Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

In this paper, we have studied the relationship between medium-range order structures in and stress relaxation in amorphous diamond-like carbon films with fluctuation microscopy. Our preliminary results show strong correlation between stress relaxation and medium-range order. Our previous results showed that annealing films that had been through stress relaxation procedures caused great increase of medium-ranger order. In this paper, we have found that the increase of medium-range order in films that have been annealed before going through stress relaxation through removal of substrates is less pronounced than that of films that have been annealed after removal of substrates. We will discuss interpretations and implications of these results.

We had studied the effects of hyperthermal (5.1eV) atomic oxygen (AO) on the structural characteristics of the silica layer and Si/SiOx interface formed by the oxidation of Si-single crystal by a variety of microcharacterization techniques. A laser detonation source was used to produce atomic oxygen with 5.1eV kinetic energy. High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) demonstrated that the silica layer formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous, compared to the oxide layer created by molecular oxygen (MO). High spatial resolution Electron Energy Loss Spectroscopy (EELS) study confirmed that the Si/SiOx interface created by atomic oxygen is abrupt containing no suboxides as opposed to the broad interface with transitional states formed by molecular oxygen. SAED technique was used to observe sharper diffraction rings present in the diffraction pattern of Si(100) oxidized by reactive atomic oxygen as opposed to the diffused haloes present in the diffraction pattern of Si(100) oxidized by molecular oxygen. Radial Distribution Function (RDF) analyses were performed on the SAED patterns of Si(100) oxidized in atomic and molecular oxygen, indicating that a more ordered oxide is formed by atomic oxygen. Initial Fluctuation Electron Microscopy (FEM) results confirmed an increased medium range ordering in SiOx formed by atomic oxygen when compared to the non-regular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen.

Fluctuation electron microscopy studies have been performed on several aluminum oxides exposed to different electrochemical conditions. Little is known about amorphous aluminum oxide structures and their relationship with their passivation behaviors. Corrosion studies have shown that exposure of aluminum oxide films to Cl ions in solution reduces the oxide's passivity, and this results in the onset of pitting corrosion. The physical changes that occur in the oxide as a result of Cl exposure have not been previously identified due to the difficulty in investigating the structure of this amorphous material. Fluctuation microscopy is a new electron microscopy technique that is able to detect the presence of medium range order structures in amorphous systems. In this paper, we will report fluctuation microscopy results on amorphous aluminum oxides that have been exposed to Cl ions in solution and compare them with oxides that have seen no electrolyte exposure or that have been exposed to electrolytes that do not contain Cl-,such as SO42- containing electrolytes. We will also compare the Cl-exposed oxides with oxides that have been implanted with Cl ions. The differences in pitting behaviors for these oxidesare consistent with our previous speculation on the effect of medium range order on the passivation behavior of aluminum oxides grown using ozone.

In this paper, we have studied medium-range order structures in amorphous diamond-like carbon films with fluctuation microscopy. Medium-range order structures are quantified by a specific form of a general four-body correlation. We name this function as a pair-pair alignment correlation function. By analyzing speckle dark-field images taken over different areas as a function of momentum transfer in reciprocal space, we measured the pair-pair alignment correlation function for both thermally annealed samples and unannealed samples. We have found that thermal annealing introduces medium-range order in amorphous diamond-like carbon films, causing more pairs of atoms to be aligned. These results agree with density-functional simulations. Larger-scale simulations will be needed to fully understand our experimental results.

We applied fluctuation microscopy technique to study medium-range order in tetrahedral semiconductor materials, such as amorphous silicon, amorphous diamond-like carbon films. It is shown that this technique is very sensitive to local structure changes in the medium range order and promises solutions to open questions that cannot be answered by current techniques. For asdeposited amorphous germanium and silicon, we previously identified a fine-grain para-crystallite structure [1, 2], which will be relaxed into a lower-energy continuous random network structure after thermal annealing. With the same fluctuation microscopy technique, we however found that thermal annealing introduces medium-range order in amorphous diamond-like carbon films. Future studies will be focused on modeling and systematic exploration of annealing effects.

In this study, we simulated gas bubble formation in glasses by in-situ ion implantation. Alkali silicate glass and Na-borosilicate glass were implanted in situ with 50 keV Xe ions at temperatures at 200°C in a Hitachi-9000 electron microscope. Bubble formation was studied by transmission electron microscopy images taken during interruptions of the ion beam after discrete implanted-ion dose steps. We present a possible mechanism of bubble formation and growth based on amorphous network structures.

A transmission electron microscope technique is used to image atomic steps at buried interfaces between silicon and silicon dioxide. We have studied the effect of processing conditions on the interfacial structure of Si/SiO2 with this technique. We observed a dramatic effect of post-oxidation annealing on silicon (100). Roughening of Si(111) interfaces due to chemical preparation is also reported.