Search

In the field of oxide semiconductor thin-film transistors (TFTs), the occurrence of charge trapping in the gate dielectric and interfaces presents significant challenges to their operational stability and reliability. In this study, we present high-performing amorphous Ga2O3 TFTs created using atomic layer deposition with varying indium doping concentrations. The channel length (Lch) and channel width (Wch) are 50 and 200 μm, respectively. As the Indium concentration increases from 0% to 60%, the charge trap density (Nit) decreases, resulting in a smaller hysteresis window. The TFTs with a doping concentration of 20% are particularly noteworthy, exhibiting high field-effect mobility (22.6 cm2 V−1 s−1), lower subthreshold swing (160 mV/dec) than amorphous Ga2O3 channel devices, a high on-off current ratio (109), an appropriate threshold voltage (−1 V), and a substantial output current (26 mA/mm at VGS = 16 V).

The interplay between topology and valley degree of freedom has attracted much interest because it can realize new phenomena and applications. Here, based on first-principles calculations, we demonstrate intrinsically valley-polarized quantum anomalous Hall effect in monolayer ferrovalley material: Janus VSiGeN4, of which the edge states are chiral-spin-valley locking. Besides, a small tensile or compressive strain can drive phase transition in the material from valley-polarized quantum anomalous Hall state to half-valley-metal state. With the increase of the strain, the material turns into ferrovalley semiconductor with valley anomalous Hall effect. The origin of phase transition is sequent band inversion of V d orbital at K valley. Moreover, we find that phase transition causes the sign reversal of Berry curvature and induces different polarized light absorption in different valley states. Our work provides an ideal material platform for practical applications and experimental exploration of the interplay between topology, spintronics, and valleytronics., Comment: 8 pages, 6 figures

Covalent organic frameworks (COFs) with redox-active moieties are potential capacitive energy storage materials. However, their performance is limited by their poor electrical conductivity and sluggish ion diffusion in their nanopores. Herein, we report coaxial one-dimensional van der Waals heterostructures (vdWHs) comprised of a carbon nanotube (CNT) core and a pyrene–pyridine COF shell synthesized by an in situ wrapping method. The coaxial structure allows efficient electronic interaction between the CNT core and COF shell and improves the electrical conductivity significantly. It also improves electrolyte ion accesses to redox-active pyridine groups in the COF, resulting in excellent capacitive energy storage performance with a high specific capacitance of ∼360 F g−1, an excellent rate capability of ∼80%, and a good stability of 92% capacitance retention after 20 000 charge/discharge cycles. Our strategy opens the door to create other multi-dimensional vdWHs for various potential applications.

Two-dimensional (2D) ferromagnetic materials with high Curie temperatures (TC) and tunable physical properties are crucial to the development of nanoscale spintronics devices. Here, we investigate the newly synthesized iodinene using first-principles calculations. Our results show that doping carriers in monolayer and bilayer iodinene can easily introduce itinerant ferromagnetism due to a flatband structure near the Fermi level, and that the associated TC is higher than room temperature. Moreover, we find that a structural phase transition can be achieved through the application of moderate tensile strain for both monolayer and bilayer iodinene. The magnetic moment, Curie temperature, band structure, carrier effective mass, and optical absorption can be changed significantly through this phase transition, and the transition can also lead to a magnetic phase transition with an appropriate doping concentration. Our work provides a feasible approach for designing 2D magnetic materials with potential for application in microelectronics devices.

Polymer-based dielectrics are widely applied in the fields of electronics and electrical power systems due to the high breakdown strength, excellent flexibility, and unique self-healing capability. However, the low stored energy density and unsatisfactory heat management of polymer dielectrics hinder the development of polymer-based film capacitors. In this research, artificial composites with improved capacitive energy storage and thermal conductivity are fabricated by blending the two-dimensional semiconductive MXene sheets with a polyimide (PI) matrix. Remarkably, a PI based composite with 1 wt. % MXene sheets increases its dielectric permittivity from ≈3.27 to ≈3.53 and enhances its discharged energy density from ≈1.93 to ≈2.38 J/cm3 while maintaining its low dielectric loss of 80%. Meanwhile, a high in-plane thermal conductivity of 0.418 W m−1 K−1 is achieved for PI/MXene composites with 5 wt. % MXene. In addition, the distribution of temperature field inside the composites has been investigated by a finite element method. These results represent a strategy in polymer dielectrics to achieve simultaneous high energy density and thermal conductivity, which may also have potential for applications in high temperature environments.

