2022

• Record 325 of
  
  Title:Picosecond Pulsed Laser Deposition Technique to Fabricate Zinc-Oxide Thin Films Through Burst Mode
  
  Author(s):Wu, Enli(1,2); Dai, Shoujun(1,2,3); Xuan, Xinxiang(4); He, Jianguo(1,2,3); Liu, Yang(1,2,3); Tan, Yu(5); Mo, Zeqiang(1,2,3); Yu, Jin(1,2)
  Source: Zhongguo Jiguang/Chinese Journal of Lasers  Volume: 49  Issue: 6  DOI: 10.3788/CJL202249.0603003  Published: March 25, 2022  
  Abstract:Objective Pulsed laser deposition (PLD) is a technique, for removing material from the surface of a target that uses laser energy pulses. It has several advantages over other depositions methods, including high particle energy to form film, fast deposition rate, and no restriction on the target materials. PLD technology has advanced rapidly in recent years, and it is now widely used in the production of metals, ceramics, transparent electrodes, and high-temperature superconducting films. For traditional PLD technology, nanosecond single-pulse lasers are commonly used as excitation sources. One disadvantage of using nanosecond pulsed laser is the possibility of selective ablation, which could result in a lack of stoichiometry during the process. This is a critical challenge that nanosecond PLD (ns-PLD) technologies for scientific research and industrial applications. With the increasing availability of commercial ultrashort laser sources, in recent years, and its distinct advantage of efficient laser ablation, the ultrashort pulse PLD is gaining popularity as a method for producing thin films. Ultrashort pulse PLD demonstrates its potential capacity to control the emission of droplets due to the diverse ablation mechanisms, even though it may not be the ultimate solution in smooth film deposition. Furthermore, the pulse sequence presented in this article has the potential to change the laser-matter interaction, which can be used to improve the deposit' s surface quality and optical properties. Methods A method for pulsed deposition of picosecond laser based on different pulse burst modes is presented, consisting of four main components: seed oscillator, pulse selector, laser amplifier, and power controller (Fig. 1). The laser burst mode is set from 1 to 4 (Fig. 2) with a 532 nm output wavelength, 100 kHz laser frequency, 33.3 ns intrapulse interval, and 10 ;is interpulse string interval. Zinc oxide (ZnO) transparent conductive thin films are deposited on glass substrates and single-crystal silicon substrates via the proposed method. The effect of different pulse burst modes on the crystal structure, surface morphology, and optical properties of the ZnO film is studied thoroughly using spectroscopic ellipsometry, atomic force microscopy, X-ray diffractometry, ultraviolet-visible spectrophotometry, and scanning electron microscopy. Results and Discussions We obtain film thickness (Fig. 3), refractive index, and extinction coefficient data (Table 1) created for various burst modes (from 1 to 4) and discover that the deposition rate decreases and are accompanied by an increase in refractive index as the number of burst modes increases. To begin, the intrapulse period in multipulse mode is set to 33.3 ns and the average plasma velocity is around 104 cm/s. Therefore, using a burst mode of 4, the plasma in the multipulse mode is not completely disengaged from the target when the last pulse is incident, resulting in laser-plasma contact and partial absorption of the pulsed laser energy by the plasma, and limiting target material extraction. Furthermore, the energy distribution of laser pulses is related to the fact that the first pulse energy gradually decreases as the multipulse burst mode increases in size, reducing the first energy interaction between the laser and the target. The roughness diminishes as the multipulse burst mode is increased (Fig. 4). As the laser-plasma interaction is strengthen, the plasma's kinetic energy increases, resulting in longer plasma lifetimes, longer diffusion durations on the substrate, and eventually favoring the orderly formation of thin films. In the single-pulse mode of laser deposition, large particles and droplets are present; however, the laser-plasma interaction in the multipulse mode can further heat up and break down the large particles in the plasma, resulting in fewer large particles on the film surface and smoother, denser films (Figs. 5 and 6). The crystal structure of the prepared films is examined using XRD (Fig. 7) and the crystal structure data for different pulse burst modes (from 1 to 4) are compared, as shown in Table 1, and it is discovered that the different pulse burst mode does not affect the crystal structure. However, when the pulse burst mode is 4, it has some subtle effects on the crystal size, diffraction peak angle, and film intensity, with larger crystal size and better film quality. The transmittance curves of the films deposited in various pulse burst modes are determined (Fig. 8), In the visible range (380-800 nm), the average transmittances of the films are 90. 31%, 92. 72%, 93. 98%, and 94. 81%, respectively. The optical band gaps (Fig.9) are 3.317, 3.343, 3.362, and 3.427 eV, which are comparable to the normal ZnO bandgap (3.3 eV), which corresponds to the tendency of the central wavelength of the absorption edge in the transmittance curve to move in the direction of short wave. Finally, we calculate resistivity curves for the deposited films under various pulse burst modes (Fig. 10) and discover that the film resistivity is lowest when the pulse burst mode is 4. Conclusions The high-quality ZnO films are deposited on glass and silicon substrates using a laser deposition process in different burst modes, with the number of subpulses in each burst increasing from 1 to 4. The effects of different burst modes of picosecond lasers on the film thickness, roughness, surface topography, crystal structure, optical properties, and electrical properties of ZnO films are investigated. When the pulse burst mode is set to 4, the film surface has less roughness, smaller particle size, higher transmittance, better crystalline quality, and lower resistivity when compared with other burst modes. This is extremely important for relevant optical applications to the production of ZnO thin film. © 2022 Science Press. All rights reserved.
  Accession Number: 20224513088976
• Record 326 of
  
