Storage Characteristics of Nano-Crystal Si Devices Using Different Measurements for MOS Capacitors

The storage characteristics of nano-crystal Si （NC-Si） devices,especially for MOS capacitors,are studied by cross sectional transmission electron microscopy （TEM） and capacitance-voltage （C-V） measurement under different conditions,including programming and erasing at different temperatures and gate voltages,as well as using ＋/-bias-temperature （BT） measurements.Physical mechanisms such as carrier trapping,interface state filling,and temperature related deterioration are revealed.The experimental results demonstrate that the degradation of the program window and threshold voltage （VT） shift at high temperature,large voltage sweep range,and bias applied to sweep voltage is strongly related to the type of majority carriers.

Modified Scherrer Equation to Estimate More Accurately Nano-Crystallite Size Using XRD

Scherrer Equation, L=Kλ/β.cosθ, was developed in 1918, to calculate the nano crystallite size (L) by XRD radiation of wavelength λ (nm) from measuring full width at half maximum of peaks (β) in radian located at any 2θ in the pattern. Shape factor of K can be 0.62 - 2.08 and is usually taken as about 0.89. But, if all of the peaks of a pattern are going to give a similar value of L, then β.cosθ must be identical. This means that for a typical 5nm crystallite size and λ Cukα1 = 0.15405 nm the peak at 2θ = 170° must be more than ten times wide with respect to the peak at 2θ = 10°, which is never observed. The purpose of modified Scherrer equation given in this paper is to provide a new approach to the kind of using Scherrer equation, so that a least squares technique can be applied to minimize the sources of errors. Modified Scherrer equation plots lnβ against ln(1/cosθ) and obtains the intercept of a least squares line regression, ln=Kλ/L, from which a single value of L is obtained through all of the available peaks. This novel technique is used for a natural Hydroxyapatite (HA) of bovine bone fired at 600°C, 700°C, 900°C and 1100°C from which nano crystallite sizes of 22.8, 35.5, 37.3 and 38.1 nm were respectively obtained and 900°C was selected for biomaterials purposes. These results show that modified Scherrer equation method is promising in nano materials applications and can distinguish between 37.3 and 38.1 nm by using the data from all of the available peaks.

A METHOD OF PREPARING SPHERICAL NANO-CRYSTAL CELLULOSE WITH MIXED CRYSTALLINE FORMS OF CELLULOSE Ⅰ AND Ⅱ

A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, theultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gelpermeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy(TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the panicle.

Krypton ion irradiation-induced amorphization and nano-crystal formation in pyrochlore Lu_2Ti_2O_7 at room temperature

Polycrystalline pyrochlore Lu2Ti2O7 pellets are irradiated with 600-keV Kr^3＋ions up to a fluence of 1.45 ×10^16Kr^3＋/cm^2. Irradiation induced structural modifications are examined by using grazing incidence x-ray diffraction（GIXRD） and cross-sectional transmission electron microscopy（TEM）. The GIXRD reveals that amorphous fraction increases with the increase of fluences up to 2 × 10^15Kr^3＋/cm^2, and the results are explained with a direct-impact model.However, when the irradiation fluence is higher than 2 × 10^15Kr^3＋/cm^2, the amorphous fraction reaches a saturation of-80%. Further TEM observations imply that nano-crystal is formed with a diameter of -10 nm within the irradiation layer at a fluence of 4 × 10^15Kr^3＋/cm^2. No full amorphization is achieved even at the highest fluence of 1.45 × 10^16Kr^3＋/cm^2（-36 displacement per atom）. The high irradiation resistance of pyrochlore Lu2Ti2O7 at higher fluence is explained on the basis of enhanced radiation tolerance of nano-crystal structure.

Effect of Anion Surface Active Agent on the Preparation of SrTiO_3 Nano-Crystals

SrTiO_3 nano-crystal samples with floccule or flake crystal morphology,which were indexed as a perovskite-type crystal structure based on the results of XRD and TEM,were successfully prepared by one-step liquid reaction method.And the growth mechanism of the SrTiO_3 nano-crystals under the liquid condition with/without adding the surface active agent was investigated.It was found that adding the surface active agent contributes to the processing in which the ions gathering bodies transit to a more stable phase through the chemical reaction and form the flake SrTiO_3 nano-crystals.

Up-conversion luminescence properties and energy transfer of Er^(3+)/Yb^(3+)co-doped oxyfluoride glass ceramic containing CaF_2 nano-crystals

The Er^3＋/yb^3＋ co-doped transparent oxyfluoride glass-ceramics containing CaF2 nano-crystals were successfully prepared. After heat treatments, transmission electron microscopy （TEM） images showed that CaF2 nano-crystals of 20-30 nm in diameter precipitated uniformly in the glass matrix. luminescence of Er^3＋ at 540 nm and 658 nm was observed in Comparing with the host glass, high efficiency upconversion the glass ceramics under the excitation of 980 nm. Moreover, the size of the precipitated nano-crystals can be controlled by heat-treatment temperature and time. With the increase of the nano-crystal size, the intensity of the red emission increased more rapidly than that of the green emission. The energy transfer process of Er^3＋ and Yb^3＋ was convinced and the possible mechanism of Er^3＋ up-conversion was discussed.

