Model studies of oxygen-intercalated graphite

The possibility of intercalating oxygen to reduce the conductivity of graphite has been investigated by modified intermediate neglect of differential overlap 3 and tight-binding methods. The cluster calculations suggest that the most stable position for the oxygen atom is 1.25 A above a carbon-carbon bond. The tight-binding band calculation predicts the stage-I intercalated graphite to be a zero-indirect-gap semiconductor. Higher-stage intercalated graphite is expected to have a finite insulating gap whose value is governed by the carbon-oxygen interaction

Comparison of CHARM-2 and Surface Potential Measurement to Monitor Plasma Induced Gate Oxide Damage

Abstract Plasma process induced gate oxide damage was found in early process development stages. Device data showed unacceptable burn-in failure. By utilizing multiple test vehicles, the underlying cause of oxide damage was identified. This study showed that no single methodology is adequate for controlling the damage. A combination of the monitoring techniques is required to understand root cause of damage and how to optimize the process or equipment. The plasma process was optimized and verified with CHARM-2 monitor response. Further device data verification indicated no gate oxide damage was found with new improved process. The fast turn around time of plasma monitors were essential to understand and determine the plasma damage source. Understanding the relationship between plasma monitor response and plasma process is a key point to identify the source of damage. A fingerprint of plasma process is very useful for process control and defect reduction

Electronic Structure of Clusters Modeling PAN Fibers

In an attempt to understand the process of electrical conduction in polyacrylonitrile (PAN)-based carbon fibers, calculations were carried out on cluster models of the fiber consisting of carbon, nitrogen, and hydrogen atoms, using the modified intermediate neglect of differential overlap (MINDO) molecular orbital (MO) method. The models were developed based on the assumption that PAN carbon fibers obtained with heat treatment temperatures (HTT) below 1000 °C retain nitrogen in a graphite-like lattice. For clusters modeling an “edge” nitrogen site, analysis of the occupied MO\u27s indicated an electron distribution similar to that of graphite. A similar analysis for the somewhat less stable “interior” nitrogen site revealed a partially localized π electron distribution around the nitrogen atom. The differences in bonding trends and structural stability between edge and interior nitrogen clusters led to a two-step process proposed for nitrogen evolution with increasing HTT