  Title:Design and Optimization of Image Slicer in Coherent Dispersive Spectrometer
  
  Author(s):Wang, Yidong(1,2); Wei, Ruyi(1,2,3,4); Xie, Zhengmao(1); Zhang, Kai(5); Chen, Shasha(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 51  Issue: 9  DOI: 10.3788/gzxb20225109.0922002  Published: September 2022  
  Abstract:Image slicer is an important optical device in astronomical observation spectrometer. It can effectively improve the resolution and energy transmittance of the instrument. The image slicer can divide the circular image spot into strips and arrange the strips in a straight line， so that all the image spots can pass through the spectrometer slit. Image slicers are commonly used in astronomical observation spectrometers to help instruments achieve high spectral resolution with medium apertures. Image slicers can be divided into 4 categories according to their working principles. Among them， Bowen-Walraven type is the most widely used image slicer type. Coherent dispersive spectroscopy is a technique that combines an interferometer and an intermediate resolution spectrometer. It measures the phase change of the interference fringes of the stellar spectral lines after the Doppler frequency shift， and calculates the radial velocity change of the star and the mass of the planet. Since the phase difference has a certain amplification factor relative to the wavelength offset， when the spectral resolution is the same， the radial velocity detection accuracy of the coherent dispersion technique can be greatly improved compared with the traditional echelle grating method.This paper is based on the coherent dispersive spectrometer used to detect exoplanets by the radial velocity method. The radial velocity detection accuracy is expected to be less than 1 m/s， and the detection target is K/M dwarf stars. The structure of the coherent dispersion spectrometer consists of collimating mirror， Sagnac interferometer， imaging mirror group， image slicer， relay mirror group， slit， dispersion grating and CCD. The working spectral range of the spectrometer is 660~900 nm， the system transmittance at the center wavelength is about 0.4， and the spectral resolution is 0.03 nm. In order to meet the requirements of energy utilization and spectral resolution， the system needs to use the image slicer to realize the target surface multiplexing of the CCD and the reasonable matching of the numerical aperture. Therefore， setting a reasonable number of segmented images and the F number of the imaging lens group to achieve a good segmentation effect is of great significance to the improvement of system performance.In order to reduce the influence of imaging defects on the system， two design schemes of the image slicer are modeled and calculated in this paper. This paper also studies the relationship between the thickness of the reflective cavity and the incident angle and the defocusing and object point repetition， and deduces the general design formula of the thickness of the optical reflective cavity， which provides an important reference for the design of the image slicer. In addition， for the coherent dispersive spectrometer system used for exoplanet detection， this paper simulates the defocus and object point repetition under different F numbers and segmentation numbers. By analyzing the simulation results， the following conclusions are obtained： 1） With the increase of the F number and the number of divisions， the defocus amount increases significantly， and the defocus phenomenon becomes more obvious. 2） The phenomenon of object point repetition appears in all simulation results， which is determined by the design principle and cannot be avoided. 3） The design results of the two design schemes are relatively similar. Since the optical path in the Bowen⁃Walraven type design is propagated through the glass medium， the defocus amount is larger than that of the simplified type. The ratio of the diffuse spot diameter to the image spot diameter is the same for both methods. Based on the comprehensive simulation effect， and considering the requirements of the coherent dispersion spectrometer system， it can be considered that the imaging defects are relatively balanced and the energy loss is less when the star image is divided into 4 under the condition of F/24， which is a relatively suitable solution. In addition， since the defocus amount of the simplified type is smaller， and only the flat mirror needs to be processed， the cost is lower， so the simplified design scheme can be adopted.The work of this paper plays an important role in achieving the expected performance of the instrument， and provides a reference and application reference for other high-resolution spectrometers to determine system parameters. At the same time， the work of this paper provides a general design idea for Bowen⁃Walraven and simplified image slicer design， which is instructive for optimizing the design process of image slicer. © 2022 Chinese Optical Society. All rights reserved.
  Accession Number: 20224413024351
• Record 327 of
  