Characteristic Investigation of Nano-Crystal Hydrogen Storage Alloys

A Ml (NiCoMnA1)5 hydrogen storage alloys was prepared by double-roller rapid quenching.Its microstructure, electrochemically and kinetic characteristic were studied.A uniform crystal phase with CaCu5 structure could be detected by XRD analyses, whose average grain size is 30 ~ 50 nm and the ratio of c/a of nano-crystal hydrogen storage alloy is larger.The hydrogen absorption/desertion p - C isotherms of alloy show that its fiat-performance is perfect and the magnetic stagnant effect is very little.An simulate cell is used for electrochemical measurement.Electrode is 10C, the capacity decreasing rate via the 450 cycles at 7C is less than 20%.

The Transmission Modes and Losses of the Poled Nano-crystal and Polymer Composite PbTiO_3 / PEK-c Thin-film Waveguides

Composite thin films of PbTiO3 nano-crystals and high transparency polymer polyetherketone （PEK-c） for application of non-linear optical devices were prepared by spin coating. The size of PbTiO3 nano-crystals was estimated to be 30-40 nm using a transmission electron microscope. The refractive index and the mode propagation losses at 633 nm were measured using the prism coupling technique and improved photographic technique respectively. They were found to be 1.6545 and 2.00 dB cm^-1 （fundamental mode）,respectively. Moreover, it is observed that this loss is increased at higher mode indices.

Determination of the Nucleation Region Location of Si Nano-Crystal Grains Prepared by Pulsed Laser Ablation through Changing Position of Substrates

To determine the nucleation region location of Si nano-crystal grains, pulsed laser ablation of Si target is performed in Ar gas of 10 Pa at room temperature with laser fluence of 4 J/cm2, the substrates are located horizontal under ablation spot with different vertical distance. Characteristics of deposited grains are described by scanning electron microscopy, Raman scattering and X-ray diffraction spectra, the results indicate that deposition position on substrates in a certain range is relative to target surface, which changes according to different vertical distance of substrates to ablation spot. Grain size increased?at first and then decreased with addition of lateral distances to target in the range, but the integral distribution rule was independent of position of substrates. Combining with hydrodynamics model, nucleation division model, thermokinetic equation and flat parabolic motion, spatial nucleation region location of grains is obtained through numerical calculations, which is 2.7 mm-43.2 mm to target surface along the plume axis.

Fabrication and Characteristics of Nano-Floating Gate Memories with ZnO Nano-Crystals as Charge-Storage Layer

Nano-floating gate memory devices with ZnO nano-crystals as charge storage layers are fabricated,and the influence of post-deposition annealing temperature and thickness of the ZnO layer are investigated.Atomic force microscopy and scanning electron microscopy reveal the morphology of discrete ZnO nano-crystals.For capacitance-voltage measurements,it is found that the memory device with 1.5 nm ZnO and annealed at 700℃shows a larger memory window of 4.3 V（at±6 V）and better retention characteristics than memoriy devices with2.5 nm ZnO or annealed at other temperatures.These results indicate that the nano-floating gate memory with ZnO nano-crystals can obtain good trade-off memory properties.

Diffusion behavior of Ni in Zr_(48)Cu_(36)Ag_8Al_8 bulk metallic glass within supercooled liquid region

Diffusion behavior of Ni in Zr48Cu36Ag8Al8 metallic glass was investigated in the temperature range of 683-723 K by secondary ion mass spectrum(SIMS) and transmission electron microscope(TEM). The diffusivity of Ni in Zr48Cu36Ag8Al8 is reasonably fitted by a single Arrhenius relation with small effective activation energy. The diffusivity of Ni in Zr48Cu36Ag8Al8 is an instantaneous function of annealing time in the supercooled liquid region. In addition, a large number of nano-crystals are detected near the interface of Ni-Zr48Cu36Ag8Al8 diffusion couple, and its width is broader than the Ni diffusion depth determined by SIMS. The results indicate that atomic inter-diffusion is an important factor to promote the formation of nano-crystals within the diffusion zone.

WS2花形纳米晶的制备和表征

采用溶胶-凝胶法,将钨酸钠水溶液经阳离子交换树脂获得的三氧化钨溶胶与硫粉混合。在高压反应釜中于650℃加热2 h。采用扫描电镜(SEM)和粉末X射线衍射(XRD)等手段对所制备的样品进行检测分析,对纳米花晶体的制备、影响因素进行初步探讨。结果证实所得灰黑色产物是花形二硫化钨纳米颗粒,组成花的片状单晶长宽约为几十个纳米,厚度约5 nm。

