Effect of Mg-Preflow for p-AlGaN Electron Blocking Layer on the Electroluminescence of Green LEDs with V-Shaped Pits

In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the（8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.

Photon-assisted electronic and spin transport through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm interferometer

We investigate the time-modulated electronic and spin transport properties through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm（A-B） interferometer. By using the Keldysh non-equilibrium Green＇s function technique, the photon-assisted spin-dependent average current is analyzed. The T-shaped three-quantum-dot molecule A-B interferometer exhibits excellent controllability in the average current resonance spectra by adjusting the interdot coupling strength, Rashba spin-orbit coupling strength, magnetic flux, and amplitude of the time-dependent external field.Efficient spin filtering and multiple electron-photon pump functions are exploited in the multi-quantum-dot molecule A-B interferometer by a time-modulated external field.

Application of real space Kerker method in simulating gate-all-around nanowire transistors with realistic discrete dopants

We adopt a self-consistent real space Kerker method to prevent the divergence from charge sloshing in the simulating transistors with realistic discrete dopants in the source and drain regions. The method achieves efficient convergence by avoiding unrealistic long range charge sloshing but keeping effects from short range charge sloshing. Numerical results show that discrete dopants in the source and drain regions could have a bigger influence on the electrical variability than the usual continuous doping without considering charge sloshing. Few discrete dopants and the narrow geometry create a situation with short range Coulomb screening and oscillations of charge density in real space. The dopants induced quasilocalized defect modes in the source region experience short range oscillations in order to reach the drain end of the device.The charging of the defect modes and the oscillations of the charge density are identified by the simulation of the electron density.

Orbital electronic heat capacity of hydrogenated monolayer and bilayer graphene

The tight-binding Harrison model and Green＇s function approach have been utilized in order to investigate the contribution of hybridized orbitals in the electronic density of states（DOS） and electronic heat capacity（EHC） for four hydrogenated structures, including monolayer chair-like, table-like, bilayer AA- and finally AB-stacked graphene. After hydrogenation, monolayer graphene and bilayer graphene are behave as semiconducting systems owning a wide direct band gap and this means that all orbitals have several states around the Fermi level. The energy gap in DOS and Schottky anomaly in EHC curves of these structures are compared together illustrating the maximum and minimum band gaps are appear for monolayer chair-like and bilayer AA-stacked graphane, respectively. In spite of these, our findings show that the maximum and minimum values of Schottky anomaly appear for hydrogenated bilayer AA-stacked and monolayer table-like configurations, respectively.

Cellulose-Based Conductive Hydrogels for Emerging Intelligent Sensors

Flexible intelligent sensing is a burgeoning field of study that covers various disciplines,including but not restricted to chemistry,physics,electronics and biology.However,the widespread use of flexible sensors remains challenging because of certain constraints,such as limited stretchability,poor biocompatibility,low responsivity,and the complexity of multifunc-tional integration.Conductive hydrogels with remarkable material properties are presently in the spotlight of flexible sens-ing.In the pursuit of high-performance and“green”conductive hydrogel-based sensors,cellulose is a promising candidate owing to its renewability,low cost,appealing mechanical properties,easy modification and other functional characteristics.Herein,cutting-edge progress in the fabrication of conductive cellulose hydrogels(CCHs)using cellulose and cellulose derivatives in terms of structural features,preparation approaches,functional properties,applications,and prospects for sensors is comprehensively summarized.The correlation between CCHs performances,reinforcement strategies and sensor properties is highlighted to gain insight into the process of developing smart sensors by utilizing CCHs.Besides,the state-of-the-art advances of CCHs toward emerging wearable sensors,including strain/pressure sensors,temperature sensors,humidity sensors,and biosensors,are systematically discussed.Finally,potential challenges and future outlooks of such attractive CCH-based flexible sensors are presented,providing valuable information for the development of next-generation cellulose-based electronic devices.

Engineering “JiaoJiao”(maltose syrup) with chopsticks: From traditional Chinese sweet food to skin-like iontronics

The advancement of technology has had a profound impact on all areas of life, with an ever more intimate integration of the digital and biological spheres, but it may also be accompanied by an environmental crisis caused by the abuse of large quantities of electronics and petrochemicals.Next-generation "green" electronics or iontronics with high biocompatibility, biodegradation, low cost and mechanical compliance promise to mitigate these adverse effects, but are often limited by the finite choices of materials and strategies.Herein, maltose syrup, a traditional water-dissolvable saccharide food called "JiaoJiao" in Chinese, is engineered to replace unsustainable conductive components of current electronic devices. After churning and pulling with two chopsticks, known as aeration, the aerated maltose syrup has optimized viscoelasticity, mechanical adaptation, robustness,remodeling and self-healing capability, yet with transient behavior. Moreover, the structural and viscoelastic evolution during aeration is also analyzed to maximize the contribution from structures. As a proof-of-concept, a type of "green" skinlike iontronics is prepared, which exhibits reliable strain sensing ability and is subsequently applied for intelligent information encryption and transmission based on a novel concept of sending Morse code. This work greatly extends the current material choice and is expected to shed light on the development of a sustainable future.

A first-principles study of dihydroazulene as a possible optical molecular switch

By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate the electronic transport properties of the dihydroazulene optical molecular switch. Three kinds of adsorption sites including the hollow, bridge and top sites are studied. The two forms of this molecule, namely the open form and the closed form, can reversibly switch from each other upon photoexcitation. Their transmission spectra are remarkably distinctive. Theoretical results show that the current of the closed form is always significantly larger than that of the open form for all three adsorption sites, which promises this system as possibly one of the good candidates for optical switches due to its unique advantage, and which may have some potential applications in the future molecular circuit.

Controlling Thermodynamic Properties of Ferromagnetic Group-Ⅳ Graphene-Like Nanosheets by Dilute Charged Impurity

Using the Kane-Mele Hamiltonian, Dirac theory and self-consistent Born approximation, we investigate the effect of dilute charged impurity on the electronic heat capacity and magnetic susceptibility of two-dimensional ferromagnetic honeycomb structure of group-Ⅳ elements including silicene, germanene and stanene within the Green's function approach. We also find these quantities in the presence of applied external electric field. Our results show that the silicene(stanene) has the maximum(minimum) heat capacity and magnetic susceptibility at uniform electric fields. From the behavior of theses quantities, the band gap has been changed with impurity concentration, impurity scattering strength and electric field. The analysis on the impurity-dependent magnetic susceptibility curves shows a phase transition from ferromagnetic to paramagnetic and antiferromagnetic phases. Interestingly, electronic heat capacity increases(decreases) with impurity concentration in silicene(germanene and stanene) structure.