  Title:An end-to-end laser-induced damage change detection approach for optical elements via siamese network and multi-layer perceptrons
  
  Author(s):Kou, Jingwei(1,2); Zhan, Tao(3); Wang, Li(2); Xie, Yu(4); Zhang, Yihui(2); Zhou, Deyun(1); Gong, Maoguo(5)
  Source: Optics Express  Volume: 30  Issue: 13  DOI: 10.1364/OE.460417  Published: June 20, 2022  
  Abstract:With the presence of complex background noise, parasitic light, and dust attachment, it is still a challenging issue to perform high-precision laser-induced damage change detection of optical elements in the captured optical images. For resolving this problem, this paper presents an end-to-end damage change detection model based on siamese network and multi-layer perceptrons (SiamMLP). Firstly, representative features of bi-temporal damage images are efficiently extracted by the cascaded multi-layer perceptron modules in the siamese network. After that, the extracted features are concatenated and then classified into changed and unchanged classes. Due to its concise architecture and strong feature representation ability, the proposed method obtains excellent damage change detection results efficiently and effectively. To address the unbalanced distribution of hard and easy samples, a novel metric called hard metric is introduced in this paper for quantitatively evaluating the classification difficulty degree of the samples. The hard metric assigns a classification difficulty for each individual sample to precisely adjust the loss assigned to the sample. In the training stage, a novel hard loss is presented to train the proposed model. Cooperating with the hard metric, the hard loss can up-weight the loss of hard samples and down-weight the loss of easy samples, which results in a more powerful online hard sample mining ability of the proposed model. The experimental results on two real datasets validate the effectiveness and superiority of the proposed method. © 2022 Optica Publishing Group
  Accession Number: 20222512252426
• Record 328 of
  
  Title:Laser Cavity-Solitons and Turing Patterns Microcombs: the Interaction of Slow and Fast Nonlinearities
  
  Author(s):Pasquazi, Alessia(1); Rowley, Maxwell(1); Hanzard, Pierre Henry(1); Cutrona, Antonio(1); Chu, Sai T.(2); Little, Brent E.(3); Morandotti, Roberto(4,5); Moss, David J.(6); Gongora, Juan Sebastian Totero(1); Peccianti, Marco(1)
  Source: 2022 Conference on Lasers and Electro-Optics, CLEO 2022 - Proceedings  Volume:   Issue:   DOI:   Published: 2022  
  Abstract:Slow nonlinearities are critical in microresonator-based frequency combs, regulating essential phenomena, from stability to soliton starting and formation. We discuss their effect in a microresonator-filtered fiber laser. © Optica Publishing Group 2022, © 2022 The Author(s)
  Accession Number: 20224212987047
• Record 329 of
  