Inorganic perovskites, such as CsPbX3 (X = Cl, Br, I), have attracted attention due to their excellent thermal stabilities and high photoluminescence quantum efficiencies. Here, we report on all-inorganic light-emitting diodes (LEDs), including inorganic perovskite emitters (CsPbBr3) based on the heterostructure of n-ZnO/Al2O3/CsPbBr3/p-GaN. The effects of the CsPbBr3 and Al2O3 interlayers on the electroluminescence performance have been systematically investigated. It is observed that the Al2O3 interlayer plays an important role in determining the emission performance. By introducing the Al2O3 layers, the electron–hole recombination can almost be limited within the perovskite. The emission peaks of the heterojunction LEDs change from blue-green to pure green with the increased luminous intensities and decreased leakage currents. It provides an idea for the preparation of all-inorganic perovskite LEDs.

Two-dimensional (2D) GaInS3 nanosheets are found to exhibit thermal and structural stabilities, good oxidation resistance, and tunable and layer-dependent electronic properties from first-principles calculations. Remarkably, the nanosheets with arbitrary thickness possess robust in-plane piezoelectricity without the odd-even effect commonly observed in other 2D piezoelectric materials, which is attributed to the retention of noncentrosymmetry resulting from their homogeneous and direct stacking patterns. The piezoelectric stress coefficient e 11 3 D of the nanosheets is about 0.23 C/m2, almost independent of the numbers of atomic layers of 2D GaInS3. The stability in piezoelectricity and the high carrier mobility of 2D GaInS3 nanosheets could endow them with promising application prospects in nanoelectronic and nanoelectromechanical devices.

Recently, a series of single-layer metal–organic frameworks (MOFs) was theoretically predicted to be two-dimensional organic topological materials. However, the experimental evidence of their nontrivial topological states has not been found. Here, combining the use of angle-resolved photoemission spectroscopy and scanning tunneling microscopy, we report the electronic structure studies on a single-layer Cu-coordinated 2,4,6-tri(4-pyridyl)-1,3,5-triazine (Cu-T4PT) MOF supported by a Cu(111) substrate and identify periodic surface states with the period of the Cu-T4PT reciprocal lattice. These periodic surface states, which have identical features to the Cu(111) Shockley surface states, can be attributed to the quantum confinement of the surface states of the underlying Cu(111) substrate by the network lattices of the Cu-T4PT MOF. Our work indicates that the surface states of the metal substrate can be tailored in a controlled manner by the network structures of MOFs with different periodic lattices. The lack of intrinsic bands and the possible topological properties of the single-layer Cu-T4PT MOF may be attributed to the strong electronic coupling between the Cu-T4PT MOF and the Cu(111) substrates. In order to exploit organic topological materials predicted in MOFs, it is necessary to grow them on weak van der Waals interaction substrates in the future.

Zinc-based hydroquinone hybrid nanoporous films were directly deposited by molecular layer deposition (MLD) without using porous templates or any post-treatment. MLD is a viable and promising method to fabricate inorganic–organic hybrid porous films for applications in catalysis, energy and gas separation.

Two-dimensional (2D) ferroelectricity and ferromagnetism have attracted a lot of attention due to their promising applications, but 2D materials with both properties are quite rare. Here, by performing first-principles calculations, we propose that monolayer γ-GeSe is a 2D ferroelectric material with an out-of-plane polarization of about 6.48 × 10−12 C/m. It has a Mexican-hat-like band structure, leading to itinerant ferromagnetism upon hole doping. This ferromagnetic phase transition occurs when the doping concentration is about 7.4 × 1012/cm2, and the ferromagnetism can be maintained near 880 K when increasing the doping concentration. Both the ferroelectricity and the induced ferromagnetism can be well modulated by strain. These features make γ-GeSe a promising material for making microelectronics and spintronics devices. Our work also paves the way for searching long-sought high temperature 2D multiferroics.

