Si(100)衬底上n-3C-SiC/p-Si异质结构研究

利用LPCVD方法在Si(100)衬底上获得了3C-SiC外延膜,扫描电子显微镜(SEM)研究表明3C-SiC/p-Si界面平整、光滑,无明显的坑洞形成。研究了以In和Al为接触电极的3C-SiC/p-Si异质结的I-V,C-V特性及I-V特性的温度依赖关系,比较了In电极的3C-SiC/p-Si异质结构和以SiGe作为缓冲层的3C-SiC/SiGe/p-Si异质结构的I-V特性,实验发现引入SiGe缓冲层后,器件的反向击穿电压由40V提高到70V以上。室温下Al电极3C-SiC/p-Si二极管的最大反向击穿电压接近100V,品质因子为1.95。     

Effect of excess Pb on crystallinity and ferroelectric properties of PZT(40/60) films on LaNiO3 coated Si substrates by MOD technique

Pb(Zr_0.4Ti_0.6)O₃ [PZT(40/60)] films were deposited onto LaNiO₃ (LNO) coated Si substrates by metal-organic decomposition (MOD) technique. Excess Pb was incorporated in the film by using excess Pb (2%–15%) in the solution. The crystallinity and ferroelectric properties of PZT films were investigated by using X-ray diffraction (XRD), RT66A test system and HP4194 impedance analyzer, respectively. Rayleigh law was employed to analyze the defect concentration in the films. The results show that all the PZT films show the (1 0 0) preferential orientation with complete perovskite structure except for the 2% film displaying some pyrochlore phase. The (1 0 0) preferential orientation is mainly attributed to LNO bottom electrode, which has the highly (1 0 0) preferential orientation. The 10% film shows the best polarization and dielectric properties. The remnant polarization and coercive field are about 10.1 μC/cm² and 73 kV/cm under an electric field around 330 kV/cm, respectively. And the dielectric constant and dissipation factor are about 656 and 0.022 at a frequency of 1 kHz, respectively. The good ferroelectric properties of the 10% film are mainly attributed to the low defect concentration in the film.     

Fe3O4/MgO(100)薄膜外场诱导电阻变化特性

采用激光分子束外延（L-MBE）方法,以MgO(100)为基底生长了Fe3O4单晶薄膜, 研究了Fe3O4/MgO(100)薄膜外场（温度、磁和激光场）诱导电阻变化特性。X射线衍射(XRD)分析表明Fe3O4薄膜是沿MgO(200)晶面外延生长的单晶薄膜;反射高能电子衍射（RHEED）强度振荡曲线分析表明Fe3O4薄膜表面平整,而且生长模式为2维层状生长;原子力显微镜（AFM）分析表明Fe3O4薄膜表面粗糙度为0.201 nm,说明薄膜表面达到原子级平整度。外场作用下Fe3O4薄膜的电阻测试表明:薄膜样品的电阻在120 K(Verwey转变温度)出现一峰值,略微下降后继续增大, 展现出半导体型的导电特性; 在激光作用下,整个测量温度范围内薄膜样品的电阻减小,样品展示出瞬间光电导的特性;从降温曲线可以看出, Verwey转变温度由无激光作用时的120 K上升到有激光作用时的140 K; 光致电阻变化率随着温度的降低而增大,这主要是由于激光作用导致电荷有序态的退局域化。     

(111)取向生长Pb(Zr0:95Ti0:05)O3纳米晶薄膜的铁电与热释电特性

" 在Pt/Ti/SiO2/Si基片上用溶胶-凝胶法与快速退火工艺制备了300 nm厚的锆钛酸铅Pb(Zr0:95Ti0:05)O3 (PZT95/5)反铁电薄膜．结果显示600~700 ℃晶化处理的钙钛矿PZT95/5薄膜具有高度(111)取向生长特性．薄膜的电性能测量采用金属-铁电-金属电容器结构．在20 V电压作用下,600~700 ℃晶化处理的PZT95/5薄膜显示出饱和电滞回线．在1 kHz下,600、650和700 ℃晶化的薄膜介电常数与损耗分别为519与0.028、677与0.029、987     

The transverse laser induced thermoelectric voltages in step flow growth （1-x）Pb(Mg1/3Nb2/3)O3-xPbTiO3 thin films

This paper reports that the transverse laser induced thermoelectric voltages (LITV) are observed for the first time in the step flow growth (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT,x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength,the largest induced voltage is observed in the 0.50Pb(Mg1/Nb2/3)O3-0.50PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.     

