原子层沉积Al2O3/n-GaN MOS结构的电容特性

利用原子层沉积技术制备了具有圆形透明电 极的Ni/Au/Al₂O₃/n-GaN金属-氧化物-半导体结构, 研究了紫外光照对样品电容特性及深能级界面态的影响, 分析了非理想样品积累区电容随偏压增加而下降的物理起源. 在无光照情形下, 由于极长的电子发射时间与极慢的少数载流子热产生速率, 样品的室温电容-电压扫描曲线表现出典型的深耗尽行为, 且准费米能级之上占据深能级界面态的电子状态保持不变. 当器件受紫外光照射时, 半导体耗尽层内的光生空穴将复合准费米能级之上的深能级界面态电子, 同时还将与氧化层内部的深能级施主态反应. 非理想样品积累区电容的下降可归因于绝缘层漏电导的急剧增大, 其诱发机理可能是与氧化层内的缺陷态及界面质量有关的“charge-to-breakdown”过程. 关键词： 原子层沉积 2O₃/n-GaN')" href="#">Al₂O₃/n-GaN 金属-氧化物-半导体结构 电容特性     

电致发光中SiO2加速层中电子的输运特性

研究作为电致发光的加速层的SiO_2中电子的输运行为.给出SiO_2层中陷阶辅助电荷输运的理论模型,并用实验对这一模型进行了验证.认为电致发光条件下SiO_1层中的电子在低场下是以陷阱跳跃的形式输运的,而在高场下陷阱中的电子离化进入导带. 关键词：     

Ta和TaN底电极对原子层淀积HfO2介质MIM电性能的影响

以Ta,TaN为衬底,采用原子层淀积方法制备高介电常数HfO2介质,比较研究了不同衬底电极对金属-绝缘体-金属(MIM)电容的性能影响.结果表明,采用TaN底电极能够获得较高的电容密度和较小的电容电压系数(VCC),在1MHz下的其电容密度为7.47fF/μm2,VCC为356ppm/V2和493ppm/V,这归因于TaN底电极与HfO2介质之间良好的界面特性.两种电容在3V时漏电流为5×10-8A/cm2左右,基于TaN底电极的MIM电容表现出具有较高的击穿强度,其在室温下的导电机理为肖特基发射.     

Al2O3介质层厚度对AlGaN/GaN金属氧化物半导体-高电子迁移率晶体管性能的影响

在蓝宝石衬底上采用原子层淀积法制作了三种不同Al₂O₃介质层厚度的绝缘栅高电子迁移率晶体管.通过对三种器件的栅电容、栅泄漏电流、输出和转移特性的测试表明：随着Al₂O₃介质层厚度的增加,器件的栅控能力逐渐减弱,但是其栅泄漏电流明显降低,击穿电压相应提高.通过分析认为薄的绝缘层能够提供大的栅电容,因此其阈值电压较小,但是绝缘性能较差,并不能很好地抑制栅电流的泄漏;其次随着介质厚度的增加,可以对栅极施加更高的正偏压,因此获 关键词： 2O₃')" href="#">Al₂O₃ 金属氧化物半导体-高电子迁移率晶体管 介质层厚度 钝化     

Ta和TaN底电极对原子层淀积HfO2介质MIM电性能的影响

以Ta,TaN为衬底,采用原子层淀积方法制备高介电常数HfO₂介质,比较研究了不同衬底电极对金属-绝缘体-金属（MIM）电容的性能影响.结果表明,采用TaN底电极能够获得较高的电容密度和较小的电容电压系数（VCC）,在1MHz下的其电容密度为7.47fF/μm²,VCC为356ppm/V²和493ppm/V,这归因于TaN底电极与HfO₂介质之间良好的界面特性.两种电容在3?V时漏电流为5×10^-8关键词： 高介电常数 MIM电容 2薄膜')" href="#">HfO₂薄膜 电极     

不连续Co/SiO_2多层膜的结构及其输运性质的研究

用射频磁控溅射方法制备了系列Co SiO_2 不连续磁性金属绝缘体多层膜 (DMIM) .经研究发现 :对 [SiO_2 (2 4nm) Co(t) ]2 0 体系 ,在Co层厚度小于 2 5nm时 ,Co层由连续变为不连续 ;Co层不连续时 ,其导电机理为热激发的电子隧穿导电 ,lnR与T- 1 2 接近正比关系 ;隧道磁电阻 (TMR)在Co层厚度为 1 4nm时出现极大值 - 3% .DMIM的性质不仅与磁性金属层厚度密切相关 ,而且与绝缘层厚度有密切的关系 .在固定Co层厚度为 1 9nm的情况下 ,研究了TMR随SiO_2 层厚度的变化关系 ,并给出定性的解释 .对 [SiO_2 (2 4nm) Co(2 0nm) ]2 0 的样品研究了TMR随温度的变化关系 ,发现TMR随温度的变化有一极大值 ,结合Helman的理论 (Phys.Rev .Lett,37,14 2 9(1976 ) ) ,认为是颗粒之间存在磁性耦合的结果     

SiOxNy薄膜高场电子陷阱和释放特性的研究

本文研究热氮氧化硅(SiO_xN_y)薄膜在高场下的电子陷阱和被陷电子的释放。发现:当样品被氮化的程度较轻时,膜中的有效电子陷阱表面浓度随着样品被氮化时间的增加而迅速增加,被陷电子的释放率近于零,与样品被短路的时间及外加反向电场的持续时间和大小(直到8MV/cm)无关,电子陷阱能级是较深的;当样品被氮化的程度较重时,随着对样品氮化时间的进一步增加,膜中的有效电子陷阱表面浓度逐渐减小,电子陷阱能级深度逐渐变浅,被陷电子的释放率逐渐增加,并与外加反向电场和外加反向电场的 关键词：     

ZrO2光学膜的特性改善

广泛用子光学多层膜的真空蒸发ZrO_2~-薄膜若用于多层增透膜则存在一个缺点,这个缺点是由薄膜的折射率随着厚度增加而降低的光学非均匀性产生的。为了改善ZrO_2~-膜的光学均匀性,在ZrO_2~-蒸发物中添加TiO_3~-和Y_2O_3,并研究了用电子束蒸发的淀职膜的晶体结构。添加TiO_2的淀积膜的光折射率几乎是均匀的,薄膜的结构是不定形的;添加Y_2~-O_3~-的淀积膜显示出相当低的光学不均匀性和稳定的立方晶构造。通过适当添加Ti_2~-和Y_2~-O_3得到了用于多层膜的最适宜的ZrO_2~-膜;这种膜具有好的光学均匀性及足够的和可变的折射率,增加了硬度,并具有可靠的重复性。此外,从一种蒸发料片反复蒸发的薄膜的X射线衍射和X射线荧光分析的结果,推测了ZrO_2~-淀积膜的不均匀性的原因。     

双势垒结构Cu-Al2O3-MgF2-Au隧道结中的电子共振隧穿与发光特性研究

制备了Cu-Al₂O₃-MgF₂-Au双势垒隧道发光结,分析了结加上一定偏压后的电子隧穿过程.指出由于构成隧道结的绝缘栅薄膜的厚度及禁带宽度的不同而导致双势垒中能级产生分裂,使电子通过栅区时产生共振隧穿现象.根据这一现象,并结合结的I-V特性,对结的发光性能进行了讨论.这种结构的结与普通单势垒MIM结相比,其发光效率(10^-6—10^-5)提高了近一个数量级,且发光光谱的波长范围及谱峰均向短波长方向 关键词：     

第一性原理研究厚度和空位缺陷对Si/SiO2界面电子结构与光学性质的影响

采用基于密度泛函理论的平面波超软赝势方法,在局域密度近似（LDA）下研究了Si纳米层厚度和O空位缺陷对Si/SiO2界面电子结构及光学性质的影响．电子结构计算结果表明：在0.815~2.580nm的Si层厚度范围内,Si/SiO2界面结构的能隙随着厚度减小而逐渐增大,表现出明显的量子尺寸效应,这与实验以及其他理论计算结果一致;三种不同的O空位缺陷的存在均使得Si/SiO2界面能隙中出现了缺陷态,费米能级向高能量方向移动,且带隙有微弱增加．光学性质计算结果表明：随着Si纳米层厚度的减小,Si/SiO2界面吸收系数产生了蓝移;O空位缺陷引入后,界面光学性质的变化主要集中在低能区,即低能区的吸收系数和光电导率显著增加．可见,改变厚度和引入缺陷能够有效地调控Si/SiO2界面体系的电子和光学性质,上述研究结果为Si/SiO2界面材料的设计与应用提供了一定的理论依据．     

A quantum chemical study of ZrO2 atomic layer deposition growth reactions on the SiO2 surface

Zirconium oxide (ZrO₂) is one of the leading candidates to replace silicon oxide (SiO₂) as the gate dielectric for future generation metal-oxide-semiconductor (MOS) based nanoelectronic devices. Experimental studies have shown that a 1–3 monolayer SiO₂ film between the high permittivity metal oxide and the substrate silicon is needed to minimize electrical degradation. This study uses density functional theory (DFT) to investigate the initial growth reactions of ZrO₂ on hydroxylated SiO₂ by atomic layer deposition (ALD). The reactants investigated in this study are zirconium tetrachloride (ZrCl₄) and water (H₂O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. For the first half-reaction, reaction of gaseous ZrCl₄ with the hydroxylated SiO₂ surface was studied. Upon adsorption, ZrCl₄ forms a stable intermediate complex with the surface SiO₂–OH^* site, followed by formation of SiO₂–O–Zr–Cl^* surface sites and HCl. For the second half-reaction, reaction of H₂O on SiO₂–O–Zr–Cl^* surface sites was investigated. The reaction pathway is analogous to that of the first half-reaction; water first forms a stable intermediate complex followed by evolution of HCl through combination of a Cl atom from the surface site and an H atom from H₂O. The results reveal that the stable intermediate complexes formed in both half-reactions can lead to a slow film growth rate unless process parameters are adjusted to lower the stability of the complex. The energetics of the two half-reactions are similar to those of ZrO₂ ALD on ZrO₂ and as well as the energetics of ZrO₂ ALD on hydroxylated silicon. The energetics of the growth reactions with two surface hydroxyl sites are also described.     

High density Al2O3/TaN-based metal--insulator-- metal capacitors in application to radio frequency integrated circuits

Metal-insulator-metal （MIM） capacitors with atomic-layer-deposited Al2O3 dielectric and reactively sputtered TaN electrodes in application to radio frequency integrated circuits have been characterized electrically. The capacitors exhibit a high density of about 6.05 fF/μm^2, a small leakage current of 4.8 × 10^-8 A/cm^2 at 3 V, a high breakdown electric field of 8.61 MV/cm as well as acceptable voltage coefficients of capacitance （VCCs） of 795 ppm/V2 and 268ppm/V at 1 MHz. The observed properties should be attributed to high-quality Al2O3 film and chemically stable TaN electrodes. Further, a logarithmically linear relationship between quadratic VCC and frequency is observed due to the change of relaxation time with carrier mobility in the dielectric. The conduction mechanism in the high field ranges is dominated by the Poole-Frenkel emission, and the leakage current in the low field ranges is likely to be associated with trap-assisted tunnelling. Meanwhile, the Al2O3 dielectric presents charge trapping under low voltage stresses, and defect generation under high voltage stresses, and it has a hard-breakdown performance.     

Interfacial properties of 2D WS2 on SiO2 substrate from X-ray photoelectron spectroscopy and first-principles calculations

Two-dimensional (2D) WS₂ films were deposited on SiO₂ wafers, and the related interfacial properties were investigated by high-resolution X-ray photoelectron spectroscopy (XPS) and first-principles calculations. Using the direct (indirect) method, the valence band offset (VBO) at monolayer WS₂/SiO₂ interface was found to be 3.97 eV (3.86 eV), and the conduction band offset (CBO) was 2.70 eV (2.81 eV). Furthermore, the VBO (CBO) at bulk WS₂/SiO₂ interface is found to be about 0.48 eV (0.33 eV) larger due to the interlayer orbital coupling and splitting of valence and conduction band edges. Therefore, the WS₂/SiO₂ heterostructure has a Type I energy-band alignment. The band offsets obtained experimentally and theoretically are consistent except the narrower theoretical bandgap of SiO₂. The theoretical calculations further reveal a binding energy of 75 meV per S atom and the totally separated partial density of states, indicating a weak interaction and negligible Fermi level pinning effect between WS₂ monolayer and SiO₂ surface. Our combined experimental and theoretical results provide proof of the sufficient VBOs and CBOs and weak interaction in 2D WS₂/SiO₂ heterostructures.     

Binding energies of elements at the interface between oxygen-ion-irradiated ZrO2–Y2O3 films and an iron substrate

Binding energies of elements at the interface of oxygen-ion-irradiated ZrO₂–Y₂O₃ films on an iron substrate were investigated by using X-ray photoelectron spectroscopy (XPS) combined with ion etching. In addition to Zr or Fe simple binary suboxides, it is found that some Zr–O–Fe-like bonding configuration is formed due to ion irradiation, which has a favorable effect on the adhesion of the film to the substrate.     

LaON/SiO2和HfON/SiO2双隧穿层MONOS存储器存储特性的比较

本文对比研究了LaON/SiO₂和HfON/SiO₂双隧穿层MONOS存储器的存储特性. 实验结果表明,LaON/SiO₂双隧穿层MONOS存储器具有较大的存储窗口,快的编程/擦除速度及好的疲劳和保持特性. 其机理在于LaON较大的介电常数有效提高了编程/擦除过程中载流子的注入效率,较小的O 扩散系数减少了界面陷阱,从而减少了保持期间存储电荷通过陷阱辅助隧穿的泄漏. 而且N的结合在界面附近形成了强的La-N,Hf-N 和O-N键,可有效降低编程/擦除循环应力对界面的损伤,使器件具有好的疲劳特性. 此外,研究了退火温度对存储特性的影响,结果表明800 ℃退火样品的存储特性比700 ℃退火的好,这是因为800 ℃时NO退火可在LaON（HfON）中引入更多的N,且能更好释放应力,使介质中缺陷减少. 关键词： MONOS 双隧穿层 LaON HfON     

二氧化硅对稀土掺杂二氧化钛薄膜形貌与发光性能的影响

为提高稀土掺杂TiO₂薄膜的上转换效率,采用溶胶-凝胶法和旋涂镀膜工艺制备了Yb³⁺-Er³⁺共掺杂SiO₂/TiO₂上转换光致发光薄膜,研究了SiO₂对TiO₂薄膜形貌以及发光性能的影响。利用FE-SEM观察了薄膜的表面形貌,利用分光光度计测试了薄膜在近红外光区域的透射率的变化,并用荧光光谱仪测试了薄膜的上转换发光光谱。结果表明：SiO₂的掺杂导致TiO₂颗粒尺寸显著减小,TiO₂薄膜在近红外的透射率也有所下降。在980 nm红外光激发下,SiO₂/TiO₂薄膜在630~670 nm处获得了明显的上转换红光发射,在516~537 nm和537~570 nm处获得了较弱的上转换绿光发射。由上转换发光强度与激光泵浦功率的关系推知,绿色和红色上转换发光均为双光子吸收发射过程。     

花状掺杂W-VO$lt;sub$gt;2$lt;/sub$gt;/ZnO热致变色纳米复合薄膜研究

为解决掺杂引起的二氧化钒薄膜的红外调制幅度下降以及二氧化钒复合薄膜相变温度需要进一步降低等问题, 采用纳米结构、掺杂改性和复合结构等多种机理协同作用的方案, 利用共溅射氧化法, 先在石英玻璃上制备高(002)取向的ZnO薄膜, 再在ZnO层上室温共溅射沉积钒钨金属薄膜, 最后经热氧化处理获得双层钨掺杂W-VO₂/ZnO纳米复合薄膜. 利用X射线衍射、X射线光电子能谱、扫描电镜和变温光谱分析等对薄膜的结构、组分、形貌和光学特性进行了分析. 结果显示, W-VO₂/ZnO 纳米复合薄膜呈花状结构, 取向性提高, 在保持掺杂薄膜相变温度(约39 ℃)和热滞回线宽度(约6 ℃)较低的情况下, 其相变前后的红外透过率差量增加近2倍, 热致变色性能得到协同增强. 关键词： 2')" href="#">VO₂ ZnO W掺杂 热致变色     

Thermodynamic modeling of the ZrO2–YO1.5 system

In the present work, an optimized set of Gibbs energy functions is proposed for the Y–Zr–O ternary system. We focus on the ZrO₂–YO_1.5 quasi-binary system, but reoptimizations of the Zr–O and Y–O binary systems are included as well. The parameters for the Y–Zr binary system were taken from a previous assessment.

The ZrO₂–YO_1.5 system was treated as a quasi-binary section of the Y–Zr–O ternary system. The existing experimental data on the ZrO₂–YO_1.5 system were carefully reviewed. The related parameters were optimized using both thermodynamic data and phase diagram data. A calculated phase diagram of the ZrO₂–YO_1.5 system is presented. Our optimization agrees well with most experimental data. Two calculated isothermal sections of the Y–Zr–O system at 1500 and 2000 K are also included.     

Characterization of SiO2 layers thermally grown on 4H-SiC using high energy photoelectron spectroscopy

Si 2p and C 1s core level spectra recorded at different electron emission angles from SiO₂/SiC samples using a photon energy of 3.0 keV show two components. These are identified as originating from SiO₂ and SiC for Si 2p while for C 1s they are identified to originate from graphite like carbon and SiC. The relative intensity of these components are extracted and compared to calculated intensity variations assuming different models for the elemental distribution in the surface region. For both samples investigated best agreement between experimental and calculated intensity variations with emission angle is obtained when assuming a graphite like layer on top of the oxide layer. Contribution from carbon at the SiC/SiO₂ interface could not be identified.