Stable ferroelectricity with an in-plane spontaneous polarization of 2.00 × 10−10 C/m is found in two-dimensional (2D) β-GeS monolayers from theoretical calculations, which can be effectively tuned by the applied tensile strains. The Curie temperature of the monolayer is evaluated to be 358 K by ab initio molecular dynamics simulations. Remarkably, the 2D ferroelectricity is found to exist in 2D few-layer β-GeS nanosheets which could be synthesized in experiments. The strong spontaneous polarization and giant pyroelectric coefficient accompanied by the appearance of phase transition near room temperature facilitate the development of β-GeS monolayers or nanosheets for applications in ferroelectric, pyroelectric, and piezoelectric devices with superior performance.

Effective propulsion of untethered micro-/nanorobots at low Reynolds numbers can offer possibilities for promising biomedical applications. Diverse locomotion modes have been proposed for propulsion at a small scale, and rolling is an alternative method which is significantly effective. Here, we demonstrate mass produced magnetic wheel-shape flaky microswimmers fabricated via a simple and cost-effective method. Locomotion behaviors under vertical rotating magnetic fields were studied, and the propulsion mechanisms were analyzed. They exhibited two modes to swim forward as tumbling and rolling, which relied on the actuating field and the fluid. The rolling microswimmers could be propelled and steered precisely and a high velocity can be easily reached. Forward velocity and transition frequency within diverse fields and fluids were analyzed, and side slip effects when rolling at a camber angle were also observed. Such microswimmers synthesized in bulk with alternative locomotion modes and excellent swimming performances may have potential in low Reynolds number fluids.

A nonvolatile memory structure with a high-k composite of ZnO-TiO2 as a charge-trapping dielectric was fabricated by using rf-sputtering and atomic layer deposition techniques, in which the potential of the conduction-band minimum of the composite was designed to be lower than that of Si by the use of the special energy-band offsets among Si, ZnO, and TiO2. Compared to the conduction-band minimum of Si, a relatively negative potential of the high-k composite leads to a continuous rise in the shift of the flat-band potential of the memory device except a drop at the beginning part of the time-dependent retention curve after a programming operation. The drop was attributed to the escape of trapped charges at the Si/Al2O3 interface. After extracting the contribution to the deterioration of the retention curve from the traps at the Si/Al2O3 interface, it was identified that the band alignment in a charge-trapping memory device dominated its retention behaviors.

We have developed a thermally conductive flexible elastomer as a composite material with slide-ring (SR) materials and boron nitride (BN) particles surface-modified via plasma in solution. This composite shows excellent properties as a flexible insulator for thermal management. Surface modification of BN particles using plasma in solution increases the tensile strength, extension ratio at break, toughness, and rubber characteristics of the composites, compared to SR and non-modified BN, while the Young's modulus values are identical. Furthermore, the thermal conductivity also improved as a result of plasma surface modification.

Flexoelectricity describes the linear response of electrical polarization to a strain gradient, which can be used to enhance the piezoelectric effect of piezoelectric material or realize the piezoelectric effect in nonpiezoelectric materials. Here, we demonstrate from thermodynamics theory that a giant piezoelectric effect exists in piezoelectric/dielectric superlattices due to flexoelectric effect. The apparent piezoelectric coefficient is calculated from the closed-form of analytical expression of the polarization distribution in the piezoelectric/dielectric superlattice subjected to a normal stress, in which the flexoelectric effect is included. It is found that there exists a strong nonlinear coupling between the flexoelectric and piezoelectric effects, which significantly enhances the apparent piezoelectric coefficient in the piezoelectric/dielectric superlattice. For a specific thickness ratio of the piezoelectric and dielectric layers, the enhanced apparent piezoelectric coefficient in the superlattice is ten times larger than that of its pure piezoelectric counterpart. The present work suggests an effective way to obtain giant apparent piezoelectric effect in piezoelectric/dielectric superlattices through flexoelectric effect.