Absence of traditional magnetoresistivity mechanisms in Sr(2)FeMoO(6) thin films grown on SrTiO(3), MgO and NdGaO(3) substrates

Magnetoresistive double perovskite Sr(2)FeMoO(6) thin films were grown with two different deposition pressures on SrTiO(3), MgO and NdGaO(3) substrates by pulsed laser deposition and thorough structural, magnetic and magneto-transport characterization was made. According to x-ray diffraction, all the films were phase pure and fully textured. Indication of substrate dependent strain and low angle grain boundaries was found, especially in films on MgO. Both the deposition pressure and the choice of the substrate have a strong influence on the saturation magnetization, M(s), and Curie temperature, T(C). The structural and magnetic data indicate the presence of anti-site disorder (ASD) in the films. The temperature dependence of resistivity showed semiconductive behaviour at temperatures below 100 K and metallic behaviour at higher temperatures. The semiconductive behaviour was found to increase with increasing ASD. In good quality films, up to 12% negative magnetoresistance (MR) was observed and films grown on MgO and NGO substrates also showed low field MR. However, the most significant observation of this study was that the magnetoresistivity of these Sr(2)FeMoO(6) thin films could not be explained with any traditional MR mechanism, but carried the clear signature of superposition of different mechanisms, in particular low angle grain boundary tunnelling and suppression of antiferromagnetically ordered domains under a magnetic field.     

SiO_x(x=1.3)薄膜的优化阻变特性与退火温度的关系探究

采用电子束蒸发技术在Si衬底上制备了亚氧化硅SiOx(x=1.3)薄膜,研究了不同温度热退火处理的SiOx薄膜作为阻变层的ITO/SiOx/Si/Al结构的阻变特性.研究发现,在电极尺寸相同的条件下,随着退火温度的增加,该结构的高低阻态比显著提高,最高可达109.X射线光电子能谱和电子顺磁共振能谱的分析表明,不同退火温度下形成的不同价态的硅悬挂键是低阻态下细丝通道的主要来源.椭偏仪的测试结果表明,经过热退火处理的SiOx薄膜折射率的增大是导致高阻态下器件电阻增大的原因.     

低工作电压聚噻吩薄膜晶体管

以高掺杂Si单晶片作为衬底且充当栅电极,采用磁控溅射法在硅片上沉积HfTiO薄膜作为栅介质层,聚三己基噻吩(P3HT)薄膜作为半导体活性层,金属Au作为源、漏电极,并采用十八烷基三氯硅烷(OTS)对栅介质层表面修饰,在空气环境下成功地制备出聚合物薄膜晶体管(PTFT).PTFT器件测试结果表明,该晶体管在低的驱动电压(<-1 V)下仍呈现出良好的饱和行为,其阈值电压和有效场效应迁移率分别为0.4 V和2.2×10^-2 cm²/V ·s.通过对金属-聚合物-氧化物 关键词： 聚合物薄膜晶体管 聚三己基噻吩 场效应迁移率 k栅介质')" href="#">高k栅介质     

Effect of Misfit Strain on Pyroelectric Properties of (111) Oriented Pb(Zr1-xTix)O3 Thin Films

