Hollow carbon spheres (HCS) have been employed as supporting materials for Pt, Ag, and Au nanoparticles (NPs) in the oxygen reduction reaction (ORR). The NPs Pt, Ag, and Au have been hydrothermally coated on HCS uniformly. The diameter of the Pt, Ag and Au NPs ranges between 11 and 32 nm, with the loading of 4.58, 4.73, and 4.07 wt.%, respectively. It is found that Pt, Ag, and Au/HCS exhibit stable catalytic activity after 5000 CV scanning and follow a four-electron route in the ORR. Among them, Tafel plots show that Ag/HCS has the fastest kinetic rates and Pt/HCS has the largest effective active area from CV curve. Hence HCS provides a stable supportive material for Pt, Ag, Au nanoparticle catalysts in the ORR due to its nanopores structure and large surface area.Graphical Abstract

A Ag2O-Cu composite filler was adopted as a sintering material between Cu finishes under compression to achieve the high-speed bonding of dies in an air atmosphere via a cost-effective paste and finish process. The commercial Cu particles had an average size of 2 μm, and the synthesized Ag2O particles were in the submicrometer range with an average size of 210 nm. The Ag2O particles in the paste started decomposing at ∼150 °C, and the liquid-type reductant in the paste effectively reduced the oxide layers on the Cu particles as well as the upper and lower Cu finishes during bonding. Therefore, the in situ-generated active Ag and fresh Cu surfaces enabled significantly rapid sinter bonding under 5 MPa compression. Only 30 s of bonding at 300 °C was required to achieve an excellent shear strength of 27.8 MPa in the created bond-line, while 90 s of bonding produced a near-full-density structure with a strength of 41.9 MPa despite solid-state sintering when the 3:7 (Cu particles:Ag2O particles) mixing ratio was used. Well-dispersed Ag2O particles did not create a non-sintered interface or form large voids upon outgassing during decomposition. The out-diffused Cu was reoxidized after sintering with Ag, forming irregularly dispersed Cu2O shells that remained in the microstructure of the full-density bond-line.Graphical Abstract

The development of hard carbon with high capacity and long cycling stability is a significant issue for lithium ion batteries. Herein, thiophene-containing conjugated microporous polymer (SCMP) was synthesized using 1,3,5-triethynylbenzene 2,5-dibromothiophene by Sonogashira-Hagihara crosscoupling reactions. Then, high sulfur doped hard carbon (SHC) and KOH activated SHC (SHC-K) are prepared by direct carbonization and KOH-assisted carbonization of SCMP, respectively. Both samples were then investigated by SEM, elemental analysis, FTIR, XPS and Nitrogen adsorption/desorption. Taking advantages of sulfur content and abundant porosity, SHC-K delivers a first charge specific capacity of 842.2 mAh g−1 at 0.1 A g−1 and a specific charge capacity of 565.9 mAh g−1 after 500 cycles at 0.6 A g−1.Graphical Abstract

Solar cell devices are one of the most promising technologies for generating green energy. Forefront perovskite-based solar cells have increased worldwide hope for solving global warming issues. Tight bandgap formamidinium lead iodide (TB-FAPbI3) perovskite as an active layer to absorb sunlight along with a desired electron transport layer (ETL) can produce efficient and stable perovskite solar cells (PSCs). Here, TB-FAPbI3 with tin oxide (SnO2) as an ETL was employed to fabricate PSCs. These PSCs recorded a low champion efficiency of 18.35%. A cobalt-doped SnO2 layer was designed to increase the efficiency of TB-FAPbI3 solar cells. The modified SnO2 boosted the solar cell efficiency to 20.10% due to the improved conductivity of the ETL and increased charge transfer phenomena in the PSCs. From one side, electron transfer is facilitated at the ETL/perovskite interface. On another side, the reduced surface defects on the fabricated perovskite layer over the modified ETL diminish charge traps in the solar cell. In addition, cobalt doping does not hinder the light transmission from the SnO2 into the perovskite layer. The modified SnO2 assists in the formation of a more compact TB-FAPbI3 layer and promotes the stability properties of PSCs.Graphical Abstract