We present a technique for patterning thin-film metals (silver and gold) without the need for photolithography. The technique involves microfluidics and can be performed on planar or curved surfaces. Patterns of thin-film metal are fabricated by flowing electroless silver or gold plating solutions through predefined microchannels made of polydimethylsiloxane sealed against a surface of interest. We demonstrate metal resistors with 100-μm-wide traces fabricated on planar and curved surfaces. The surface profile, mechanical gauge factor, and temperature coefficient of resistance have been characterized. Application of the resistors as hot-wire flow sensors has also been demonstrated.

Diluted magnetic semiconductor Zn1−xCoxO nanorods with a Curie temperature higher than 350K have been synthesized by in situ doping of Co in ZnO nanorods using a simple thermal chemical vapor deposition method. Structural analyses indicated that the nanorod possesses the single-crystalline wurtzite structure and there is no segregated cluster of impurity phase appearing throughout the nanorod. The transparence of the Zn1−xCoxO nanorods in the visible region has been examined by UV-visible absorption. The fundamental absorptions of the Zn1−xCoxO nanorods estimated from the absorption spectra do not reveal pronounced difference from that of pure ZnO nanorods.

This letter reports an architecture for a microfluidic chip that dresses (inks) multiple nanolithography tips in a high-density array in a parallel and multiplexed fashion. The microfluidic chip consists of multiple precision patterned thin-film poly(dimethylsiloxane) (PDMS) patches serving as porous inking pads. Inking chemicals are supplied from loading reservoirs to the inking pads through microfluidic channels. The gas-permeable thin PDMS membranes allow ink molecules to diffuse through while preventing bulk liquid from overflowing or evaporating. The inking chip provides high-density inking, easy loading of inks, and reduced evaporation losses. We present the fabrication process and inking of scanning probe contact printing probes and commercial nitride probes.

In dip-pen nanolithography (DPN), nanoscale chemical patterns are created by directly transferring chemical molecules from the tip of an atomic force microscope probe to a surface. We report the development of a thermally actuated probe array for DPN applications. The array consists of ten thermal bimorph actuated probes, each 300 μm long, with a lateral spacing of 100 μm. The probes are actuated by passing dc current through a heater embedded in the probe base. The array is demonstrated by using it to simultaneously write ten different octadecanethiol patterns on a gold surface.

This letter reports a contact sensing method for dip-pen nanolithography which functions by monitoring the conductivity between the lithography probe and the substrate. Experimental results show that this method has high sensitivity and is suitable for dip-pen nanolithography applications with large probe arrays.

A simple scheme to produce strong magnetic fields due to cold electron flow in an open-ended coil heated by high power laser pulses is proposed. It differs from previous generation of magnetic fields driven by fast electron current in a capacitor-coil target [S. Fujioka et al., Sci. Rep. 3, 1170 (2013)]. The fields in our experiments are measured by B-dot detectors and proton radiography, respectively. A 205 T strong magnetic field at the center of the coil target is generated in the free space at Iλ2 of 6.85 × 1014 W cm−2 μm2, where I is the laser intensity, and λ is the laser wavelength. The magnetic field strength is proportional to Iλ2. Compared with the capacitor-coil target, the generation mechanism of the magnetic field is straightforward and the coil is easy to be fabricated.

A two-dimensional (2D) material, the holey 2D C2N (h2D-C2N) crystal, has recently been synthesized. Here, we investigate the strain effects on the properties of this material by first-principles calculations. We show that the material is quite soft with a small stiffness constant and can sustain large strains ≥12%. It remains a direct gap semiconductor under strain, and the bandgap size can be tuned in a wide range as large as 1 eV. Interestingly, for biaxial strain, a band crossing effect occurs at the valence band maximum close to a 8% strain, leading to a dramatic increase of the hole effective mass. Strong optical absorption can be achieved by strain tuning with absorption coefficient ∼106 cm−1 covering a wide spectrum. Our findings suggest the great potential of strain-engineered h2D-C2N in electronic and optoelectronic device applications.

