Planar SiC/Si heterostructures were formed by high dose carbon implantation using a metal vapor vacuum arc ion source. The variations of the field emission properties with the implant dose and annealing conditions were studied. A remarkably low turn-on field of IV/μm was observed from a sample implanted at 35 keV to a dose of 1.0×10 18 cm −2 with subsequent annealing in nitrogen at 1200°C for 2h. The chemical composition depth profiles were determined from x-ray photoelectron spectroscopy and the surface morphology was observed by atomic force microscopy. The formation of a thin surface stoichiometric SiC layer and the formation of densely distributed small protrusions on the surface are believed to be the two factors responsible for the efficient electron field emission.

Application of SOI in high-power integrated circuit is limited by the self-heating effect, caused by the poor thermal conductivity of the buried SiO2 layers. It is important to investigate new buried insulator with good thermal conductivity. We simulated the self-heating effects of AlN and SiO2 thin films caused by power consumption of SOI devices with the help of ANSYS v6.1. Then prepared AlN thin films through ion beam enhanced deposition (IBED) system. The microstructure and dielectric properties were characterized through AFM, XPS, C–V, I–V and SRP. Our results show that the AlN thin films we prepared have excellent insulating properties and better thermal conductivity compared with SiO2 films.

AlN thin films were prepared through IBED. The microstructure and electronic characteristics of AlN films were studied through XPS and C–V/I–V test. N2 gas added into IBED system during deposition could enhance N/Al ratio near to stoichiometrical structure and improve dielectric properties of AlN films. Some important dielectric parameters for AlN thin films were obtained.

The nanometer-scale interface morphology of top Si/buried oxide in SIMOX (separation by implantation of oxygen) and the influence of nano-size Si clusters to the electronic properties of the buried oxide (BOX) layer were studied by Conducting Atomic Force Microscopy (C-AFM). With C-AFM, the interface morphology and the current–voltage (I–V) curves of the BOX can be obtained simultaneously. The results found that the interface of Si/BOX in SIMOX had a very smooth surface morphology and there were some nanometer-size Si clusters distributed in the BOX, forming conducting channels. Furthermore, the high-resolution transmission electron microscope (HRTEM) and spreading resistance probe (SRP) were used to characterize the BOX.

The morphological evolution and nature of the degradation of the moisture-exposed tris(8-hydroxyquinoline) aluminum (Alq3) thin films have been microscopically investigated by variable-temperature tapping mode atomic force microscopy and complementarily by thickness-shear mode acoustic wave sensor. It is plausibly ascertained that the dark hole in the Alq3 films results from the release of the volatile 8-hydroxyquinoline, a product of the reaction of Alq3 with moisture.

The formation of nano-cavities in silicon, induced by hydrogen implantation, has been studied by Rutherford Back-Scattering Channeling (RBS/C), Atomic Force Microscope (AFM) and infrared reflection spectra (IR). The Specimens, implanted with 160 keV hydrogen ions to a dose of 8.2/spl times/10/sup 16/ cm/sup -1/, are annealed at 400/spl deg/C for times of 30 minutes. The result of RBS shows that the surface damage due to implantator is little after annealing. AFM validates the swelling caused by the implantation of Hydrogen. By detailed theoretical analysis and computer simulation of IR reflection interference spectra with the model described in the text, the depth distribution of the cavities concentration was obtained.

The effects of low dose (109/cm2) ion irradiation on the ferroelectric domains and on the ferroelectric↔paraelectric phase transition of triglycine sulfate (TGS) single crystals has been studied by using variable temperature dynamic contact electrostatic force microscopy. The evolution with temperature of ferroelectric domains of virgin and ion irradiated samples was observed in situ. In general, the phase transition of ion unirradiated samples is similar to that of virgin samples, which can be well described by Landau's mean field theory. However, on ion irradiated samples, there is a strong asymmetry of spontaneous polarization P for positive and negative domains. This asymmetry is due to the defects produced by ion implantation.

In this Letter, we present a study on mapping the morphology of the top interface on Si/buried oxide (BOX) in nanometer scale and the influence of nano-sized Si islands to the electronic properties of the BOX layer in separation by implantation of oxygen with conducting atomic force microscopy (C-AFM). By using C-AFM, both the morphology of the top interface on Si/BOX and the electronic properties of the BOX can be obtained simultaneously. Based on the analysis of the current–voltage (I–V) curves, the electronic properties of the BOX are also discussed.

