Cadmium and zinc are transition elements belonging to group II B in periodical table and they share similar chemical properties. However, their morphological and physiological effects on plants are quite difference. Cadmium not only consequences changes of plant structure at the light and electron microscopic levels, but also results in the induction of phytochelatin synthesis. In the present studies, The distribution of cadmium in different parts of plants was measured and its effects on plant structure were also examined.

Three to six-week-old Zinnia elegans were grown Hoagland's solution containing different concentrations of cadmium from one to two weeks. Atomic absorption spectroscopic studies showed that the distribution of cadmium was mainly in root. The accumulation of cadmium in stems was higher than that of in leaves. In leaves, the ability of cadmium accumulation in young leaves was much higher than that of old leaves.

The embryo sac (ES) of Plumbago zeylanica, unlike most other flowering plants, lacks synergidsthe cell type that usually receives the pollen tube and the male gametes. Normally, synergids store copious amounts of calcium, estimated to exceed 15% by weight; this is believed to attract pollen tubes, which penetrate the ES, and may trigger the release of the sperm cells within one of the two synergids. If high concentrations of calcium are truly required for fertilization, the ES of Plumbago should also contain significant quantities. Synergids in normal flowering plants are preprogrammed for cell death, receiving the contents of the pollen tube directly in their cells, whereas synergid-lacking angiosperms apparently do not have such an apoptotic cell in the ES. Potassium pyroantimonate labeling was used to localize principally loosely-bound calcium, because it is a relatively mobile form of the Ca2+ ion that is available for redistribution during fertilization events.

The appressoria formation of Colletotrichum graminicola was monitored by scanning electron microscopy (SEM) coupled with an X Ray microanalysis system (EDS - Oxford Instrument LINK ISIS). Recently formed appressoria, an infection structure of plant pathogenic fungi, firmly glues itself to an artificial surface (polystyrene) as a consequence of the production of an adhesive material (AM). The nature of this material was already demonstrated to be mainly constituted of a glycoprotein (Sugui et al, PMPP, 1998). The objective of this work was to verify the involvement of divalent ions, specially calcium, in the process as whole.

The AM was isolated and purified from conidia that germinated on polystyrene Petri dishes. The primary AM was dialyzed against three liters of distilled water before being lyophilized. Subsequently, the material was placed on top of a carbon tape and observed by scanning electron microscopy under high vacuum (Fig. 1 and 2A). On the other hand, the same material was submitted to X Ray microanalysis without coating.

Mature sperm cells of Ceratopteris richardii are spiraled over three revolutions and contain a locomotory apparatus with approximately 70 flagella attached at the cell anterior (Fig. 1). Abundant organelles are dispersed along the inner surface of an elongated, coiled nucleus (Figs. 1, 3, 8). The cytoskeleton comprises a network of microfilaments that encases the nucleus (Fig. 6) and two distinct microtubule arrays: a microtubular ribbon (spline) and flagella with anchoring basal bodies (Fig. 3). This study uses light, fluorescence, transmission electron (TEM), and scanning electron microscopy (SEM) to characterize cell organization in a motility impaired sperm mutant line of Ceratopteris. Because motility mutations likely involve the cytoskeleton, emphasis was placed on observing microtubule and actin arrays in the mutant compared to wild-type sperm cells. Protocols follow Hoffman and Vaughn for TEM and Schmitt and Renzaglia for SEM. Microfilament arrays in relation to the nucleus were examined by rhodamine-phalloidin and DAPI fluorescence.

The accommodation of strain in metal films can lead to complex phenomena, both structurally and chemically. It can generically lead to the formation of dislocations. These dislocations play an important role in defining the evolution and response of the film to further growth and external forces. The structures of the dislocations are directly analogous to bulk dislocations, but their properties are very different due to the presence of the surface. In addition, the strain can greatly affect the chemical properties of the film, leading to alternative strain relief mechanisms involving vacancy formation resulting from reaction with gases such as sulfur and oxygen. Using STM and LEEM, we have investigated these phenomena in the prototype systems of Cu and Ag on Ru(0001).

