perovskite heterostructures. With careful design of different electrostatic boundary conditions, a magnetic transition as well as a metal-insulator transition of the MnO2 monolayer is unveiled, providing a fundamental understanding of dimensionality-confined strongly correlated electron systems and a direction to design new electronic devices.

Atomic-scale mapping of electronic structures across heterointerfaces by cross-sectional scanning tunneling microscopy.

Interfacial science has received much attention recently based on the development of state-of-the-art analytical tools that can create and manipulate the charge, spin, orbital, and lattice degrees of freedom at interfaces. Motivated by the importance of nanoscale interfacial science that governs device operation, we present a technique to probe the electronic characteristics of heterointerfaces with atomic resolution. In this work, the interfacial characteristics of heteroepitaxial structures are investigated and the fundamental mechanisms that pertain in these systems are elucidated through cross-sectional scanning tunneling microscopy (XSTM). The XSTM technique is employed here to directly observe epitaxial interfacial structures and probe local electronic properties with atomic-level capability. Scanning tunneling microscopy and spectroscopy experiments with atomic precision provide insight into the origin and spatial distribution of electronic properties across heterointerfaces. The first part of this report provides a brief description of the cleavage technique and spectroscopy analysis in XSTM measurements. The second part addresses interfacial electronic structures of several model heterostructures in current condensed matter research using XSTM. Topics to be discussed include high-κ's/III-V's semiconductors, polymer heterojunctions, and complex oxide heterostructures, which are all material systems whose investigation using this technique is expected to benefit the research community. Finally, practical aspects and perspectives of using XSTM in interface science are presented.

Parallel p-n junctions across nanowires by one-step ex situ doping.

The bottom-up synthesis of nanoscale building blocks is a versatile approach for the formation of a vast array of materials with controlled structures and compositions. This approach is one of the main driving forces for the immense progress in materials science and nanotechnology witnessed over the past few decades. Despite the overwhelming advances in the bottom-up synthesis of nanoscale building blocks and the fine control of accessible compositions and structures, certain aspects are still lacking. In particular, the transformation of symmetric nanostructures to asymmetric nanostructures by highly controlled processes while preserving the modified structural orientation still poses a significant challenge. We present a one-step ex situ doping process for the transformation of undoped silicon nanowires (i-Si NWs) to p-type/n-type (p-n) parallel p-n junction configuration across NWs. The vertical p-n junctions were measured by scanning tunneling microscopy (STM) in concert with scanning tunneling spectroscopy (STS), termed STM/S, to obtain the spatial electronic properties of the junction formed across the NWs. Additionally, the parallel p-n junction configuration was characterized by off-axis electron holography in a transmission electron microscope to provide an independent verification of junction formation. The doping process was simulated to elucidate the doping mechanisms involved in the one-step p-i-n junction formation.

Ferroelectric control of the conduction at the LaAlO3/SrTiO3 heterointerface.

Modulation of band bending at a complex oxide heterointerface by a ferroelectric layer is demonstrated. The as-grown polarization (Pup ) leads to charge depletion and consequently low conduction. Switching the polarization direction (Pdown ) results in charge accumulation and enhances the conduction at the interface. The metal-insulator transition at a conducting polar/nonpolar oxide heterointerface can be controlled by ferroelectric doping.