Search

p-NiO/n-Ga 2 O 3 heterojunction (HJ) diodes exhibit much larger changes in their properties upon 1.1 MeV proton irradiation than Schottky diodes (SDs) prepared on the same material. In p-NiO/Ga 2 O 3 HJ diodes, the narrow region adjacent to the HJ boundary is found to contain a high density of relatively deep centers with levels near E C -0.17 eV and a depleted region in the immediate vicinity of the HJ boundary. The series resistance of the HJ diodes is slightly higher than for the Schottky diodes and shows a temperature dependence with activation energy ~ 0.12 eV, like the temperature dependence of the NiO film resistivity. Irradiation with 1.1 MeV protons leads to a decrease of the hole concentration in the NiO, with a high carrier removal rate of ~ 1.3 × 10 5  cm -1 and a strong compensation of the interfacial region where the concentration of the E C -0.17 eV centers decreases with a high rate of ~ 7 × 10 3  cm -1 . The combined action of these two effects gives rise to the much stronger increase of the series resistance of the HJ diodes compared to Schottky diodes. The observed differences between the radiation response of the HJs and SDs cannot be credibly attributed to the changes of the density of any of the deep electron and hole traps detected in our experiments., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

The prevalence of breast cancer in women underscores the urgent need for innovative and efficient detection methods. This study addresses this imperative by harnessing salivary biomarkers, offering a noninvasive and accessible means of identifying breast cancer. In this study, commercially available disposable based strips similar to the commonly used glucose detection strips were utilized and functionalized to detect breast cancer with biomarkers of HER2 and CA15-3. The results demonstrated limits of detection for these two biomarkers reached as low as 1 fg/ml much lower than those of conventional enzyme-linked immunosorbent assay in the range of 1∼4 ng/ml. By employing a synchronized double-pulse method to apply 10 of 1.2 ms voltage pulses to the electrode of sensing strip and drain electrode of the transistor for amplifying the detected signal, and the detected signal was the average of 10 digital output readings corresponding to those 10 voltage pulses. The sensor sensitivities were achieved approximately 70/dec and 30/dec for HER2 and CA15-3, respectively. Moreover, the efficiency of this novel technique is underscored by its swift testing time of less than 15 ms and its minimal sample requirement of only 3  μ l of saliva. The simplicity of operation and the potential for widespread public use in the future position this approach as a transformative tool in the early detection of breast cancer. This research not only provides a crucial advancement in diagnostic methodologies but also holds the promise of revolutionizing public health practices., Competing Interests: The authors have no conflicts to disclose., (© 2024 Author(s).)

In this study, the structural and electrical properties of orthorhombic κ-Ga 2 O 3 films prepared using Halide Vapor Phase Epitaxy (HVPE) on AlN/Si and GaN/sapphire templates were studied. For κ-Ga 2 O 3 /AlN/Si structures, the formation of two-dimensional hole layers in the Ga 2 O 3 was studied and, based on theoretical calculations, was explained by the impact of the difference in the spontaneous polarizations of κ-Ga 2 O 3 and AlN. Structural studies indicated that in the thickest κ-Ga 2 O 3 /GaN/sapphire layer used, the formation of rotational nanodomains was suppressed. For thick (23 μm and 86 μm) κ-Ga 2 O 3 films grown on GaN/sapphire, the good rectifying characteristics of Ni Schottky diodes were observed. In addition, deep trap spectra and electron beam-induced current measurements were performed for the first time in this polytype. These experiments show that the uppermost 2 µm layer of the grown films contains a high density of rather deep electron traps near E c - 0.3 eV and E c - 0.7 eV, whose presence results in the relatively high series resistance of the structures. The diffusion length of the excess charge carriers was measured for the first time in κ-Ga 2 O 3 . The film with the greatest thickness of 86 μm was irradiated with protons and the carrier removal rate was about 10 cm -1 , which is considerably lower than that for β-Ga 2 O 3 .

Oral squamous cell carcinoma (OSCC) is one of the most common lip and oral cavity cancer types. It requires early detection via various medical technologies to improve the survival rate. While most detection techniques for OSCC require testing in a centralized lab to confirm cancer type, a point of care detection technique is preferred for on-site use and quick result readout. The modular biological sensor utilizing transistor-based technology has been leveraged for testing CIP2A, and optimal transistor gate voltage and load resistance for sensing setup was investigated. Sensitivities of 1 × 10 -15  g/ml have been obtained for both detections of pure CIP2A protein and HeLa cell lysate using identical test conditions via serial dilution. The superior time-saving and high accuracy testing provides opportunities for rapid clinical diagnosis in the medical space., (© 2022 Author(s).)

There is increasing interest in deep UV Light-Emitting Diodes (LEDs) for applications in water purification, virus inactivation, sterilization, bioagent detection, and UV curing, as well as charge management control in the Laser Interferometer Space Antenna (LISA), which will be the first gravitational wave detector in space. To fully understand the current state of commercial UV LEDs and assess their performance for use on LISA, large numbers of UV LEDs need to be tested across a range of temperatures while operating in air or in a vacuum. We describe a new hardware system designed to accommodate a high volume of UV LED performance tests and present the performance testing results from over 200 UV LEDs with wavelengths in the 250 nm range.

Leakage of human cerebrospinal fluid (CSF) caused by trauma or other reasons presents exceptional challenges in clinical analysis and can have severe medical repercussions. Conventional test methods, including enzyme-linked immunosorbent assay and immunofixation electrophoresis testing, typically are performed at a few clinical reference laboratories, which may potentially delay proper diagnosis and treatment. At the same time, medical imaging can serve as a secondary diagnosis tool. This work presented here reports the use of a point-of-care electrochemical sensor for detection of beta-2-transferrin (B2T), a unique isomer of transferrin that is present exclusively in human CSF but is absent in other bodily fluids. Limits of detection were examined via serial dilution of human samples with known B2T concentrations down to 7 × 10 -12 g B2T/ml while maintaining excellent sensitivity. Nine human samples with varying levels of B2T were compared using up to 100 times dilution to confirm the validity of sensor output across different patient samples., (© 2022 Author(s).)

The SARS-CoV-2 pandemic has had a significant impact worldwide. Currently, the most common detection methods for the virus are polymerase chain reaction (PCR) and lateral flow tests. PCR takes more than an hour to obtain the results and lateral flow tests have difficulty with detecting the virus at low concentrations. In this study, 60 clinical human saliva samples, which included 30 positive and 30 negative samples confirmed with RT-PCR, were screened for COVID-19 using disposable glucose biosensor strips and a reusable printed circuit board. The disposable strips were gold plated and functionalized to immobilize antibodies on the gold film. After functionalization, the strips were connected to the gate electrode of a metal-oxide-semiconductor field-effect transistor on the printed circuit board to amplify the test signals. A synchronous double-pulsed bias voltage was applied to the drain of the transistor and strips. The resulting change in drain waveforms was converted to digital readings. The RT-PCR-confirmed saliva samples were tested again using quantitative PCR (RT-qPCR) to determine cycling threshold (Ct) values. Ct values up to 45 refer to the number of amplification cycles needed to detect the presence of the virus. These PCR results were compared with digital readings from the sensor to better evaluate the sensor technology. The results indicate that the samples with a range of Ct values from 17.8 to 35 can be differentiated, which highlights the increased sensitivity of this sensor technology. This research exhibits the potential of this biosensor technology to be further developed into a cost-effective, point-of-care, and portable rapid detection method for SARS-CoV-2., (© 2022 Author(s).)

Neuromorphic systems, which emulate neural functionalities of a human brain, are considered to be an attractive next-generation computing approach, with advantages of high energy efficiency and fast computing speed. After these neuromorphic systems are proposed, it is demonstrated that artificial synapses and neurons can mimic neural functions of biological synapses and neurons. However, since the neuromorphic functionalities are highly related to the surface properties of materials, bulk material-based neuromorphic devices suffer from uncontrollable defects at surfaces and strong scattering caused by dangling bonds. Therefore, 2D materials which have dangling-bond-free surfaces and excellent crystallinity have emerged as promising candidates for neuromorphic computing hardware. First, the fundamental synaptic behavior is reviewed, such as synaptic plasticity and learning rule, and requirements of artificial synapses to emulate biological synapses. In addition, an overview of recent advances on 2D materials-based synaptic devices is summarized by categorizing these into various working principles of artificial synapses. Second, the compulsory behavior and requirements of artificial neurons such as the all-or-nothing law and refractory periods to simulate a spike neural network are described, and the implementation of 2D materials-based artificial neurons to date is reviewed. Finally, future challenges and outlooks of 2D materials-based neuromorphic devices are discussed., (© 2021 Wiley-VCH GmbH.)

Detection of the SARS-CoV-2 spike protein and inactivated virus was achieved using disposable and biofunctionalized functional strips, which can be connected externally to a reusable printed circuit board for signal amplification with an embedded metal-oxide-semiconductor field-effect transistor (MOSFET). A series of chemical reactions was performed to immobilize both a monoclonal antibody and a polyclonal antibody onto the Au-plated electrode used as the sensing surface. An important step in the biofunctionalization, namely, the formation of Au-plated clusters on the sensor strips, was verified by scanning electron microscopy, as well as electrical measurements, to confirm successful binding of thiol groups on this Au surface. The functionalized sensor was externally connected to the gate electrode of the MOSFET, and synchronous pulses were applied to both the sensing strip and the drain contact of the MOSFET. The resulting changes in the dynamics of drain waveforms were converted into analog voltages and digital readouts, which correlate with the concentration of proteins and virus present in the tested solution. A broad range of protein concentrations from 1 fg/ml to 10  μ g/ml and virus concentrations from 100 to 2500 PFU/ml were detectable for the sensor functionalized with both antibodies. The results show the potential of this approach for the development of a portable, low-cost, and disposable cartridge sensor system for point-of-care detection of viral diseases., (© 2021 Author(s).)

Layered heterojunctions are widely applied as fundamental building blocks for semiconductor devices. For the construction of nanoelectronic and nanophotonic devices, the implementation of two-dimensional materials (2DMs) is essential. However, studies of junction devices composed of 2DMs are still largely focused on single p-n junction devices. In this study, we demonstrate a novel pnp double heterojunction fabricated by the vertical stacking of 2DMs (black phosphorus (BP) and MoS 2 ) using dry-transfer techniques and the formation of high-quality p-n heterojunctions between the BP and MoS 2 in the vertically stacked BP/MoS 2 /BP structure. The pnp double heterojunctions allowed us to modulate the output currents by controlling the input current. These results can be applied for the fabrication of advanced heterojunction devices composed of 2DMs for nano(opto)electronics.

The robust radiation resistance of wide-band gap materials is advantageous for space applications, where the high-energy particle irradiation deteriorates the performance of electronic devices. We report on the effects of proton irradiation of β-Ga 2 O 3 nanobelts, whose energy band gap is ∼4.85 eV at room temperature. Back-gated field-effect transistor (FET) based on exfoliated quasi-two-dimensional β-Ga 2 O 3 nanobelts were exposed to a 10 MeV proton beam. The proton-dose- and time-dependent characteristics of the radiation-damaged FETs were systematically analyzed. A 73% decrease in the field-effect mobility and a positive shift of the threshold voltage were observed after proton irradiation at a fluence of 2 × 10 15 cm -2 . Greater radiation-induced degradation occurs in the conductive channel of the β-Ga 2 O 3 nanobelt than at the contact between the metal and β-Ga 2 O 3 . The on/off ratio of the exfoliated β-Ga 2 O 3 FETs was maintained even after proton doses up to 2 × 10 15 cm -2 . The radiation-induced damage in the β-Ga 2 O 3 -based FETs was significantly recovered after rapid thermal annealing at 500 °C. The outstanding radiation durability of β-Ga 2 O 3 renders it a promising building block for space applications.

Conventional thin-film diffusion barriers consist of 3D bulk films with high chemical and thermal stability. The purpose of the barrier material is to prevent intermixing or penetration from the two materials that encase it. Adhesion to both top and bottom materials is critical to the success of the barrier. Here, the effectiveness of a single atomic layer of graphene as a solid-state diffusion barrier for common metal schemes used in microelectronics is reviewed, and specific examples are discussed. Initial studies of electrical contacts to graphene show a distinct separation in behavior between metallic groups that strongly or weakly bond to it. The two basic classes of metal reactions with graphene are either physisorbed metals, which bond weakly with graphene, or chemisorbed metals, which bond strongly to graphene. For graphene diffusion barrier testing on Si substrates, an effective barrier can be achieved through the formation of a carbide layer with metals that are chemisorbed. For physisorbed metals, the barrier failure mechanism is loss of adhesion at the metal–graphene interface. A graphene layer encased between two metal layers, in certain cases, can increase the binding energy of both films with graphene, however, certain combinations of metal films are detrimental to the bonding with graphene. While the prospects for graphene's future as a solid-state diffusion barrier are positive, there are open questions, and areas for future research are discussed. A better understanding of the mechanisms which influence graphene's ability to be an effective diffusion barrier in microelectronic applications is required, and additional experiments are needed on a broader range of metals, as well as common metal stack contact structures used in microelectronic applications. The role of defects in the graphene is also a key area, since they will probably influence the barrier properties., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The valence band discontinuity (ΔE(v)) of Y2O3/InGaZnO4 (IGZO) heterojunctions was measured by a core-level photoemission method. The Y2O3 exhibited a band gap of -6.27 eV from absorption measurements. A value of ΔE(v) = 0.44 ± 0.21 eV was obtained by using the Ga 2p3/2, Zn 2p3/2 and in 3d5/2 energy levels as references. Given the experimental bandgap of 3.2 eV for the IGZO, this would indicate a conduction band offset ΔE(c) of - 2.63 eV in the Y2O3/IGZO heterostructures and a nested interface band alignment.

We demonstrate GaN-based thin light-emitting diodes (LEDs) on flexible polymer and paper substrates covered with chemical vapor deposited graphene as a transparent-conductive layer. Thin LEDs were fabricated by lifting the sapphire substrate off by Excimer laser heating, followed by transfer of the LEDs to the flexible substrates. These substrates were coated with tri-layer graphene by a wet transfer method. Optical and electrical properties of thin laser lift-offed LEDs on the flexible substrates were characterized under both relaxed and strained conditions. The graphene on paper substrates remained conducting when the graphene/paper structure was folded. The high transmittance, low sheet resistance and high failure strain of the graphene make it an ideal candidate as the transparent and conductive layer in flexible optoelectronics.

We demonstrate AuCl3-doped graphene transparent conductive electrodes integrated in GaN-based ultraviolet (UV) light-emitting diodes (LEDs) with an emission peak of 363 nm. AuCl3 doping was accomplished by dipping the graphene electrodes in 5, 10 and 20 mM concentrations of AuCl3 solutions. The effects of AuCl3 doping on graphene electrodes were investigated by current-voltage characteristics, sheet resistance, scanning electron microscope, optical transmittance, micro-Raman scattering and electroluminescence images. The optical transmittance was decreased with increasing the AuCl3 concentrations. However, the forward currents of UV LEDs with p-doped (5, 10 and 20 mM of AuCl3 solutions) graphene transparent conductive electrodes at a forward bias of 8 V were increased by ~48, 63 and 73%, respectively, which can be attributed to the reduction of sheet resistance and the increase of work function of the graphene. The performance of UV LEDs was drastically improved by AuCl3 doping of graphene transparent conductive electrodes.

We report on a simple and reproducible method for fabricating InGaN/GaN multi-quantum-well (MQW) nanorod light-emitting diodes (LEDs), prepared by combining a SiO 2 nanosphere lithography and dry-etch process. Focused-ion-beam (FIB)-deposited Pt was contacted to both ends of the nanorod LEDs, producing bright electroluminescence from the LEDs under forward bias conditions. The turn-on voltage in these nanorod LEDs was higher (13 V) than in companion thin film devices (3 V) and this can be attributed to the high contact resistance between the FIB-deposited Pt and nanorod LEDs and the damage induced by inductively-coupled plasma and Ga + -ions. Our method to obtain uniform MQW nanorod LEDs shows promise for improving the reproducibility of nano-optoelectronics.

Graphene-based, flexible NO(2) sensors on paper substrates exhibited an immediate response (32-39%) once exposed to 200 ppm NO(2) gas under a strain of 0.5%. Chemical vapor deposition-grown graphene with a supporting poly(methyl methacrylate) layer was transferred onto paper substrates, followed by formation of two electrodes using silver paste. Current-voltage characteristics and dynamic sensing response were obtained under both relaxed and strained conditions. We demonstrate a facile method without complex photo-lithography and high vacuum processes for fabricating graphene-based flexible NO(2) sensors on paper substrates with high sensing response.

Background: Immobilized aluminum gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) have shown great potential in the areas of pH, chloride ion, and glucose detection in exhaled breath condensate (EBC). HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. This technology offers the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology of detecting glucose in EBC without the need for clinical visits., Methods: HEMT structures, consisting of a 3-microm-thick undoped GaN buffer, 30-A-thick Al(0.3)Ga(0.7)N spacer, and 220-A-thick silicon-doped Al(0.3)Ga(0.7)N cap layer, were used for fabricating the HEMT sensors. The gate area of the pH, chloride ion, and glucose detection was immobilized with scandium oxide (Sc(2)O(3)), silver chloride (AgCl) thin film, and zinc oxide (ZnO) nanorods, respectively., Results: The Sc(2)O(3)-gated sensor could detect the pH of solutions ranging from 3 to 10 with a resolution of approximately 0.1 pH. A chloride ion detection limit of 10(-8) M was achieved with a HEMT sensor immobilized with the AgCl thin film. The drain-source current of the ZnO nanorod-gated AlGaN/GaN HEMT sensor immobilized with glucose oxidase showed a rapid response of less than 5 seconds when the sensor was exposed to the target glucose in a buffer with a pH value of 7.4. The sensor could detect a wide range of concentrations from 0.5 nM to 125 microM., Conclusion: There is great promise for using HEMT-based sensors to enhance the detection sensitivity for glucose detection in EBC. Depending on the immobilized material, HEMT-based sensors can be used for sensing different materials. These electronic detection approaches with rapid response and good repeatability show potential for the investigation of airway pathology. The devices can also be integrated into a wireless data transmission system for remote monitoring applications. This sensor technology could use the exhaled breath condensate to measure the glucose concentration for diabetic applications., (2010 Diabetes Technology Society.)

A recent publication by Kim et al. on penetrating both human embryonic kidney cells and mouse embryonic stem cells with Si nanowires highlights the increasing interest in using proven semiconductor materials not only to detect specific biomolecules in solutions but also to deliver genetic material or potentially screen for the presence of particular molecules at the cell level. Many semiconductors are biocompatible and this recent work has shown that penetrating cells with large diameters compared with those of the semiconductor nanowire is not fatal to the cell and that the cells remain functional for a few days.

Thin, uniform, single-walled carbon nanotube films, made by a simple filtration process, subsequently coated with palladium, are shown to be promising detectors of hydrogen. The films detected hydrogen with relative responses of 20% at 100 ppm and 40% at 500 ppm concentrations. Most of the initial film conductance was recovered within 30 s by exposing the samples to air. This quick and easy recoverability make the Pd-coated nanotubes suitable for practical applications in room temperature hydrogen sensing while consuming only approximately 0.25 mW power. The film fabrication process provides highly reproducible control over the film thickness; an important ingredient for commercial production. In the course of this research strong evidence was obtained indicating that sputter deposition of metal onto the nanotubes, even under very low power, short exposure time conditions, does damage to the nanotubes.