In the mid to late 80's there was considerable effort directed at the hetroepitaxial growth of III-V's (GaAs, GaP and InP) on Si substrates for solar cell applications. The primary incentive for this work was the cost reduction of expensive substrate materials. This is particularly important when considering large scale production of terrestrial photovoltaic modules. In the U.S. these efforts produced cell efficiencies up to 21% and continued development of this solar cell structure is currently being pursued in Japan. Similar cost effective structures are being investigated at NREL such as the growth of polycrystalline GaAs films on inexpensive glass substrates for solar cell applications. Polycrystalline films, however, tend to contain a high density of grain boundaries which are regions for carrier recombination and enhanced dopant diffusion which can limit cell performance. In order to reduce the detrimental effects of grain boundaries, the growth of large grain (hence low boundary area) GaAs is being investigated

Cubic boron nitride films were prepared by helicon wave plasma CVD process on (100) Si. The film deposited under the intense impact of energetic ions is usually delaminated from the substrate after deposition. The delamination behavior of c-BN film was investigated with transmission electron microscopy. It is found that moisture in the air, surface roughness of the film and substrate, as well as severe compressive stresses in the film are the primary contributors to film delamination. An aqueous oxidation was verified by EDXS analysis, which generate local stress by volume expansion at the crack region in the c-BN layer.

The cross-sectional TEM micrograph of c-BN film in Fig. 1 shows that a very thin layer of h-BN is deposited before the c-BN layer starts to grow at an early stage of film growth. A columnar structured thin h-BN layer about 20 nm thickness at the interface is clearly separated from the c-BN layer in an aspect of microstructure.

Currently, the aim of research in diamond film synthesis on silicon substrates is to gain an understanding of the mechanisms responsible for the development of highly oriented film and for the formation of epitaxial nuclei. With this as our goal we have applied plan-view transmission electron microscopy (TEM) for analysis of a diamond film grown on Si at various stages of film growth.

An ASTeX™ MPCVD system was used to deposit diamond on a single-crystal (100) Si substrate under the following conditions: 970°C, 700W microwave power, 2% CH4 in H2, 90 torr., and 4 hours. The growth step was preceded by a BEN stage in which a negative potential of 200V was applied to the substrate for 25 minutes at 600°C, 700W, 4% CH4 in H2, and 20 torr.. Three different types of plan-view TEM samples were prepared. For one the common procedure of backthinning, dimpling, and ion milling was applied to produce a specimen which reveals microstructures at the film surface.

GaN has been intensively studied because of its potential applications for the fabrication of blue- or ultraviolet-light emitting devices. Sapphire (α-Al2O3) is generally used as the substrate for growth of GaN film. However, the large lattice mismatch between GaN and Al2O3is a possible cause of the large defect density in the GaN films. Consequently, alternative substrates are being studied with the aim of growing films of lesser defect densities and improved opto-electronic properties. In this paper, we report a transmission electron microscopy (TEM) study of a GaN film grown on cubic SiC which has been obtained by carbonization of the top silicon layer of a SIMOX substrate, i.e. the system GaN/SiC/Si/SiO2/Si.

Cross-sectional TEM specimens were prepared by the conventional sandwich technique with the foil surface normal to the Si[l10] direction. The composite sample was ground and dimpled to a thickness of ∼ 10μm, and subsequently ion thinned to electron transparency.

Amorphous carbon coatings, including highly sp3-bonded amorphous diamond (a-D), also referred to as tetrahedral amorphous carbon (ta-C), and diamond-like carbon (DLC), have recently been explored for field emission applications [1-3]. These coatings can be deposited uniformly at low temperatures, and possess chemical and mechanical properties similar to those of diamond. They also can be doped with nitrogen to form n-type semiconductors [4]. Diamond coatings, on the other hand, are microscopically nonuniform, usually require deposition temperatures greater than 600 °C, and cannot be doped to produce shallow donor levels [2]. Diamond, a-D, and DLC coated emitters all show enhanced electron emission properties [1-3].

The major emphasis of the work presented here is on the parallel electron energy loss spectroscopy (PEELS) characterization of the sp2 and sp3 bonded carbon in the coatings. PEELS spectra and TEM images were recorded with a Philips CM300 FEG TEM, equipped with a Gatan model 666 parallel acquisition EELS spectrometer. The operating voltage was 300 keV.

