衬底温度对Mg0.1Zn0.9O薄膜结构及光学性能的影响

利用射频磁控溅射技术在不同温度的(100)Si和玻璃衬底上成功地制备了c轴择优取向的Mg0.1Zn0.9O薄膜.通过X射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外可见光分光光度计和光致发光谱研究了衬底温度对Mg0.1Zn0.9O薄膜结构、表面形貌和光学性能的影响,结果表明,在衬底温度为400℃时生长的Mg0.1Zn0.9O薄膜具有很好的c轴取向和较好的光学性能.用激发波长为300nm的氙灯作为激发光源得到不同衬底温度下Mg0.1Zn0.9O薄膜的室温PL谱.分析表明,紫外发光峰与薄膜的结晶质量密切相关,蓝光发射与氧空位有关.简单探讨了衬底温度影响紫外光致发光峰红移和蓝移的可能机理.     

Zn0.85Co0.15O薄膜的制备及其结构分析

用电子束蒸镀方法在(100)单晶Si衬底上,生长Zn0.85Co0.15O薄膜,并研究了衬底温度对薄膜质量的影响,结果表明当衬底温度为400℃时,外延膜取向性最好,且其(002)衍射峰半高宽最窄(为0.4834°)。     

Mg2Si半导体薄膜的热蒸发制备

采用电阻式热蒸发方法和退火工艺制备出了Mg2Si半导体薄膜。研究了退火时间对Mg2Si薄膜的形成和结构的影响。首先在Si(111)衬底上沉积380nm Mg膜,然后在退火炉低真空10-1～10-2Pa氛围400℃退火,退火时间分别为3、4、5、6和7h。通过X射线衍射仪(XRD)、场发射扫描电镜(FESEM)和拉曼光谱仪对薄膜的结构、形貌和光学性质进行了表征。结果表明,采用电阻式热蒸发方法成功地制备了半导体Mg2Si薄膜,Mg2Si薄膜具有Mg2Si(220)的择优生长特性。最强衍射峰出现在40.12°位置,随着退火时间的延长,Mg2Si(220)衍射峰强度先逐渐变强后变弱,退火4h时该峰强度最强。在256和690cm-1附近有两个Mg2Si拉曼特征峰,退火时间为4和7h时,256cm-1附近Mg2Si拉曼特征峰较强。     

Mg2Si半导体薄膜的磁控溅射制备

采用磁控溅射技术和退火工艺制备出Mg2Si半导体薄膜,研究了退火时间对Mg2Si薄膜的形成和结构的影响.首先在Si(111)衬底上溅射沉积380nm Mg膜,然后在退火炉内氩气氛围500℃退火,退火时间分别为3.5h、4.5h、5.0h、5.5h、6.0h.采用X射线衍射和扫描电镜对薄膜的结构和形貌进行了表征.结果表明,采用磁控溅射方法成功地制备了环境友好的半导体Mg2Si薄膜.Mg2Si薄膜具有Mg2Si(220)的择优生长特性,最强衍射峰出现在40.12°位置;随着退火时间的延长,Mg2Si外延薄膜的衍射峰强度先逐渐增强后逐渐减弱,退火5h后,样品的衍射峰最强.Mg2Si晶粒随着退火时间的延长,先逐渐增大,退火5h后逐渐减小.     

Zn0.9Mg0.1O:Ga宽带隙导电膜的 PLD制备及性能研究

利用脉冲激光沉积法(PLD)制备了Ga掺杂的Zn0.9Mg0.1O(ZMOGa)宽带隙透明导电薄膜.采用各种分析手段研究了沉积温度和真空退火处理对薄膜结构、表面形貌及光电性能的影响.结果表明,制备的薄膜具有ZnO(002)择优取向;200℃下沉积的薄膜通过3×10-3Pa的真空400℃退火2h后,其电阻率由8.12×10-4Ω·cm减小到4.74×10-4Ω·cm,禁带宽度则由原来的3.83eV增加到3.90eV.退火处理增强了薄膜的择优取向和结晶度、增加了禁带宽度、提高了载流子浓度并使其透射谱线的光学吸收边发生蓝移现象.     