The development of triple oxide semiconductor nanostructures (NS) with special optical window is critical for the optoelectronics and the luminescent industry. The present article describes the synthesis of Smx:Gd(1−x)@SrO (x = 0.4, 0.6, 0.8) NS by simple Coprecipitation method. The NS were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), SEM–EDS (energy dispersive spectra), Fourier transform infrared (FT-IR), UV–visible, X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller analytical methods. The results of the powdered XRD pattern revealed the formation of mixed-phase of hexagonal crystal structure, with grain size between 62 and 78 nm. Redshift in optical absorption spectra for the Sm3+ doped Gd(1−x) SrO NS appeared when compared to Gd(1−x) SrO NS. Photoluminescence (PL) spectroscopy demonstrated broad deep defect levels in Smx: Gd(1−x) SrO NS when compared to Gd(1−x) SrO NS. PL studies of Gd0.6, SrO exhibited three emission peaks detected at 373.6 nm, 382.1 nm, and 392.7 nm when excited at 325 nm. PL studies of Smx: Gd(1−x) SrO NS (x = 0.8) showed four emission peaks appeared at 415 nm (violet), 472 nm (blue), 532.1 nm (green) and 569.6 nm (yellow) due to f–f transition of Sm3+ in 4f5 configuration. Higher values of dielectric constant (3.86 × 104), dielectric permittivity (103–105) resulted for the Smx:Gd(1−x)@SrO (x = 0.8) NS with negligibly small dielectric loss (< 0.03) when compared to Gd0.6 SrO NS. The synthesised materials demonstrated excellent luminescence properties with good dielectric properties therefore these materials could be good candidates to be used as high-luminescent devices.Graphical Abstract

Two-dimensional layered tin diselenide (SnSe2) is a promising material for NO2 gas detection at room temperature because of its high adsorption energy of NO2 and a good intrinsic conductivity. However, there are only a few reports on dependence on its morphology and NO2 gas detection properties. Here, we investigate the correlation with the morphologies and NO2 gas detection properties of SnSe2 synthesized by a hydrothermal route. With increasing the reaction time, the morphologies of SnSe2 are changed from disk-like shape to flower-like hierarchical one caused by the inherent self-assembly behavior, while preserving the hexagonal crystal structure. Based on various morphologies of SnSe2, we fabricated gas sensor devices with interdigitated electrodes. Among various morphologies of SnSe2, the hierarchical SnSe2 device exhibits the highest NO2 gas detection properties at room temperature, achieving gas response of 22% toward 100 ppm NO2 and superior gas selectivity with respect to other gas species. This is attributed to the higher specific surface area of hierarchical morphology than other morphologies and improved crystallinity.Graphic Abstract

AbstractThe effect of electron-beam irradiation (EBI) on MoS2-based photodetectors with various electrode structures was investigated to improve the electrical and photoelectrical properties. The MoS2 films were deposited at room temperature by RF magnetron sputtering and subsequently transformed into a two-dimensional layered structure by EBI treatment with the electron energy of 3 kV for 1 min. The electrical resistance and photoelectrical properties, such as photocurrent and photoresponsivity, of MoS2 films were examined with patterned Au/Ti electrodes as a top contact (TC) and a bottom contact structure. In addition, the interfacial effect of high-k dielectric materials of thin HfO2 film between MoS2 and the SiO2/Si substrate was investigated to enhance the photoelectrical property. The MoS2 photodetectors fabricated by the EBI before TC formation on HfO2 exhibited the highest photoresponsivity of 11.88 mA/W, which was an increase of 6500% from the EBI before TC structure on SiO2. We believe that this work contributes to the improvement of contact and interface properties of MoS2-based photodetectors readily and quickly compared with conventional high-temperature thermal treatment.Graphical Abstract

Next-generation and solution-processed thin-film solar cells have been attracted considerable attention because of their low cost, light weight, flexibility, and aesthetics. However, most of solution-processed thin-film solar cells are now focused on the use of photovoltaic absorbers containing the toxic element of Pb. In this study, eco-friendly silver-bismuth-iodide (Ag-Bi-I) thin-film photovoltaic devices with high open-circuit voltages (VOC) are developed by utilizing polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7) as the hole transport layer (HTL). The solution-processed AgBi2I7 semiconductor, which is an Ag-Bi-I ternary compound, exhibit features suitable for photovoltaic layers in thin-film solar cells, including a three-dimensional (3D) crystal structure, good surface morphology, and low optical bandgaps of 1.87 eV. Meanwhile, the solution-processed AgBi2I7 thin-film solar cell based on the PTB7 HTL exhibit a power conversion efficiency of 0.94% with an improved VOC value of 0.71 V owing to the deeper highest occupied molecular orbital (HOMO) energy level compared to that of poly(3-hexylthiophene-2,5-diyl) (P3HT). In other words, the VOC of the PTB7 HTL-based device is 20% higher than that of the P3HT HTL-based control device. Our results provide a new approach for increasing the VOC of eco-friendly Ag-Bi-I thin-film photovoltaics and indicate that further HTL engineering is necessary to simultaneously improve the VOC and performance of the devices.Graphical Abstract

