Search

Transition-metal dichalcogenide (TMDC) homo- and heterostacks hold tantalizing prospects for being integrated as active components in future van der Waals (vdW) electronics and optoelectronics. How...

The in-plane piezoelectricity or ferroelectricity of two-dimensional (2D) materials can vanish due to the appearance of inversion symmetry with increasing flake thickness, which drastically limits ...

Two-dimensional transition metal dichalcogenide nanoribbons are touted as the future extreme device downscaling for advanced logic and memory devices but remain a formidable synthetic challenge. Here, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer and single-crystalline MoS2 nanoribbons on β-gallium (iii) oxide (β-Ga2O3) (100) substrates. LDE MoS2 nanoribbons have spatial uniformity over a long range and transport characteristics on par with those seen in exfoliated benchmarks. Prototype MoS2-nanoribbon-based field-effect transistors exhibit high on/off ratios of 108 and an averaged room temperature electron mobility of 65 cm2 V−1 s−1. The MoS2 nanoribbons can be readily transferred to arbitrary substrates while the underlying β-Ga2O3 can be reused after mechanical exfoliation. We further demonstrate LDE as a versatile epitaxy platform for the growth of p-type WSe2 nanoribbons and lateral heterostructures made of p-WSe2 and n-MoS2 nanoribbons for futuristic electronics applications. Aligned arrays of single-crystalline monolayer TMD nanoribbons with high aspect ratios, as well as their lateral heterostructures, are realized, with the growth directed by the ledges on the β-Ga2O3 substrate. This approach provides an epitaxy platform for advanced electronics applications of TMD nanoribbons.

To explore the potential of field-effect transistors (FETs) based on monolayers (MLs) of the two-dimensional semiconducting channel (SC) for spintronics, the two most important issues are to ensure the formation of variable low-resistive tunnel ferromagnetic contacts (FCs) and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts, and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated ML WSe2 FETs using bilayer hexagonal boron nitride (h-BN) as a tunnel barrier at the FC/SC interface. We investigate the electrical transport in ML WSe2 FETs with the current-in-plane geometry that yields hole mobilities of ∼38.3 cm2 V-1 s-1 at 240 K and on/off ratios of the order of 107, limited by the contact regions. We have achieved an ultralow effective Schottky barrier (∼5.34 meV) with an encapsulated tunneling device as opposed to a nonencapsulated device in which the barrier heights are considerably higher. These observations provide an insight into the electrical behavior of the FC/h-BN/SC/h-BN heterostructures, and such control over the barrier heights opens up the possibilities for WSe2-based spintronic devices.

Two-dimensional (2D) semiconducting monolayers such as transition metal dichalcogenides (TMDs) are promising channel materials to extend Moore's Law in advanced electronics. Synthetic TMD layers from chemical vapor deposition (CVD) are scalable for fabrication but notorious for their high defect densities. Therefore, innovative endeavors on growth reaction to enhance their quality are urgently needed. Here, we report that the hydroxide W species, an extremely pure vapor phase metal precursor form, is very efficient for sulfurization, leading to about one order of magnitude lower defect density compared to those from conventional CVD methods. The field-effect transistor (FET) devices based on the proposed growth reach a peak electron mobility ~200 cm

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and accounts for the fourth leading cause of all cancer deaths. Scientific evidence has found that plant extracts seem to be a reliable choice due to their multitarget effects against HCC. Juniperus communis has been used for centuries in traditional medicine and its anticancer properties have been reported. As a result, the purpose of the study was to investigate the anticancer effect and mechanism of J. communis extract (JCo extract) on HCC in vitro and in vivo. In the present study, we found that JCo extract inhibited the growth of human HCC cells by inducing cell cycle arrest at the G0/G1 phase, extensive apoptosis and suppressing metastatic protein expressions in HCC cells. Moreover, the combinational treatment of JCo and VP-16 was found to enhance the anticancer effect, revealing that JCo extract might have the potential to be utilized as an adjuvant to promote HCC treatment. Furthermore, in vivo study, JCo extract significantly suppressed HCC tumor growth and extended the lifespan with no or low systemic and pathological toxicity. JCo extract significantly up-regulated the expression of pro-apoptotic proteins and tumor suppressor p53, suppressed VEGF/VEGFR autocrine signaling, down-regulated cell cycle regulatory proteins and MMP2/MMP9 proteins. Overall, our results provide a basis for exploiting JCo extract as a potential anticancer agent against HCC.

