Nonlinear Optical Properties of Al-Doped nc-Si-SiO_2 Composite Films

The nonlinear optical properties of Al-doped nc-Si-SiO2 composite films have been investigated using the time-resolved four-wave mixing technique with a femtosecond laser. The off-resonant third-order nonlinear susceptibility is observed to be 1.0 × 10-10 esu at 800nm. The relaxation time of the optical nonlinearity in the films is as short as 60fs. The optical nonlinearity is enhanced due to the quantum confinement of electrons in Si nanocrystals embedded in the SiO2 films. The enhanced optical nonlinearity does not originate from Al dopant because there are no Al clusters in the films.

Heteroepitaxial Growth and Characterization of 3C-SiC Films on Si Substrates Using LPVCVD

3C-SiC films have been deposited on Si （111） substrates by the low-pressure vertical chemical vapor deposition （LPVCVD） with gas mixtures of SiH4, Calls and H2. The growth mechanism of SiC films can be obtained through the observations using field emission scanning electron microscope （FESEM）. It is found that the growth process varies from surface control to diffusion control when the deposition temperature increases from 1270 to 1350℃. The X-ray diffraction （XRD） patterns show that the SiC films have good crystallinity and strong preferred orientation.The results of the high resolution transmission electron microscopy （HRTEM） image and the transmission electron diffraction （TED） pattern indicate a peculiar superlattice structure of the film. The values of the binding energy in the high resolution X-ray photoelectron spectra （XPS） further confirm the formation of SiC.

The influence of SiNx substrate on crystallinity of μc-Si film used in thin film transistors

This paper found that the crystalline volume ratio （Xc） of μc-Si deposited on SiNx substrate is higher than that on 7059 glass. At the same silane concentration （SC） （for example, at SC=2%）, the Xc of μc-Si deposited on SiNx is more than 64%, but just 44% if deposited on Conning 7059. It considered that the ‘hills＇ on SiNx substrate would promote the crystalline growth of μc-Si thin film, which has been confirmed by atomic force microscope （AFM） observation. Comparing several thin film transistor （TFT） samples whose active-layer were deposited under various SC, this paper found that the appropriate SC for the μc-Si thin film used in TFT as active layer should be more than 2%, and Xc should be around 50%. Additionally, the stability comparison of μc-Si TFT and a-Si TFT is shown in this paper.

Structural Un-uniformity and Electrical Anisotropy of μc-Si:H Films

Structural un-uniformity and electrical anisotropy of μc-Si∶H film are investigated in this paper. It is found that the structure of μc-Si∶H film along the direction perpendicular to the substrate is not uniform, which is modulated by film thickness. In addition, there is a dark conductivity anisotropy along the direction parallel(σ∥) and perpendicular(σ⊥)to the substrate in μc-Si∶H film. The reasons for such an property of μc-Si∶H film and the effect of oxygen contamination are analyzed.

Photoluminescence Properties of Nanocrystalline 3C-SiC Films

Nanocrystalline （nc） 3C-SiC films on the Si substrate were prepared by the helicon wave plasma enhanced chemical vapor deposition （HW-PECVD） technique. With the SiH4-CH4 gas flow ratio changing, the films exhibit different photoluminescence （PL） characteristics. Under the stoichiometric condition, the PL peak redshift from 470 nm to 515 nm is detected with the increase of excitation wavelength, which can be attributed to the quantum confinement effect radiation of 3C-SiC nanocrystals of different sizes. However, the appearance of an additional PL band at 436 nm in Si-rich film might be sourced back to the excess of Si defect centers in it. This is also the case for C-rich film for its PL band lying at 570 nm. The results above quoted indicate an important influence of gas flow ratio on the PL properties of the SiC films providing an effective guidance for analyzing the luminescence mechanism and exploring the high-efficiency light emission of the SiC films.

