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A random laser carrying the scattering information on a biological host is a promising tool for the characterization of biophysical properties. In this work, random lasing from label-free living cells is proposed to achieve rapid cytometry of apoptosis. Random lasing is achieved by adding biocompatible gain medium to a confocal dish containing cells under optically pumped conditions. The random lasing characteristics are distinct at different stages of cell apoptosis after drug treatment. By analyzing the power Fourier transform results of the random lasing spectra, the percentage of apoptotic cells could be distinguished within two seconds, which is more than an order of magnitude faster than traditional flow cytometry. These results provide a label-free approach for rapid cytometry of apoptosis, which is advantageous for further research of random lasers in the biological field.

Multiferroic materials have great potential in non-volatile devices for low-power and ultra-high density information storage, owing to their unique characteristic of coexisting ferroelectric and ferromagnetic orders. The effective manipulation of their intrinsic anisotropy makes it promising to control the multiple degrees of freedom of the storage "medium". Here, we have discovered intriguing electrical and magnetic anisotropies within the intralayer of CuCrP2S6, a promising van der Waals multiferroic material. The in-plane uniaxial anisotropies of the current rectifications, magnetic properties and magnon modes are demonstrated and manipulated by electric direction/polarity, temperature variation and magnetic field. More important, we have observed spin-flop transition corresponding to specific magnon modes, and it is well supported by theoretical calculations. Our work provides the first observation of electrical and magnetic anisotropies with same easy axis in van der Waals multiferroics, which will stimulate novel device applications of artificial bionic synapses, multi-terminal spintronic chips and magnetoelectric devices.

The non-collinear antiferromagnetic Weyl semimetal Mn3X (X = Ga, Ge, Sn) system has attracted a lot of attentions owing to its robust anomalous Hall effect (AHE), large spin Hall angle and small net magnetization at room temperature. The high spin-charge interconversion efficiency makes it a super candidate in topological antiferromagnetic spintronic devices, which could facilitate ultra-fast operation of high-density devices with low energy consumption. In this work, we have realized to obtain different chiral spin structures in Heusler alloy Mn3Ge thin films, which originate from different crystalline orientations. The high-quality (0002)- and (20 2 ¯ 0)-oriented single phase hexagonal Mn3Ge films are achieved by controllable growth, annealing process and ion implantation. The various magnetic properties and AHE behaviors are observed along a and c crystal axes, equivalent to magnetic field in and out of the inverse triangular spin plane. The observation demonstrates the manipulation of crystal structure accompanied with chiral spin order in a non-collinear antiferromagnetic Mn3Ge film, which is induced by energy conversion and defect introduction. The in situ thermal treatment induces crystal phase rotation up to 90° and robust AHE modulation, which is significantly important and highly desirable for flexible spin memory device applications.

An ultrathin-film microring laser was fabricated using inkjet printing and a simple lift-off technique. Whispering-gallery-mode lasing was observed under optically pumped conditions in the film. The freestanding laser can be transferred to arbitrary surfaces for multifunctional applications, such as acoustic and relative humidity sensing. Using the first eigenmode of a membrane vibration, an acoustic sensor with a 0.15 Pa limit of detection was demonstrated via laser bandwidth broadening. A relative humidity sensor with a 1.1% limit of detection via wavelength shifts was demonstrated by placing the device on an optical fiber facet. These cost-effective, transferrable, multifunctional laser sensors will have many additional applications.

Topological Weyl semimetals have attracted considerable interest because they manifest underlying physics and device potential in spintronics. Large anomalous Hall effect (AHE) in non-collinear antiferromagnets (AFMs) represents a striking Weyl phase, which is associated with Bloch-band topological features. In this work, we report robust AHE and Lifshitz transition in high-quality Weyl semimetal Mn3Ge thin film, comprising stacked Kagome lattice and chiral antiferromagnetism. We successfully achieved giant AHE in our Mn3Ge film, with a strong Berry curvature enhanced by the Weyl phase. The enormous coercive field HC in our AHE curve at 5 K reached an unprecedented 5.3 T among hexagonal Mn3X systems. Our results provide direct experimental evidence of an electronic topological transition in the chiral AFMs. The temperature was demonstrated to play an efficient role in tuning the carrier concentration, which could be quantitatively determined by the two-band model. The electronic band structure crosses the Fermi energy level and leads to the reversal of carrier type around 50 K. The results not only offer new functionality for effectively modulating the Fermi level location in topological Weyl semimetals but also present a promising route of manipulating the carrier concentration in antiferromagnetic spintronic devices.