  Title:Versatile, high bandwidth, RF and microwave photonic Hilbert transformers based on Kerr micro-combs
  
  Author(s):Li, Yang(1); Tan, Mengxi(2); Wu, Jiayang(1); Xu, Xingyuan(3); Sun, Yang(1); Boes, Andreas(2); Corcoran, Bill(4); Nguyen, Thach G.(2); Chu, Sai T.(5); Little, Brent E.(6); Morandotti, Roberto(7); Mitchell, Arnan(2); Moss, David J.(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 12004  Issue:   DOI: 10.1117/12.2607903  Published: 2022  
  Abstract:We experimentally demonstrate bandwidth-tunable RF photonic Hilbert transformer based on an integrated Kerr microcomb source. The micro-comb is generated by an integrated micro-ring resonator with a free spectral range of 48.9 GHz, yielding 75 micro-comb lines in the telecom C-band. By programming and shaping the generated comb lines according to calculated tap weights, we demonstrate high-speed Hilbert transform functions with tunable bandwidths ranging from 1.2 GHz to 15.3 GHz, switchable center frequencies from baseband to 9.5 GHz, and arbitrary fractional orders. The experimental results show good agreement with theory and confirm the effectiveness of our approach. © 2022 SPIE.
  Accession Number: 20222312194149
• Record 330 of
  
  Title:Modified active disturbance rejection control scheme with sliding mode compensation for airborne star tracker driven by Permanent Magnet Synchronous Motor
  
  Author(s):Wang, Fan(1,3,5); Cheng, Tianji(1,2,4); Zhu, Hua(1,2,4); Liu, Zhiwen(1,2,4); Han, Chongyang(1,2,4); Wang, Ranjun(1,4); Liu, Enhai(1,4)
  Source: Control Engineering Practice  Volume: 127  Issue:   DOI: 10.1016/j.conengprac.2022.105267  Published: October 2022  
  Abstract:For an airborne star tracker, pointing and switching the target stars with high precision and fast response is necessary for the star observation. However, under airborne circumstances, the control performance of star tracker will be deteriorated by multiple types of disturbance. Therefore, the disturbance suppression is indispensable. In this paper, a high-precision position control scheme for a Permanent Magnet Synchronous Motor (PMSM) driven airborne star tracker is presented based on active disturbance rejection control (ADRC) to overcome the disturbance and improve the robustness of the system. Firstly, to reduce the disturbance estimation error, a modified extended state observer (MESO) with predictive factor is proposed. The stability analysis verifies its feasibility based on input to state stability (ISS) framework and parameter tuning method of MESO via frequency domain analysis is also given. Secondly, aiming at the problem of insufficient disturbance compensation ability of classical ADRC because of the estimation error in control gain and of chattering phenomenon in the conventional sliding mode control, a chattering-reduced sliding mode (SM) component is added to the state error feedback. It is proved that the SM component can make the system reach the sliding surface in limited time via Lyapunov theory and the closed loop stability of the controller can also be ensured. Finally, comparative simulations and experiments are conducted to verify the effectiveness of the proposed control scheme. The simulations show the superiorities of the proposed methods in anti-disturbance capability and robustness. The experimental results testify to the feasibility and better performance of the proposed methods in practical applications of star tracker. © 2022 Elsevier Ltd
  Accession Number: 20223112457238
• Record 331 of
  
  Title:Enhanced Photoluminescence of Monolayer MoSe2 in a Double Resonant Plasmonic Nanocavity with Fano Resonance and Mode Matching
  