Significantly Improved High-Temperature Energy Storage Performance of BOPP Films by Coating Nanoscale Inorganic Layer

Biaxially oriented polypropylene(BOPP)is one of the most commonly used commercial capacitor films,but its upper operating temperature is below 105℃due to the sharply increased electrical conduction loss at high temperature.In this study,growing an inorganic nanoscale coating layer onto the BOPP film's surface is proposed to suppress electrical conduction loss at high temperature,as well as increase its upper operating temperature.Four kinds of inorganic coating layers that have different energy band structure and dielectric property are grown onto the both surface of BOPP films,respectively.The effect of inorganic coating layer on the high-temperature energy storage performance has been systematically investigated.The favorable coating layer materials and appropriate thickness enable the BOPP films to have a significant improvement in high-temperature energy storage performance.Specifically,when the aluminum nitride(AIN)acts as a coating layer,the AIN-BOPP-AIN sandwich-structured films possess a discharged energy density of 1.5 J cm^(-3)with an efficiency of 90%at 125℃,accompanying an outstandingly cyclic property.Both the discharged energy density and operation temperature are significantly enhanced,indicating that this efficient and facile method provides an important reference to improve the high-temperature energy storage performance of polymer-based dielectric films.

n-nc-Si:H低温制备工艺及其在柔性钙钛矿太阳电池中的应用

【目的】为在低温工艺下制备出适用于柔性钙钛矿太阳电池的高性能电子传输层,需要对电子传输层材料及制备条件进行研究。【方法】将n型氢化纳米晶硅薄膜作为柔性钙钛矿太阳电池电子传输层,研究衬底温度对薄膜性能的影响,并优化电子传输层与钙钛矿层界面处理工艺和结构。【结果】得到暗电导率、光透过率、表面形貌适用于柔性钙钛矿太阳电池电子传输层的n型氢化纳米晶硅薄膜低温制备条件,经过界面优化处理的柔性钙钛矿太阳电池转换效率达到14.66%。【结论】在低温工艺下制备出了高性能的电子传输层及柔性钙钛矿太阳电池,对进一步开展叠层钙钛矿太阳电池的研究具有指导意义。

Influence of substrate temperature on the deposition and structural properties of μc-Si:H thin films fabricated with VHF-PECVD

With in situ optical emission spectroscopy （OES） diagnosis on VHF-generated H2 ＋ SiH4 plasmas,and with the measurements of deposition rate and structure of μc-Si. H thin films fabricated with VHFPECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si.H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature,the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for μc-Si：H thin films deposition under our current growth system is about 210 ℃ ,at which deposition rate O. 8 nm/s of pc-Si;H thin film with Xc-60% and d-9 nm can be obtained.

Flexible, Transparent and Conductive Metal Mesh Films with Ultra‑High FoM for Stretchable Heating and Electromagnetic Interference Shielding

Despite the growing demand for transparent conductive films in smart and wearable electronics for electromagnetic interference(EMI)shielding,achieving a flexible EMI shielding film,while maintaining a high transmittance remains a significant challenge.Herein,a flexible,transparent,and conductive copper(Cu)metal mesh film for EMI shielding is fabricated by self-forming crackle template method and electroplating technique.The Cu mesh film shows an ultra-low sheet resistance(0.18Ω□^(-1)),high transmittance(85.8%@550 nm),and ultra-high figure of merit(>13,000).It also has satisfactory stretchability and mechanical stability,with a resistance increases of only 1.3%after 1,000 bending cycles.As a stretchable heater(ε>30%),the saturation temperature of the film can reach over 110°C within 60 s at 1.00 V applied voltage.Moreover,the metal mesh film exhibits outstanding average EMI shielding effectiveness of 40.4 dB in the X-band at the thickness of 2.5μm.As a demonstration,it is used as a transparent window for shielding the wireless communication electromagnetic waves.Therefore,the flexible and transparent conductive Cu mesh film proposed in this work provides a promising candidate for the next-generation EMI shielding applications.