Photocatalytic decomposition of carbamazepine using Au nanoparticles modified β-Ga2O3 film was investigated. The crystallization, morphology, optical properties, and electrical properties of the samples were investigated using XRD, SEM, UV–vis absorption spectroscopy, photoluminescence spectra, and photocurrent measurements. In the photocatalytic experiments of carbamazepine degradation, the Au nanoparticles modified β-Ga2O3 films presented a better photocatalytic property than the pure β-Ga2O3 film. The optical transmittance spectra verify that the present of Au nanoparticles can enhance the light harvesting and shrink the bandgap of the β-Ga2O3 film. The photocurrent density and photoluminescence emission spectra indicate that the localized surface plasmon resonance of Au nanoparticles promoted the charge separation and suppressed the charge recombination of photoinduced electron–hole pairs in β-Ga2O3.

Surface plasmonic effect of metal nanoparticles is an effective method to improve the power conversion efficiency (PCE) of solar cells. In this work, the PCE of bulk heterojunction (BHJ) polymer solar cells was improved by Au nanoparticles (NPs). The Au NPs were embedded into PEDOT:PSS hole transport layer by spin coating on the ITO substrates. The Au NPs with a diameter of ~16 nm were prepared by the micellar method using polystyrene-block-poly (2-vinylpyridine) diblock polymer. The Au NPs prepared by this method are distributed uniformly in size and without agglomeration on the substrates. From both experimental and theoretical results, it can be seen that the light absorption of the active layer was increased because of the surface plasmonic effect of Au NPs. Meanwhile, the carrier transport performance of PEDOT:PSS was enhanced with introduced Au NPs. As a result, the PCE of BHJ solar cells was improved from 2.81 to 3.25% by incorporating Au NPs.

The precipitation of calcium carbonate induced by Sporosarcina pasteurii (S. pasteurii) has garnered considerable attention as a novel rock and soil reinforcement technique. The content and structure of calcium carbonate produced through this reaction play a crucial role in determining the rocks’ and soil’s reinforcement effects in the later stages. Different potential gradients were introduced during the bacterial culture process to enhance the performance of the cementation and mineralization reactions of the bacterial solution to investigate the effects of electrification on the physical and chemical characteristics, such as the growth and reproduction of S. pasteurii. The results demonstrate that the concentration, activity, and number of viable bacteria of S. pasteurii were substantially enhanced under an electric field, particularly the weak electric field generated by 0.5 V/cm. The increased number of bacteria provides more nucleation sites for calcium carbonate deposition. Moreover, as the urease activity increased, the calcium carbonate content generated under an electric potential gradient of 0.5 V/cm surpassed that of other potential gradient groups. The growth rate increased by 9.78% compared to the calcium carbonate induced without electrification. Significantly, the suitable electric field enhances the crystal morphology of calcium carbonate and augments its quantity, thereby offering a novel approach for utilizing MICP in enhancing soil strength, controlling water pollution, and mitigating seepage. These findings elevate the applicability of microbial mineralization in engineering practices.

The BiFeO3/YBCO heterostructures were fabricated on (001)-oriented SrTiO3 substrates by pulsed laser deposition. The superconducting transition temperature of YBCO was found to decline with increasing the c-axis parameter. The microstructure and dislocations in BiFeO3/YBCO heterostructure were detected by transmission electron microscopy (TEM) proving the epitaxial growth of BiFeO3/YBCO heterostructures on SrTiO3. The edge dislocation with a Burgers vector [100] was observed in BiFeO3, which contributed to the relaxation of BiFeO3. The results of magnetization hysteresis cycles indicated that the saturation magnetization increased from 14 emu/cm3 of BiFeO3/SrTiO3 to 42 emu/cm3 of BiFeO3/YBCO/SrTiO3. The second phase Fe2O3 on the surface of BiFeO3 was found to be α-Fe2O3 with weak magnetization at room temperature. Therefore, the increased magnetization could be accounted for by the induced ferromagnetism at the interface of BiFeO3/YBCO.