  Author(s):Li, Chenyang(1); Wang, Qifa(1); Diao, Hang(1); Hao, Zhen(1); Yu, Weixing(2); Liu, Kaihui(3); Gan, Xuetao(1); Xiao, Fajun(1); Zhao, Jianlin(1)
  Source: Laser and Photonics Reviews  Volume: 16  Issue: 2  DOI: 10.1002/lpor.202100199  Published: February 2022  
  Abstract:Two-dimensional transition metal dichalcogenides exhibit remarkable optical properties. However, their applications in electronics and photonics are severely limited by the intrinsically low absorption and emission rates. Here, the photoluminescence (PL) enhancement by integrating the monolayer MoSe2 into an Ag nanowire-on-mirror (NWoM) nanocavity is reported. From the dark-field scattering spectrum, a Fano resonance resulting from the coupling between discrete exciton state of MoSe2 and broad plasmon mode of nanocavity is observed. This Fano resonance, as a characteristic of intermediate plasmon–exciton coupling, shows remarkable ability to accelerate emission rate of MoSe2. Furthermore, the nanocavity with multiple resonances provides an excellent spatial mode overlap at excitation and emission wavelengths that affords the intriguing opportunity to resonantly enhance the absorption and PL quantum yield at the same location. The combination of Fano resonance and mode matching allows the attainment of over 1800-fold PL enhancement. These results provide a facile way to enhance the PL intensity of monolayer MoSe2 that may facilitate highly efficient optoelectronic devices. © 2021 Wiley-VCH GmbH
  Accession Number: 20215011328383
• Record 332 of
  
  Title:Large Dispersion-Managed Broadband High-Energy Fiber Femtosecond Laser System with Sub 300 Fs Pulses and High Beam Quality Output
  
  Author(s):Li, Feng(1); Zhao, Wei(1); Wang, Yishan(1); Li, Dongjuan(1); Li, Qianglong(1); Yang, Yang(1); Wen, Wenlong(1); Song, Dongdong(1)
  Source: SSRN  Volume:   Issue:   DOI: 10.2139/ssrn.4094138  Published: April 26, 2022  
  Abstract:We experimentally demonstrate a high-energy sub 300 fs polarization maintaining fiber chirped pulse amplification (CPA) system. The preamplifier is a monolithic fiberized system that uses two cascaded temperature-assisted dispersion-tuning broadband chirped fiber Bragg gratings (CFBGs) with a reflected bandwidth of 20 nm as stretchers. To make full use of the stretcher to lower the system’s nonlinearity accumulation, a homemade mode locked fiber laser with a spectral width of 14.8 nm (full width at half maximum) is selected as the seeder to offer a stretched pulse width of 1.69 ns. The main amplifier is based on a one-stage simple Yb:YAG single crystal fiber amplifier with an amplified output power of 40.6 W at a repetition rate of 200 kHz, and the beam quality is conserved in a single mode beam profile with beam quality of 1.246 and 1.142 in the horizontal direction and vertical direction, respectively. During amplification, the spectral gain narrowing effect is observed. To achieve the high-speed switch of the laser, an acoustical optical modulator (AOM) is inserted before the compressor to achieve high-speed turn-on/off control. The compressor is based on a diffraction grating pair with a groove density of 1600 line/mm to offer a dispersion match with the stretcher of the CFBGs. With the CFBG’s fine-tuned capacity of second-order dispersion and higher-order dispersion, the compressed average power of 29.6 W and pulse duration of 278 fs, corresponding to a pulse energy of 148 µJ and a peak power of 532 MW, is obtained. The beam quality is well conserved after compression, and the beam quality is 1.250 and 1.196 in the horizontal direction and vertical direction, respectively. A power fluctuation of 0.1% (root mean square) and a beam pointing drift of 8.47 µrad/°C over 8 hours are realized. This high peak power and high beam quality femtosecond laser is promising in science and industrial applications. © 2022, The Authors. All rights reserved.
  Accession Number: 20220091664
• Record 333 of
  
  Title:Rotation-Invariant Attention Network for Hyperspectral Image Classification
  