首次报道了用不同浓度的Al离子注入于蓝宝石衬底上的GaN薄膜(注入能量为500keV、注入浓度为1014～1015 cm-2), 在做了不同温度和不同时间的快速热退火处理以及常规热退火处理后,在12K下用He-Cd 激光(325nm)激发得到其发射谱.结果显示, 经大剂量Al注入后的样品,其光致发光谱中3.45eV的带边激子发光以及2.9 ～ 3.3eV的4个声子伴随峰消失.此表明大剂量Al注入对GaN的晶体结构造成严重的损伤,以致本征发光消失.经1014cm-2剂量Al注入后的样品,在N2气氛中退火处理后,2.2eV缺陷发光峰得到了一定程度的恢复.而且,经常规退火处理后,此发射峰比快速退火处理的样品发射峰恢复得更好(其积分光强高3倍).相似的结果亦显示于1015 cm-2 浓度的Al 注入的样品.2.2eV 黄色荧光源于GaN的缺陷(如Ga空位(VGa), 或VGa-H2,或VGa-ON 复合体),其能级位于价带顶以上约1.1eV处.荧光发射可以来自"导带-缺陷能级"的跃迁,也可能来自浅施主(如N位O,能级位于导带下～10 meV)至上述缺陷能级之间的跃迁.I-V 测量显示,Al的注入区成为～ 1012 Ω*cm-1高阻膜,这表明Al的注入可能产生了某种深的电子陷阱,由于电子陷阱可俘获导带电子,导致发光猝灭.而退火可使与黄色荧光相关的缺陷得到部分恢复,因而2.2eV发射峰有所恢复.

Polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE) 70/30 mol%] copolymer can be transformed from a ferroelectric to a relaxor material after proton irradiation. The phase transition peak broadens and shifts towards lower temperature as the measurement frequency decreases. In the present study, 0-3 composites are fabricated by incorporating 0-9Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.1PbTiO/sub 3/ ceramic powder into a P(VDF-TrFE) 70/30 mol% copolymer matrix. 0.9PMN-0.1PT ceramic is a relaxor ferroelectric with high dielectric permittivity. It was found that the relative permittivity of PMN-PT/P(VDF-TrFE) 0-3 composite increases with increasing ceramic volume fraction. Composites with 0.3 and 0.4 volume fraction of 0.9PMN-0.1PT were subjected to proton irradiation. With a 80 Mrad (4.76 /spl times/ 10/sup 13/ ions/cm/sup 2/) proton dosage, the relative permittivity of the 0.4 volume fraction 0-3 composites can go up to 130 near room temperature (at 1 kHz).

In this work, a semi-insulating GaN film is obtained in the Al+ implanted (by energy and dose: 500 keV and 1014∼1015 cm−2, respectively) area. Measurements of double crystal X-ray diffraction (XRD) rocking curve shows that the implanted samples still remain a good quality of crystallinity. This may identify that the vanishment of the band edge emission with phonon replicas is due to the ion implantation-induced deep traps located in the forbidden gap, but not due to the change of the crystal structure. In order to detect the position of the traps, we developed a new method, namely photo-stimulated current spectroscopy (PSCS) in our measurement. Three two-component deep traps located at 1.77 eV (with 1.90 and 1.77 eV components), 1.17 eV (1.24 and 1.16 eV components) and 0.88 eV (0.90 and 0.86 eV components) below the conduction band minimum were found in the annealed sample. The two components may be due to the different levels in one trap. It is expected that the PSCS is suitable for measuring the deep levels in all semi-insulating semiconductor films.

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.

Ferroelectric relaxation of sol–gel prepared tetragonal (Pb0.76Ca0.24)TiO3 (PCT) thin film was investigated with piezoelectric response atomic force microscopy (AFM). The result was compared with the dielectric relaxation measured by LCR meter. It is found that the dielectric relaxation is much slower than ferroelectric relaxation. On the basis of a comprehensive survey of retention loss models and detailed analysis of experimental data it is proposed that the dielectric relaxation is due to domain wall depression and the ferroelectric relaxation was due to the depolarisation effect. An activation field of 668kV/cm was obtained from model fitting and it is higher than existing data for PZT. This higher activation field contributes to the good retention property of the film.

A comparative study of Ti and TiN IBAD films as diffusion barriers for Cu has been done. It is found that amorphous Ti (a-Ti) and TiN (a-TiN) films show better thermal stability than (010) oriented Ti (c-Ti) and (111) oriented TiN (c-TiN) films. Such thermal stability can be attributed to their microstructure lacking grains that are fast diffusion paths compared to the imperfect preferentially oriented films prepared by IBAD. The absence of excess impurities in the c-TiN film also impedes the ‘stuffing effect’ and deteriorates its thermal stability. The 600 Å c-Ti/a-TiN multilayer shows inferior thermal stability compared to 300 Å a-TiN while the improvement resulting from the 600 Å a-Ti/a-TiN multilayer is observed. The detrimental effect of the c-Ti layer inserted between the surface Cu and a-TiN can be attributed to the presence of its grain boundaries, making the interdiffusion between Cu and a-TiN much easier than at the interface of Cu/a-TiN.