Effect of electron irradiation on electronic structure of Ni41Co6Mn43Sn10 alloys were investigated by X-ray absorption fine structure, X-ray magnetic circular dichroism spectrometry and Mössbauer spectrometry. The local coordination environment of magnetic element significant changes after electron irradiation, the change in the peak intensity of the Co L3 edge is opposite to the Ni/Mn element, indicating that there is an electronic exchange between them. The crystal field symmetry is broken, the hyperfine field Hin of the Ni41Co6Mn43Sn10 alloy increases from 8.80 to 9.06 T. Meanwhile, the spin magnetic moment of the Mn atom is significantly increased after electron irradiation.Graphical Abstract

MXene, as a new type of two-dimensional material, has attracted much interest since it was discovered in 2011. However, only few articles discussed the effect of MXene flake size on its electrochemical performance. Here, a sand milling way is explored to produce nano-size MXene and the MILD method is used to prepare micron-size MXene (1 μm) as a comparison. Meanwhile, a mask-assisted interdigital micro-supercapacitors is prepared to explore the dependence of the electrochemical properties of MXene on their flake size. We show that nano-size MXene (200 nm) has a higher ionic conductivity as compared to normal micron-size MXene (1 μm). On the contrary, the larger flake size has higher electrical conductivities. As a result, the capacitance of micron-size MXene is better than nano-size MXene (200 nm) because the electrical conductivities are dominant. This research is helpful for further understanding of the influence of MXene flake size on its electrochemical performance.Graphical abstract

AbstractIn this work, initial stage of diamond growth at 300℃ by hot filament chemical vapor deposition (HFCVD) was studied using a single layer graphene membrane for transmission electron microscopy (TEM) observations. The graphene membrane was exposed to a temperature of 300℃, 60 mm below the hot filament, for 1 s, 10 s, 30 s, 120 s, and 30 min at 20 Torr with a gas mixture of 1% CH4–99% H2. Under this condition, only the gas phase is stable at 300℃. As the exposure time increases, the average size of nanocarbon particles also increases. The growth of nanoparticles at 300℃, where only the gas phase is stable, indicates that the growth occurred by non-classical crystallization, where the building blocks are nanoparticles. At 1 and 10 s, only i-carbon nanoparticles were captured, whereas the hexagonal diamond and n-diamond ones were additionally captured at 30 and 120 s. A cubic diamond nanoparticle was captured only at 30 min. The structural stability of nanocarbon changes depending on the size, in the order of amorphous, i-carbon, hexagonal diamond, n-diamond, and cubic diamond, as the size increases. Observed n-diamond nanoparticles have a core-shell structure surrounded by an i-carbon layer. I-carbon nanoparticles larger than ~ 10 nm had a polycrystalline structure, whereas hexagonal diamond and n-diamond nanoparticles had a single crystal structure. A lattice of the i-carbon layer in contact with n-diamond nanoparticles was partially oriented in the same direction as that of the n-diamond nanoparticles.Graphical abstract

The mechanically exfoliated ultrathin 3R α-In2Se3 nanosheets were transferred onto a SiO2/Si substrate. Using atomic force microscopy, it was confirmed that the transferred α-In2Se3 transferred had a thickness of 15–120 nm. The thickness-dependence of Raman peaks of \({E}^{2}\), \({A}_{1}^{1}\), \({E}^{4}\), and \({A}_{1}^{2}\) was observed from the Raman spectra. Moreover, the measured photoluminescence peak values in the range of 869–895 nm indicate a blue shift as the thickness decreases. The field-effect transistor based on α-In2Se3 exhibited an n-type semiconductor behavior. From the transfer curve at gate voltage of 10 V, the derived values of the mobility and ON/OFF ratio are 24.26 cm2 V− 1 s− 1 and 1.84, respectively. In addition, it was confirmed that the 3R α-In2Se3 layers had a high photoresponsivity of up to approximately 34,500 A/W under illumination (\(\lambda\) = 750 nm).Graphical abstract