退火对立方相 MgxZn1-xO薄膜的结构和光学性质影响

在蓝宝石（0001）衬底上低温生长立方相MgxZn1-xO（x〉0．5）晶体薄膜，用X射线衍射（XRD）和透射光谱分析高温退火对薄膜的结构和光学性质的影响．结果表明;对Mg0．53Zn0．47O薄膜，在900℃的退火温度下，（0002）衍射峰以及透射光谱上双吸收边的出现均表明有六方结构从其立方结构中分离出来；但对于Mg含量高于55％的样品，即使经历了1000℃的高温退火，也不会有任何相分裂现象出现．而电学测试结果表明，高温下热稳定性良好的立方相Mg0．55Zn0．45O晶体薄膜还能用于金属-绝缘体-半导体的绝缘层，并且漏电流小．由此可以判断，x≥0．55的超饱和MgZn1-xO薄膜具有稳定的立方相晶体结构和优良的光学、电学性质，因而是制作高质量的光电子器件和量子阱激光器的理想材料．     

衬底温度对Zn0.85 Mg0.13 Al0.020薄膜结构和发光特性的影响

采用射频磁控溅射方法,在Si(111)基片上制备出Zn0.85Mg0.13Al0.02O薄膜。X射线衍射(XRD)证实Zn0.85Mg0.13Al0.02O薄膜为单相六角钎锌矿结构,衬底温度从室温升高到500℃,薄膜沿c轴择优生长。原子力显微镜(AFM)测量显示薄膜表面粗糙度随衬底温度的升高由9.32nm增加到19.94nm。荧光光谱仪(PL)测量显示薄膜在397nm附近有强的紫光发射,在486nm处有弱的蓝光峰,随衬底温度的升高紫峰强度提高15倍。在可见光范围内,薄膜平均透过率随衬底温度的升高由75%增加到95%,薄膜光学带隙分别为3.18,3.18和3.19eV。分析表明紫峰来自于自由激子复合,蓝峰由俘获在施主能级Zn填隙中的电子与俘获在受主能级Zn空位中的空穴复合而产生发光。     

镁含量和热处理对Zn_(1-x)Mg_xO薄膜结构的影响

采用溶胶-凝胶法在玻璃衬底上制备了Zn1-xMgxO(x=0.1、0.2、0.3、0.4、0.5、0.6)薄膜。X射线衍射谱测试结果发现,在0.1x0.3范围内薄膜仍然保持纤锌矿结构,(002)衍射峰向大角度方向移动,超过0.3时出现氧化镁立方相。对于Zn0.7Mg0.3O薄膜,在5、5.5、6℃/min的升温速率下,升温速率越快结晶程度越好。在相同升温速率下,随着退火温度从500℃升高到560℃,样品的结晶程度变好,当退火温度达到590℃时结晶程度变差。     

O2气流量对MOCVD法生长ZnO薄膜性质的影响

采用低压MOCVD方法,在(0001)Al2O3衬底上沉积了ZnO薄膜.研究了Ⅵ族源O2气流量的变化对薄膜结构、表面形貌及光致发光特性的影响.增加O2气流量,ZnO薄膜结晶质量有所降低,半高宽从0.20°展宽至0.30°,由单一c轴取向变成无取向薄膜.同时,生成的柱状晶粒平均尺寸减少,晶粒更加均匀,均方根粗糙度减小.PL谱分析表明随O2气流量加大,带边峰明显增强,深能级峰明显减弱,ZnO薄膜光学质量提高.这些事实说明在本实验条件下,采用低压MOCVD方法生长的ZnO薄膜在光致发光特性主要依赖于Zn、O组份配比,而不是薄膜的微观结构质量.     

等离子体辅助MOCVD生长的ZnO薄膜退火改性研究

用等离子体辅助MOCVD法在蓝宝石 (α Al2 O3)上生长了ZnO薄膜 ,测试了其退火和未退火薄膜的电阻率、电子浓度、迁移率、激光阈值 ,并通过X光衍射、光致发光方法表征了ZnO薄膜的质量 ,其结果是 :退火薄膜的电子浓度低达 10 15/cm3 量级、激光阈值降低近 30倍、X光衍射峰半高宽是 0 .2 9°、在 388nm附近的光致发光谱峰半高宽为 0 .32nm。这表明退火使ZnO薄膜的质量得到大幅度提高     