Sol–gel derived lead zirconate titanate (PbZr0.4Ti0.6O3, PZT) films, 2 μm thick, were deposited on ruthenium dioxide (RuO2)/SiO2/Si substrates. The domain structure and polarization switching of the PZT films were studied by conducting atomic force microscopy (AFM). Large self-polarization along the film thickness direction and asymmetric piezoresponse hysteresis loop were observed in the as-deposited RuO2/PZT/RuO2 films. The room-temperature pyroelectric coefficient of the as-deposited films was about 230 μC/m2 K. The internal field associated with charged defects was believed to be responsible for the self-polarization and asymmetric piezoelectric response in the as-deposited RuO2/PZT/RuO2 films.

Piezoelectric response AFM was used to characterize (Pb0.76Ca0.24)TiO3 (PCT) thin films prepared by sol-gel method. Compared to lead zirconate titanate (PZT) films, better piezoelectric response contrast was obtained for the PCT film with relatively smaller remanent polarisation. This is attributed to the large electrostriction coefficient and weak clamping effect by substrate, which is related to the high piezoelectric anisotropy of PCT material. Remanent polarisation and spontaneous polarisation images reveal the existence of ferroelectricity in the PCT film with a thickness of 40 nm. (C) 2002 Elsevier Science B.V. All rights reserved.

La0.67Ca0.33MnO3 films are known to release oxygen upon vacuum annealing due to lattice expansion caused by change of valence state of Mn from Mn4+ to Mn3+. RBS measurements using O(α,α) resonance reaction at 3.043 MeV show that oxygen concentration decreases from 60% to 57% in 450 °C-vacuum annealed samples. There is also oxygen loss from the SrTiO3 substrate upto a certain depth. The measure of crystalline quality χmin degrades from 5.9% to 10%. A 45° in-plane orientation is observed which is due to the dominant presence of [110]0 texture in the epilayer. The measured channeling half width ψ1/2 decreases upon vacuum annealing. In the samples annealed in oxygen at high pressure at 700 °C, there is no measurable change in oxygen concentration and χmin improved to 4.4%. ψ1/2 increases upon high pressure oxygen annealing. Our measurements directly show that there is lattice disorder upon vacuum annealing and ordering upon high pressure oxygen annealing and it is the largest for the oxygen lattice sites.

我们最近报道了大剂量Al+注入原生GaN后对其光学性质的影响.表明Al+的注入可能产生了某种深能级电子陷阱,由于电子陷阱俘获导带电子,导致发光猝灭.而经一定条件的退火处理,可使深的电子陷阱发生变化,因而与缺陷间的跃迁相关的黄色荧光可得到一定程度的恢复.由于注入样品的电阻率高达1012 Ωcm, 因此不能用已有的常规方法测量.我们为此发展了一种称为"光增强电流谱"(PSCS)新方法,用于测量高阻样品中的深能级.研究发现,在经过快速退火处理的样品中,不能消除由于注入产生的准连续深能级带;而在某种常规条件退火的样品中,发现了5个位于导带下1.77eV, 1.24eV, 1.16eV, 0.90eV和0.86eV的深电子陷阱,它们都是Al+ 注入经退火后形成的稳定结构.实验发现退火使注入产生的准连续深能级带转变为独立的深能级结构,虽不能使GaN的本征发光得到恢复,但对黄色荧光的恢复是有利的.此研究有助于了解退火处理对离子注入的GaN的电学结构与发光产生的影响.PSCS的意义在于它适用于测量一切高阻半导体样品中与非辐射跃迁相联系的深陷阱能级,而不仅仅适用于测量Al+注入GaN产生的深陷阱能级.

The high-field electron conduction of tetrahedral amorphous carbon (ta-C) thin films substrate has been studied using a conducting atomic force microscope (C-AFM). The ta-C thin films with a high concentration of sp3 bonding (80–90%) were deposited on Si by field arc deposition (FAD). The high-field “conductance” and surface morphology were mapped simultaneously. At low bias, the “conductance” exhibits inhomogeneities on a large scale, presumably due to thickness variations or interface defects. However, at high bias, the small difference in “conductance” due to thickness variations or interface defects was buried by the high intrinsic “conductivity.” It has also been shown that high field causes electric breakdown in these films by converting sp3 bonding to sp2 at high electric field.

(1−x)Pb(Mg1/3Nb2/3)−xPbTiO3 (x=0.3–0.35) ferroelectric thin films were prepared by pulsed laser deposition on (001) single crystal LaAlO3 substrates coated with YBa2Cu3O7 electrodes. X-ray diffraction (XRD) measurements showed the as-grown lead magnesium niobate (PMN)-lead titanate (PT) films are epitaxial and have a (001)-oriented perovskite structure. A scanning force microscope (SFM) was employed to probe the domain configuration and piezoelectric response of the films. A comparison of the topographic and domain images showed that the large grains possessed a polydomain configuration. The average value of the piezo-response signal implied that there was a net spontaneous polarization pointing towards the bottom electrode in the as-grown films, presumably due to the presence of an internal field. The piezo-response hysteresis loop obtained while the films were subjected to a dc bias voltage exhibited a behavior that was dependent on the PbTiO3 content, indicating that the mechanism behind the field-induced strain depended on the composition and structure.