Suppression of Co(Ⅱ)ion deposition and hazards:Regulation of SEI film composition and structure

Despite the presence of Li F components in the solid electrolyte interphase(SEI)formed on the graphite anode surface by conventional electrolyte,these Li F components primarily exist in an amorphous state,rendering them incapable of effectively inhibiting the exchange reaction between lithium ions and transition metal ions in the electrolyte.Consequently,nearly all lithium ions within the SEI film are replaced by transition metal ions,resulting in an increase in interphacial impedance and a decrease in stability.Herein,we demonstrate that the SEI film,constructed by fluoroethylene carbonate(FEC)additive rich in crystalline Li F,effectively inhibits the undesired Li^(+)/Co^(2+)ion exchange reaction,thereby suppressing the deposition of cobalt compounds and metallic cobalt.Furthermore,the deposited cobalt compounds exhibit enhanced structural stability and reduced catalytic activity with minimal impact on the interphacial stability of the graphite anode.Our findings reveal the crucial influence of SEI film composition and structure on the deposition and hazards associated with transition metal ions,providing valuable guidance for designing next-generation electrolytes.

OptoGPT: A foundation model for inverse design in optical multilayer thin film structures

Optical multilayer thin film structures have been widely used in numerous photonic applications.However,existing inverse design methods have many drawbacks because they either fail to quickly adapt to different design targets,or are difficult to suit for different types of structures,e.g.,designing for different materials at each layer.These methods also cannot accommodate versatile design situations under different angles and polarizations.In addition,how to benefit practical fabrications and manufacturing has not been extensively considered yet.In this work,we introduce OptoGPT(Opto Generative Pretrained Transformer),a decoder-only transformer,to solve all these drawbacks and issues simultaneously.

Numerical and experimental study on the falling film flow characteristics with the effect of co-current gas flow in hydrogen liquefaction process

Liquid hydrogen storage and transportation is an effective method for large-scale transportation and utilization of hydrogen energy. Revealing the flow mechanism of cryogenic working fluid is the key to optimize heat exchanger structure and hydrogen liquefaction process(LH2). The methods of cryogenic visualization experiment, theoretical analysis and numerical simulation are conducted to study the falling film flow characteristics with the effect of co-current gas flow in LH2spiral wound heat exchanger.The results show that the flow rate of mixed refrigerant has a great influence on liquid film spreading process, falling film flow pattern and heat transfer performance. The liquid film of LH2mixed refrigerant with column flow pattern can not uniformly and completely cover the tube wall surface. As liquid flow rate increases, the falling film flow pattern evolves into sheet-column flow and sheet flow, and liquid film completely covers the surface of tube wall. With the increase of shear effect of gas-phase mixed refrigerant in the same direction, the liquid film gradually becomes unstable, and the flow pattern eventually evolves into a mist flow.

Highly Flexible Graphene-Film-Based Rectenna for Wireless Energy Harvesting

Herein,we report the design,fabrication,and performance of two wireless energy harvesting devices based on highly flexible graphene macroscopic films(FGMFs).We first demonstrate that benefiting from the high conductivity of up to 1×10^(6)S m^(-1)and good resistive stability of FGMFs even under extensive bending,the FGMFs-based rectifying circuit(GRC)exhibits good flexibility and RF-to-DC efficiency of 53%at 2.1 GHz.Moreover,we further expand the application of FGMFs to a flexible wideband monopole rectenna and a 2.45 GHz wearable rectenna for harvesting wireless energy.The wideband rectenna at various bending conditions produces a maximum conversion efficiency of 52%,46%,and 44%at the 5th Generation(5G)2.1 GHz,Industrial Long-Term Evolution(LTE)2.3 GHz,and Scientific Medical(ISM)2.45 GHz,respectively.A 2.45 GHz GRC is optimized and integrated with an AMC-backed wearable antenna.The proposed 2.45 GHz wearable rectenna shows a maximum conversion efficiency of 55.7%.All the results indicate that the highly flexible graphene-film-based rectennas have great potential as a wireless power supplier for smart Internet of Things(loT)applications.

Instability of nc-Si: H Films Fabricated by PECVD

An analysis is given to explain the instability of the high conductivity property of nc-Si:H fabricated. Detailed discussion is carried out concentrating on the conductivity and growth mechanism. It is assumed that the instability of the conductivity of the nc-Si:H stems from two part: the phase transition from nanocrystallites into a-Si:H, and the oxygen incorporation of the thin layer of the film, which contributes more to the effect when the film suffers the exposure to air. The theory is in agreement with the experiment and measurement.

Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective devices.Self-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin films.However,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection performance.Here it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent repeatability.No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film.In addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”X-rays.Finally,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.