Zinc oxide (ZnO) thin films with different concentrations of lithium, from 0 to 15 mol%, have been grown on Si(100) substrates by employing aerosol-assisted chemical vapor deposition (AACVD). The structural, electronic, and magnetic properties of the ZnO thin films were investigated as the effect of Li doping concentration. SEM images of surface morphology reveal that the undoped and low-concentration Li-doped ZnO thin films exhibit irregular ellipsoid grains. In comparison, the ZnO thin films with higher Li concentration consist of multi-aligned rod-like and hexagonal-shaped grains. XRD pattern analysis confirms that all grown ZnO thin films exhibit a single polycrystalline phase of hexagonal wurtzite crystal. The lattice reduction was observed in the Li-doped thin films indicating that the substitutional Li effectively occupied the Zn lattice site. The Hall effect measurement demonstrates that Li-doped ZnO films possess p-type conductivity. The resistivity of Li-doped ZnO thin films decreases with an increase in Li doping concentration while the hole carrier density increases. The Hall mobility tends to increase as more Li doping concentration is given, with the highest Hall mobility obtained from 15 mol% Li-doped film with a value of 85.88 cm2/V s. The VSM study demonstrates that all grown ZnO thin films exhibit an M-H hysteresis curve, indicating d0 ferromagnetism behavior at room temperature, with coercivity ranging from 202 to 373 Oe. The highest saturation magnetization was obtained from 10 mol% Li-doped films, with a value of 5.55 × 10–2 emu/g.Graphical Abstract

Since the emergence of layered two-dimensional materials, the development of methods for their large-scale synthesis has become crucial for integrating these materials into existing fabrication processes. In this study, we report the synthesis of a NiTe2 single crystal on the near-centimeter scale using the molten salt flux method (MSFM). The single-crystal nature of the synthesized NiTe2 sample was confirmed using X-ray diffraction analysis, while its chemical characteristics were analyzed using X-ray photoelectron spectroscopy, which confirmed Ni–Te chemical binding. The layered structure of the ingot was confirmed using Raman spectroscopy; two prominent signals were observed, at 84 and 138 cm−1, which were consistent with the in-plane vibrational mode, Eg, and out-of-plane vibrational mode, A1g. In addition, analyses performed on different flakes confirmed the structural uniformity of the single crystal, as only a small variation in the peak-to-peak position of the full width at half maximum was observed. Using Kelvin probe force microscopy, the electronic structure of the NiTe2 multilayered surface was investigated to determine its surface work function, which was found to be 4.4–4.8 eV. A back-gate field-effect transistor was fabricated using the single-crystal NiTe2 to evaluate its semimetallic characteristics; the transfer characteristic of the NiTe2 FET, determined by applying a back-gate bias, showed weak gate voltage dependence and linear I–V characteristics, in keeping with the linear ID-VD output characteristics. Therefore, the synthesis of NiTe2 via the MSFM should facilitate the integration of layered materials with existing fabrication processes for the mass production of electronic devices.Graphical Abstract

Carbon nanotube field-effect transistor (CNT-FET) based sensor devices are widely used in sensing applications of biomolecules in high sensitivity. In addition, covalent functionalization process can increase the interaction between the CNTs and biological molecules. In this article, we present the effect of boronic acid functionalization on the electrical properties of the CNT-FET due to boronic acid and its derivatives have been widely used for the glucose recognition. For this purpose, CNT-FET transistors were fabricated on SiO2/Si substrates utilising high purity semiconducting nanotubes as the channel layer and functionalized with pyrene-1-boronic acid. It was found that boronic acid functionalization causes a variation in electrical parameters of CNT-FET transistors such as conductance, transconductance, threshold voltage, field effect mobility, resistance, hysteresis gap, and charge transfer of carriers per unit length. The results show that pyrene-1-boronic acid treatment was observed to have a significant beneficial effect on the electrical properties of the CNT-FET and pyrene-1-boronic acid functionalized CNT-FET sensor devices may have great potential for glucose sensing applications. Graphical Abstract

We report structural, dielectric, ferroelectric, magnetic, and low frequency magnetoelectric (ME) properties of (1−x) Bi0.5Na0.5TiO3 (BNT)–xNi0.5Zn0.5Fe2O4 (NZFO) (x = 0.05–0.30) microwave sintered particulate composites. Distinct phases of BNT and NZFO were confirmed by X-ray diffraction and scanning electron microscopy. Raman spectroscopy measurement showed the absence of micro-strains within the composite. The temperature dependent dielectric studies revealed the ferroelectric to anti-ferroelectric transition at 220 °C and anti-ferroelectric to paraelectric transition at 320 °C. The ac conductivity showed both frequency dependent and independent behavior. Temperature dependent dc conductivity showed that upto 200 °C charge conduction is due to hopping of electrons, whereas at higher temperature diffusion of oxygen vacancies are responsible for the conduction. Ferroelectric and leakage current density measurements showed enhanced conduction losses with NZFO content. The maximum ME coefficient at 10 Hz frequency is obtained for 0.80BNT–0.20NZFO (4.33 mV/cm.Oe at 800 Oe).Graphical abstract

Safe and efficient detection of hazardous n-butanol gas is very great significance to the health of workers and researchers in chemical environments. In this work, we successfully developed a GaN gas sensor by a simple solvothermal method and a low-temperature nitridation process. Material characterization results show that one-dimensional nanorods structures were obtained and the products presented a superior growth orientation along with (101) plane. The gas sensing test results show that the sensor exhibits excellent responsivity, repeatability, and selectivity to n-butanol at room temperature. The response and recovery time of the sensor to 200 ppm n-butanol gas was 45 s/34 s. Gas adsorption model and electron depletion layer theory were established to understand the n-butanol sensing mechanism. This work provides the possibility for its real application in n-butanol detection with safe and efficient at room temperature.Graphical Abstract

Bismuth sodium titanate (Bi0.5Na0.5TiO3, BNT) based ferroelectric ceramic is one of the important lead free dielectric materials for high energy storage applications due to its large polarization. Herein, we reported a modified BNT based relaxor ferroelectric ceramics composited with relaxor Sr0.7Bi0.2TiO3 (SBT) and ferroelectric BaTiO3 (BT), which exhibits a high recoverable energy density of 5.59 J/cm3 and a high energy storage efficiency of 84.0% under large breakdown electric strength of 420 kV/cm. A core–shell grain structure is observed in the BNT-SBT-BT ceramics with high content BT additive, which plays crucial role on the enhancement of the energy storage performance. This ceramic also exhibits superior temperature stability with small energy density variation of less than 6.5% in wide temperature range from room temperature to 180 °C. The impedance spectroscopies show that the ceramics have good insulation properties at high temperature. These characteristics demonstrate that the BNT-SBT-BT ceramic is a promising candidate for high-power energy storage applications. Graphical Abstract

Low voltage oxide thin-film transistors (TFTs) operating below 1.0 V were developed using a high dielectric constant tantalum oxide produced by thermal oxidation. Thermal oxidation was carried out at 400, 500 and 600 °C under an oxygen atmosphere. The tantalum oxide was evaluated by X-ray photoelectron spectroscopy (XPS). XPS confirmed the binding energy of Ta4f, indicating the binding state of tantalum oxide. The bottom gate oxide TFT with the gate insulator of tantalum oxide grown at 500 °C exhibited mobility of 26.7 cm2/V s and a threshold voltage of 1.3 V. The transfer characteristics at the drain voltages below 1.0 V show its applicability to low voltage operation below 1 V. The bootstrapped inverter with developed oxide TFTs operated well at the 1.0 and 2.0 V operation voltages.Graphical Abstract

As semiconductor device scaling faces a severe technical bottleneck, vertical die stacking technologies have been developed to obtain high performance, high density, low latency, cost effectiveness and a small form factor. This stacking technology is receiving great attention from industry as a core technology from the point of view of recent heterogeneous integration technology. Most importantly, bonding using copper is aggressively studied to stack various wafers or dies and realize genuine three-dimensional packaging. Copper is emerging as the most attractive bonding material due to its fine-pitch patternability and high electrical performance with a CMOS-friendly process. Unfortunately, copper is quickly oxidized, and a high bonding temperature is required for complete Cu bonding, which greatly exceeds the thermal budget for the packaging process. Additionally, the size of Cu pads is decreasing to increase the density of interconnections. Therefore, various copper bonding methods have been studied to realize copper oxidation prevention, a low bonding temperature, and a fine-pitch Cu pad structure with a high density. Furthermore, recently, hybrid bonding, which refers to the simultaneous bonding of copper pads and surrounding dielectrics, has been considered a possible solution for advanced bonding technology. This paper reviews recent studies on various copper bonding technologies, including Cu/oxide hybrid bonding.Graphical Abstract