Polarity reversal and strain modulation of Janus MoSSe/GaN polar semiconductor heterostructures.

Beyond three-dimensional (3D) architectures, polar semiconductor heterostructures are developing in the direction of two-dimensional (2D) scale with mix-dimensional integration for novel properties and multifunctional applications. Herein, we stacked 2D Janus MoSSe and 3D wurtzite GaN polar semiconductors to construct MoSSe/GaN polar heterostructures by polarity configurations. The structural stability was enhanced as binding energy changed from -0.

2D-materials-integrated optoelectromechanics: recent progress and future perspectives.

The discovery of two-dimensional (2D) materials has gained worldwide attention owing to their extraordinary optical, electrical, and mechanical properties. Due to their atomic layer thicknesses, the emerging 2D materials have great advantages of enhanced interaction strength, broad operating bandwidth, and ultralow power consumption for optoelectromechanical coupling. The van der Waals (vdW) epitaxy or multidimensional integration of 2D material family provides a promising platform for on-chip advanced nano-optoelectromechanical systems (NOEMS).

Interfacial carrier transport properties of a gallium nitride epilayer/quantum dot hybrid structure.

Electron transport layers (ETLs) play a key role in the electron transport properties and photovoltaic performance of solar cells. Although the existing ETLs such as TiO, ZnO and SnO have been widely used to fabricate high performance solar cells, they still suffer from several inherent drawbacks such as low electron mobility and poor chemical stability. Therefore, exploring other novel and effective electron transport materials is of great importance.

Two-Step Deposition of an Ultrathin GaN Film on a Monolayer MoS Template.

Ultrathin gallium nitride (GaN) application can be profoundly influenced by its quality, especially the issue of amorphous interfacial layers formed on conventional substrates. Herein, we report a two-step deposition of an ultrathin GaN film via the plasma-enhanced atomic layer deposition (PEALD) technique on a mono-MoS template over a SiO/Si substrate for quality improvement, by starting the deposition temperature at 260 °C and then ramping it to 320 °C. It was found that a lower initiating deposition temperature could be conducive to maintaining the mono-MoS template to support the subsequent growth of GaN.

Dynamic real-time imaging of living cell traction force by piezo-phototronic light nano-antenna array.

Dynamic mapping of the cell-generated force of cardiomyocytes will help provide an intrinsic understanding of the heart. However, a real-time, dynamic, and high-resolution mapping of the force distribution across a single living cell remains a challenge. Here, we established a force mapping method based on a "light nano-antenna" array with the use of piezo-phototronic effect.

Interfacial Tailoring for the Suppression of Impurities in GaN by In Situ Plasma Pretreatment via Atomic Layer Deposition.

A method for suppressing impurities in GaN thin films grown via plasma-enhanced atomic deposition (PEALD) through the in situ pretreatment of Si (100) substrate with plasma was developed. This approach leads to a superior GaN/Si (100) interface. After pretreatment, the thickness of the interfacial layer between GaN films and the substrates decreases from 2.

A large-scale, ultrahigh-resolution nanoemitter ordered array with PL brightness enhanced by PEALD-grown AlN coating.

III-nitride solid-state microdisplays have significant advantages, including high brightness and high resolution, for the development of advanced displays, high-definition projectors, head-mounted displays, large-capacity optical communication systems, and so forth. Herein, a high-brightness InGaN/GaN multiple-quantum-well (MQW) nanoemitter array with an ultrahigh resolution of 31 750 dpi was achieved by combining a top-down fabrication with surface passivation of plasma-enhanced atomic layer deposition (PEALD)-grown AlN coating. With regard to the nanometer-level top-down etching, the surface damage or defects on the newly-formed sidewall play a significant role in the photoluminescence (PL) quality.

Electric-field driven photoluminescence probe of photoelectric conversion in InGaN-based photovoltaics.

The spatial distribution of electric field in photovoltaic multiple quantum wells (MQWs) is extremely important to dictate the mutual competition of photoelectric conversion and optical transition. Here, electric-field-driven photoluminescence (PL) in both steady-state and transient-state has been utilized to directly investigate the internal photoelectric conversion processes in InGaN-based MQW photovoltaic cell. As applying the reversed external electric field, the compensation of the quantum confined stark effect (QCSE) in InGaN QW is beneficial to help the photoabsorbed minor carriers drift out from the localized states, whereas extremely weakening the PL radiative recombination.

PEALD-Grown Crystalline AlN Films on Si (100) with Sharp Interface and Good Uniformity.