The measurement of the absolute crystal polarity is crucial to understanding the structural properties of planar defects in the sphalerite structure. Due to the directionality of the chemical bond between cations and anions in this lattice, grain boundaries in sphalerite can be described by two distinct structural models. Each model is distinguished by the relative orientation of the polar axis in the grains adjoining the interface. In order to evaluate the polarity of twinned grains in GaP, a dynamical diffraction technique is used to determine the Ga to P bond direction across a coherent twin boundary.

The characterization of the polarity in GaP was performed using a convergent-beam electron diffraction technique developed by Tafto and Spence.CBED can be used to identify the direction of the crystal polarity by observing asymmetries in dynamical diffraction contrast in reflections from crystal planes of opposite polarity. Such contrast arises when the Ewald sphere intercepts a weak {002} reflection plus two or more higher order, odd indexed reflections.

CVD TiN films offer promise as a barrier to Al deposition as a result of the improved conformai step coverage of this film in 0.25 μm contact holes. As an underlayer, the TiN performs a secondary role by improving electromigration (EM) resistance. This is a result of the crystal orientation of the TiN film and its influence on the orientation of the subsequent Al layer. A <111>Al orientation shows improved EM resistance; however, CVD TiN has a preferred <200> orientation as opposed to a <111>PVD TiN orientation.

In this study, two parts were investigated: 1) obtain a qualified PVD Al film on a CVD <200> TiN barrier in terms of sheet resistance and reflectivity utilizing MRC's Eclipse™ Mark II PVD system; 2) examine the texture of the Al film utilizing Philips XL30 SEM equipped with EDAX-DX4 EDS system and Electron Back Scatter Pattern (EBSP) system.

It is known that scanning a focussed laser beam across the surface of a semi conductor wafer, can produce a photon induced voltage (PIV) at electrically active sites. This technique depends upon the incident photons inducing charge carriers, both electrons and holes, on or just below the surface of the semi conductor. These charge carriers drift through the device until they are captured by a defect, at which stage they accumulate, producing a voltage at the surface. These voltages are only associated with a charge carrier capture site, which means that a voltage build up only occurs at a defect. This PIV technique has been used for contactless imaging of semiconductor wafers, allowing easy identification of electrically active sites such as crystallographic defects, imperfections and inhomogenieties on or just below the surface [1,2].

Nothing in the above mechanism excludes the use of an electron beam to induce charge carriers and produce an electron induced voltage (EIV).

Multi layer structures are widely used in micro electronics devices and visualisation of their sub surface layers is important to understand the nature and properties of these devices. One of the more common methods of sub surface imaging is ion beam milling, in which sections of the overlaying material are removed to reveal sub surface details. Some disadvantages of this technique are that the equipment required is expensive and the technique is destructive. Another technique is to image a device at different accelerating voltages and determine at which voltage a particular feature is first detected. A major disadvantage of this technique is that the underlying layers are always observed partially obscured by the overlaying material. The development of a non destructive technique for three dimensional characterisation of electronic, physical, compositional and/or topological properties of these structures could be useful.

One such technique is micro tomography using the backscattered electron (BSE) signal in the scanning electron microscope SEM [1].

In recent years, the critical dimension in “Very Large Scale Integrated” devices has dramatically decreased. The microelectronics industry road map predicts that by the year 2000 the critical dimension will be below 250 nm. This reduction in scale will imply the development of new techniques to control the fabrication of such devices. This paper presents a novel approach to characterize VLSI devices based on Monte Carlo calculations. The principle of this technique is to use information from backscattered electrons (BE). The energies of those electrons are related to their maximum range within the structure. Thus it is possible to distinguish the layer from which they are backscattered. In order to collect this information an energy filtered backscattered electron detector must be used.

Figure 1 shows a cross section of a structure produces using a typical VLSI process. The two metal layers are usually patterned to define small lines and contacts.

Recent developments in microelectronic devices have increased the need for new investigative techniques. Much of the development on Electron Beam Induced Current (EBIC) occurred in the early 70's. Since that time, much of the work has been devoted to using this technique to investigate defects in semiconductor devices. Less attention has been focused on electrical measurement of semiconductor properties.