  Author(s):Zheng, Xiangtao(1); Sun, Hao(1,2); Lu, Xiaoqiang(1); Xie, Wei(3)
  Source: IEEE Transactions on Image Processing  Volume: 31  Issue:   DOI: 10.1109/TIP.2022.3177322  Published: 2022  
  Abstract:Hyperspectral image (HSI) classification refers to identifying land-cover categories of pixels based on spectral signatures and spatial information of HSIs. In recent deep learning-based methods, to explore the spatial information of HSIs, the HSI patch is usually cropped from original HSI as the input. And 3 × 3 convolution is utilized as a key component to capture spatial features for HSI classification. However, the 3 × 3 convolution is sensitive to the spatial rotation of inputs, which results in that recent methods perform worse in rotated HSIs. To alleviate this problem, a rotation-invariant attention network (RIAN) is proposed for HSI classification. First, a center spectral attention (CSpeA) module is designed to avoid the influence of other categories of pixels to suppress redundant spectral bands. Then, a rectified spatial attention (RSpaA) module is proposed to replace 3 × 3 convolution for extracting rotation-invariant spectral-spatial features from HSI patches. The CSpeA module, the 1 × 1 convolution and the RSpaA module are utilized to build the proposed RIAN for HSI classification. Experimental results demonstrate that RIAN is invariant to the spatial rotation of HSIs and has superior performance, e.g., achieving an overall accuracy of 86.53% (1.04% improvement) on the Houston database. The codes of this work are available at https://github.com/spectralpublic/RIAN. © 1992-2012 IEEE.
  Accession Number: 20222412225942
• Record 334 of
  
  Title:A Large Area Dynode-MCP-PMT Design With High CE and Good Time Performance
  
  Author(s):Chen, Lin(1); Wang, Xingchao(2,3); He, Jianli(4); Tian, Li Liping(1); Tian, Jinshou(5); Wang, Qilong(2); Shen, Lingbin(1); Wang, Yunji(1); Ding, Dongyan(1); Ji, Ke(1); Yang, Jie(1)
  Source: IEEE Transactions on Nuclear Science  Volume: 69  Issue: 10  DOI: 10.1109/TNS.2022.3204791  Published: October 1, 2022  
  Abstract:A 20-in. photomultiplier tube based on dynode and microchannel plates (Dynode-MCP-PMT) with high collection efficiency (CE) and good time performance is proposed in this article. To obtain a tailless time distribution, a pair of uncoated MCPs are employed. For a high CE, a dynode with two large openings is placed in front of the MCPs. The dynode is designed as a spherical shape to prevent secondaries from escaping the multiplication system and assist them moving to the MCPs for further multiplication. A 3-D model is developed by CST Studio Suite to validate its feasibility. Finite integral technique and Monte Carlo method are combined to simulate the photoelectron collection and multiplication processes. Results predict that for the shielded Dynode-MCP-PMT, CE is expected to be 100%. Tailless transit time distributions are observed. Transit time spread (TTS) of the photoelectrons from the cathode top point to the dynode achieves 3.7 ns. If this PMT is exposed to the geomagnetic field, it should be operated in the north and south direction, in which CE and TTS are expected to be 100% and 3.8 ns, respectively. © 1963-2012 IEEE.
  Accession Number: 20223812755051
• Record 335 of
  
  Title:R&D and application of the Abyssal Bottom Boundary Layer Observation System (ABBLOS)
  
