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Incorporating rare-earth elements into wurtzite nitride semiconductors, such as scandium-alloyed aluminum nitride (ScAlN), significantly enhances the piezoelectric response, which is vital for a broad range of acoustic, electronic, photonic, and quantum applications. To date, however, the measured piezoelectric response of nitride semiconductors is far below what theory has predicted. Herein, we demonstrate a simple, scalable, post-growth thermal annealing process that can dramatically boost the piezoelectric response of ScAlN. We achieve a 3.5-fold increase in the piezoelectric modulus, d 33 for ScAlN, from 12.3 pC/N in the as-grown state to 45.5 pC/N, which is eight times larger than that of AlN commercially used in 5 G cellphones. The observed enhancement is unambiguously confirmed by three separate measurement techniques. Detailed material characterization techniques reveal that optimized annealing conditions significantly improve the macroscopic structural quality, achieving a more homogeneous and ordered domain orientation, and reduces the lattice parameter ratio (c/a) in the wurtzite crystal structure. The dramatic enhancement of d 33 in ScAlN thin films promises extreme frequency scaling opportunities for bulk acoustic wave resonators for beyond-5 G applications. The authors present a process that boosts the piezoelectric properties of ScAlN thin films by 3.5 times, enhancing their performance for use in acoustic devices. The technique is scalable, cost effective, and could enable advanced sensors, clocks, and communication technologies.

ZnO and ZnMgO nanorods have proven to be promising materials for sensing, UV and deep UV based optoelectronic applications. A major drawback of ZnO and ZnMgO based thin films and nanorods is the presence of native point defects which deteriorates their optical efficiency and becomes an impediment to their efficient device applications. The furnace and rapid thermal annealing processes have overcome this up to a great extent but being high temperature processes, they put many fabrication and technological limits in device fabrication. Especially keeping an eye on the future flexible devices, herein we report ultraviolet-ozone (UVO) annealing as a room-temperature, simple and cost-effective annealing method to improve the optical efficiency of ZnO and ZnMgO nanorods along with control of defect states. The ZnO and ZnMgO nanorods were grown by hydrothermal method and annealed in UVO irradiation. UVO annealing substantially improved near band emission and suppressed defect band emissions. It is found that zinc interstitial atoms migrate from the top portion of ZnO nanorods towards the bottom of nanorods after UVO annealing, resulting in reduced zinc interstitial defects in the top portion of nanorods. X-ray diffraction results showed improvement in structural properties. XPS results confirmed suppression of oxygen vacancies and zinc interstitials and improvement in lattice oxygen in the ZnO nanorods after UVO annealing. Optimum times of UVO annealing for ZnO and ZnMgO nanorods were 30 and 50 min respectively. These findings will be helpful for the further development of ZnO and ZnMgO nanorods based high performance optoelectronic devices and sensors.

In this work, the authors have propounded a novel Gallium Nitride High Electron Mobility Transistor (GaN-HEMT) structure and have analyzed its DC, RF and noise performance parameters. The DC characteristics reveal a high ON-state current in the order of 10 −2  A/mm complemented by a near ideal sub-threshold swing of 70 mV/decade. High values of cut-off frequency ( f t  = 126 GHz) and maximum oscillation frequency ( f max  = 224 GHz) are obtained which indicate high frequency range of operation. A minimum noise figure in the order of 10 −5  dB has been achieved for lower frequencies of operation that remains considerably low even beyond 30 GHz (1.7 dB at 45 GHz and 4 dB at 100 GHz), indicating low-noise performance at practical operational frequencies. Further, a resistive load inverter based on GaN-HEMT has been proposed to supplant existing Silicon-based Complementary Metal Oxide Semiconductor (CMOS) technology which suffers from extensive scaling limitations. A thorough analysis of the inverter circuit has been carried out through mixed-mode simulation and the effect of the composition of the barrier layer in the GaN-HEMT, as well as the supply voltage of the inverter has been reported. With Si-technology reaching its bottleneck, GaN based device circuits will surely foster further research in this domain.

Is there any possibility that foreign aid may negatively affect African social ties? To answer such a question, this paper examines the impact of local Chinese aid projects on social capital in Africa. China or Chinese contractors directly control or operate Chinese projects in Africa. This feature may disengage Africans from participating in their own local development activities. Likewise, China gives unconditional aid, which may nurture corruption. By creating losers and winners, corruption may make people unhappy. Because of these features, Chinese aid projects may hinder the formation of social capital. This paper puts this claim to an empirical test using data from the Afrobarometer surveys and AidData. Conditional on a set of controls, I find several interesting results. First, Chinese aid is negatively associated with generalized trust. Second, Chinese aid projects are related to disengagement from associational life. Third, no similar pattern is found when the main analysis is replicated on aid from the World Bank. Finally, neither the Chinese nor the World Bank's aid is related to subjective wellbeing. The results suggest that Chinese aid may wither local social ties through social disengagement. Overall, the findings imply that it is vital to engage local citizens in the design and implementation of Chinese aid projects.