Macroscopically long ropes of aligned single-walled carbon nanotubes (SWNTs), synthesized by a hydrogen and argon arc discharge method, were cold pressed into tablets without any binder for measurements of their volumetric hydrogen storage capacity. The typical apparent density of the tablets was measured to be around 1.7 g/cm(3) with respect to a molding pressure of 0.75 Gpa. A volumetric and mass hydrogen storage capacity of 68 kg H-2/m(3) and 4.0 wt %, respectively, was achieved at room temperature under a pressure of 11 MPa for suitably pretreated SWNT tablets, and more than 70% of the hydrogen adsorbed can be released under ambient pressure at room temperature. Pore structure analysis indicated that the molding process diminished the mesopore volume of the SWNT ropes, but exerts little influence on their intrinsic pore textures. (C) 2002 American Institute of Physics.

Highly efficient semiconductor photoelectrodes for solar hydrogen production through photocatalytic water splitting are a promising and challenge solution to solve the energy problems. In this work, Ag/Cu2O/ZnO tandem triple-junction photoelectrode was designed and prepared. An increase of 11 times of photocurrent is achieved in the Ag/Cu2O/ZnO photoelectrode comparing to that of the Cu2O film. The high performance of the Ag/Cu2O/ZnO film is due to the optimized design of the tandem triple-junction structure, where the localized surface Plasmon resonance of Ag and the hetero-junctions efficiently absorb solar energy, produce, and separate electron-hole pairs in the photocathode.

This paper introduces a cancer cell capture/release microchip based on the self-sacrificed MnO2 nanofibers. Through electrospinning, lift-off and soft-lithography procedures, MnO2 nanofibers are tactfully fabricated in microchannels to implement enrichment and release of cancer cells in liquid samples. The MnO2 nanofiber net which mimics the extra cellular matrix can lead to high capture ability with the help of a cancer cell-specific antibody bio-conjugation. Subsequently, an effective and friendly release method is carried out by using low concentration of oxalic acid to dissolve the MnO2 nanofiber substrate while keeping high viability of those released cancer cells at the same time. It is conceivable that our microchip may have potentials in realizing biomedical analysis of circulating tumor cells for biological and clinical researches in oncology.

Raman measurements were performed on molecular beam epitaxially grown GaN before and after implantation with Ar+, Mg+, P+, C+, and Ca+ ions. With increasing ion dose, new Raman peaks arise at 300, 360, 420, and 670 cm−1, independent of the ion species. After rapid thermal annealing at temperatures between 900 and 1150 °C for 15 s, the intensities of the Raman modes decrease with increasing temperature with the exception of the 360 cm−1 mode which shows a maximum in intensity after annealing at 900 °C. The mode at 300 cm−1 is attributed to disorder-activated Raman scattering, whereas the other three modes are assigned to local vibrations of vacancy-related defects.

Ag-assisted anisotropic lateral etching along the ⟨100⟩ directions in Si nanowire arrays (Si NWAs) is investigated. It is found that Ag ions, generated by H2O2 oxidation of Ag particles, re-nucleate on the sidewalls of the nanowires, causing side etching and tapering of the wires. By enhancing the side etching effect, fractures can be formed at specific positions along the nanowires. This technique is applied to transfer large-area Si NWAs onto a glass substrate.

Nonpolar m-plane ZnO films are deposited on GaN (0002) with a 10 nm Al2O3 interlayer by atomic layer deposition. The growth direction of the ZnO films directly on GaN (0002) is [707¯4] (perpendicular to (101¯1) plane), whereas with the Al2O3 interlayer it changes into [101¯0]. With the Al2O3 interlayer, the m-plane ZnO films are presented and the leakage current of the heterojunctions dramatically reduces. The electroluminescence spectra of the n-ZnO/Al2O3/p-GaN heterojunctions are dominated by a blue emission under forward biases, whereas it is violet under reverse biases.

Surface activation of carbon nanotubes (CNTs) as forests and yarns, depolytmerization of candidate polymers, and uniform deposition and re-polymerization onto the activated CNTs are simultaneously achieved by exposing CNTs and polymer targets to light with a narrow wavelength distribution from a vacuum ultraviolet lamp. Both polystyrene and poly (methyl methacrylate) are deposited onto the surface of CNTs in the CNT-forest and yarn in a N2 environment for 30 min during which the polymer uniformly coats the carbon nanotubes. X-ray photoelectron spectroscopy data reveal that covalent bonding occurs at the CNT-polymer interface.