For example, figure la - d shows a sequence of STM images of a 2 layer Cu film on Ru(0001) during exposure to oxygen. Dislocations present in the film are altered by reaction with oxygen.

Understanding how defects alter physical properties of materials has lead to improvements in materials growth as well as device performance. Transmission electron microscopy (TEM) provides an invaluable tool for structural characterization of defects. Our current knowledge of crystallographic defects, such as dislocations, would not have been possible without TEM. Recently, scanning tunneling microscopy and scanning force microscopy (SFM) have shown the capability of imaging surface defects with atomic or near-atomic resolution in topographic images. What is more important is to gain knowledge on how the presence of a certain type of defects changes the physical properties of materials. For example, how is the carrier lifetime altered near electrically active defects? How does photoresponse vary near grain boundaries? Where are defect levels in the forbidden bandgap? This talk will discuss several examples of how scanning probe microscopies (SPMs) can contribute to this aspect of defect studies in semiconductors.

Possible applications of ferroelectric materials in non-volatile memories, MEMS, microwave ceramics, PTCR devices and sensors draw significant interest to these materials. Operation of most of these devices relies heavily on the surface (FRAM and other thin-film devices) and interface (PTCR, varistors) properties of ferroeiectrics, particularly on the polarization and charge distribution in the surface or interface region. Electrostatic scanning probe techniques such as electrostatic force microscopy (EFM), scanning surface potential microscopy (SSPM) and piezoresponse imaging (PRI) can be successfully employed for the characterization of ferroelectric surfaces on the micron and submicron level. The former technique is based on the detection of the resonant frequency shift of mechanically driven cantilever, which is proportional to gradient of electrostatic force acting on the tip. The latter two techniques are based on the voltage modulation approach, i.e. during imaging the piezoelectric actuator driving the cantilever is disengaged and the AC bias is applied directly to conductive tip.

The stability of polar and neutral MgO surfaces has been addressed by theory and experiment as an ideal example of ionic oxides with rock-salt structure, but with unresolved controversial results. For example, energy-minimization theory predicted that higher energy polar MgO (111) and neutral MgO (110) surfaces could thermally facet into the lowest energy MgO (100) planes. Early low-energy electron diffraction (LEED) experiments reported diffraction spot splitting, interpreted as evidence for thermal faceting to ﹛100﹜ planes. However, a recent study found MgO (111) faceting was caused by chemical etching with nitric or phosphoric acid, and not promoted by annealing. Quantitative atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurement of the facet angles revealed them to be vicinal planes rather than the predicted ﹛100﹜ planes. A recent AFM study reported thermal faceting of MgO (110) into vicinal planes.

Thin films (<100nm) of diblock copolymers are being investigated for various applications including templates for nanopatterning [1], electronic packaging materials, and biomedical applications. In such applications it is essential that stable defect free films be produced repeatedly. Because long and short range forces (like van der Waals) dominate thin polymer films, instabilities are introduced in the films when they are spin-coated onto hydrophobic substrates resulting in dewetting of the film from the substrate. Dewetting is initiated at a nucleation site in a metastable film leading to the formation of a dry patch and proceeds to grow by transport of material away from the nucleation site, forming a lip that surrounds the hole. Highly symmetrical structures form during progression of the dewetting process and completion of the process can be identified when all holes coalesce forming polygons outlined by droplets of the polymer film [2].

Surface plasmons have been used to detect single molecular layers for many years. The most common examples are biosensor systems and the detection of self-assembled monolayers (SAMs). A surface plasmon is a two-dimensional electromagnetic wave that travels on the surface of a noble metal, most commonly gold or silver. This electromagnetic wave is extremely sensitive to changes in the dielectric constant 100 nm above the metal surface. When the dielectric constant above the metal changes due to the addition of a molecular layer, the intensity of the surface plasmon will decrease. In this way monolayers may be indirectly imaged on a surface by mapping the surface plasmon intensity.

Although there are many reasons for imaging ultrathin films or molecular layers over large distances (10-100 μm), there are several difficulties involved. Typically the substrate has a roughness greater than the height of a single monolayer. This can mask the presence of the monolayer on large area scans.