Aluminum nitride (AlN) thin films were deposited on Si (100) substrates by using plasma-enhanced atomic layer deposition method (PEALD). Optimal PEALD parameters for AlN deposition were investigated. Under saturated deposition conditions, the clearly resolved fringes are observed from X-ray reflectivity (XRR) measurements, showing the perfectly smooth interface between the AlN film and Si (100).

Self-Powered Random Number Generator Based on Coupled Triboelectric and Electrostatic Induction Effects at the Liquid-Dielectric Interface.

Modern cryptography increasingly employs random numbers generated from physical sources in lieu of conventional software-based pseudorandom numbers, primarily owing to the great demand of unpredictable, indecipherable cryptographic keys from true random numbers for information security. Thus, far, the sole demonstration of true random numbers has been generated through thermal noise and/or quantum effects, which suffers from expensive and complex equipment. In this paper, we demonstrate a method for self-powered creation of true random numbers by using triboelectric technology to collect random signals from nature.

Raman study of 2D anatase TiO nanosheets.

Herein, we present for the first time a spectroscopic study of two-dimensional (2D) anatase TiO nanosheets. Previous publications demonstrated that Raman spectroscopy was mostly employed to characterize the TiO nanoparticle size and the phase transition of amorphous-anatase and anatase-rutile. In this study, TiO nanosheets were characterized by XRD, AFM and Raman spectroscopy, which demonstrated a shift toward higher frequency and broadening in the full width at half maximum of the characteristic E mode by decreasing the thickness of anatase TiO with a 2D nanostructure.

Piezo-phototronic effect enhanced UV photodetector based on CuI/ZnO double-shell grown on flexible copper microwire.

In this work, we present a facile, low-cost, and effective approach to fabricate the UV photodetector with a CuI/ZnO double-shell nanostructure which was grown on common copper microwire. The enhanced performances of Cu/CuI/ZnO core/double-shell microwire photodetector resulted from the formation of heterojunction. Benefiting from the piezo-phototronic effect, the presentation of piezocharges can lower the barrier height and facilitate the charge transport across heterojunction.

Triboelectric Nanogenerator as a Self-Powered Communication Unit for Processing and Transmitting Information.

In this paper, we demonstrate an application of a triboelectric nanogenerator (TENG) as a self-powered communication unit. An elaborately designed TENG is used to translate a series of environmental triggering signals into binary digital signals and drives an electronic-optical device to transmit binary digital data in real-time without an external power supply. The elaborately designed TENG is built in a membrane structure that can effectively drive the electronic-optical device in a bandwidth from 1.

Lattice Strain Induced Remarkable Enhancement in Piezoelectric Performance of ZnO-Based Flexible Nanogenerators.

In this work, by employing halogen elements (fluorine, chlorine, bromine, and iodine) as dopant we demonstrate a unique strategy to enhance the output performance of ZnO-based flexible piezoelectric nanogenerators. For a halogen-doped ZnO nanowire film, dopants and doping concentration dependent lattice strain along the ZnO c-axis are established and confirmed by the EDS, XRD, and HRTEM analysis. Although lattice strain induced charge separation was theoretically proposed, it has not been experimentally investigated for wurtzite structured ZnO nanomaterials.

Flexible Self-Powered GaN Ultraviolet Photoswitch with Piezo-Phototronic Effect Enhanced On/Off Ratio.

Flexible self-powered sensing is urgently needed for wearable, portable, sustainable, maintenance-free and long-term applications. Here, we developed a flexible and self-powered GaN membrane-based ultraviolet (UV) photoswitch with high on/off ratio and excellent sensitivity. Even without any power supply, the driving force of UV photogenerated carriers can be well boosted by the combination of both built-in electric field and piezoelectric polarization field.

High-resolution dynamic pressure sensor array based on piezo-phototronic effect tuned photoluminescence imaging.

A high-resolution dynamic tactile/pressure display is indispensable to the comprehensive perception of force/mechanical stimulations such as electronic skin, biomechanical imaging/analysis, or personalized signatures. Here, we present a dynamic pressure sensor array based on pressure/strain tuned photoluminescence imaging without the need for electricity. Each sensor is a nanopillar that consists of InGaN/GaN multiple quantum wells.

Magnetic-mechanical-electrical-optical coupling effects in GaN-based LED/rare-earth terfenol-D structures.

A multi-field coupling structure is designed and investigated, which combines GaN-based optoelectronic devices and Terfenol-D. The abundant coupling effects and multifunctionalities among magnetics, mechanics, electrics, and optics are investigated by a combination of non-magnetic GaN-based piezoelectronic optoelectronic characteristics and the giant magnetomechanical properties of Terfenol-D. A few potential new areas of studies are proposed.