Juniperus communis (JCo) is a well-known traditional Chinese medicinal plant that has been used to treat wounds, fever, swelling, and rheumatism. However, the mechanism underlying the anticancer effect of JCo extract on colorectal cancer (CRC) has not yet been elucidated. This study investigated the anticancer effects of JCo extract in vitro and in vivo as well as the precise molecular mechanisms. Cell viability was evaluated using the MTT assay. Cell cycle distribution was examined by flow cytometry analysis, and cell apoptosis was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Protein expression was analyzed using western blotting. The in vivo activity of the JCo extract was evaluated using a xenograft BALB/c mouse model. The tumors and organs were examined through hematoxylin-eosin (HE) staining and immunohistochemistry. The results showed that JCo extract exhibited higher cytotoxicity against CRC cells than against normal cells and showed synergistic effects when combined with 5-fluorouracil. JCo extract induced cell cycle arrest at the G0/G1 phase via regulation of p53/p21 and CDK4/cyclin D1 and induced cell apoptosis via the extrinsic (FasL/Fas/caspase-8) and intrinsic (Bax/Bcl-2/caspase-9) apoptotic pathways. In vivo studies revealed that JCo extract suppressed tumor growth through the inhibition of proliferation and induction of apoptosis. In addition, there was no obvious change in body weight or histological morphology of normal organs after treatment. JCo extract suppressed CRC progression by inducing cell cycle arrest and apoptosis in vitro and in vivo, suggesting the potential application of JCo extract in the treatment of CRC.

Two-dimensional transition metal dichalcogenide nanoribbons are touted as the future extreme device downscaling for advanced logic and memory devices but remain a formidable synthetic challenge. Here, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer and single-crystalline MoS

Single crystalline Ag films on dielectric substrates have received tremendous attention recently due to their technological potentials as low loss plasmonic materials. Two different growth approaches have been used to produce single crystalline Ag films previously. One approach is based on repetitive cycles of a two-step process (low temperature deposition followed by RT annealing) using molecular beam epitaxy (MBE), which is extremely time-consuming due to the need for repeat growth cycles. Another approach is based on rapid e-beam deposition which is capable of growing thick single crystalline Ag films (300 nm) but lacks the precision in thickness control of thin epitaxial films. Here, we report a universal approach to grow atomically smooth epitaxial Ag films by eliminating the repetitive cycles used in the previous two-step MBE method while maintaining the precise thickness control from a few monolayers to the optically thick regime, thus overcoming the limitations of the two aforementioned methods. In addition, we develop an in situ growth of aluminum oxide as the capping layer to protect the epitaxial Ag films. The quality of the epitaxial Ag films was evaluated using a variety of techniques, and the superior optical performance of the films is demonstrated by measuring the propagation length of surface plasmon polaritons (∼80 μm at 632 nm) as well as their capability to support a plasmonic nanolaser in infrared incorporating an InGaAsP quantum well as the gain media.

To explore the potential of field-effect transistors (FETs) based on monolayers (MLs) of the two-dimensional semiconducting channel (SC) for spintronics, the two most important issues are to ensure the formation of variable low-resistive tunnel ferromagnetic contacts (FCs) and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts, and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated ML WSe

We report on the first demonstration of metal–insulator–semiconductor-type plasmonic lasers at the telecom wavelength (∼1.3 μm) using top-down fabricated semiconductor waveguides on single-crystalline metallic platforms formed using epitaxially grown Ag films. The critical role of the Ag film thickness in sustaining plasmonic lasing at the telecom wavelength is investigated systematically. Low-threshold (0.2 MW/cm2) and continuous-wave operation of plasmonic lasing at cryogenic temperatures can be achieved on a 150 nm Ag platform with minimum radiation leakage into the substrate. Plasmonic lasing occurs preferentially through higher-order surface-plasmon-polariton modes, which exhibit a higher mode confinement factor, lower propagation loss, and better field–gain coupling. We observed plasmonic lasing up to ∼200 K under pulsed excitations. The plasmonic lasers on large-area epitaxial Ag films open up a scalable platform for on-chip integrations of plasmonics and optoelectronics at the telecom wavelength.

Two-dimensional (2D) semiconductors, particularly the direct-gap monolayer transition metal dichalcogenides (TMDs), are currently being developed for various atomically thin optoelectronic devices. However, practical applications are hindered by their low quantum efficiencies in light emissions and absorptions. While photonic cavities and metallic plasmonic structures can significantly enhance the light–matter interactions in TMDs, the narrow spectral resonance and the local hot spots considerably limit the applications when broadband and large area are required. Here, we demonstrate that a properly designed distributed Bragg reflector (DBR) can be an ideal platform for light-coupling enhancement in 2D TMDs. The main idea is based on engineering the amplitude and phase of optical reflection from the DBR to produce optimal substrate-induced interference. We show that the photoluminescence, Raman, and second harmonic generation signals of monolayer WSe2 can be enhanced by a factor of 26, 34, and 58, respect...