Varistor properties of ZnO-Pr6O11-CoO-Cr2O3-Y2O3-In2O3 ceramics

The varistor properties of the ZnO-Pr₆O₁₁-CoO-Cr₂O₃-Y₂O₃-In₂O₃ ceramics were investigated for different concentrations of In₂O₃. The increase of In₂O₃ concentration slightly increased the sintered density (5.60-5.63 g/cm³) and slightly decreased the average grain size (3.4-2.9 μm). The breakdown field increased from 6023 to 14822 V/cm with increasing concentration of In₂O₃. The nonlinear coefficient increased from 17.6 to 44.6 for up to 0.005 mol%, whereas the further doping caused it to decrease to 36.8. In₂O₃ acted as an acceptor due to the donor concentration, which decreases in the range of 1.02 × 10¹⁷ to 0.24 × 10¹⁷/cm³ with increasing concentration of In₂O₃.     

Nanocrystallization of SrBi2Nb2O9 from glasses in the system Li2B4O7---SrO---Bi2O3---Nb2O5

Transparent glasses in the system (100−x)Li₂B₄O₇–x(SrO---Bi₂O₃---Nb₂O₅) (10≤x≤60) (in molar ratio) were fabricated by a conventional melt-quenching technique. Amorphous and glassy characteristics of the as-quenched samples were established via X-ray powder diffraction (XRD) and differential thermal analyses (DTA) respectively. Glass–ceramics embedded with strontium bismuth niobate, SrBi₂Nb₂O₉ (SBN) nanocrystals were produced by heat-treating the as-quenched glasses at temperatures higher than 500 °C. Perovskite SBN phase formation through an intermediate fluorite phase in the glass matrix was confirmed by XRD and transmission electron microscopy (TEM). Infrared and Raman spectroscopic studies corroborate the observation of fluorite phase formation. The dielectric constant (_r) and the loss factor (D) for the lithium borate, Li₂B₄O₇ (LBO) glass comprising randomly oriented SBN nanocrystals were determined and compared with those predicted based on the various dielectric mixture rule formalism. The dielectric constant was found to increase with increasing SBN content in LBO glass matrix.     

Characterization of YBa2Cu3O7/PrBa2Cu3O7 superlattices

We investigated the structural and superconducting properties ofc-axis oriented (YBa₂Cu₃O₇) _nY /(PrBa₂Cu₃O₇) _npr superlattices with thicknesses of the individual layers down to one unit cell (10nY1; 18>nPr 1). By transmission electron microscopy and X-ray diffraction we find an excellent structural quality of the samples, though the quantitative analysis shows the existence of defects. In superlattices with decoupled YBa₂Cu₃O₇ layers of two unit cell thickness we find a highT _c value of 75 K. We probed the flux line structure in the superlattices by measurements of the critical current density in magnetic fields. The experiments show that the flux-line dynamics is dominated by the movement of pancake vortices.     

Syntheses of hollandite type Rb2Cr8O16, K2Cr2V6O16 and K2V8O16

Hollandite-type compounds, Rb₂Cr₈O₁₆, K₂Cr₂V₆O₁₆ and K₂V₈O₁₆, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb₂Cr₈O₁₆ confirms that the structure is similar to that of K₂Cr₈O₁₆. Magnetic measurements indicate that Rb₂Cr₈O₁₆ is ferromagnetic below 295K, K₂Cr₂V₆O₁₆ paramagnetic down to 77K and K₂V₈O₁₆ has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies.     

Magnetic coupling in La0.67Ca0.33MnO3/La0.67Sr0.33CoO3/La0.67Ca0.33MnO3 sandwiches

La_0.67Ca_0.33MnO₃ (LCMO)/La_0.67Sr_0.33CoO₃ (LSCO)/LCMO trilayer films are fabricated on single-crystal substrates NdGaO₃ (110) and the interlayer coupling are investigated. Compared with LCMO single layer, sandwiches showed the enhanced metal-insulator transition temperature of LCMO layers. The magnetoresistance is dependent on spacer thickness and the peak value dramatically decreases when LSCO layer is thick enough because of shorting by the LSCO layer. The magnetic coercivity H_C shows a nonmonotonic behavior with changing spacer layer thickness and the waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom LCMO layers across the spacer layer.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.     