A digital EBIC method to characterize semiconductors has been developed and is presented here. The sample current is measured using a Keithley 670 electrometer controlled through a GPIB interface by a standard computer. The electron beam from the scanning electron microscope (SEM) is synchronized with the current acquisition. All the acquisition is controlled by a Labview virtual instrument (Figure 1).

As an example of the performance of this method, a special sample was analyzed. A novel method of resistless lithography process was developed in our laboratory. This technique is dedicated to overcome limits of conventional resist based electron beam lithography.

From the viewpoint of variety in molecular design, organic molecules have great potential because some of them have large optical nonlinearities. Organic molecules due to a delocalized π-conjugated systems have a number of applications. Since the nitro group is one of the strongest electron-acceptor group, the noncentrosymmetric structures of MNA [2-methyl-4-nitroaniline] and MAP [methyl-(2,4-dinitrophenyl)-aminopropanoate] provide a successful approach for nonlinear optical (NLO) properties.

Heteroepitaxy has become one of the important methods in modern semiconductor technology. In this work the polymeric thin films have grown on crystalline materials by organic molecular beam deposition (OMBD) technique. This provides a highly controlled process of film growth of various organic thin films.

The behaviors of film formation and preliminary results of some properties of mixed MNA-MAP thin films are reported. A surface scientist studying organic interfaces must apply traditional surface science tools with great care. The experimental procedure is followed here in order to examine their morphological features.

In our previous papers on the same topic we have shown how the finite thickness of the specimen influences the magnetic field distribution associated to a single superconducting vortex. Fortunately, Clem found an approximate, but analytical, solution for this problem predicting that the field lines are bent within the specimen and fan out near the surfaces, giving an external field topography broader than the bulk one. This is shown in Figure 1 (a) which reports the projected phase maps of the magnetic field, i.e., the phase shift experienced by a coherent electron plane wave in an ideal experiment where the beam direction is parallel to the specimen surface and the apparent infinite thickness of the specimen is overlooked. The specimen thickness has been taken equal to 2 λL, the bulk London penetration depth. Figure 1 (b) shows the trends of the z-component of the magnetic field calculated up to a distance from the core of 5 λL at the film surface (lower curve), at the film center (intermediate curve) and, for reference, the bulk Clem model (upper curve).

The out-of-focus method has been successfully employed in the dynamical observation of superconducting fluxons. However, owing to the large defocus distance needed to image fluxons with enough contrast it turns out that their correlation with structural defects, better imaged at focus, is troublesome. Among the standard methods of Lorentz microscopy the Foucault technique is a good candidate for removing this drawback, since it generates phase contrast in the focused image by masking part of the transmitted beam by means of an aperture.

Therefore, simulations have been carried out both for one-dimensional fluxon models and more realistic two dimensional ones, with the result that enough contrast can be generated in the focused image in order to detect them. However, although these theoretical results suggest the feasibility of Foucault experiments, filling the gap between theory and practice is not an easy task, especially when considering the small angular deflections involved, of the order of 10−5 rad.

Individual flux lines in superconducting specimens have been recently observed using a 300kV holography electron microscope equipped with a cold field emission gun in the transmission mode by means of the out-of-focus method. In this way it has been possible to observe the dynamic behaviour of fluxons depending upon the variations of the temperature and/or the applied magnetic field or current. The main disadvantage of this method is that correlation with structural defects is troublesome owing to the large defocus distance (of the order of 1 cm for conventional superconductors) necessary for the detection of flux lines.

This drawback is not present in the Foucault technique, where the contrast is generated in the focused image by masking part of the transmitted beam by means of an aperture. Therefore, some preliminary calculations have been made recently using one-dimensional models, which allow for a quick and easy simulation of the factors affecting the experimental conditions .