Nonploar m-plane ZnO films were grown on p-Si (111) substrates by using atomic layer deposition. X-ray diffraction and high resolution tunneling electron microscopy measurements showed that the ZnO films were 〈101¯0〉 oriented, and the crystalline quality of ZnO films was improved with an Al2O3 buffer layer, which significantly enhances the photoluminescence and reduces the reverse leakage current of ZnO/Si heterojuction.

Based on the resonant level concept, we presented an analytic calculation for the enhancement of the thermoelectric properties of semiconductor materials with element doping. We show that the power factor can be significantly enhanced due to a resonant energy level introduced by some element lies in the host bands and near the Fermi level and band edge. Our calculations reveal that by choosing optimal parameters for the element doping, such as impurity level, and doping concentration, one can obtain an optimum power factor for improved thermoelectric performance.

Fish use their lateral line system to detect minute water motions. The lateral line consists of superficial neuromasts and canal neuromasts. The response properties of canal neuromasts differ from those of superficial ones. Here, we report the design, fabrication, and characterization of an artificial lateral line canal system. The characterization was done under various fluid conditions, including dipolar excitation and turbulent flow. The experimental results with dipole excitation match well with a mathematical model. Canal sensors also demonstrate significantly better noise immunity compared with superficial ones. Canal-type artificial lateral lines may become important for underwater flow sensing.

The ordered PbTe/Pb quasi-one-dimensional nanowires array was electrodeposited on the SiO2/Si substrate. There are two essential factors for the formation of such kind of change in nanowire morphology and structure. One is the charges distribution at the tips of electrodeposit, the other one is the change in ion concentration in front of growth tip. We research the current versus bias voltage characteristics of single PbTe/Pb nanowire by four-probe scanning tunneling microscopy system.

Epitaxial ferroelectric YMnO3 (YMO) thin films were fabricated on (0001) GaN substrates by pulsed laser deposition followed by rapid thermal annealing. The temperature and field dependence of the leakage current of YMO/GaN interface was studied in a temperature range from 150 to 300 K and for an applied voltage up to 10 V. In a low temperature region from 180 to 220 K, the YMO/GaN interface acted as a Schottky barrier with a height of 0.27 eV for a field below 1.4 MV/cm, while the leakage mechanism was governed by the Fowler–Nordheim tunneling for a field above 1.4 MV/cm. Moreover, a space-charge-limited-current behavior was observed in a high field for a temperature above 270 K, while an Ohmic behavior was observed in a low field. In comparison, the dominant leakage mechanism of In/YMO interface was an Ohmic behavior in the whole measured voltage and temperature ranges.

The properties of Cr-doped GaN epilayers grown by rf-plasma-assisted molecular beam epitaxy were studied. The deep acceptor nature of Cr was used to grow semi-insulating GaN epilayers on sapphire substrates for electronic device applications. The room-temperature (RT) sheet resistivity of the epilayers reached 1010 Ω/square. The activation energy of dark conductivity was about 0.48 eV. Step-graded AlxGa1−xN/GaN (x=0.3−0.2) superlattices (SLs) were designed to filter dislocations. Transmission electron microscopy images showed that the SLs can dramatically reduce dislocation density. Al0.35Ga0.65N/GaN heterostructure grown on Cr-doped semi-insulating GaN epilayer exhibited a RT mobility of 960 cm2/V s and sheet carrier density of 2.1×1013 cm−2.

Impedance analysis was employed to study the frequency response characteristics of supercapacitors utilizing single-walled carbon nanotubes (SWNTs) as electrode material. The knee frequency is around 631 Hz for the electrochemically oxidized SWNT supercapacitor, much higher than that of the as-prepared one (around 316 Hz) and the common activated carbon supercapacitor (< 1 Hz). The good frequency response observed in this work is due to the introduction of nanosized mesopores and oxygen-containing groups formed during the electrochemical oxidization of SWNTs. The capacitance of electrochemically oxidized SWNT supercapacitor is 113 F/g, which is much higher than the value of the as-prepared one (20 F/g). (C) 2008 American Institute of Physics.

In this letter, we present a gas sensor using a single ZnO nanowire as a sensing unit. This ZnO nanowire-based sensor has quick and high sensitive response to H2S in air at room temperature. It has also been found that the gas sensitivity of the ZnO nanowires could be modulated and enhanced by He+ implantation at an appropriate dose. A possible explanation is given based on the modulation model of the depletion layer.