Based on the Landau-Dovenshire theory, the thermodynamic potential of (111) oriented films is constructed to investigate the pyroelectric properties of Pb(Zr_1-xTi_x)O₃ thin films. Due to the presence of nonlinear coupling terms resulted from the (111) epitaxy with substrates, the effects of misfit strain and electric field on the phase transitions at room temperature are more complex than that of (001) and (110) oriented films. Pb(Zr_0.5Ti_0.5)O₃ thin films with the Ti composition around the morphotropic phase boundary (MPB) have the giant dielectric and pyroelectric properties. Moreover, Pb(Zr_1-xTi_x)O₃ thin films grown on the tensile substrates which induce the triclinic γ phase have the larger dielectric and pyroelectric properties than that on the compressive substrates. Therefore, the physical properties of (111) oriented Pb(Zr_1-xTi_x)O₃ thin films can be adjusted by choosing the suitable substrates.     

不同生长方向的La0.7Sr0.3MnO3薄膜结构及性能研究

利用磁控溅射方法,在(100),(110)和(111)LaAlO3(LAO)衬底上制备得到了不同生长方向的La0.7Sr0.3MnO3(LSMO)薄膜并对其结构及磁电学性能进行了系统研究.结果表明:LSMO薄膜完全按LAO衬底取向生长;(111)生长方向的薄膜由于晶格畸变程度最小,磁畴方向能较好的保持一致性,从而具有最大的磁饱和强度值;高的磁有序度减弱了巡游电子eg的自旋无序相关散射,有效降低了电阻.但外加磁场后电阻变化不明显,最大磁电阻值只有5.1%.     

Dielectric enhancement in pulsed-laser-deposited (Pb,Sr)TiO3/(Pb,La)TiO3 multilayered films

Multilayered (Pb_0.5Sr_0.5)TiO₃(PST)/Pb_0.8La_0.2TiO₃(PLT)/PST and PLT/PST/PLT films were prepared on platinum coated silicon substrates by pulsed laser deposition. Significant enhancement of the dielectric constant over the whole temperature region from 30 °C up to 220 °C has been observed for both multilayers with respect to the identically prepared single-component PST and PLT films. However, larger frequency dispersion of dielectric properties has also been obtained in the multilayers. This effect is attributed to the compositional fluctuation revealed by the atomic interdiffusion in the interface regions of the multilayers. Thermally and electric-field driven space charges at relative low temperature and low electric field were found in the PLT/PST/PLT and PLT films, attributed to the substitution of La³⁺ non-isovalent for Pb²⁺ in these films. PACS 81.15.Fg; 42.70.Mp; 79.60.Jv     

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb_1−XLa_XTiO₃ thin films, (X=0.0; 13 and 0.27 mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO₂/Si (1 1 1), Si (1 0 0) and glass substrates by spin coating, and annealed in the 200-300°C range in an O₂ atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO₃. The films deposited on Pt/Ti/SiO₂/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration.     

不同衬底上Pb(Zr0.52Ti0.48)O3择优取向铁电薄膜的制备和研究

通过MOD法在Si(100)和Pt(111)/Ti/SiO₂/Si基片上制备出LaNiO₃ ( LNO)薄膜.再通过修 正的Sol-gel法，在Pt(111)/Ti/SiO₂/Si,LNO/Si(100)和LNO/Pt/Ti/SiO_{2< /sub>/Si三种衬底上 制备出具有择优取向的Pb(Zr0.52Ti0.48)O3铁电薄膜. 经XRD分析表明，L NO薄膜具有(100)择优取向的类钙钛矿结构；PZT薄膜均具有钙钛矿结构，且在Pt(111)/Ti/S iO2/Si衬底上的薄膜以(110)择优取向，在LNO/Pt/Ti/SiO2/Si和LN O/Si(100)衬底上的 薄膜以(100)择优取向.经场发射SEM分析和介电、铁电性能测试表明，在LNO/Si和LNO/Pt/Ti /SiO2/Si衬底上的PZT薄膜的平均粒径、介电常数以及剩余极化强度均比以Pt/T i/SiO2/Si为衬底的薄膜大. 关键词： 3}薄膜')" href="#">LaNiO₃薄膜 PZT铁电薄膜 择优取向 剩余极化强度     