Quasi-two-dimensional (quasi-2D) perovskites are efficient luminescent materials due to their self-assembled quantum-well structure. We found that the organic cations have a significant effect on the structure and performance of quasi-2D perovskite-based light-emitting diodes (LEDs). Two classic organic cations, formamidinium (FA) and methylammonium (MA), were chosen for investigation. The MA-based quasi-2D perovskite has the largest band-gap n = 1 phase and a photoluminescence quantum yield (PLQY) as high as 85.3%, whereas this n = 1 phase is almost absent in the FA-based quasi-2D perovskite, which shows a moderate PLQY of 73.5%. However, the FA-based perovskite shows a much higher external quantum efficiency (15.4%) than the MA-based perovskite (0.93%) in LEDs. The lower electroluminescence efficiency of the MA-based perovskite could be ascribed to the poor hole injection. These results showed the importance of rational design of the quasi-2D perovskite for efficient LEDs.

To investigate the effect of thickness on the structural and optical properties of niobium-doped beta gallium oxide ( β -Ga 2 O 3 :Nb) thin films, a series of β -Ga 2 O 3 :Nb thin films with different thicknesses were prepared by radio-frequency magnetron method. The crystalline quality is highly improved when the film thickness exceeds 145 nm. The surface exhibits different morphologies under different film thicknesses. The average transmittance of all the films are over 80% in visible range, and that the ultraviolet absorption edge shifts to longer wavelength indicates the bandgap shrinks with increasing the film thickness. Moreover, the photoluminescence spectrum measurements indicate that fewer defects were formed when the film thickness is around 145 nm.

Hall-effect in semiconductors has wide applications for magnetic field sensing. Yet, a standard Hall sensor retains two problems: its linearity is affected by the non-uniformity of the current distribution; the sensitivity is bias-dependent, with linearity decreasing with increasing bias current. In order to improve the performance, we here propose a novel structure which realizes bias-free, photo-induced Hall sensors. The system consists of a semi-transparent metal Pt and a semiconductor Si or GaAs to form a Schottky contact. We systematically compared the photo-induced Schottky behaviors and Hall effects without net current flowing, depending on various magnetic fields, light intensities and wavelengths of Pt/GaAs and Pt/Si junctions. The electrical characteristics of the Schottky photo-diodes were fitted to obtain the barrier height as a function of light intensity. We show that the open-circuit Hall voltage of Pt/GaAs junction is orders of magnitude lower than that of Pt/Si, and the barrier height of GaAs is smaller. It should be attributed to the surface states in GaAs which block the carrier drifting. This work not only realizes the physical investigations of photo-induced Hall effects in Pt/GaAs and Pt/Si Schottky junctions, but also opens a new pathway for bias-free magnetic sensing with high linearity and sensitivity comparing to commercial Hall-sensors.

Spintronics and molecular chemistry have achieved remarkable achievements separately. Their combination can apply the superiority of molecular diversity to intervene or manipulate the spin-related properties. It inevitably brings in a new type of functional devices with a molecular interface, which has become an emerging field in information storage and processing. Normally, spin polarization has to be realized by magnetic materials as manipulated by magnetic fields. Recently, chiral-induced spin selectivity (CISS) was discovered surprisingly that non-magnetic chiral molecules can generate spin polarization through their structural chirality. Here, the recent progress of integrating the strengths of molecular chemistry and spintronics is reviewed by introducing the experimental results, theoretical models, and device performances of the CISS effect. Compared to normal ferromagnetic metals, CISS originating from a chiral structure has great advantages of high spin polarization, excellent interface, simple preparation process, and low cost. It has the potential to obtain high efficiency of spin injection into metals and semiconductors, getting rid of magnetic fields and ferromagnetic electrodes. The physical mechanisms, unique advantages, and device performances of CISS are sequentially clarified, revealing important issues to current scientific research and industrial applications. This mini-review points out a key technology of information storage for future spintronic devices without magnetic components.