Processes at dislocation sites are frequently predominant mechanisms of surface evaporation or growth and thus determine resulting surface morphologies. Dislocation-induced evaporation patterns are also a convenient object for observation of dynamics of step motion on crystal surfaces, as such patterns have “fixed” origins, being pinned at the point of dislocation emergence. In the present work, observations of evaporation spirals formed on ﹛111﹜ and ﹛001﹜ surfaces of MgAl2O4 spinel are reported.

2x2x1 mm samples of single-crystal MgAl2O4 spinel of ﹛111﹜ and ﹛001﹜ orientation were annealed in a spinel crucible in vacuum (10-4—10-5 Torr) in a Centorr™ furnace at 1800°C for 8 hours. SPM images were collected in air in contact mode on a Nanoscope III (Digital Instruments, Santa Barbara, CA), using Si3N4 cantilevers (Ultralevers, Park Inst., Sunnyvale, CA) with a nominal spring constant of 0.12 N/m. Selected sample surfaces were examined for impurities by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoemission spectroscopy (XPS).

Sintering and many problems in adsorption and catalysis require an understanding of the surface structures of crystals, which have been subjected to various types of heat treatment. For example, heat treatment of m-plane sapphire surfaces can cause a transformation from a flat vicinal surface into those of a faceted hill-and-valley structure. Many technologically interesting materials form with the garnet structure, including YIG, YAG, GGG and many silicates. However, there has been relatively little discussion of the structure and behavior of such surfaces. This paper illustrates the use of visible-light microscopy (VLM), atomic-force microscopy (AFM) and scanning electron microscopy (SEM) for studying the ﹛111﹜ surface of gadolinium gallium garnet (GGG or Gd3Ga5O12).

2x2x1 mm samples of monocrystalline GGG with ﹛111﹜ surface orientation were heat treated in air at 1575°C for 24 hours in order to study the processes a surface undertakes while reaching its equilibrium state.

The local chemistry of many surface reactions is unknown, since no techniques exist for identifying atom types at individual defect sites on extended crystal surfaces. An STM has therefore been constructed which allows atomic clusters of interest to be transferred into a time-of-flight spectrometer for species identification. Atoms are first transferred from the STM sample to the tip, using a small voltage pulse. The sample is then removed, and these atoms ejected into a time-of-flight (TOF) analyzer for mass identification. A 75mm flat Chevron MCP is used as TOF-detector. The output is led to a digital oscilloscope, whose trace is triggered by the tip pulse. Scope, triggering and high voltage are under Labview control, spectra are transferred into the PC and the mass to charge ratio of the ionized species is calculated. The STM has a vertical axis and is based on the Burleigh Inchworm with tube scanner for sample movement.

A combination of electrostatic force microscopy (EFM) and scanning surface potential microscopy (SSPM) is used to quantify nanometer scale field variations for the general case of electronically inhomogeneous surfaces. The specific example illustrated here is the intersection of a Σ5 grain boundary in donor doped SrTiO3 intersecting the (100) surface. ‘The topographic structure is compared to the surface potential, the positive and the negative electrostatic force images in figure 1. The EFM contrast changes sign with the polarity of the applied bias, as expected for an electrostatic attractive/repulsive interaction. There is a significant localization of surface potential at the grain boundary that is manifest as a protrusion in the SPPM image.

To quantify the properties at the surface, rather than above the surface where the measurements are acquired, a relationship connecting the sample-tip interaction is required. It has been shown that models based on simple geometric assumptions do not represent the behavior well.

Reliability of thin polymer films is strongly dependent on interfacial adhesion. This paper concerns the application of indentation combined with atomic force microscopy (AFM) for the evaluation of polymer-non-polymer adhesion. Interfacial toughness calculations have been made using AFM measurement of geometry of delaminations induced by indentation. Fracture surfaces characterized with AFM are also presented here.

The interface chosen for study is that between polystyrene (PS) and a glass substrate. Spin coating has been used to prepare PS films. PS, dissolved in toluene, was spun onto the soda-lime glass and then dried at 60°C for 3h to remove residual solvent. The thickness of the PS film was approximately 660nm. To enhance the driving force for delamination, poly(methyl methacrylate) (PMMA) overlayers were applied on top of the PS films. The PMMA overlayer, of thickness approximately 1.5 μm, was first solvent cast onto a second glass slide, floated off the glass onto deionized water, and then laid on top of a first glass substrate which had been coated with PS.

