Temperature-Dependent Spin-to-Charge Conversion and Efficient Manipulation of Elliptical THz Waves in Bi2Te3/TbFeCo Heterostructures.

Topological insulators (TIs) with spin-momentum-locked surface states and considerable spin-to-charge conversion (SCC) efficiency are ideal substitutes for the nonmagnetic layer in the traditional ferromagnetic/nonmagnetic (FM/NM) spintronic terahertz (THz) emitters. Here, the TI/ferrimagnetic structure as an effective polarization tunable THz source is verified by terahertz emission spectroscopy. The emitted THz electric field can be separated into two THz components utilizing their opposite symmetry on pump polarization and the magnetic field. TI not only emits a THz electric field via the linear photogalvanic effect (LPGE) but also serves as the medium of SCC via the inverse Edelstein effect (IEE) in the heterostructure. In addition, the amplitude and polarity of the SCC component can be efficiently manipulated by temperature in our ferrimagnetic TbFeCo layer compared with Co or Fe. Once these two THz components are delicately set orthogonally, an elliptical THz wave is generated by the intrinsic phase difference at the THz frequency range. The feasible control of its polarization and chirality is demonstrated by three means: pump polarization, magnetic field, and temperature. These appealing observations may pave the way for the development of elliptical THz wave emitters and polarization-sensitive THz spectroscopy.

Nanoscale Channel Length MoS2 Vertical Field-Effect Transistor Arrays with Side-Wall Source/Drain Electrodes.

Two-dimensional transition metal dichalcogenides (TMDCs) have natural advantages in overcoming the short-channel effect in field-effect transistors (FETs) and in fabricating three-dimensional FETs, which benefit in increasing device density. However, so far, most reported works related to MoS2 FETs with a sub-100 nm channel employ mechanically exfoliated materials and all of the works involve electron beam lithography (EBL), which may limit their application in fabricating wafer-scale device arrays as demanded in integrated circuits (ICs). In this work, MoS2 FET arrays with a side-wall source and drain electrodes vertically distributed are designed and fabricated. The channel length of the as-fabricated FET is basically determined by the thickness of an insulating layer between the source and drain electrodes. The vertically distributed source and drain electrodes enable to reduce the electrode-occupied area and increase in the device density. The as-fabricated vertical FETs exhibit on/off ratios comparable to those of mechanically exfoliated MoS2 FETs with a nanoscale channel length under identical VDS. In addition, the as-fabricated FETs can work at a VDS as low as 10 mV with a desirable on/off ratio (1.9 × 107), which benefits in developing low-power devices. Moreover, the fabrication process is free from EBL and can be applied to wafer-scale device arrays. The statistical results show that the fabricated FET arrays have a device yield of 87.5% and an average on/off ratio of about 1.7 × 106 at a VDS of 10 mV, with the lowest and highest ones to be about 1.3 × 104 and 1.9 × 107, respectively, demonstrating the good reliability of our fabrication process. Our work promises a bright future for TMDCs in realizing high-density and low-power nanoelectronic devices in ICs.

Combining pathological risk factors and T, N staging to optimize the assessment for risk stratification and prognostication in low-risk stage III colon cancer.