  Author(s):Ji, Chunsheng(1); Jia, Yonggang(1,2); Zhu, Junjiang(3,4); Hu, Naili(1); Fan, Zhihan(1); Hu, Cong(1); Feng, Xuezhi(1); Yu, Heyu(1); Liu, Bo(5)
  Source: Earth Science Frontiers  Volume: 29  Issue: 5  DOI: 10.13745/j.esf.sf.2021.9.28  Published: September 2022  
  Abstract:In order to further study the influence of marine dynamics on the bottom boundary layer (BLL) of the northern slope, South China Sea, the Abyssal Bottom Boundary Layer Observation System (ABBLOS) was developed for in situ observations. The ABBLOS-a carrier platform with a maximum operating water depth of 6700 m (actual depth limits depend on the carried equipment)-is an important technological innovation for studying the deep-sea BBL. The platform is compose of upper and lower frames. The upper frame is used to carry and recover observation equipment, and the lower supporting frame is a counterweight and used to provide an observational space 1 meter from the seabed. A simple and effective "slot positioning with bolt fastening" connection was designed to connect the two frames to ensure a successful upper frame recovery. The ABBLOS integrates 75k-ADCP, high-frequency ADCP, ADV, high-precision pressure gauge, as well as sensors for methane, temperature, salinity, turbidity, dissolved oxygen, and ORP. For the first time, the ABBLOS achieves simultaneous observation of marine dynamic processes (such as internal waves and midscale vortices) and dynamic changes of physical and chemical parameters in the deep-sea BBL. In particular, the water flow velocity profile at 1 meter height above the seafloor can be observed with a 7 mm vertical layer resolution. The platform was successfully deployed and recovered in 2020 in the Shenhu sea area, northern slope of the South China Sea, at water depths of 655 and 1405 m. The total observation time was 34 days, and the seawater velocity profile structure was obtained. Also captured were a once-a-day (on average) internal wave action process and a set of physicochemical parameters for the BBL. After a preliminary analysis of the observation data at 655 m water depth, it was found that the temperature, pressure, dissolved oxygen, density and salinity in the BBL were controlled by the tidal process; especially, the change of temperature and pressure was in synch with tide. During a tidal cycle, the oxidative environment of the BBL was relatively stable, whilst the concentration of dissolved methane decreased with time but kept within the global background value range. Compared to the tidal process, internal waves had little impact on the abyssal BBL, but could obviously cause sediment resuspension. The turbidity of the BBL caused by internal waves increased from 0.01 to 48 NTU and meanwhile the submarine cameras also recorded turbid seawater in the BBL during the internal wave propagation, indicating the internal waves in the South China Sea can affect the transport of submarine sediment. © 2022 Science Frontiers editorial department. All rights reserved.
  Accession Number: 20223912802110
• Record 336 of
  
  Title:Remote Epitaxy and Exfoliation of GaN via Graphene
  
  Author(s):Han, Xu(1,2,3); Yu, Jiadong(1,2,3); Li, Zhenhao(1,3); Wang, Xun(1,3); Hao, Zhibiao(1,2,3,3); Luo, Yi(1,2,3); Sun, Changzheng(1,2,3); Han, Yanjun(1,2,3); Xiong, Bing(1,2,3); Wang, Jian(1,2,3); Li, Hongtao(1,2,3); Zhang, Yuantao(3,4); Duan, Bin(3,5); Ning, Jing(3,6); Wu, Haidi(3,6); Wang, Lai(1,2,3)
  Source: ACS Applied Electronic Materials  Volume: 4  Issue: 11  DOI: 10.1021/acsaelm.2c00997  Published: November 22, 2022  
  Abstract:The remote epitaxy of GaN via graphene has attracted much attention due to the potential of easy mechanical exfoliation, and the exfoliated layers can be transferred onto foreign substrates according to the application needs, which is beneficial to improve the performance of GaN-based devices. In this work, a GaN epi-layer was grown by metal-organic chemical vapor deposition on the monolayer-graphene-coated AlN/sapphire or GaN substrates. The influence of growth temperature, carrier gas, and substrate on the exfoliation of the GaN epi-layer was studied. When the growth temperature is no more than 800 °C and N2is used as the carrier gas, the monolayer graphene can be retained on the AlN/sapphire substrate during the growth process. Thus, the GaN epi-layer can be exfoliated successfully. However, the monolayer graphene will be destroyed under a growth temperature of 850 °C, and lead to the failure of exfoliation. Besides, the monolayer graphene can also be damaged when the H2carrier gas or GaN substrate is employed with a growth temperature of 800 °C. This causes the GaN epi-layer to be exfoliated not as well. The experimental results illustrate that suitable growth conditions and substrate are important for realizing the exfoliation of a GaN epi-layer. © 2022 Authors. All rights reserved.
  Accession Number: 20224513055384