垂吊式、环式花饰的好材料——铁线莲

毛茛科铁线莲属植物为风行世界的园艺花卉品种;通过对东北野生藤本铁线莲的考查、形态详述以及特种花饰的具体应用效果,阐述了藤本铁线莲作为特殊切花材料的开发价值。

硫化钨花形二维纳米晶的控制生长研究

以氧化钨为原料,硫化氢为气源在阳极氧化铝(AAO)模板基底上采用气固法制备出了硫化钨花形二维纳米晶体。采用X射线衍射(XRD)、电子透射显微镜(TEM)和场发射电子扫描显微镜(SEM)等手段对所制备的样品进行了检测分析,证实所得灰黑色产物是硫化钨单晶,片状单晶长宽约为几个微米,厚度约30nm。本文对纳米花晶体的制备、影响因素等进行了初步探讨。

硒化钨花状纳米晶的可控合成及电催化产氢性能研究

采用胶体化学法,以氧化钨(W_(18)O_(49))为钨源制备出花状硒化钨纳米晶。采用透射电子显微镜(TEM)、高分辨透射电镜(HRTEM)和X射线衍射(XRD)手段对硒化钨纳米晶进行表征。本文对硒化钨花状纳米晶体的可控合成进行了初步探索,同时对烧结后的硒化钨纳米晶进行了电催化产氢测试。结果表明,硒化钨花状纳米晶具有良好的电催化性能。

A novel synthesis method and up-conversion properties of hexagonal-phase NaYF_4:Er nano-crystals

A novel synthesis method for hexagonal （]3）ophase NaYF4：Er nano-crystals （NCs） which showed up-conversion （UC） from infrared to visible spectral region was developed. The NaYF4：Er NCs were synthesized in oleie acid （OA） and 1-0ctadeeene （ODE） with Y2（COa）3＇xH20, Er2（COa）3xH20, Na2CO3 and NH4F as precursors. This proposed method was simple and less toxic compared with generally used method so far. The XRD results showed that the molar ratio of OA/ODE and the temperature were key factors for phase control ofNaYF4：Er NCs. The UC emission spectra were obtained with the emission wavelength at about 980 nm （4111/2--4115/2）, 800 nm （41912--415/2）, 660 nm （4F912--4115/2） and 540 nm （453/2----4115/2） from Er3＋ ions, by excitation wavelength of 1550 nm. The slope values, n, in the pump-power dependence, showed that the emission at 980 and 800 um were generated by 2-step UC and at 660 nm and 540 um were 3-step UC. The optical process for the UC excitation was discussed.

Grain evolution of nano-crystals ZnO under HP and HT

Grain evolution of nano-crystals ZnO under high temperature and pressure is studied using a cubic high pressure apparatus. The structure, grain sizes and morphology of the samples are characterized by X-ray diffraction and field emission scanning electron microscopy. The results show that the grain sizes of ZnO grow rapidly at temperature 200℃ under pressure. At temperature lower than 300 ℃ (including 300 ℃), the grain sizes of the samples first increase with the pressure increasing from 1 to 3 GPa and later de- crease from 4 to 6 GPa. The activation volume from 1 to 3 GPa and from 4 to 6 GPa is calculated respectively using the phenomenological kinetic grain growth equation at temperature 300 ℃. At temperature higher than 400℃ (including 400 ℃), the grain sizes of the samples increase with the pressure increasing from 1 to 6 GPa. ZnO nano-bulks with good quality can be obtained under the specific conditions.

SYNTHESIS OF Ni-Mo ALLOYS BY MECHANICAL ALLOYING

Ni_(100-x)Mo_x(x=20,30,38)alloys have been synthesized by mechanical alloying.The structure evolution of powders in mechanical alloying process has been monitored by X-ray diffraction,scanning electron microscopy and transmission electron microscopy analyses.The results show that the Ni_(62)Mo_(38)sample becomes partially amorphous after high energy ball milling,while the Ni_(80)Mo_(20)and Ni_(70)Mo_(30)become non-equilibrium nanocrystals.

Structural and mechanical properties of nano-crystal TiN coatings

The structural and mechanical properties of TiN coatings prepared by ion beam assisted deposition (IBAD) were studied. The coatings have a polycrystal structure with grain size of ～10 nm or less. The hardness of the coatings increases with increasing grain size of TiN crystallites. The coating with grain size of 10.3 nm even has a superhardness of 44.7GPa. The relationship between the hardness and the grain size in the nano-crystalline coatings was discussed on the basis of grain-boundary triple junctions.

A novel 2 T P-channel nano-crystal memory for low power/high speed embedded NVM applications

We introduce a novel 2 T P-channel nano-crystal memory structure for low power and high speed embedded non-volatile memory（NVM） applications.By using the band-to-band tunneling-induced hot-electron （BTBTIHE） injection scheme,both high-speed and low power programming can be achieved at the same time. Due to the use of a select transistor,the ＂erased states＂ can be set to below 0 V,so that the periphery HV circuit （high-voltage generating and management） and read-out circuit can be simplified.Good memory cell performance has also been achieved,including a fast program/erase（P/E） speed（a 1.15 V memory window under 10μs program pulse）,an excellent data retention（only 20%charge loss for 10 years）.The data shows that the device has strong potential for future embedded NVM applications.