Introduction. By volume of material produced, optical disc manufacturing is the world's large nanotechnology industry, far surpassing semiconductors and magnetic disks. The development of various optical disc media has introduced a variety of challenges, which necessitate viewing the geometrical structure of the bumps, pits, or grooves on the surface of the discs. The Atomic Force Microscope (AFM) has the resolution and sensitivity needed for device analysis, but in the past has been limited by magnification errors, image distortion, data handling, and calibration. Furthermore, the common measurement procedure for AFM images consists of manual dimensional measurements. This introduces error and limits the number of measurements taken at one time. We have developed an automated process, which overcomes these limitations and provides a comprehensive approach to feature measurement, data analysis, calibration, and reporting.

The electrochemical formation of gradients in self assembled monolayers has been demonstrated recently [1]. The capacity to image these gradients provides useful information on the physical chemistry of electrochemical striping.

Imaging chemical gradients requires the ability to sense the chemical moiety on the top of the self-assembled monolayer. This has been accomplished by derivatizing an atomic force microscope (AFM) tip with molecules selected to have specific interactions with the sample in a technique known as chemical force microscopy [2]. Typical tapping mode AFM is then used to image the sample; the tip is oscillated vertically above the sample and the tip-sample interaction modulates the amplitude of the tip.

The sample adhesion, sample stiffness, and sample topography all influence the oscillation amplitude of the tip. Pulsed Force Mode (PFM) [3] is an extension for atomic force microscopes. The PFM electronics introduces a sinusoidal modulation to the z-piezo of the AFM with an amplitude between 10 to 500 nm at a user selectable frequency between 100 Hz and 2 kHz.

Silicon Drift Detectors (SDD) are being developed for analytical x-ray spectrometry having large active area, high-energy resolution and capability of operating at high counting rates. The development derives from the charged coupled device (CCD) for light-signal imaging, utilizing the extremely low capacitance of the detector and readout electronics and subsequent developments of silicon drift detectors for high-energy physics applications and more recently, x-ray spectroscopy applications. The now well-known advantage of the drift detector design is that, unlike traditional planar detectors, it allows for relatively large active area while still maintaining a very low anode capacitance (60 fF). This low value of detector capacitance results in a lowering of the series-noise component and hence the overall inherent electronic noise. Additionally, the reduction of the series noise leads to faster optimal shaping time, and as a consequence this provides for extremely high count rates.

Samples to be studied using EELS techniques are more or less sensitive to the effects of the radiation exposed to them by the beam. Quite often the sample is damaged due to the high radiation doses in the areas where the beam has been focused. Secondly, the build up of carbon contamination on the surface of the sample caused by the beam affects the results of the analysis if the sample itself contains carbon. The solution to these problems is to minimize the exposure times needed to record the spectrum, which will lower the radiation-doses on the sample. In addition, problems related to beam instabilities would be reduced due to the shortened acquisition times. However, in order still to achieve an acceptable signal-to-noise ratio the need for a detector with high detective quantum efficiency is essential. We have investigated the possibilities using silicon detectors such as photodiode arrays (PDA) and charge coupled devices (CCD) in direct electron detection mode using 100 keV incident electrons.

Excellent linearity and high sensitivity have made SSCs the ideal image detector for almost every TEM application. Their ability to make high quality digital images available within fraction of seconds for further evaluation and processing in a PC, have made them a non-dispensable accessory for any modern TEM. However, despite their excellent characteristics, SSCs provide a restricted number of individual image points in respect to a negative, what is considered to be the main disadvantage of this detector. To compensate for this, CCDs with 2048x2048 pixel are available since some time. SSCs using these 2kx2k CCD arrays not only provide 4 times the pixel number but also offer a lot more options people have waiting for: e. g. highly resolved low-dose or ESI images with significantly improved signal to noise ratio, or higher resolved images for diffraction analysis and holographic reconstruction.