The electron spin polarization scanning electron microscopy (Spin-SEM) has been used to image the surface magnetic structures of magnetic materials in the order of nra scale. However, the sensitivity of the Spin-SEM so far used is very low. To improve the sensitivity, it is necessary to find the best condition for the electron detection system. The Mott polarimeter has commonly been used in the Spin-SEM. In the present study the performance of the Mott polarimeter is discussed. The geometrical configuration and the value of the post acceleration of secondary electrons to the detector have been experimentally determined or analized by a simple theoretical consideration. On the other hand, in the present study the condition to obtain the highest intensity and the highest signal contrast is seached by using an electron trajectory simulation in the Mott polarimeter. A series of electron scattering events and the electron energy loss in the target of the polarimeter is calculated, and not only the three dimensional scattering trajectory of electrons, but also the spin polarization transfer at every scattering event are traced in the target.

The further development of computer hard disk technology involves ever increasing density of information storage. Current levels of recording are about 1 Gbit per square inch, which will increase by a factor often over the next couple of years. The methodology is well-established: ferromagnetic cobalt alloy thin films (≈20 nm) are sputtered onto an appropriate substrate. Improvement in the magnetic performance (e.g., coercivity, signal-to-noise) requires manipulation of the microstructure by the deposition conditions. Transmission electron microscopy (TEM) is really the only characterization tool which can yield all the necessary information (structural, chemical and magnetic) because of the dimensions involved (e.g., grain sizes of 10-20 nm, with grain boundary segregation an important consideration). This article illustrates some recent contributions to understanding the structure-property-processing combination in this rapidly developing area.

The typical hard disk is made up from an aluminum alloy substrate, a 5-10 micron thick, hard NiP electrodeposited layer, a chromium underlayer, the magnetic Co alloy and a protective thin carbon overcoat.

Electron holography has been successfully used in the observation of phase objects such as magnetic fields and electrostatic potentials. Electron holograms are constructed by the interference of a modulated object wave and a well-defined reference wave and in most cases the reference wave is required to be a plane wave. Frequently, however, the magnetic or electric field extends beyond the interference region, resulting in a distorted reference wave. The reconstructed wave from a hologram made with a distorted reference wave does not accurately express the object wave but the difference from the reference wave.

Differential interferometry is a useful technique in the absence of a well-defined reference wave. Some electron holography techniques using two-beam illumination for differential interferometry have been proposed. We have also proposed a new technique for differential microscopy by conventional electron off-axis holography, which utilizes an electron biprism to shear the object wave. Shearing of the object wave is essential for differential interferometry.

The mean specimen potentials across a series of short period coherent face centered ferromagnetic Fe-Cu multilayers, grown on (001) Cu by UHV DC magnetron getter sputtering, have been measured using Fresnel contrast analysis1 in the transmission electron microscope. Multilayers A, B and C nominally had 100 repeats of (Fe2/Cu15), (Fe4Cu13) and (Fe6/Cu9) in units of atomic layers, and saturation magnetizations at 0K of 1.7, 0.7 and 0.8μB/Fe atom, respectively. X-ray diffraction measurements showed that the average (002) spacing in each multilayer was much greater than conventional elasticity theory would predict from the bulk elastic constants of face centered Fe and Cu.

Energy-filtered through focal image series of each multilayer (examined in cross-section) were obtained at 397kV using a JEOL 4000FX microscope equipped with a Gatan imaging filter, and a 3.4mrad objective aperture. Fig.1 shows two of the images obtained from multilayer A. The intensity in selected regions of each such image was projected parallel to the layers, the specimen thicknesses (t) of the regions were measured and the contrast of the resulting one dimensional fringe profiles was compared with calculations in order to determine both the shapes and the magnitudes of the potential profiles across the Fe layers.

Traditional electron microscopy techniques for imaging magnetic microstructure include out-of-focus Fresnel or Lorentz imaging, Foucault imaging and differential phase contrast (DPC). Off-axis electron holography provides access to both the amplitude and phase of the electron wave which has passed through the sample and therefore can provide direct, quantitative information about the in-plane component of the magnetic induction. The Philips CM200-FEG microscope which was used for the holography described here is equipped with a powerful mini-lens below the specimen enabling 2nm spatial resolution and only a small residual field at the sample. The combination of high coherence and increased magnification enable quantitative mapping of magnetic induction at the nanometer scale.

Electrostatic or magnetic potentials give rise to phase shifts in the holographic interference fringes which can be quantified following reconstruction. In the presence of a magnetic field, the phase equation (for constant composition and neglecting diffraction effects) becomes: