SiNx/SiOxNy叠层结构防潮能力的研究

研究了等离子体增强化学气相沉积(PECVD)工艺参数对SiN_x及SiO_xN_y防潮能力的影响,并测试了SiN_x/SiO_xN_y叠层薄膜的水汽渗透速率(WVTR)。实验结果表明:单层SiN_x薄膜和SiO_xN_y薄膜都存在临界厚度,当膜厚大于临界值时,继续增大厚度不会明显改善薄膜的WVTR。当沉积温度从50℃提高到250℃,SiN_x薄膜的WVTR从0.031g/(m²·day)降至0.010g/(m²·day)。SiO_xN_y沉积时,增大N₂O通入量对薄膜的WVTR影响不明显,但可以有效改善薄膜的弯曲性能。最后,4个SiN_x/SiO_xN_y叠层膜的WVTR下降到了4.4×10-4g/(m²·day)。叠层膜防潮能力的显著提升归因于叠层结构可以有效解耦层与层之间的缺陷,延长水汽渗透路径。     

高频低温漂TC-SAW滤波器的设计

该文设计了一款温度补偿型声表面波（TC-SAW）滤波器,建立了弹性材料及压电材料温度方程,对滤波器的温度场进行仿真分析。通过在压电材料（128°YX-LiNbO₃）上沉积SiO₂作为温度补偿层,降低了滤波器的频率温度系数。为了解决在沉积SiO₂温度补偿层后,谐振器的反谐振频率处出现杂散响应,通过增加电极厚度,降低了谐振器杂散响应对滤波器性能的影响。采用四阶级联提高滤波器的带外抑制。仿真结果表明,设计的TC-SAW滤波器中心频率为2 497 MHz,频率温度系数为-9.89×10^-6/℃,-30~85 ℃工作温度范围内的带内最大插损为1.95 dB,带外抑制大于30 dB,-3 dB损耗带宽大于97 MHz。     

基于 InSe/MoTe2 异质结构的超灵敏宽光谱光电探测器

基于光栅效应的二维材料垂直结构可实现高灵敏度和宽光谱光探测器。本文报告了一种基于硒化铟（InSe）/二碲化钼（MoTe₂）垂直异质结构的高灵敏度光电探测器,该探测器在 365~965 nm 波长范围内具有出色的宽光谱探测能力。顶层的InSe用作调节沟道电流的光栅层,MoTe₂ 则用作传输层。通过结合两种材料的优势,该光电探测器的响应时间为 21.6 ms,比探测率在365 nm光照下可以达到1.05×10¹³ Jones,在965nm光照下也可达到10⁹ Jones数量级。外量子效率可达 1.03×10⁵%,显示出强大的光电转换能力。     

Gd2O3:Yb3+,Er3+纳米粉体的水热合成及上转换发光研究

采用Gd₂O₃,Yb₂O₃,Er₂O₃,HNO₃,CO(NH₂)₂和C ₁₂H₂₅SO₄Na为实验原料,通过水热法合成了纳米Gd₂O₃:Yb³⁺,Er ³⁺上转换发光粉体。通过X射线衍射(XRD )、差示扫描量热 -热重分析(DSC-TGA )、傅里叶变换红外光谱(FT-IR ) 、透射电子显微镜(TEM )和 上转换发射光谱(UCL )等对样品进行表征。研究结果表明:CO(NH₂)₂与Gd ³⁺ 离子的摩尔比m影响前驱体的组成,当m=4时,前驱体是由晶态的 Gd₂(CO₃)₃·xH₂O构成。该 前驱体在空气气氛下800℃煅烧2h可获得单相的Gd₂O₃纳米粉体 ,粉体呈近球状,平均粒 径约为30～40nm。上转换发光光谱表明,在980nm波长红外光激发下,Gd₂O₃:Yb³⁺,Er³⁺的主发射峰 位于664nm波长处,呈红光发射,对应于Er³⁺的 ⁴F9/2→⁴I15/2跃迁。在波长为539 nm和562nm附近呈现绿光发射,分别对应于Er³⁺的²H11/2→⁴I15/2和⁴S3/2→⁴I15/2跃迁。Er³⁺的猝 灭浓度为1%。800℃煅烧合成的Gd₂O₃:Yb³⁺,Er³⁺ 纳米粉体的上转换发光机制为双光子模型, 而1200℃煅烧合成的Gd₂O₃:Yb³⁺,E r³⁺纳米粉体的上转换发光机制则为三光子模型。     

截止波长2.2 µm的平面型延伸波长InGaAs探测器

采用闭管扩散的方法成功研制了截止波长2.2 μm的平面型延伸波长InGaAs探测器芯片。在分子束外延法（MBE）生长的In_0.75Al_0.25As/ In_0.75Ga_0.25As/ In_0.75Al_0.25As外延材料上,采用砷化锌作为扩散掺杂源、SiN_x作为扩散掩膜层,实现了扩散成结。分析了扩散结深和载流子侧向收集宽度、I-V特性、光谱响应特性和探测率,结果表明：150 K温度下,器件暗电流密度0.69 nA/cm²@-10 mV,响应截止波长和峰值波长分别为2.12 μm和1.97 μm,峰值响应率为1.29 A/W,峰值量子效率达82%,峰值探测率为1.01×10¹² cmHz^1/2/W。这些结果对后续进一步优化平面型延伸波长InGaAs焦平面探测器有重要的指导意义。     

Tb3+,Eu3+共掺杂SrMoO4的合成及发光性能研究

采用水热法合成SrMoO₄:Eu³⁺,SrMoO₄:T b³⁺,Eu³⁺系列荧光粉。利用X射线衍射(XRD)、扫描电镜(SEM)、光电子能谱(EDS)、荧光光谱以及色坐标等研究了所制备荧光粉的结构、形貌和发光性能。XRD检测表 明,试样的 结构属四方晶系。EDS测试证明,合成样品含有相应组分元素,没有杂质元素。荧光光谱测 试表明, 在364、397、467nm波长紫 外光和可见光的激发下,SrMoO₄:xEu³⁺的发光光 谱由[MoO₄]原子团的³T₁,³T₂－¹A₁电荷迁移跃 迁峰(536nm波长,绿光),以及Eu³⁺的⁵D 0→⁷F₁(593nm波长,橙红光), ⁵D₀→⁷F₂(615nm,红光),⁵D₀→⁷F ₃(646nm,红光)跃迁发光峰组成。在243、288和396nm波长紫外 可见光激发下,SrMoO₄:0.05Tb³⁺,0.05Eu³⁺的发射光谱包含了:Tb³⁺ 的⁵D₄→⁷F₆(489nm波长,蓝光 )、⁵D ₄→⁷F₅(546nm波长,绿光)、⁵D₄→⁷F₄(582nm波长,黄光)跃迁的发射峰,Eu³⁺的⁵D₀→⁷F 1(593 nm波长,橙红光),⁵D₀→⁷F 2(615nm 波长,红光),⁵D₀→⁷F₃(646nm波 长,红光)的发射峰。改 变激发波长,可以调节SrMoO₄:0.05Tb³⁺,0.05Eu³⁺的发光颜色,存在Tb 3+→Eu³⁺的能量传递。     

基于X-LiNbO3/SiO2/Si低温漂、大机电耦合SH-SAW谐振器的设计

铌酸锂(LN)单晶薄膜具有较高的机电耦合系数(k² eff＞30%),其水平剪切(SH)声学模式常被应用于开发具有大机电耦合系数的薄膜声学谐振器和超宽带滤波器。但LN 的频率温度系数较大(TCF ＞ -50×10^-6/℃),这不仅会降低滤波器的可用有效带宽,同时也会限制器件的功率处理能力。采用3D周期有限元模型对基于X 切LN/SiO₂/Si结构SH 声表面波(SH-SAW)谐振器进行了优化研究。研究结果表明,当SH-SAW 传播角ψ=-10°~-20°、LN和SiO₂ 膜厚分别为hLN=0.1λ 和h_SiO2 =0.2λ(λ 为叉指换能器周期)、铝电极金属化率η=0.4、电极相对厚度h_Al/λ=5%~10%时,SH-SAW 谐振器的 k² eff 约为30%,且其TCF＜-20×10^-6/℃,有望用于开发新一代的低温漂、超宽带5G SAW 滤波器。     

YPO4:Ln3+(Ln=Eu,Tb)球形荧光粉的合成及其发光性能优化

采用水热法结合高温退火处理制备了YPO₄:Ln³⁺(Ln=Eu,T b)荧光粉。通过X射线 粉末衍射(XRD)、扫描电镜(SEM)和荧光光谱(PL)对样品的结构、形貌和发光性能进行 表征。结果 表明:在水热条件下合成了含结晶水六角相结构的YPO₄·0.8H₂O :Eu³⁺和YPO₄·0.8H₂O:Tb³⁺前躯体;经过 800 ℃高温烧结2h后,前躯体 失去结晶水后得到球形、尺寸均一、表面光滑、四方锆石结构的YPO₄:Eu³⁺和 YPO₄:Tb³⁺荧光粉,颗粒平均粒径约为200 nm。在396 nm波长激发下,YPO₄:Eu³⁺荧光粉可以获得Eu³⁺离 子的跃迁能级⁵D₀→⁷FJ(J=1－4)特征发射,以磁偶极跃迁⁵D₀→⁷F₁(596 nm)的发光强度最强,观察到橙 红色发射,且Eu³⁺的最佳掺杂摩尔分数为11%。同时,YPO₄: Tb³⁺荧光粉在372 nm的光激发下,在548 nm 处的⁵D₄→⁷F₅跃迁具有最高的荧光强度,观察到绿光发 射,且Tb³⁺最佳掺杂摩尔分数为7%。     

荧光粉Sr2SiO4:Eu2+中不同格位发光研究

采用高温固相反应法制备了Sr₂SiO₄:xEu²⁺荧光粉,研究Eu²⁺所占据的 Sr₂SiO₄中Sr1和Sr2两个不同格位及掺杂浓度和激发波长对格位发光的影响。荧 光粉发射光谱为一双峰的宽发射光谱,可拟合为峰值位置位于480nm 和530nm的两条高斯曲线,分别对应Eu²⁺所占据的Sr1和Sr2两 个不同格位的发射。随着 Eu²⁺掺杂浓度增加,Sr1和Sr2格位的发光强度均出现浓度猝灭现象,Sr2格位的 长波长发射峰出现明显红移现象,而Sr1格位的短波长发射峰发生红移-蓝移-红 移现象,这与Sr1和Sr2格位的优先占据以及格位间能量传递有关。随着激发波 长的增加,Sr2格位的长波长发射的发光强度与Sr1格位的短波长发射的发光强 度比值增加,占据不同格位的Eu²⁺对不同激发波长表现出明显的选择激发效应。     

Ca3Y2(Si3O9)2:Tb3+绿色荧光粉的光谱特性

采用高温固相法制备了Ca₃Y₂(Si₃O₉)₂: Tb³⁺绿色荧光粉,研究了材料的光学性能。X 射线衍射(XRD)结果显示,掺杂少量的Tb³⁺,并未影响Ca₃Y₂(Si₃O₉)₂材料 的晶相结构。Ca₃Y₂(Si₃O₉)₂:Tb³⁺ 荧光粉的激发光谱由较强的4f^75d1宽带吸收(200～300 nm )和较弱的4f-4f电子跃迁吸收 (300～500 nm)构成,主激发峰位于236nm。取波长分别为236、376和482nm的光 作为激发源时,发现样品的主发射峰均位于544 nm,对应Tb³⁺的⁵D 4→⁷F₅跃迁发射。以236nm 紫外光作为激发源,监测544nm主发射峰,随Tb³⁺浓度 的增大,Ca₃Y₂(Si ₃O₉)₂:Tb³⁺的荧光寿命逐渐减小,但在实验范围内并未出现浓度猝灭现象。     

High‐Performance Ultraviolet Photodetector Based on a Few‐Layered 2D NiPS3 Nanosheet

2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small bandgap (<2 eV), the application of traditional TMDs into solar‐blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS₃ nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific A_g modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few‐layered 2D NiPS₃ nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 10¹² Jones, outperforming some traditional wide‐bandgap UV detectors. The wavelength‐dependent photoresponsivity measurement allows the direct observation of an admirable cut‐off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection.     

The properties of photo chemical-vapor deposition SiO<Subscript>2</Subscript> and its application in GaN metal-insulator semiconductor ultraviolet photodetectors

High-quality SiO₂ insulating layers were successfully deposited onto GaN by a photo chemical-vapor deposition (photo-CVD) technique using a deuterium (D₂) lamp as the excitation source. The interface-trap density, D_it, was estimated to be 8.4×10¹¹ cm⁻²eV⁻¹ for the photo-CVD SiO₂ layers prepared at 300°C. It was found that the leakage current was only 6.6×10⁻⁷ A/cm² with an applied field of 4 MV/cm for the 300°C photo-CVD-grown Al/SiO₂/GaN metal-insulator semiconductor (MIS) capacitor. It was also found that the photo-CVD SiO₂ layer could be used to suppress the dark current of nitride-based photodetectors. A large photocurrent to dark-current contrast ratio higher than three orders of magnitude and a maximum 0.12 A/W responsivity were observed from the fabricated indium tin oxide (ITO)/photo-SiO₂/GaN MIS ultraviolet (UV) photodetectors. Furthermore, it was found that corresponding noise-equivalent power (NEP) and normalized detectivity, D*, of our ITO/photo-SiO₂/GaN MIS UV photodetectors was 2.19×10⁻⁹ W and 2.03 × 10⁸ cmHz_0.5W⁻¹, respectively, for a given bandwidth of 500 Hz.     

