Zhangda Lin

Aluminum/polyimide interface formation: An x‐ray photoelectron spectroscopy study of selective chemical bonding

High‐resolution x‐ray photoelectron spectroscopy has been used to study the formation of the aluminum/polyimide (Al/PI) interface at room temperature. Aluminum films up to 80 A thick were vapor deposited onto cured polyimide in situ. Our results show that Al is chemically active for coverages below ∼20 A. Preferential aluminum bonding with PI occurs at carbonyl sites, as evidenced by the rapid attenuation of the carbonyl C 1s core level photoemission intensity. In the initial reaction stage (1–2 A), Al preferentially occupies planar imide rings. These adatoms transfer charge to carbonyl carbon atoms via oxygen and this resonance hybrid state of C–O–Al weakens, but does not break, carbonyl bonds. With increasing Al coverage, the formation of strong Al–O bonds is observed and is attributed to a C–O–Al complex compound. Metallic Al is observed at a nominal coverage of 2 to 5 A. The Al/PI interface exhibits the attenuation behavior characteristic of cluster growth through both reacted and unreacted regions. A...

Surface segregation at metalndashIII-V-compound-semiconductor interfaces.

This paper focuses on the interesting observation that semiconductor atoms segregate to the free surface for many evolving metal/semiconductor interfaces. Their presence contributes to a range of intriguing properties of interfaces and their study offers insight into complicated interface behavior. The purpose of this paper is to develop a simple model for surface segregation for evolving metal/semiconductor interfaces. The starting point for this modeling is recent theories developed to qualitatively interpret grain-boundary segregation and surface segregation on alloy systems. As we will show, our approach will yield excellent agreement when compared with the wealth of experimental information available in the literature, including our own experimental results and those of others. We focus on interfaces grown under the cleanest of conditions. We do not summarize the large device literature because devices are grown under less controlled conditions and the presence of impurities will alter the atom distribution.

SYNCHROTRON RADIATION PHOTOEMISSION-STUDIES ON THE PALLADIUM COMPOUND SEMICONDUCTOR INTERFACES - VALENCE BAND STUDIES

Abstract A synchrotron radiation (SR) photoemission study on the valence band of the Pd/GaAs (110), Pd/InP (110), Pd/InSb (110) and Pd/PbS (100) systems has been presented. It was observed in the study that at Pd coverages ranging from 0.2 to 40 A, all of the valence bands of the interface systems are composed of a main structure characterizing the Pd 4 d band, and a shoulder near the Fermi level representing the antibonding states coming from the interaction of Pd with the substrates. With increasing Pd coverages, the main peak in the valence bands developed gradually into the bulk Pd 4 d band, and the shoulder appeared to merge into the main band. Two interfaces processes, namely surface segregation and chemical interaction, have been investigated for the interface systems with the help of peak decomposition and curve fitting for the Pd 4 d band, which revealed the evolution of the band shape parameters at various coverages. It is found that for the semiconductor substrate with more reactive anions, chemical interaction will dominate the interface processes at the first stage of interface formation.