Multifunctional MXene/Carbon Nanotube Janus Film for Electromagnetic Shielding and Infrared Shielding/Detection in Harsh Environments

Multifunctional,flexible,and robust thin films capable of operating in demanding harsh temperature environments are crucial for various cutting-edge applications.This study presents a multifunctional Janus film integrating highly-crystalline Ti_(3)C_(2)T_(x) MXene and mechanically-robust carbon nanotube(CNT)film through strong hydrogen bonding.The hybrid film not only exhibits high electrical conductivity(4250 S cm^(-1)),but also demonstrates robust mechanical strength and durability in both extremely low and high temperature environments,showing exceptional resistance to thermal shock.This hybrid Janus film of 15μm thickness reveals remarkable multifunctionality,including efficient electromagnetic shielding effectiveness of 72 dB in X band frequency range,excellent infrared(IR)shielding capability with an average emissivity of 0.09(a minimal value of 0.02),superior thermal camouflage performance over a wide temperature range(−1 to 300℃)achieving a notable reduction in the radiated temperature by 243℃ against a background temperature of 300℃,and outstanding IR detection capability characterized by a 44%increase in resistance when exposed to 250 W IR radiation.This multifunctional MXene/CNT Janus film offers a feasible solution for electromagnetic shielding and IR shielding/detection under challenging conditions.

Analysis on Conductivity of nc-Si: H Films

A conduction channel model is proposed to explain the high conductivity property of nc-Si: H. Detailed energy band diagram is developed based on the analysis and calculation, and the conductivity of the nc-Si: H was then analysed on the basis of energy band theory. It is assumed that the conductivity of the nc-Si: H stems from two parts: the conductance of the interface, where the transport mechanism is identified as a thermal-assisted tunnelling process, and the conductance along the channel around the grain, which mainly determined the high conductivity of the nc -Si: H. The conductivity of nc - Si: H is calculated and compared with the experiment data. The theory is in agreement with the experiment.

Author Correction to “Enhanced Property of Thin Cuprous Oxide Film Prepared through Green Synthetic Route”

This correction adds some information to our publication[Chin.J.Chem.Phys.32,365–372(2019)]that we previously missed to include.Our previous work published in[Appl.Catal.B Env-iron.186,10(2016)]was based on the same sample series but with the focus of explaining the interplay between the catalytic behavior and properties of the cuprous thin films.A superior catalytic performance was demonstrated when water was added in the deposition process[1](see Ref.[47]in our publication corrected here).

Centimeter-Scale Above-Room-Temperature Ferromagnetic Fe_(3)GaTe_(2)Thin Films by Molecular Beam Epitaxy

Fe_(3)GaTe_(2),as a layered ferromagnetic material,has a Curie temperature(T_(c))higher than room temperature,making it the key material in next-generation spintronic devices.To be used in practical devices,large-sized high-quality Fe_(3)GaTe_(2)thin films need to be prepared.Here,the centimeter-scale thin film samples with high crystal quality and above-room-temperature ferromagnetism with strong perpendicular magnetic anisotropy were prepared by molecular beam epitaxy technology.Furthermore,the Tc of the samples raises as the film thickness increases,and reaches 367K when the film thickness is 60 nm.This study provides material foundations for the new generation of van der Waals spintronic devices and paves the way for the commercial application of Fe_(3)GaTe_(2).

Ultrathin Limit on the Anisotropic Superconductivity of Single-Layered Cuprate Films

Exploring dimensionality effects on cuprates is important for understanding the nature of high-temperature superconductivity.By atomically layer-by-layer growth with oxide molecular beam epitaxy,we demonstrate that La_(2−x)Sr_(x)CuO_(4)(x=0.15)thin films remain superconducting down to 2 unit cells of thickness but quickly reach the maximum superconducting transition temperature at and above 4 unit cells.By fitting the critical magnetic field(μ0H_(c2)),we show that the anisotropy of the film’s superconductivity increases with decreasing film thickness,indicating that the superconductivity of the film gradually evolves from weak three-to two-dimensional character.These results are helpful to gain more insight into the nature of high-temperature superconductivity with dimensionality.