The pursuit of extreme device miniaturization and the exploration of novel physical phenomena have spurred significant interest in crystallographic phase control and ferroelectric switching in reduced dimensions. Recently, wurtzite ferroelectrics have emerged as a new class of functional materials, offering intriguing piezoelectric and ferroelectric properties, CMOS compatibility, and seamless integration with mainstream semiconductor technology. However, the exploration of crystallographic phase and ferroelectric switching in reduced dimensions, especially in nanostructures, has remained a largely uncharted territory. In this study, we present the first comprehensive investigation into the crystallographic phase transition of ScAlN nanowires across the full Sc compositional range. While a gradual transition from wurtzite to cubic phase was observed with increasing Sc composition, we further demonstrated that a highly ordered wurtzite phase ScAlN could be confined at the ScAlN/GaN interface for Sc contents surpassing what is possible in conventional films, holding great potential to addressing the fundamental high coercive field of wurtzite ferroelectrics. In addition, we provide the first evidence of ferroelectric switching in ScAlN nanowires, a result that holds significant implications for future device miniaturization. Our demonstration of tunable ferroelectric ScAlN nanowires opens new possibilities for nanoscale, domain, alloy, strain, and quantum engineering of wurtzite ferroelectrics, representing a significant stride towards the development of next-generation, miniaturized devices based on wurtzite ferroelectrics.

Mid and deep ultraviolet (UV) laser diodes remain among the least explored devices in semiconductor optoelectronics, despite their importance for spectroscopy, biochemical sensing, disinfection, and emerging quantum photonics. Here, we demonstrate an electrically pumped AlGaN-based laser diode operating in the UV-B band (280-315 nm). The device is grown by molecular beam epitaxy (MBE) on single-crystal AlN substrate and fabricated in a ridge-waveguide geometry. The laser diode operates at 298.5 nm and exhibits a relatively low threshold current density of 3.4 kA/cm\\(^2\\). Clear nonlinear light-current characteristics and pronounced spectral narrowing with a full-width-at-half-maximum (FWHM) of 0.2 nm are measured above threshold.

The incorporation of rare-earth elements in wurtzite nitride semiconductors, e.g., scandium alloyed aluminum nitride (ScAlN), promises dramatically enhanced piezoelectric responses, critical to a broad range of acoustic, electronic, photonic, and quantum devices and applications. Experimentally, however, the measured piezoelectric responses of nitride semiconductors are far below what theory has predicted. Here, we show that the use of a simple, scalable, post-growth thermal annealing process can dramatically boost the piezoelectric response of ScAlN thin films. We achieve a remarkable 3.5-fold increase in the piezoelectric modulus, d33 for 30% Sc content ScAlN, from 12.3 pC/N in the as-grown state to 45.5 pC/N, which is eight times larger than that of AlN. The enhancement in piezoelectricity has been unambiguously confirmed by three separate measurement techniques. Such a dramatic enhancement of d33 has been shown to impact the effective electromechanical coupling coefficient kt2 : increasing it from 13.8% to 76.2%, which matches the highest reported values in millimeter thick lithium niobate films but is achieved in a 100 nm ScAlN with a 10,000 fold reduction in thickness, thus promising extreme frequency scaling opportunities for bulk acoustic wave resonators for beyond 5G applications. By utilizing a range of material characterization techniques, we have elucidated the underlying mechanisms for the dramatically enhanced piezoelectric responses, including improved structural quality at the macroscopic scale, more homogeneous and ordered distribution of domain structures at the mesoscopic scale, and the reduction of lattice parameter ratio (c/a) for the wurtzite crystal structure at the atomic scale. Overall, the findings present a simple yet highly effective pathway that can be extended to other material families to further enhance their piezo responses.

Non-invasive vagus nerve stimulation (nVNS) is an established neurostimulation therapy used in the treatment of epilepsy, migraine and cluster headache. In this randomized, double-blind, sham-controlled trial we explored the role of nVNS in the treatment of gait and other motor symptoms in Parkinson’s disease (PD) patients. In a subgroup of patients, we measured selected neurotrophins, inflammatory markers and markers of oxidative stress in serum. Thirty-three PD patients with freezing of gait (FOG) were randomized to either active nVNS or sham nVNS. After baseline assessments, patients were instructed to deliver six 2  min stimulations (12  min/day) of the active nVNS/sham nVNS device for 1  month at home. Patients were then re-assessed. After a one-month washout period, they were allocated to the alternate treatment arm and the same process was followed. Significant improvements in key gait parameters (speed, stance time and step length) were observed with active nVNS. While serum tumor necrosis factor- α decreased, glutathione and brain-derived neurotrophic factor levels increased significantly ( p  < 0.05) after active nVNS treatment. Here we present the first evidence of the efficacy and safety of nVNS in the treatment of gait in PD patients, and propose that nVNS can be used as an adjunctive therapy in the management of PD patients, especially those suffering from FOG. Clinical trial registration : identifier ISRCTN14797144.

Anatomical changes during adjuvant radiotherapy (RT) for post-operative oral cavity squamous cell carcinoma (OCSCC) have greater dosimetric effects with highly conformal techniques, thereby necessitating plan adaptation. We compared conventional adaptive RT (cART) with deformable image registration (DIR)-based ART (dART). Post-operative OCSCC patients receiving adjuvant RT with a ≥ 5 mm change in skin contour on cone beam computed tomography (CBCT) were enrolled. After re-simulation, planning CT (pCT) and extended CBCT were imported into Velocity ® to generate a synthetic CT (sCT) using DIR. Separate plans were created on the re-simulation CT (rCT) and sCT. The initial plan he was also projected onto the sCT anatomy and compared with the original plan on the pCT. Geometric (volume, Dice similarity coefficient [DSC], mean distance to agreement [MDA]) and dosimetric (mean dose, dose-volume histogram [DVH]) differences were evaluated between rCT- and sCT-based plans. Twenty-five patients were prospectively enrolled. Based on DSC and MDA, DIR showed acceptable geometric accuracy for all structures except the spinal cord (DSC = 0.75). Compared to pCT, most structures had significant volume reduction on sCT, except the low-risk planning target volume (PTV LR ) ( p  = 0.14) and the larynx (increased, p  = 0.04). Projection of the initial plan onto sCT revealed significant loss in PTV LR coverage (V 95% p  = 0.001; D 98% p  = 0.01) and a non-significant loss for the high-risk PTV (PTV HR ). Organs at risk (OARs) doses increased non-significantly, except for the mandible ( p  = 0.007). Comparison of rCT and sCT volumes showed a 3.7% increases in PTV HR ( p  = 0.009) and 5.7% in PTV LR ( p  = 0.049), with non-significant OAR volume increases (2.4%–6.3%) except for the larynx (decreased). DVH comparison showed non-significant dose reductions to the parotids (0.6%), the mandible (0.5%), and the larynx (5.8%), but slight increases for the spinal cord (2.6%) and its planning organ at risk volume (PRV) (3.7%). Target coverage was significantly lower with sCT-based plans (PTV HR V 95% by 3.2%, D 98% by 3.8%, PTV LR V 95% by 4.1% and D 98% by 4.3%). dART improved OAR sparing but was compromised in a few target coverage parameters. Further enhancement of DIR accuracy is needed. Currently, DIR is primarily used in ART for dose accumulation to assess the need for plan adaptation.

A flexible nano-engineered natural mineral (carbon dot doped natural microcline) based membrane (MCPV) has been developed, which can efficiently detect the presence of hexavalent chromium (Cr 6+ ) and trivalent iron (Fe 3+ ) ions in water by altering its fluorescence emission. Detailed characterization of the membrane was carried out using XRD, FT-IR spectroscopy, FESEM, TEM, and UV-Vis spectroscopy. Mechanical and temperature stabilities were also investigated. This new-generation sensor membrane is designed in such a way that it does not dissolve in water, keeping the water quality unaffected. The fluorescence studies were conducted at 414 nm and “turn-off” response was observed specifically for Fe 3+ at 489 nm. A prominent red shift (530 nm) of the fluorescence maxima takes place when it comes to Cr 6+ . Figures of merit, such as LOD (8.7 μM for Cr 6+ and 18.4 μM for Fe 3+ ) and LOQ (29.1 μM for Cr 6+ and 61.6 μM for Fe 3+ ), were evaluated from the linear range (0–60 μM for Cr 6+ and 0–30 μM for Fe 3+ ) of the calibration curve (Stern-Volmer plots) showing high sensitivity of this sensing probe toward Cr 6+ and Fe 3+ . Recovery and RSD calculations were done in various real-life water samples on intraday-interday basis to determine the accuracy of the sensor. This work validates the fact that the synthesized sensor membrane is capable of detecting these heavy metals in glutathione environment as well, which could be beneficial for early-stage carcinogen detection in living cells. Graphical abstract