Reduction of Deep Level Defects in Unintentionally Doped 4H-SiC Homo-epilayers by Ion Implantation

In order to reduce deep level defects, the theory and process design of 4H-SiC homoepitaxial layer implanted by carbon ion are studied. With the Monte Carlo simulator TRIM, the ion implantation range, location of peak concentration and longitudinal straggling of carbon are calculated. The process for improving deep energy level in undoped 4H-SiC homoepitaxial layer by three times carbon ion-implantation is proposed, including implantation energy, dose, the SiO2 resist mask, annealing temperature, annealing time and annealing protection. The deep energy level in 4H-SiC material can be significantly improved by implantation of carbon atoms into a shallow surface layer. The damage of crystal lattice can be repaired well, and the carbon ions are effectively activated after 1 600 ℃ annealing, meanwhile, deep level defects are decreased.

A Qualitative Perstective on Idempotency Defect of Two Level System Interacting with Laser and Quantized Field

Entanglement due to the interaction of a two level atom with a laser and quantized field is investigated. The role of the nonlinearity due to these interactions is discussed. It is found that the nonlinearity changes strongly the behavior of the entanglement also the detuning parameters have important role in the structure of the measure of entanglement.

Influence of a deep-level-defect band formed in a heavily Mg-doped GaN contact layer on the Ni/Au contact to p-GaN

The influence of a deep-level-defect（DLD） band formed in a heavily Mg-doped GaN contact layer on the performance of Ni/Au contact to p-GaN is investigated. The thin heavily Mg-doped GaN（p^＋＋-GaN） contact layer with DLD band can effectively improve the performance of Ni/Au ohmic contact to p-GaN. The temperature-dependent I–V measurement shows that the variable-range hopping（VRH） transportation through the DLD band plays a dominant role in the ohmic contact. The thickness and Mg/Ga flow ratio of p^＋＋-GaN contact layer have a significant effect on ohmic contact by controlling the Mg impurity doping and the formation of a proper DLD band. When the thickness of the p^＋＋-GaN contact layer is 25 nm thick and the Mg/Ga flow rate ratio is 10.29%, an ohmic contact with low specific contact resistivity of 6.97×10^-4Ω·cm^2 is achieved.

In-doping collaboratively controlling back interface and bulk defects to achieve efficient flexible CZTSSe solar cells

Focusing on the low open circuit voltage(V_(OC))and fill factor(FF)in flexible Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells,indium(In)ions are introduced into the CZTSSe absorbers near Mo foils to modify the back interface and passivate deep level defects in CZTSSe bulk concurrently for improving the performance of flexible device.The results show that In doping effectively inhibits the formation of secondary phase(Cu(S,Se)_(2))and VSndefects.Further studies demonstrate that the barrier height at the back interface is decreased and the deep level defects(Cu_(Sn)defects)in CZTSSe bulk are passivated.Moreover,the carrier concentration is increased and the V_(OC) deficit(V_(OC,def))is decreased significantly due to In doping.Finally,the flexible CZTSSe solar cell with 10.01%power conversion efficiency(PCE)has been obtained.The synergistic strategy of interface modification and bulk defects passivation through In incorporation provides a new thought for the fabrication of efficient flexible kesterite-based solar cells.

体相二硫化铼中点缺陷的形成与稳定性

二硫化铼是过渡金属二硫族化合物的成员,由于层间的范德华作用、合适的带隙、高的光吸收系数和长的载流子迁移距离在光电子研究领域引起广泛的关注.其中光电材料及器件的优良特性由电子结构决定,而半导体的缺陷能级对电子结构具有重要的调控,且体相二硫化铼的缺陷研究尚且缺乏.本文基于密度泛函理论的第一性原理计算,对体相二硫化铼的铼空位、硫空位、钨掺杂(或替代)铼、钨掺杂硫、锝掺杂铼和锝掺杂硫的缺陷形成能和稳定性进行了研究.结果表明:钨掺杂硫和锝掺杂硫形成深施主能级缺陷,铼空位形成浅施主能级缺陷.在富铼和富硫条件下,钨掺杂铼的缺陷形成能低且能有效降低体系总能,提高体系稳定性.钨掺杂硫的缺陷虽然能降低体系的总能提高二硫化铼的稳定性,但较大的缺陷形成能表明钨掺杂硫缺陷难以形成.上述研究结果有助于理解缺陷能级对半导体深浅能级和稳定性的影响,同时也为未来实验上设计基于二硫化铼的高效的光电子器件提供理论依据.

Identifying the relationships between subsurface absorber defects and the characteristics of kesterite solar cells

Understanding the defect characteristics that occur near the space-charge regions(SCRs)of kesterite(CZTSSe)solar cells is important because the recombination loss at the CZTSSe/CdS interface is considered the main cause of their low efficiency.CZTSSe surfaces with different elemental compositions were formed without polishing(C00)and with polishing for 20 s(C20)and 60 s(C60).For C60,a specific region near the SCR was excessively Cu-rich and Zn-poor compared to C00 and C20.Various charged defects formed where the elemental variation was large.As the main deep acceptor defect energy level(E_(a2))near the SCR increased,the efficiency,open-circuit voltage deficit,and current density degraded,and this phenomenon was especially rapid for large E_(a2) values.As the E_(a2) near the SCR became deep,the carrier diffusion length decreased more for the CZTSSe solar cells with a low carrier mobility than for the CuInGaSe_(2)(CIGSe)solar cells.The large amplitude of the electrostatic potential fluctuation in the CZTSSe solar cells induced a high carrier recombination and a short carrier lifetime.Consequently,the properties of the CZTSSe solar cells were more strongly degraded by defects with deep energy levels near the SCR than those of the CIGSe solar cells.

桩周土对桩身振动波传递及缺陷识别影响研究

针对基桩完整性的低应变检测方法仅能定性识别桩身缺陷程度,不能定量识别问题,本文根据动力学理论,建立了考虑桩周土作用的基桩动力控制方程,利用波动理论求得桩身任意截面的速度响应。通过不同龄期下模型桩试验和数值计算结果,研究发现:随着龄期的增加桩周土阻尼逐渐增大,速度反射波幅值与入射波幅值之比逐渐衰减的规律,依据此衰减规律和截面阻抗变化处的反射规律,建立了缺陷程度定量识别关系式,利用该关系式可以简便、快捷地定量识别桩身缺陷程度。

Charge-sensitive deep level transient spectroscopy of helium-ion-irradiated silicon,as-irradiated and after thermal annealing

Electrically active defects in the phosphor-doped single-crystal silicon, induced by helium-ion irradiation under thermal annealing, have been investigated. Isothermal charge-sensitive deep-level transient spectroscopy was employed to study the activation energy and capture cross-section of helium-induced defects in silicon samples. It was shown that the activation energy levels produced by helium-ion irradiation first increased with increasing annealing temperature, with the maximum value of the activation energy occurring at 873 K, and reduced with further increase of the annealing temperature. The energy levels of defects in the samples annealed at 873 and 1073 K are found to be located near the mid-forbidden energy gap level so that they can act as thermally stable carrier recombination centres.

改进水平集协同FLICM的汽车零部件表面缺陷识别

针对汽车机械零部件中检测效率低、误检率高等瓶颈问题,提出了一种结合图像处理技术的方法。基于汽车副车架表面结构复杂以及缺陷异形等特征,首先通过小波邻域收缩去噪和多尺度增强算法对零件图像进行预处理,再通过水平集函数初步定位缺陷区域,最后结合空间模糊聚类进一步精确定位缺陷区域,达到对零件表面缺陷识别的目的。对工件表面划伤、压痕、气孔三种缺陷进行检测。实验结果表明:该算法相对于其它两种算法的检测率分别93.3%、86%和90%,具有较高的检测成功率。为后续缺陷零部件分类奠定良好的基础且可以满足工业检测要求。

Detection of fabric defects based on frequency-tuned salient algorithm

The correct rate of detection for fabric defect is affected by low contrast of images. Aiming at the problem,frequencytuned salient map is used to detect the fabric defect. Firstly,the images of fabric defect are divided into blocks. Then,the blocks are highlighted by frequency-tuned salient algorithm. Simultaneously,gray-level co-occurrence matrix is used to extract the characteristic value of each rectangular patch. Finally,PNN is used to detect the defect on the fabric image. The performance of proposed algorithm is estimated off-line by two sets of fabric defect images. The theoretical argument is supported by experimental results.

实景三维模型缺陷修复关键技术

为了有效提高实景三维模型反映各类型地理要素的准确度和精细度以充分支撑实景三维中国建设工作,首先将当前无人机倾斜摄影三维重建后的三维模型中存在的模型缺陷系统性分为四大类型,并分析其产生的原因。随后,针对性地提出了三种关键技术:一是基于连通性和欧氏距离聚类的交互式悬浮物去除,利用图割理论和随机一致性抽样算法识别和删除悬浮物;二是基于图割理论的水面半自动整平,在利用Grabcut算法提取水面区域的同时为其赋予统一高程以实现水面的平整;三是基于深度网络模型的水体纹理inpainting填充,利用卷积神经网络和深度对抗训练以获得水体纹理的特征和结构从而实现水体缺失纹理的修复。最后,利用湖北省宜昌市的实际生产数据进行了修复实验,实验结果表明本文提出的各项关键技术能够有效修复三维模型缺陷,从而使实景三维模型具备更精细的地理实体和地理景观还原度。

正畸联合骨水平种植体修复在牙列缺损中的应用效果评价

目的:评价正畸联合骨水平种植体修复在牙列缺损中的应用效果。方法 :回顾分析2020年1月—2022年1月因牙列缺损就诊的88例下颌后牙区单牙种植患者的资料,其中,骨水平种植体修复44例(对照组),正畸联合骨水平种植体修复44例(试验组)。比较2组种植体植入成功率、种植体牙周健康情况、咀嚼功能、种植体稳定情况、术后并发症及患者满意度。采用SPSS 18.0软件包对数据进行统计学分析。结果:2组植入3个月、6个月的成功率相比,差异无统计学意义(P>0.05),试验组植入12个月的成功率显著高于对照组(P<0.05)。试验组植入12个月的龈沟出血指数(gingival sulci bleeding index,SBI)、探诊深度(probing depth,PD)显著低于对照组(P<0.05),2组植入12个月的骨吸收量相比,差异无统计学意义(P>0.05)。2组治疗后最大力咬合时咬肌、颞肌肌电活动显著高于治疗前(P<0.05),试验组治疗后最大力咬合时咬肌、颞肌肌电活动显著高于对照组(P<0.05)。2组6个月、12个月时的种植体稳定系数显著高于3个月(P<0.05),2组12个月时的种植体稳定系数显著高于6个月(P<0.05),试验组6个月、12个月时的种植体稳定系数显著高于对照组(P<0.05)。2组总并发症发生率相比,差异无统计学意义(P>0.05)。试验组患者满意度显著高于对照组(P<0.05)。结论:正畸联合骨水平种植体修复牙列缺损可提高种植成功率及咀嚼效能,改善种植体牙周健康情况,提升患者满意度。

Nonlinear change of ion-induced secondary electron emission in theκ-Al_(2)O_(3) surface charging from first-principle modelling

Secondary electron emission(SEE)induced by the positive ion is an essential physical process to influence the dynamics of gas discharge which relies on the specific surface material.Surface charging has a significant impact on the material properties,thereby affecting the SEE in the plasma-surface interactions.However,it does not attract enough attention in the previous studies.In this paper,SEE dependent on the charged surface of specific materials is described with the computational method combining a density functional theory(DFT)model from the first-principle theory and the theory of Auger neutralization.The effect ofκ-Al2O3 surface charge,as an example,on the ion-induced secondary electron emission coefficient(SEEC)is investigated by analyzing the defect energy level and band structure on the charged surface.Simulation results indicate that,with the surface charge from negative to positive,the SEEC of a part of low ionization energy ions(such as Ei=12.6 eV)increases first and then decreases,exhibiting a nonlinear changing trend.This is quite different from the monotonic decreasing tendency observed in the previous model which simplifies the electronic structure.This irregular increase of the SEEC can be attributed to the lower escaped probability of orbital energy.The results further illustrate that the excessive charge could cause the bottom of the conduction band close to the valence band,thus leading to the decrease of the orbital energy occupied by the excited electrons.The nonlinear change of SEEC demonstrates a more realistic situation of how the electronic structure of material surface influences the SEE process.This work provides an accurate method of calculating SEEC from specific materials,which is urgent in widespread physical scenarios sensitive to surface materials,such as increasingly growing practical applications concerning plasma-surface interactions.

电子辐照对4H-SiC MOS材料缺陷的影响

4H-SiC金属氧化物半导体(MOS)基器件在电子辐照环境下应用时可能产生新的材料缺陷,导致其电学性能发生退化。本文选取结构最简单的MOS基器件(4H-SiC MOS电容器)为对象,研究了一系列电子辐照剂量下材料缺陷的演变情况。在10 MeV电子束下对MOS样品进行30、50、100、500、1 000 kGy剂量的辐照,对辐照前、后样品进行深能级瞬态谱测试(DLTS)和电容-电压(C-V)曲线表征。DLTS实验结果表明,低剂量电子辐照前、后4H-SiC/SiO_(2)界面及近界面处的缺陷没有发生明显变化,而高剂量辐照导致双碳间隙原子缺陷的构型发生了改变,演变后的构型能级位置更深,化学结构更加稳定。C-V曲线测试结果发现,不同电子辐照剂量导致MOS电容器平带电压发生不同程度的负向漂移,这很可能是SiO_(2)氧化层中氧空位数量和4H-SiC/SiO_(2)界面及近界面处缺陷数量共同影响的结果。本文研究结果对研发和优化抗电子辐照的4H-SiC MOS制备工艺具有一定的参考价值。

纤锌矿结构砷化镓纳米线中的深能级缺陷研究

深能级缺陷是造成纤锌矿结构砷化镓纳米线中持续光电导效应的主要原因。采用基于高斯分布的缺陷复合动力学方程分析了纤锌矿结构砷化镓纳米线的光电导衰减曲线,得到平均载流子捕获势垒为60.2 meV。通过分析光照下光电导瞬态行为,提出了基于缺陷光电离模型来提取特定缺陷能级水平特征的方法。通过拟合纤锌矿结构砷化镓纳米线的光离化谱,得到了0.69 eV的光电离能。光离化能和热捕获能之间的较大能量差异意味着缺陷与晶格有强耦合作用,这与闪锌矿结构砷化镓中EL2中心的行为相似。

基于台架试验数据的铸件疲劳寿命分析与应用

以商用车铸造后桥壳为研究对象,对多个类型桥壳台架试验疲劳寿命进行数据分析处理,得到失效时的加载循环次数。应用基于时间历程载荷的有限元疲劳分析方法,得到铸造桥壳在对应载荷循环下的疲劳等效应力,联合疲劳等效应力与失效次数获得铸造桥壳的S-N曲线。结果表明,当前分析的铸造桥壳存在缺陷控制水平低的问题,需要提升制造工艺水平,并提出在设计中制定缺陷等级分类的重要性。应用有限元疲劳分析联合试验数据,可以在工艺水平稳定的前提下,提前有效预测新设计结构的疲劳寿命,将有限元分析结果与制造工艺联系起来,扩展了试验数据的实用性。