Topological Weyl semimetals have attracted considerable interest because they manifest underlying physics and device potential in spintronics. Large anomalous Hall effect (AHE) in non-collinear antiferromagnets (AFMs) represents a striking Weyl phase, which is associated with Bloch-band topological features. In this work, we report robust AHE and Lifshitz transition in high-quality Weyl semimetal Mn3Ge thin film, comprising stacked Kagome lattice and chiral antiferromagnetism. We successfully achieved giant AHE in our Mn3Ge film, with a strong Berry curvature enhanced by the Weyl phase. The enormous coercive field HC in our AHE curve at 5 K reached an unprecedented 5.3 T among hexagonal Mn3X systems. Our results provide direct experimental evidence of an electronic topological transition in the chiral AFMs. The temperature was demonstrated to play an efficient role in tuning the carrier concentration, which could be quantitatively determined by the two-band model. The electronic band structure crosses the Fermi energy level and leads to the reversal of carrier type around 50 K. The results not only offer new functionality for effectively modulating the Fermi level location in topological Weyl semimetals but also present a promising route of manipulating the carrier concentration in antiferromagnetic spintronic devices.

Herein, a quantum dot random laser was achieved using a silicon nanowire array. The silicon nanowire array was grown by a metal-assisted chemical etching method. A colloidal quantum dot solution was spin-coated on silicon nanowires to form the random laser. The performance of the random laser was controlled by the resistivity of silicon wafers and the length of silicon nanowires. A transition from incoherent random lasing to coherent random lasing was obtained by increasing the resistivity of the silicon wafers. The random lasing threshold increased with an increase in the length of the silicon nanowires. These results may be useful to explore high-performance silicon-based random lasers.

A compound cavity was proposed to achieve both whispering gallery mode (WGM) lasing and random lasing. The WGM-random compound cavity consisted of a random structure with an annular boundary, which was fabricated by a method combining both inkjet printing and metal-assisted chemical etching methods. An ultrathin polymer membrane was attached to the WGM-random compound cavity, forming a polymer laser device. A transformation from WGM lasing to random lasing was observed under optical pumping conditions. The laser performance could be easily tailored by changing the parameter of the WGM-random compound cavity. These results provide a new avenue for the design of integrated light sources for sensing applications.

p-Si/n-β-Ga2O3:Nb heterojunctions were fabricated by RF magnetron sputtering of β-Ga2O3:Nb layers on the p-Si substrates. The effects of annealing and Nb doping on the properties of heterojunctions were studied. The crystallinity of the β-Ga2O3:Nb film was enhanced by annealing, which also improved the electrical properties of the heterojunctions. The Nb doping greatly affected the I–V characteristics of annealed heterojunctions. The ideality factor was calculated by performing plots from the forward bias I–V characteristics. The charge transport properties of the heterojunction were discussed. The activation energy of β-Ga2O3:Nb films were estimated based on the temperature dependence of resistance.

The Nb-doped β-Ga2O3 (β-Ga2O3:Nb) thin films have been deposited on the p-Si and Au nanoparticles decorated p-Si substrates by radio frequency magnetron technique in argon ambient. All the annealed β-Ga2O3:Nb films are composed of similar crystallite sizes obtained by XRD and SEM measurements. The β-Ga2O3:Nb thin film grown on the Au nanoparticles decorated substrate shows lower transmittance and narrower band gap compared to that of grown on p-Si reference substrate. Photoluminescence intensity was quenched because of the short separation distance between semiconductor and the Au nanoparticles. The current density was enhanced and the barrier height of the β-Ga2O3:Nb/p-Si heterojunction was reduced by inserting Au nanoparticles in the interface of β-Ga2O3:Nb/p-Si heterojunction.

The growth of trace amount of niobium (Nb) doped β -Ga 2 O 3 thin films have been demonstrated on (0001) sapphire substrates by radio frequency magnetron co-sputtering method. The crystallization, morphology and optical properties of Nb doped β -Ga 2 O 3 films have been investigated. The deep ultraviolet (DUV) photodetector with a metal–semiconductor–metal structure based on trace amount of Nb doped β -Ga 2 O 3 thin film was fabricated. The DUV photodetector exhibits high photo-to-dark-current ratio and fast photo-response speed, suggesting the performance of β -Ga 2 O 3 photodetector can be improved by doping trace amount of Nb in β -Ga 2 O 3 thin film.