BACKGROUND: This study aimed to investigate the combined pathological risk factors (PRFs) to stratify low-risk (pT1-3N1) stage III colon cancer (CC), providing a basis for individualized treatment in the future. PATIENTS AND METHODS: PRFs for low-risk stage III CC were identified using COX model. Low-risk stage III CC was risk-grouped combining with PRFs, and survival analysis were performed using Kaplan-Meier. The Surveillance, Epidemiology, and End Results (SEER) databases was used for external validation. RESULTS: Nine hundred sixty-two stage III CC patients were included with 634 (65.9%) as low risk and 328 (34.1%) as high risk. Poor differentiation (OS: P = 0.048; DFS: P = 0.011), perineural invasion (OS: P = 0.003; DFS: P < 0.001) and tumor deposits (OS: P = 0.012; DFS: P = 0.003) were identified as PRFs. The prognosis of low-risk CC combined with 2 PRFs (OS: HR = 3.871, 95%CI, 2.004-7.479, P < 0.001; DFS: HR = 3.479, 95%CI, 2.158-5.610, P < 0.001) or 3 PRFs (OS: HR = 5.915, 95%CI, 1.953-17.420, P = 0.002; DFS: HR = 5.915, 95%CI, 2.623-13.335, P < 0.001) was similar to that of high-risk CC (OS: HR = 3.927, 95%CI, 2.317-6.656, P < 0.001; DFS: HR = 4.132, 95%CI, 2.858-5.974, P < 0.001). In the SEER database, 18,547 CC patients were enrolled with 10,023 (54.0%) as low risk and 8524 (46.0%) as high risk. Low-risk CC combined with 2 PRFs (OS: HR = 1.857, 95%CI, 1.613-2.139, P < 0.001) was similar to that of high-risk CC without PRFs (HR = 1.876, 95%CI, 1.731-2.033, P < 0.001). CONCLUSION: Combined PRFs improved the risk stratification of low-risk stage III CC, which could reduce the incidence of undertreatment and guide adjuvant chemotherapy.

Controlling the 2D Magnetism of CrBr3 by van der Waals Stacking Engineering.

The manipulation of two-dimensional (2D) magnetic order is of significant importance to facilitate future 2D magnets for low-power and high-speed spintronic devices. van der Waals stacking engineering makes promises for controllable magnetism via interlayer magnetic coupling. However, directly examining the stacking order changes accompanying magnetic order transitions at the atomic scale and preparing device-ready 2D magnets with controllable magnetic orders remain elusive. Here, we demonstrate the effective control of interlayer stacking in exfoliated CrBr3 via thermally assisted strain engineering. The stable interlayer ferromagnetic (FM), antiferromagnetic (AFM), and FM-AFM coexistent ground states confirmed by the magnetic circular dichroism measurements are realized. Combined with the first-principles calculations, the atomically resolved imaging technique reveals the correlation between magnetic order and interlayer stacking order in CrBr3 flakes unambiguously. A tunable exchange bias effect is obtained in the mixed phase of FM and AFM states. This work will introduce new magnetic properties by controlling the stacking order and sequence of 2D magnets, providing ample opportunities for their application in spintronic devices.

Coplanar MoS2 -MoTe2 Heterojunction With the Same Crystal Orientation.

Two-dimensional (2D) coplanar heterostructure enables high-performance optoelectronic devices, such as p-n heterojunctions. However, realizing site-controllable and shape-specific 2D coplanar heterojunctions composed of two semiconductors with the same crystal orientation still requires the development of new growth methods. Here, a route to fabricate MoS2 -MoTe2 coplanar heterojunctions with the same crystal orientation is reported by exploiting the properties of phase transition and atomic rearrangement during the growth of 2H-MoTe2 . Raman spectroscopy and electron microscopy techniques reveal the chemical composition and lattice structure of the heterostructure. Both MoS2 and MoTe2 in the heterojunction are single crystals and have the same lattice orientation, and their shapes can be arbitrarily defined by electron beam lithography. Electrical measurements show that the MoS2 and MoTe2 channels exhibit n-type and p-type transfer characteristics, respectively. The coplanar epitaxy technology can be used to prepare more coplanar heterostructures with novel device functions.

Large-Scale Vertically Interconnected Complementary Field-Effect Transistors Based on Thermal Evaporation.

With the rapid development of integrated circuits, there is an increasing need to boost transistor density. In addition to shrinking the device size to the atomic scale, vertically stacked interlayer interconnection technology is also an effective solution. However, realizing large-scale vertically interconnected complementary field-effect transistors (CFETs) has never been easy. Currently-used semiconductor channel synthesis and doping technologies often suffer from complex fabrication processes, poor vertical integration, low device yield, and inability to large-scale production. Here, a method to prepare large-scale vertically interconnected CFETs based on a thermal evaporation process is reported. Thermally-evaporated etching-free Te and Bi2 S3 serve as p-type and n-type semiconductor channels and exhibit FET on-off ratios of 103 and 105 , respectively. The vertically interconnected CFET inverter exhibits a clear switching behavior with a voltage gain of 17 at a 4 V supply voltage and a device yield of 100%. Based on the ability of thermal evaporation to prepare large-scale uniform semiconductor channels on arbitrary surfaces, repeated upward manufacturing can realize multi-level interlayer interconnection integrated circuits.

The effects of COVID-19 event strength on job burnout among primary medical staff.

BACKGROUND: As a global pandemic, The Corona Virus Disease 2019 (COVID-19) has brought significant challenges to the primary health care (PHC) system. Health professionals are constantly affected by the pandemic's harmful impact on their mental health and are at significant risk of job burnout. Therefore, it is essential to gain a comprehensive understanding of how their burnout was affected. The study aimed to examine the relationship between COVID-19 event strength and job burnout among PHC providers and to explore the single mediating effect of job stress and work engagement and the chain mediating effect of these two variables on this relationship. METHODS: Multilevel stratified convenience sampling method was used to recruit 1148 primary medical staff from 48 PHC institutions in Jilin Province, China. All participants completed questionnaires regarding sociodemographic characteristics, COVID-19 event strength, job stress, work engagement, and job burnout. The chain mediation model was analyzed using SPSS PROCESS 3.5 Macro Model 6. RESULTS: COVID-19 event strength not only positively predicted job burnout, but also indirectly influenced job burnout through the mediation of job stress and work engagement, thereby influencing job burnout through the "job stress → work engagement" chain. CONCLUSIONS: This study extends the application of event systems theory and enriches the literature about how the COVID-19 pandemic impacted PHC medical staff job burnout. The findings derived from our study have critical implications for current and future emergency response and public policy in the long-term COVID-19 disease management period.

Functional limitation and happiness among older adults: the multiple mediating role of intergenerational support and intergenerational relationship.

Objectives: This study aimed to investigate the relationship between the functional limitation and happiness among Chinese older people and examined the multiple mediating effects of intergenerational support (instrumental support and financial support) and intergenerational relationship. Method: Data was drawn from the Chinese Family Panel Survey (CFPS) 2018 and 2020. Structural equation modeling was adopted to analyze the association among functional limitations, intergenerational support, intergenerational relationship, and the older adults happiness. Results: There was a significant association between the functional limitations and the lower happiness levels among the older adults. The instrumental support from adult children positively mediated the relationship between the functional limitation and the happiness. However, intergenerational relationships were reduced due to the dysfunction of the older adults, and played a negatively mediated role between the functional limitation and the happiness. In addition, instrumental and financial support play chain-mediating roles between functional limitation and happiness in older adults through intergenerational relationships. Conclusion: Intergenerational relationships and instrumental support enhance the happiness of older adults with functional impairments, but their role is limited by the changing structure of modern families. Long-term care programs combined with the intergenerational support from families for people with functional impairments in old age would be more effective to reduce the burden on adult children and maintain the quality of life of the older adults.

Survival outcomes of different neoadjuvant treatment regimens in patients with locally advanced rectal cancer and MRI-detected extramural venous invasion.

PURPOSE: MRI-detected extramural venous invasion (mrEMVI) is associated with poor survival outcomes in patients with locally advanced rectal cancer (LARC). An mrEMVI-positive status is considered a strong indication for neoadjuvant treatment, but the optimal regimen is unknown. PATIENTS AND METHODS: We retrospectively compared pathological and survival outcomes of 584 patients diagnosed with mrEMVI-positive rectal cancer between January 2013 and October 2021, and receiving either neoadjuvant chemotherapy (NCT) alone, neoadjuvant chemoradiotherapy (nCRT) alone, or nCRT plus NCT, prior to total mesorectal excision. Propensity score matching (PSM) was used to balance clinical bias between groups, which were compared using chi-square testing and Kaplan-Meier curves. RESULTS: Median follow-up was 33.9 (range, 10.2-100.4) months. The 3-year overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRFS) rates for all patients were 90.4%, 57.5%, 61.1%, and 85.7%, respectively. Of 584 mrEMVI-positive patients at the time of diagnosis, 457 (78.3%) were EMVI-negative on surgical pathology, and they had significantly better 3-year OS, DMFS, DFS, and LRFS rates (all p < 0.001) than patients who remained EMVI-positive. After PSM was applied, patients receiving nCRT alone had significantly better 3-year OS (96.8% vs. 86.5%, p = 0.005) and DMFS (67.1% vs. 53.5%, p = 0.03) rates than those receiving NCT alone. Patients receiving NCT plus nCRT had higher pathological complete response (PCR) (10.8% vs. 2.7%, p = 0.04) and downstaging (33.8% vs. 5.3%, p < 0.001) rates than those receiving nCRT alone, but survival rates did not differ (all p > 0.05). CONCLUSION: Most EMVI-positive patients with LARC converted to EMVI-negative after neoadjuvant treatment, resulting in improved OS and DFS. Patients receiving nCRT had more favorable survival outcomes than those receiving NCT, suggesting the importance of including neoadjuvant radiotherapy. Patients receiving NCT in addition to nCRT had higher rates of PCR and downstaging, but their survival rates were not better.

High Efficiency and Flexible Modulation of Spintronic Terahertz Emitters in Synthetic Antiferromagnets.

Spintronic terahertz (THz) emitters based on synthetic antiferromagnets (SAFs) of FM1/Ru/FM2 (FM: ferromagnet) have shown great potential for achieving coherent superposition and significant THz power enhancement due to antiparallel magnetization alignment. However, key issues regarding the effects of interlayer exchange coupling and net magnetization on THz emissions remain unclear, which will inevitably hinder the performance improvement and practical application of THz devices. In this work, we have investigated the femtosecond laser-induced THz emission in Pt (3)/CoFe (3)/Ru (tRu = 0-3.5)/CoFe (tCoFe = 1.5-10)/Pt (3) (in units of nm) films with compensated and uncompensated magnetic moments. Antiferromagnetic (AF) coupling occurs in the Ru thickness ranges of 0.2-1.1 and 1.9-2.3 nm, with the first peak (tRu = 0.4 nm) of the AF coupling field (Hex) significantly higher than that of the second peak (2.0 nm). Rather high THz amplitude is found for the samples with strong AF coupling. Nevertheless, despite the same remanence ratio of zero, the THz amplitude for the symmetric SAF films declines significantly as the tRu decreases from 0.8 to 0.4 nm, which is mainly ascribed to the noncolinear magnetization vectors due to the increased biquadratic coupling term. Specifically, we demonstrate that an asymmetric SAF structure with a dominant FM layer is more favored than the completely compensated one, which could generate significantly enhanced THz electric field with well-controlled polarity and intensity. In addition, as the temperature decreases, the THz emission intensity increases for the SAF samples of tRu = 0.9 nm with negligible biquadratic coupling, which is contrary to the decreasing trend of the tRu = 0.4 nm sample and has been attributed to the greatly enhanced Hex.

Construction and Validation of a Novel Prognosis Model in Colon Cancer Based on Cuproptosis-Related Long Non-Coding RNAs.

Colon cancer (CC) is one of the most common (6%) malignancies and leading cause of cancer-associated death (more than 0.5 million) worldwide, which demands reliable prognostic biomarkers. Cuproptosis is a novel modality of regulated cell death triggered by the accumulation of intracellular copper. LncRNAs have been reported as prognostic signatures in different types of tumors. However, the correlation between cuproptosis-related lncRNAs (CRLs) and CC remains unclear. Data of CC patients were downloaded from public databases. The prognosis-associated CRLs were identified by co-expression analysis and univariate Cox. Least absolute shrinkage and selection operator were utilized to construct the CRLs-based prognostic signature in silico for CC patients. CRLs level was validated in human CC cell lines and patient tissues. ROC curve and Kaplan-Meier curve results revealed that high CRLs-risk score was associated with poor prognosis in CC patients. Moreover, the nomogram revealed that this model possessed a steady prognostic prediction capability with C-index as 0.68. More importantly, CC patients with high CRLs-risk score were more sensitive to eight targeted therapy drugs. The prognostic prediction power of the CRLs-risk score was further confirmed by cell lines, tissues and two independent CC cohorts. This study constructed a novel ten-CRLs-based prognosis model for CC patients. The CRLs-risk score is expected to serve as a promising prognostic biomarker and predict targeted therapy response in CC patients.

Ultra-Wide Band Gap Ga2O3-on-SiC MOSFETs.

Ultra-wide band gap semiconductor devices based on ß-phase gallium oxide (Ga2O3) offer the potential to achieve higher switching performance and efficiency and lower manufacturing cost than that of today's wide band gap power electronics. However, the most critical challenge to the commercialization of Ga2O3 electronics is overheating, which impacts the device performance and reliability. We fabricated a Ga2O3/4H-SiC composite wafer using a fusion-bonding method. A low-temperature (≤600 °C) epitaxy and device processing scheme was developed to fabricate MOSFETs on the composite wafer. The low-temperature-grown epitaxial Ga2O3 devices deliver high thermal performance (56% reduction in channel temperature) and a power figure of merit of (∼300 MW/cm2), which is the highest among heterogeneously integrated Ga2O3 devices reported to date. Simulations calibrated based on thermal characterization results of the Ga2O3-on-SiC MOSFET reveal that a Ga2O3/diamond composite wafer with a reduced Ga2O3 thickness (∼1 µm) and a thinner bonding interlayer (<10 nm) can reduce the device thermal impedance to a level lower than that of today's GaN-on-SiC power switches.

Academic Performance and Peer or Parental Tobacco Use among Non-Smoking Adolescents: Influence of Smoking Interactions on Intention to Smoke.

BACKGROUND: Intention to smoke is an important predictor of future smoking among adolescents. The purpose of our study was to examine the interaction between academic performance and parents/peer tobacco use on adolescents' intention to smoke. METHODS: A multi-stage stratified sampling was used to select participants, involving 9394 students aged between 9-16 years in Changchun city, northeastern China. Multiple logistic regression analyses were conducted to examine the individual effect of academic performance and peer/parental smoking behavior. Stratified logistic regressions were conducted to examine the protective effect of academic performance based on peer or parental smoking. Interaction effects of academic performance × peer/parental smoking on adolescents' intention to smoke were tested. RESULTS: Of all the non-smoking students sampled, 11.9% intended to smoke within the next five years. The individual effect of academic performance and peer/parental smoking was significant. The protective effect of academic performance on the intention to smoke was significant regardless of whether peers smoked or not. However, the protective effect was not significant among adolescents with only maternal smoking and both parental smoking. The current study found the significant interaction effects of academic performance × peer smoking and the academic performance × both parents' smoking. Students with poor academic performance were more likely to intend to smoke if their peers or both parents smoked. CONCLUSION: These preliminary results suggest that peer smoking or smoking by both parents reinforces the association between low academic performance and the intention to smoke among adolescents. Enhancing school engagement, focusing on social interaction among adolescents with low academic performance, and building smoke-free families may reduce adolescents' intention to smoke.

Red-emitting carbon dots aggregates-based fluorescent probe for monitoring Cu2.

R-CDAs have been synthesized in a one-pot solvothermal procedure starting from 3,4-diaminobenzoic acid in an acidic medium. Transmission electron microscopy (TEM) revealed that R-CDAs nanoparticles exhibited a much larger diameter of 7.2-28.8 nm than traditional monodisperse carbon dots. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed the presence of polar functional groups (hydroxyl, amino, carboxyl) on the surface of R-CDAs. Upon excitation with visible light (550 nm), R-CDAs emit stable, red fluorescence with a maximum at 610 nm. Under the optimum conditions, Cu2+ ions quench the fluorescence of this probe, and the signal is linear in a concentration range of copper ions between 5 and 600 nM with the detection limit of only 0.4 nM. Recoveries from 98.0 to 105.0% and relative standard deviations (RSD) from 2.8 to 4.5% have been obtained for detection of Cu2+ in real water samples. Furthermore, the R-CDAs fluorescent probe showed negligible cytotoxicity toward HeLa cells and good bioimaging ability, suggesting its potential applicability as a diagnostic tool in biomedicine.

The effect of recombinant human epidermal growth factor on radiation dermatitis in rectal and anal cancer patients: a self-controlled study.

BACKGROUND: Our previous study reported that recombinant human epidermal growth factor (rhEGF)-triggered EGFR internalization promoted radioresistance. Here, we aimed to evaluate the effect of rhEGF on the skin protection of rectal and anal cancer patients receiving radiotherapy. METHODS: One hundred and ninety-three rectal and anal cancer patients who received radiotherapy were prospectively enrolled from January 2019 to December 2020. To perform self-controlled study, the left and right pelvic skin area (separated by midline) were randomly assigned to the rhEGF and control side. The association between radiation dermatitis and factors including rhEGF, the dose of radiotherapy and tumor distance from anal edge were analyzed. RESULTS: Among 193 enrolled patients, 41 patients (21.2%) did not develop radiation dermatitis, and 152 patients (78.8%) suffered radiation dermatitis on at least one side of pelvic skin at the end of radiotherapy. For the effect on radiation dermatitis grade, rhEGF had improved effect on 6 (4.0%) patients, detrimental effect on 2 (1.3%) patients, and no effect on 144 (94.7%) patients. Whereas for the effect on radiation dermatitis area, rhEGF showed improved effect on the radiation dermatitis area of 46 (30.2%) patients, detrimental effect on 15 (9.9%) patients, and no effect on 91 (59.9%) patients. The radiation dermatitis area of rhEGF side was significantly smaller than that of control side (P = 0.0007). CONCLUSIONS: rhEGF is a skin protective reagent for rectal and anal cancer patients receiving radiotherapy. TRIAL REGISTRATION: Chinese Clinical Trial Registry identifier: ChiCTR1900020842; Date of registration: 20/01/2019.

A Novel m7G-Related Gene Signature Predicts the Prognosis of Colon Cancer.

Colon cancer (CC), one of the most common malignancies worldwide, lacks an effective prognostic prediction biomarker. N7-methylguanosine (m7G) methylation is a common RNA modification type and has been proven to influence tumorigenesis. However, the correlation between m7G-related genes and CC remains unclear. The gene expression levels and clinical information of CC patients were downloaded from public databases. Twenty-nine m7G-related genes were obtained from the published literature. Via unsupervised clustering based on the expression levels of m7G-related genes, CC patients were divided into three m7G clusters. Based on differentially expressed genes (DEGs) from the above three groups, CC patients were further divided into three gene clusters. The m7G score, a prognostic model, was established using principal component analysis (PCA) based on 15 prognosis-associated m7G genes. KM curve analysis demonstrated that the overall survival rate was remarkably higher in the high-m7G score group, which was much more significant in advanced CC patients as confirmed by subgroup analysis. Correlation analysis indicated that the m7G score was associated with tumor mutational burden (TMB), PD-L1 expression, immune infiltration, and drug sensitivity. The expression level of prognosis-related m7G genes was further confirmed in human CC cell lines and samples. This study established an m7G gene-based prognostic model (m7G score), which demonstrated the important roles of m7G-related genes during CC initiation and progression. The m7G score could be a practical biomarker to predict immunotherapy response and prognosis in CC patients.

Wafer-Scale Demonstration of MBC-FET and C-FET Arrays Based on Two-Dimensional Semiconductors.

Two-dimentional semiconductors have shown potential applications in multi-bridge channel field-effect transistors (MBC-FETs) and complementary field-effect transistors (C-FETs) due to their atomic thickness, stackability, and excellent electrical properties. However, the exploration of MBC-FET and C-FET based on large-scale 2D semiconductors is still lacking. Here, based on a reliable vertical stacking of wafer-scale 2D semiconductors, large-scale MBC-FETs and C-FETs using n-type MoS2 and p-type MoTe2 are successfully fabricated. The drive current of an MBC-FET with two layers of MoS2 channel (20 µm/10 µm) is up to 60 µA under 1 V bias. Compared with the single-gate MoS2 FET, the carrier mobility of MBC-FET is 2.3 times higher and the sub-threshold swing is 70% smaller. Furthermore, NAND and NOR logic circuits are also constructed based on two vertically stacked MoS2 channels. Then, C-FET arrays are fabricated by 3D integrating n-type MoS2 FET and p-type MoTe2 FET, which exhibit a voltage gain of 7 V/V when VDD  = 4 V. In addition, this C-FET device can directly convert light signals to an electrical digital signal within a single device. The demonstration of MBC-FET and C-FET based on large-scale 2D semiconductors will promote the application of 2D semiconductors in next-generation circuits.

The Clinical Guiding Role of the Distribution of Corneal Nerves in the Selection of Incision for Penetrating Corneal Surgery in Canines.

The cornea is one of the regions with the highest density of nerve terminals in the animal body and it bears such functions as nourishing the cornea and maintaining corneal sensation. In veterinary clinical practice, the corneoscleral limbus incision is frequently applied in cataract surgery, peripheral iridectomy, and other procedures for glaucoma. Inevitably, it would cause damage to the nerve roots that enter the cornea from the corneal limbus, thus inducing a series of complications. In this paper, the in vitro cornea (39 corneas from 23 canines, with ages ranging from 8 months old to 3 years old, including 12 male canines and 11 female canines) was divided into 6 zones, and the whole cornea was stained with gold chloride. After staining, corneal nerves formed neural networks at different levels of cornea. There was no significant difference in the number of nerve roots at the corneoscleral limbus between different zones (F = 1.983, p = 0.082), and the nerve roots at the corneoscleral limbus (mean value, 24.43; 95% CI, 23.43-25.42) were evenly distributed. Additionally, there was no significant difference in the number of corneal nerve roots between male and female canines (p = 0.143). There was also no significant difference in the number of corneal nerve roots between adult canines and puppies (p = 0.324). The results of the above analysis will provide a reasonable anatomical basis for selecting the incision location and orientation of penetrating surgery for the canine cornea in veterinary practice.

Ga2O3-on-SiC Composite Wafer for Thermal Management of Ultrawide Bandgap Electronics.

ß-phase gallium oxide (Ga2O3) is an emerging ultrawide bandgap (UWBG) semiconductor (EG ∼ 4.8 eV), which promises generational improvements in the performance and manufacturing cost over today's commercial wide bandgap power electronics based on GaN and SiC. However, overheating has been identified as a major bottleneck to the performance and commercialization of Ga2O3 device technologies. In this work, a novel Ga2O3/4H-SiC composite wafer with high heat transfer performance and an epi-ready surface finish has been developed using a fusion-bonding method. By taking advantage of low-temperature metalorganic vapor phase epitaxy, a Ga2O3 epitaxial layer was successfully grown on the composite wafer while maintaining the structural integrity of the composite wafer without causing interface damage. An atomically smooth homoepitaxial film with a room-temperature Hall mobility of ∼94 cm2/Vs and a volume charge of ∼3 × 1017 cm-3 was achieved at a growth temperature of 600 °C. Phonon transport across the Ga2O3/4H-SiC interface has been studied using frequency-domain thermoreflectance and a differential steady-state thermoreflectance approach. Scanning transmission electron microscopy analysis suggests that phonon transport across the Ga2O3/4H-SiC interface is dominated by the thickness of the SiNx bonding layer and an unintentionally formed SiOx interlayer. Extrinsic effects that impact the thermal conductivity of the 6.5 µm thick Ga2O3 layer were studied via time-domain thermoreflectance. Thermal simulation was performed to estimate the improvement of the thermal performance of a hypothetical single-finger Ga2O3 metal-semiconductor field-effect transistor fabricated on the composite substrate. This novel power transistor topology resulted in a ∼4.3× reduction in the junction-to-package device thermal resistance. Furthermore, an even more pronounced cooling effect is demonstrated when the composite wafer is implemented into the device design of practical multifinger devices. These innovations in device-level thermal management give promise to the full exploitation of the promising benefits of the UWBG material, which will lead to significant improvements in the power density and efficiency of power electronics over current state-of-the-art commercial devices.

Thermal Conductivity of ß-Phase Ga2O3 and (AlxGa1-x)2O3 Heteroepitaxial Thin Films.

Heteroepitaxy of ß-phase gallium oxide (ß-Ga2O3) thin films on foreign substrates shows promise for the development of next-generation deep ultraviolet solar blind photodetectors and power electronic devices. In this work, the influences of the film thickness and crystallinity on the thermal conductivity of (2̅01)-oriented ß-Ga2O3 heteroepitaxial thin films were investigated. Unintentionally doped ß-Ga2O3 thin films were grown on c-plane sapphire substrates with off-axis angles of 0° and 6° toward ⟨112̅0⟩ via metal-organic vapor phase epitaxy (MOVPE) and low-pressure chemical vapor deposition. The surface morphology and crystal quality of the ß-Ga2O3 thin films were characterized using scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The thermal conductivities of the ß-Ga2O3 films were measured via time-domain thermoreflectance. The interface quality was studied using scanning transmission electron microscopy. The measured thermal conductivities of the submicron-thick ß-Ga2O3 thin films were relatively low as compared to the intrinsic bulk value. The measured thin film thermal conductivities were compared with the Debye-Callaway model incorporating phononic parameters derived from first-principles calculations. The comparison suggests that the reduction in the thin film thermal conductivity can be partially attributed to the enhanced phonon-boundary scattering when the film thickness decreases. They were found to be a strong function of not only the layer thickness but also the film quality, resulting from growth on substrates with different offcut angles. Growth of ß-Ga2O3 films on 6° offcut sapphire substrates was found to result in higher crystallinity and thermal conductivity than films grown on on-axis c-plane sapphire. However, the ß-Ga2O3 films grown on 6° offcut sapphire exhibit a lower thermal boundary conductance at the ß-Ga2O3/sapphire heterointerface. In addition, the thermal conductivity of MOVPE-grown (2̅01)-oriented ß-(AlxGa1-x)2O3 thin films with Al compositions ranging from 2% to 43% was characterized. Because of phonon-alloy disorder scattering, the ß-(AlxGa1-x)2O3 films exhibit lower thermal conductivities (2.8-4.7 W/m·K) than the ß-Ga2O3 thin films. The dominance of the alloy disorder scattering in ß-(AlxGa1-x)2O3 is further evidenced by the weak temperature dependence of the thermal conductivity. This work provides fundamental insight into the physical interactions that govern phonon transport within heteroepitaxially grown ß-phase Ga2O3 and (AlxGa1-x)2O3 thin films and lays the groundwork for the thermal modeling and design of ß-Ga2O3 electronic and optoelectronic devices.