Growth and characterization of La2/3Ca1/3MnO3 thin films on ‘silicon on insulator’ substrates

La_2/3Ca_1/3MnO₃ thin films have been grown on SrTiO₃, LaAlO₃, and yttria-stabilized zirconia buffered silicon-on-insulator (SOI) substrates by the pulsed laser deposition technique. While full cube-on-cube epitaxy was achieved on the SrTiO₃ and LaAlO₃ substrates, a coexistence of the cube-on-cube and cube-on-diagonal epitaxy was observed in the the manganite films on SOI substrates. Besides the intrinsic four-fold magnetocrystalline anisotropy, a uniaxial anisotropy also exists in the films, which is determined by the demagnetization field and the mismatch-induced strain. A tensile strain leads to an easy plane, while a compressive strain favors an easy axis. The different magnetization configurations in the films on different substrates are the reason for their varied transport and magnetic properties. Due to a combined effect of these magnetic anisotropy, the magnetization in the two crystallography domains in the film on SOI tends to lie in the film plane but align in their respective easy axes. There are always large spin angles across the domain boundaries. As a result, a quite large low-field magnetoresistance (LFMR) based on spin-dependent tunnelling was observed. It shows a resistance change of ∼20% at 50 K in a magnetic field ∼700 Oe, which is promising for real applications. PACS 75.47.Lx; 72.25.Mk     

Optical Analysis of Nanocrystalline ZnO Films Coated on Porous Silicon by Radio Frequency (RF) Magnetron Sputtering

Zinc oxide thin films have been deposited onto porous silicon (PSi) substrates at high growth rates by radio frequency (RF) sputtering using a ZnO target. The advantages of the porous Si template are economical and it provides a rigid structural material. Porous silicon is applied as an intermediate layer between silicon and ZnO films and it contributed a large area composed of an array of voids. The nanoporous silicon samples were adapted by photo electrochemical (PEC) etching technique on n-type silicon wafer with (111) and (100) orientation. Micro-Raman and photoluminescence (PL) spectroscopy are powerful and non-destructive optical tools to study vibrational and optical properties of ZnO nanostructures. Both the Raman and PL measurements were also operated at room temperature. Micro-Raman results showed that the A₁(LO) of hexagonal ZnO/Si(111) and ZnO/Si(100) have been observed at around 522 and 530 cm^–1, re- spectively. PL spectra peaks are distinctly apparent at 366 and 368 cm^–1 for ZnO film grown on porous Si(111) and Si(100) substrates, respectively. The peak luminescence energy in nanocrystalline ZnO on porous silicon is blue-shifted with regard to that in bulk ZnO (381 nm). The Raman and PL spectra pointed to oxygen vacancies or Zn interstitials which are responsible for the green emission in the nanocrystalline ZnO.     

Mn掺杂对多铁性BiFeO_3薄膜铁电性能以及漏电流的影响

本文利用脉冲激光沉积技术在(LaAlO3)0.3(Sr2AlTaO6)0.7(001)衬底上生长了BiFe1-xMnxO3(x=0～5%)外延薄膜,研究了Mn掺杂对BiFeO3(BFO)薄膜结构、铁电特性和漏电流的影响.XRD和SEM结果表明薄膜具有良好的结晶质量.漏电流测量显示Mn掺杂有效地减小了BFO薄膜的漏电流密度,因而在室温下5%Mn掺杂的BFO薄膜能够获得饱和的电滞回线.XPS分析证明,Mn掺杂改善BFO薄膜性能的可能原因在于其极大地减少了BFO薄膜中的Fe2+离子.     