High‐Performance Ferroelectric Polymer Side‐Gated CdS Nanowire Ultraviolet Photodetectors

An efficient ferroelectric‐enhanced side‐gated single CdS nanowire (NW) ultraviolet (UV) photodetector at room temperature is demonstrated. With the ultrahigh electrostatic field from polarization of ferroelectric polymer, the depletion of the intrinsic carriers in the CdS NW channel is achieved, which significantly reduces the dark current and increases the sensitivity of the UV photodetector even after the gate voltage is removed. Meanwhile, the low frequency noise current power of the device reaches as low as 4.6 × 10^?28 A² at a source‐drain voltage V_ds = 1 V. The single CdS NW UV photodetector exhibits high photoconductive gain of 8.6 × 10⁵, responsivity of 2.6 × 10⁵ A W^?1, and specific detectivity (D*) of 2.3 × 10¹⁶ Jones at a low power density of 0.01 mW cm^?2 for λ = 375 nm. In addition, the spatially resolved scanning photocurrent mapping across the device shows strong photocurrent signals near the metal contacts. This is promising for the design of a controllable, high‐performance, and low power consumption ultraviolet photodetector.     

Transition‐Metal‐Carbide (Mo2C) Multiperiod Gratings for Realization of High‐Sensitivity and Broad‐Spectrum Photodetection

A novel hybrid phototransistor consisting of molybdenum carbide (Mo₂C) and molybdenum disulfide (MoS₂) is proposed. By exploiting the interface properties of MoS₂ and Mo₂C, a highly sensitive and broad‐spectral response photodetector is fabricated. The underlying mechanism of the enhanced performance is the efficient hot carrier injection from Mo₂C to MoS₂. The strong coupling of MoS₂ and Mo₂C at the interface provides the significantly low Schottky barrier height (≈70 meV), which gives rise to the significantly efficient hot carrier transfer from Mo₂C to MoS₂. The grating of metallic Mo₂C produces plasmonic resonance, which provides hot carriers to the MoS₂ channel. By adjusting the grating period of Mo₂C (400–1000 nm), the optimal photoresponse of light can be controlled, from visible to NIR. By integrating various Mo₂C multigrating periods (400–1000 nm) with MoS₂, a novel photodetector is demonstrated with high responsivity (R > 10³ A W^?1) and light‐to‐dark current ratio (>10²) over a broad spectral range (405–1310 nm). The proposed novel hybrid photodetector, 2D semiconductors with multigrating 2D metallic stripes, exhibits high sensitivity and broad spectral detection of light and can overcome the inherent weakness of conventional 2D photodetectors, paving the way forward for next‐generation photoelectric devices.     

High Performance BiOCl Nanosheets/TiO2 Nanotube Arrays Heterojunction UV Photodetector: The Influences of Self‐Induced Inner Electric Fields in the BiOCl Nanosheets

BiOCl nanosheets/TiO₂ nanotube arrays heterojunction UV photodetector (PD) with high performance is fabricated by a facile anodization process and an impregnation method. The heterojunction at the interface and the internal electric fields in the BiOCl nanosheets faciliate the separation of photogenerated charge carriers and regulate the transportation of the electrons. Compared with the large dark current (≈10^?5 A), low on/off ratio (8.5), and slow decay time (>60 s) of the TiO₂ PD, the optimized heterojunction PD (6‐BiOCl–TiO₂) yields dramatically decreased dark current (≈1 nA), ultrahigh on/off ratio (up to 2.2 × 10⁵), and fast decay speed (0.81 s) under 350 nm light illumination at ?5 V. Moreover, it exhibits an increased responsivity of 41.94 A W^?1, a remarkable detectivity (D*) of 1.41 × 10¹⁴ Jones, and a high linear dynamic range of 103.59 dB. The loading amount and growth orientations of the BiOCl nanosheets alter the roles of the self‐induced internal electric field in regulating the behaviors of the charge carriers, thus affecting the photoelectric properties of the heterojunction PDs. These results demonstrate that rational construction of novel heterojunctions hold great potentials for fabricating photodetectors with high performance.     

Effects of gate dielectric surface modification on phototransistors with polymer-blended benzothieno[2,3-b]benzothiophene semiconductor thin films

In the present work, we investigated effects of the dielectric/semiconductor interface modification on the photoelectrical properties of phototransistors comprising a UV responsive semiconductor blend 2,7-dipentyl-[1]benzothieno[2,3-b][1]benzothiophene (C5-BTBT) and a linear unsaturated polyester (L-upe). Using various self-assembly monolayers with different end-groups at the dielectric/semiconductor interface we modulated the drain photocurrent and response times under the UV light illumination of phototransistors. Treatment of the SiO₂ dielectric surface with organosilanes led to the variation of the max mobility in the dark 0.10–0.18 cm² V⁻¹ s⁻¹ and under UV light 0.08–0.50 cm² V⁻¹ s⁻¹. Interestingly, detailed crystal structure analysis using 2D X-ray diffraction and photoelectrical characterization revealed that mobility in the dark predominantly depends on the alignment of C5-BTBT crystallites at the interface. Under UV light, the mobility increased with the electron withdrawing/donating nature of the SAM end-functional group. Additionally, chemical modification of the SiO₂ dielectric surface increased photocurrent relaxation/decay times upon UV light removal while retaining fast response times when exposed to UV light, which enhanced memory properties of fabricated phototransistors (fast UV response = writing and long relaxation = long data storage).     

Optical properties of photodetectors based on single GaN nanowires with a transparent graphene contact

We report the fabrication and optical and electrical characterization of photodetectors for the UV spectral range based on single p–n junction nanowires with a transparent contact of a new type. The contact is based on CVD-grown (chemical-vapor deposition) graphene. The active region of the nitride nanowires contains a set of 30 radial In_0.18Ga_0.82N/GaN quantum wells. The structure is grown by metal-organic vaporphase epitaxy. The photodetectors are fabricated using electron-beam lithography. The current–voltage characteristics exhibit a rectifying behavior. The spectral sensitivity of the photodetector is recorded starting from 3 eV and extending far in the UV range. The maximal photoresponse is observed at a wavelength of 367 nm (sensitivity 1.9 mA/W). The response switching time of the photodetector is less than 0.1 s.     

Novel and Simple Solution-processed MIS Ultraviolet (UV) Detector Based on Core–Shell Si/SiO2 Nanocrystals

In the present study, we report a simple and solution-processed visible blind metal–insulator–semiconductor (MIS) ultraviolet (UV) detector based on core–shell Si/SiO₂ nanocrystals that are fabricated on interdigitated electrodes. The fabricated photo detector shows high photosensitivity in the UV-B and UV-C wavelength ranges. The absorption spectra of the nano-structured materials used in this work is simulated by the density functional theory (DFT) method and analyzed based on the electronic structure. It is then compared with the experimental results. The synthesized nano materials show very low density of structural defects based on the measured photoluminescence spectra, which results in a fast response time for the fabricated photodetector. Compared to the previously reported similar Si/SiO₂-based photo-detectors, the fabricated detector shows very good photo responsivity.     

A High-Performance Ultraviolet Photoconductive Detector Based on a ZnO Film Grown by RF Sputtering

A high-performance metal-semiconductor-metal (MSM) ultraviolet photodetector was fabricated based on a ZnO film with Al interdigitated (IDT) electrodes. A c-axis-oriented ZnO film was grown on a SiO₂/Si (100) substrate at room temperature by a reactive radiofrequency (RF) sputtering technique and then annealed at 900°C in pure O₂ ambient for 1 h. The fabricated ZnO ultraviolet (UV) detector demonstrated a high responsivity of 2069 A/W when biased at 5 V, which could be attributed to the influence of the annealing process in pure O₂ ambient. The response time measurement showed a rise time (10–90%) of 45.1 ns and a decay time (1 − 1/e) of 541 μs.     

Ultraviolet-visible metal-semiconductor-metal photodetectors fabricated from InxGa1−xN (0≤x≤0.13)

Metal-semiconductor-metal (MSM) photodetectors have been fabricated on In_xGa_1−xN epitaxial films grown by metalorganic chemical vapor deposition within the composition range 0≤x≤0.13. The dark current and spectral response were measured for devices with a varying In mole fraction x. The devices, which had nominal finger widths and finger spacing of 5 μm, were biased with modest voltages in the range 2≤V_bias≤5 V. In general, turn-on wave-length and dark current increased with increasing x. Turn-on wavelengths ranged from λ=370 nm to 430 nm and dark current densities ranged from I_dark=2×10⁻² A/cm² (V_bias=5 V, x≈0.05) to 9×10⁴ A/cm² (V_bias=2 V, x≈0.13) depending on the In content, x, of the device active area.