In this paper, a soft IP kernel of LVDS (low-voltage differential signaling) receivers is proposed for multichannel ultrasound imaging applications. By means of careful cell-based design, a high-speed de-serializer is developed with control-able bit-shift and delay-adjustment operations. Furthermore, using the proposed hybrid coarse-tune and two-level fine-tune schemes, a synchronization controller can perform efficient and robust multichannel LVDS signal synchronizing processes in cooperation with the de-serializer. The proposed LVDS IP kernel is synthesiz-able cell-based design, which is soft/portable to different circuit technology and system applications. Based on the proposed LVDS structure, four sets of 8-channel LVDS receivers were designed and implemented on a 32-channel FPGA-based ultrasound imaging platform. Integrated with the ultrasound AFE/HVFE (analog and high-voltage front-end) module, a throughput of 480 Mb/s per channel can be achieved for test patterns, 32-channel ultrasound image and color-Doppler display.

We demonstrate a plasmonic cavity based on a hybrid semiconductor-insulator-metal structure, which can support plasmonic whispering-gallery modes (WGMs) in the insulator layer. The hybrid structure consists of a semiconductor microdisk with embedded gain medium on top of a single-crystalline gold flake with a nanometer-thick dielectric gap in between. By optimizing the dielectric gap thickness, it is possible to form coupled modes consisting of both photonic WGM in the microdisk and plasmonic WGM in the dielectric gap, by which a high field-gain overlap and an efficient cavity feedback can be achieved for investigating strong light-matter interactions and laser applications.

In this work, we develop a high-frequency and power-efficiency ultrasound beam-forming processor which consists of two 8-channel Low-Voltage Differential Signaling (LVDS) receivers and a 16-channel beam-forming module. The proposed LVDS receiver includes the front-end receiving buffer of a pre-amplifier, a hysteresis comparator and an adjustable delay chain, and the back-end signal extractor of a de-serializer. Here, the telescopic pre-amplifier and hysteresis comparator are designed to have high gain-bandwidth products to fulfill highspeed operations. The de-serializer adopts a double triggering technique to expedite serial-to-parallel data conversion. Particularly, the self-adaptive mechanism is developed to automatically adjust a phase delay of each channel. The beam-forming module performs delay and sum operations of input signals from all channels. The proposed 16-channel beam-forming processor implemented by TSMC 0.18µm 1P6M CMOS technology has a die size of 5.0mm×6.0mm, and consumes fairly low power. Additionally, it can support 30MHz ultrasound images via LVDS transmissions at a bit rate of 2Gbps. Therefore, the beam-forming processor proposed herein can be widely applied to various handheld ultrasound systems.

The application of high clearance haemodialysis (HD) for removal of small molecules of waste metabolites, has been practised for many years. Haemoperfusion (HP) is capable of effective removal of middle and protein-bound molecules. The combined HD/HP system is thought to give a more effective treatment for patients of renal failure or drug intoxication. This paper discusses the performance characteristics of removal of toxic substances (e.g. paraquat and creatinine), using the combined HD/HP recycled system in two different arrangements (HD–HP and HP–HD). The results demonstrate that for most favourable adsorbing solutes, the HD–HP arrangement gives higher performance whereas, HP–HD arrangement is more suitable and gives more effective detoxication characteristics for unfavourable adsorbing solutes.

We experimentally explore the temporal dynamics of diode-pumped Nd:YVO4 CW self-Raman lasers. In the single-transverse-mode operation, we find that the real-time trace of the self-Raman laser displays the characteristics of self-mode locking.

In this paper, a soft IP core of LVDS (low-voltage differential signaling) receivers is proposed for multichannel ultrasound imaging systems or other applications. By careful cellbased design, a high-speed de-serializer is developed with control-able bit-shift and delay-adjustment operations. Moreover, using the proposed hybrid coarse-tune and two-level fine-tune schemes, a synchronization controller can perform efficient and robust multichannel LVDS signal synchronizing processes in cooperation with the de-serializer. The proposed LVDS IP core is synthesiz-able cell-based design, which is soft/portable to different circuit technology and system applications. Based on the proposed LVDS structure, four sets of 8-channel LVDS receivers were designed and implemented on a 32-channel FPGA-based ultrasound imag-ing platform. Integrated with the ultrasound AFE/HVFE (analog and high-voltage front-end) module, a throughput of 480 Mb/s per channel can be achieved for test patterns, 32-channel ultrasound image and color-Doppler display.