Electrically and magnetically tunable microwave device using (Ba, Sr) TiO3/Y3Fe5O12 multilayer

Ferroelectric (Ba_0.6Sr_0.4)TiO₃ (BST) thin films have been deposited by pulsed laser deposition onto single-crystal Y₃Fe₅O₁₂ (YIG) substrates with/without a MgO buffer layer. The structure and microwave properties of the BST films have been investigated as a function of substrate orientation and O₂ deposition pressures (50-800 mTorr). The crystallographic orientation of BST film varies with the deposition conditions. The dielectric properties of the ferroelectric were measured using interdigitated capacitors deposited on top of the BST film. BST films exhibit high tunability (20-40%) and high dielectric Q=1/cos' (30-50) with a dc bias field of 67 kV/cm at 10 GHz. A coplanar waveguide transmission line was fabricated from a (001)-oriented BST film on (111)YIG which exhibited a 17° differential phase shift with an applied dc bias field of 21 kV/cm (10 GHz). An equivalent differential phase shift was achieved with a magnetic field of 160 Gauss.     

铌镁酸铅-钛酸铅铁电阴极电子发射特性

研究了铌镁酸铅-钛酸铅铁电材料的铁电、介电性能对阴极发射阈值电压的影响, 以及铁电阴极发射电流与激励脉冲电压和抽取电压之间的关系, 并分析了其发射机理. 结果表明, 室温介电常数高、极化强度变化量大的弛豫铁电体0.9Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃具有较小的发射阈值电压; 铁电阴极电子发射与快极化反转和等离子体的形成有关; 由极化反转所致电子发射的自发射电流随激励脉冲电压的增大呈幂律增长关系, 其发射电流开始于激励脉冲电压的下降沿; 在抽取电压较大时, 发射电流随抽取电压的增大呈线性增长关系, 说明大电流主要取决于抽取电压; 其发射电流开始于激励脉冲电压的上升沿, 与“三介点”处的场增强效应和等离子体的形成有关; 当抽取电压为2500 V 时, 得到的发射电流幅值为210 A, 相应的电流密度为447 A/cm².     

Improving the tribological performances of graphite-like carbon films on Si3N4 and SiC by using Si interlayers

Si interlayers were used to obtain the excellent tribological performances of graphite-like carbon (GLC) film on silicon nitride (Si₃N₄) and silicon carbide (SiC). The microstructure and mechanical characteristics of the as-prepared GLC films with Si interlayers were investigated by scanning electron microscopy, Raman spectroscopy, nanoindention and scratch test. The tribological behaviors of GLC-coated and uncoated Si₃N₄ and SiC were comparatively studied by a ball-on-disc tribo-meter in both dry and water environments. Results showed that the Si interlayers were dense and bonded well with both the substrates and GLC layers. The as-prepared GLC films exhibited excellent tribological performances in both dry and water environments. More importantly, the stably mild wear without any delamination was obtained in water by using Si interlayer. The mechanisms of friction reduction and anti-wear performances of GLC films on the two ceramics with Si interlayers under different environmental conditions were discussed, as well as the corresponding models were deduced.     

The effect of Si surface nitridation on the interfacial structure and electrical properties of (La2O3)0.5(SiO2)0.5 high-k gate dielectric films

Thermal stability, interfacial structures and electrical properties of amorphous (La₂O₃)_0.5(SiO₂)_0.5 (LSO) films deposited by using pulsed laser deposition (PLD) on Si (1 0 0) and NH₃ nitrided Si (1 0 0) substrates were comparatively investigated. The LSO films keep the amorphous state up to a high annealing temperature of 900 °C. HRTEM observations and XPS analyses showed that the surface nitridation of silicon wafer using NH₃ can result in the formation of the passivation layer, which effectively suppresses the excessive growth of the interfacial layer between LSO film and silicon wafer after high-temperature annealing process. The Pt/LSO/nitrided Si capacitors annealed at high temperature exhibit smaller CET and EOT, a less flatband voltage shift, a negligible hysteresis loop, a smaller equivalent dielectric charge density, and a much lower gate leakage current density as compared with that of the Pt/LSO/Si capacitors without Si surface nitridation.