Lateral effect photodiodes sense the position of a laser beam by measuring the change of current between opposite anodes and a common cathode. They either require a bias current or the current is photogenerated. In either case, their linearity is affected by the non-uniformity of the current distribution between the anodes. We here propose a bias-free, lateral photo-diode, which consists of a resistive layer forming an extended Schottky contact to an intrinsic semiconductor. In our sensor, the photo-generated carriers do not diffuse laterally. Rather, their localization under the laser-beam results in a reduction of the barrier height due to image force effect. An open-circuit voltage appears between two opposite electrodes that is linear with the laser-beam position. A tetra-lateral configuration, with four anodes at the edges of a square-shaped sensor, allows sensing in two dimensions.

The intrinsic and Nb-doped β-Ga2O3 (β-Ga2O3:Nb) thin films have been deposited on the Si and quartz substrates by radio frequency magnetron technique in argon ambient. The effects of Nb doping on the structural and optical properties of Ga2O3:Nb thin films have been investigated. After Nb-doping, the crystal lattice, surface morphology, optical transmittance and optical energy gap of the β-Ga2O3 films are greatly changed. The crystal lattice of the β-Ga2O3:Nb films is augmented, the energy gap shrinks and the crystalline quality is improved. XPS spectra shows that niobium is incorporated into the oxide matrix and present in the β-Ga2O3 as Nb(Ⅳ).

Monoclinic β phase Ga2O3 has been considered as a promising candidate for next generation radio frequency and high-power devices because of its ultrawide bandgap and high breakdown field. The development of epitaxial growth techniques and the synthesis of high quality β-Ga2O3 thin films are crucial for the device applications. In this work, the heteroepitaxial β-Ga2O3 thin films were grown on sapphire (0001) substrates by low pressure chemical vapor deposition. The influence of growth parameters such as the source/substrate temperatures, the oxygen/Ar gas flow rates, and the surface morphology of substrate on the resultant crystallinity and surface roughness of the β-Ga2O3 films were investigated. The β-Ga2O3 heteroepitaxial layer on sapphire exhibits an RMS roughness of 1.82 nm, an XRD rocking curve of 1.18°, and a growth rate of 0.72 μm/h. The β-Ga2O3 film grown on the buffer layer exhibit a smoother surface, whereas the chemical etching and annealing lead to an improved crystallinity and a rough surface. However, there is a trade-off between the crystallization and the surface roughness.

Rubrene thin film was deposited by thermal evaporation technique under high vacuum (∼10−4 Pa). The film surface morphology was characterized by atomic force microscopy (AFM). Ellipsometric studies on rubrene thin film were presented for understanding its growth and optical characteristics by the Classical-Oscillator model. The analysis of the absorption coefficient (α) revealed the direct allowed transition with corresponding energy 2.21 eV of the rubrene film. In order to exploring the rubrene applications, Al/rubrene/ITO Schottky diode was fabricated. The basic device parameters, barrier height and ideality factor were determined by the I–V measurement. The log(I)–log(V) characteristic indicated three distinct regions. These regions followed ohmic conduction, TCL conduction and SCLC conduction mechanisms.

CH3NH3PbI3 thin film was deposited by a dual-source evaporation system under high vacuum (∼10−4 Pa). The crystallographic phase was analyzed by X-ray diffraction and confirmed as the perovskite structure. The optical properties of the thin film have been investigated in the spectral range 300-1800 nm. The analysis of the absorption coefficient () reveals direct allowed transition with corresponding energy 1.58 eV. The surface morphology of the film was characterized by atomic force microscopy (AFM). The observed features exhibited by CH3NH3PbI3 give a vital chance to explore its application for various optoelectronic devices. To see its other potential utility, Al/CH3NH3PbI3 /ITO Schottky diodes were fabricated. Based on the analyzing the I-V measurement for the Al/CH3NH3PbI3/ ITO device, the basic device parameters such as barrier height and ideality factor were determined. At the low-voltage region, the current conduction in the device is ohmic type. The charge transport phenomenon appears to be space charge limited current (SCLC) at higher-voltage regions.