MoO3-V2O5-P2O5-Fe2O3玻璃的制备及性能研究

制备了MoO3-V2O5-P2O5-Fe2O3系磷酸盐玻璃,研究了玻璃形成能力、热膨胀系数和抗潮解等性能.结果表明,MoO3-V2O5-P2O5-Fe2O3系统具有较宽的玻璃形成区和较强的玻璃形成能力,当MoO3/V2O5≈1.5时,玻璃形成能力最强.MoO3-V2O5-P2O5-Fe2O3玻璃的热膨胀系数约为60～110×10-7/℃,并且随着Fe2O3含量的增加而逐渐增大.加入适量的Fe2O3能够显著改善MoO3-V2O5-P2O5玻璃的抗潮解性能,在90℃的去离子水中的溶解速率达到8.0×10-9g·cm-2·min-1.     

Structural study of Sr0.3Ba0.7Nb2O6 and La0.030Sr0.255Ba0.700Nb2O6 ceramic systems

Sr_0.3Ba_0.7Nb₂O₆ (SBN) and La_0.030Sr_0.255Ba_0.700Nb₂O₆ (LSBN) ceramic compounds have been prepared using the traditional ceramic method at two different calcination temperatures (900 and 1000 °C) and later sintered both at 1400 °C. A study of the effects of the calcination temperatures and La substitution on the morphological, compositional, and structural properties of SBN and LSBN is presented using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. From Rietveld refinement processes, the XRD patterns were interpreted to evaluate such effects in the structural parameters and the site occupation factors of the heavy metals and oxygen atoms. The effect of the incorporation of La resulted in a 0.25% cell contraction and turned out to be higher than the 0.08% dilation effect produced by the increase of calcination temperature. The La ion with similar effective ionic radius and higher electronegativity is incorporated into the structure occupying the A₁ site just like the Sr ions in the SBN compound. Differences in the site occupation factors between the SBN and LSBN samples lead to substantial changes in the physical properties such as temperature of relative dielectric constant maximum, relative dielectric constant, and dielectric loss, correlated with the distortion and the relative orientation of the oxygen octahedra.     

Microstructures of YBa2Cu3O7/La0.7Ca0.3MnO3 and La0.7Ca0.3MnO3/YBa2Cu3O7 bi-layers grown on (001)LaAlO3

Epitaxial YBa₂Cu₃O₇/La_0.7Ca_0.3MnO₃ (YBCO/LCMO) bi-layers and La_0.7Ca_0.3MnO₃/YBa₂Cu₃O₇ (LCMO/YBCO) bi-layers were grown on (001)LaAlO₃ by pulsed laser deposition, and their microstructures were compared by transmission electron microscopy investigation. In the YBCO(100 nm)/LCMO(150 nm) bi-layers, the LCMO layer consists of columnar grains of ~ 17 nm in diameter and contains mixed orientation domains of [100]_c, [010]_c and [001]_c. The YBCO layer is totally c-axis oriented and the YBCO lattices are tilted − 2.5° to + 2.5° as they grew on the rough surfaces of LCMO columnar grains. For the LCMO(140 nm)/YBCO(140 nm) bi-layers, the LCMO/YBCO interface is sharp and flat. The initial 12-nm thickness of the YBCO layer is composed of c-axis oriented domains, and the upper part of YBCO layer is [100] oriented. The LCMO layer was predominantly [001]_c oriented while [100]_c-oriented domains were occasionally observed.     

MgO-Al2O3-SiO2-TiO2-Y2O3玻璃的弹性模量

根据硬盘基板用材料的要求，制备了MgO-Al2O3-SiO2-TiO2-Y2O3高弹性模量玻璃（120GPa)，玻璃的弹性模量随组成的变化服从Makishima-Mackenzie理论，MgO,Al2O3,TiO2,Y2O3等具有较高单位体积离解能的氧化物有利于提高玻璃的弹性模量，但玻璃弹性模量的理论计算值低于测试值，这是因为Makishima-Mackenzie理论没有考虑玻璃内阳离子的具体配位，对MgO,Y2O3堆积密度因子的堆导存在误差，因此利用Makishima-Mackenzie理论发展高弹性模量玻璃时应对MgO,Y2O3等氧化物的计算进行修正。