In this letter, a model to calculate the emission intensities of different rare-earth (RE) dopants in GaN is proposed based on the quantum collision theory and Judd-Ofelt approximation. The possible white light emission from Eu-, Er-, and Tm-codoped GaN is predicted according to the Commission International de I’Eclairage chromaticity diagram. Variable-wavelength emissions can be realized by adjusting the relative concentrations of different RE dopants in GaN and the bias voltage of the applied electric field. The availability of voltage-controlled light emissions and white light emission of the RE-doped GaN electroluminescent devices may have great potential for application in displays.

The authors present a simple polydimethysiloxane (PDMS) device for nanoscale surface patterning by controllably bringing a hard silicon nitride tip on a PDMS membrane in and out of contact with surfaces using pressurized gas to inflate the membrane. The writing process is analogous to contact printing. By regulating the pressured gas to actuate the silicon nitride tip on the PDMS membrane, the nanometer size features can be easily fabricated on substrates. Moreover, using the dot matrix method, this PDMS device can masklessly fabricate arbitrary patterns. In this letter, a nanometer scale three-line pattern is demonstrated.

Here the authors show a method for inking scanning probes based on local thermal evaporative inking transfer. This method results in low loss, rapid, and parallel inking action. Scanning probes are accommodated at openings of ink reservoirs. A resistive heater is used to initiate vaporization of inks to uniformly coat probes. 1mM 16-mercaptohexadecanoic acid in ethanol solution is used to characterize this inking chip. Moreover, an array of scanning probes can be inked simultaneously using an array of inking reservoirs. During the inking process, each probe is tightly sealed inside individual reservoir so cross contamination is limited.

Single-crystalline Sc2O3 was grown on GaN/sapphire template using pulsed laser deposition and the interface characteristics of the Sc2O3∕GaN heterostructure were investigated. An epitaxial relationship of [112]Sc2O3‖[213¯0]GaN and (222)Sc2O3‖(0002)GaN was revealed by x-ray diffraction and cross-sectional transmission electron microscopy. A valence band offset of 0.84eV was obtained by x-ray photoelectron spectroscopy, indicating a conduction band offset of 2.04eV across the Sc2O3∕GaN heterointerface. In addition, a low interface state density of 4×1011eV−1cm−2 was estimated from capacitance-voltage measurements. The epitaxial nature with good interface characteristics has rendered a substantially low leakage current of 1μA∕cm2 at a reverse gate bias of 30V in the Sc2O3∕GaN metal-oxide-semiconductor structures.

Cu ions were implanted at 180keV into silica with doses ranging from 5×1016to2×1017ions∕cm2. Cross-sectional transmission electron microscopy and high-resolution transmission electron microscopy images showed that Cu nanoclusters containing nanovoids have been formed for doses higher than 1×1017ions∕cm2. The nanovoids grew when the samples were annealed in a reducing atmosphere at 900°C for 1h and then disappeared at 900°C for 4h. The mechanisms for the formation and disappearance of nanovoids are discussed.

We report the studies of AlGaN∕GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) using reactive-sputtered HfO2 as the gate dielectric and the surface passivation layer. X-ray photoemission method reveals a conduction-band offset of 1.71eV for the HfO2∕GaN heterostructure. The dielectric constant of HfO2 is estimated to be 21 by capacitance-voltage measurements. MOS-HEMTs with a 1.5-μm-long gate exhibit a maximum drain current of 830mA∕mm and a peak transconductance of 115mS∕mm, while the gate leakage current is at least five orders of magnitude lower than that of the reference HEMTs. Good surface passivation effects of HfO2 have also been confirmed by pulsed gate measurements, with MOS-HEMTs showing a significant drain current recovery from current collapse observed in HEMTs.

We report a simple and practical sensor for monitoring both the absolute position and advancing speed of liquid front in a microfluidic channel. The sensor consists of a longitudinal hot wire element—a two-terminal electrical device, with its length spanning the entire channel. The design, materials, fabrication method, and use of this sensor are extremely simple. Characterization results are presented.