矿用带式输送机胶带表面缺陷检测系统研究

针对矿用带式输送机胶带表面缺陷识别困难、定位不准确的问题,提出了基于可靠区域融合的矿用带式输送机胶带表面缺陷检测系统。首先,利用迁移学习方法和公开数据集训练了YOLOv4及SSD模型,并根据预测分数和重叠情况提出了缺陷检测结果决策级融合方法,决策级融合YOLOv4和SSD两个模型的最大化可靠区域,以此实现带式输送机胶带缺陷识别和定位。结合公开数据集和胶带表面缺陷数据集对所提方法的有效性和可靠性进行了测试和分析,结果表明所提方法能够充分利用YOLOv4和SSD模型的检测结果,取得较高的准确率、召回率和重叠率,且在胶带表面缺陷数据集中达到超过85%的准确率和0.6以上的重叠率,这有利于胶带的缺陷检测和维修保养,从而保证矿用带式输送机的安全可靠运行。

基于决策级融合的曳引钢带表面缺陷检测方法

由于电梯曳引钢带的工况环境恶劣,钢带表面容易出现缺陷,而复杂昏暗的环境导致缺陷识别和定位困难。为此,提出了基于决策级融合的曳引钢带缺陷检测方法,利用迁移学习的方法微调YOLOv4及SSD的预训练模型,并将其应用于曳引钢带缺陷检测,得到不同的原始检测结果,利用所提方法在决策级融合YOLOv4及SSD模型的原始检测结果,以此提高钢带表面缺陷识别和定位的准确率。利用东北大学钢带表面缺陷公开数据集对所提方法的有效性和可靠性进行测试,缺陷识别和定位结果表明所提方法能够充分利用YOLOv4和SSD模型的原始检测结果,通过决策级融合初始检测结果取得较高的缺陷识别和定位准确性,准确率和召回率提高约15%,交并比达到0.6左右,这对于电梯曳引钢带的缺陷检测和维修保养有重要意义,并进一步保证电梯能够安全可靠运行。

基于YOLOv8s的轻量级绝缘子多缺陷检测模型

YOLO系列算法已广泛用于识别电力线路中的各类缺陷目标。由于巡检图像背景复杂、缺陷目标的尺度不一等,直接利用YOLO算法难以有效避免绝缘子闪络、破损等小目标的错检漏检问题。为解决这一问题,在YOLOv8s模型的基础上提出一种轻量化绝缘子缺陷检测算法。在骨干网络中引入双层路由注意力机制(BRA),以提升对全局特征的关注度,抑制背景噪声,降低小目标缺陷的错检漏检率。通过加权双向特征金字塔网络(BiFPN)实现跨尺度特征之间的加权融合,获取各类缺陷更全面的特征信息。重构Neck网络来消除低贡献度的网络节点,在增强检测性能的同时减少了模型的参数量,实现了性能提升和参数效率之间的平衡。实验结果显示,改进后的网络模型平均检测精度达到84.9%,而参数量仅为8.4×10^(6),可实现对绝缘子缺陷的快速准确检测。

基于RbGeI_(3)全无机钙钛矿太阳电池的数值分析

为了开发高效稳定的新型太阳电池,采用SCAPS-1D软件,对以RbGeI_(3)为吸收层的全无机无铅钙钛矿太阳电池进行数值模拟,其电池结构为FTO/TiO_(2)/RbGeI_(3)/Spiro-OMeTAD/Au。影响电池性能的因素包括RbGeI_(3)吸收层厚度及缺陷态密度、掺杂浓度和金属背电极的功函数。通过数值模拟对这些参数进行了优化,提高了电池性能。结果表明:当RbGeI_(3)吸收层厚度为600 nm,缺陷态密度为1013 cm^(-3),RbGeI_(3)吸收层掺杂浓度为1017 cm^(-3),TiO_(2)和Spiro-OMeTAD掺杂浓度分别为1020和1017 cm^(-3)时,电池效率趋于稳定。基于以上参数,优化后的电池输出特性为:V_(oc)=0.92 V,J_(sc)=32.97 mA/cm^(2),FF=78.10%,hPCE=23.65%。研究表明RbGeI_(3)钙钛矿太阳电池具有成为新型高效光伏器件的潜力。