M. A. Bica de Moraes

Plasma polymerized hexamethyldisiloxane: Discharge and film studies

Films were grown in hexamethyldisiloxane (HMDS)-argon mixtures in a diode sputtering system with a gold cathode. Quantitative optical emission spectroscopy (OES)-actinometry revealed that the electron density or mean electron energy (or both) increased with increasing Ar concentrations in the gas feed. Increasing concentrations of Ar produced greater sputtering of the cathode and hence greater plasma Au concentrations. Fragmentation of the HMDS molecule resulted in species such as CH, H, and Si which were detected by OES. Film deposition rate, as determined by optical interferometry, was found to be increased by the inclusion of Ar in the gas feed. Transmission electron microscopy revealed particles, probably of Au, embedded in the polymer films. Actinometric measurements of Au in the discharge and electron probe microscopy of the deposited material showed that film Au concentrations increase with increasing concentrations of Au in the plasma. A relatively low fragmentation of HMDS molecules in the dc plasma was revealed by the very small Si-H IR absorption band which is usually prominent in spectra of plasma polymerized HMDS films.

Electronic structure at InP organic polymer layer interfaces

Organic polymer layer/p-InP(100) interfaces have been investigated using surface photovoltage spectroscopy (SPS) in conjunction with ultraviolet-visible absorption spectroscopy (AS), infrared transmission spectroscopy (IRTS), time-resolved photoluminescence (PL), and x-ray photoemission spectroscopy (XPS). Prior to deposition, the etched p-InP(100) surfaces exhibited two gap states, attributed to excess surface P and adsorbed O, respectively. Postdeposition measurements show that N-containing layers suppress the former state at the interface, while the latter state is suppressed if S and F are present in the organic polymer film. A mechanism of these interfacial phenomena is suggested.

Electron emission enhanced chemical vapor deposition (EEECVD) for the fabrication of diverse silicon-containing films☆

Amorphous films (a-C:H:Si and a-C:H:Si:O) were grown in a vacuum chamber containing a hot filament on substrates held on a copper plate to which a bias voltage could be applied. This modified hot-filament chemical vapor deposition process was used to fabricate various types of amorphous thin film from mixtures of tetramethylsilane (TMS) or hexamethyldisiloxane (HMDSO) diluted in argon or argon/nitrogen mixtures. Electrical characteristics of the process, deposition rates, and film structures were investigated as a function of the deposition parameters, particularly the proportion of nitrogen in the chamber feed. For film characterization, transmission infrared spectroscopy (IRS) was employed. Without a significant substrate current, deposition rates were negligible. Thus, electron impact fragmentation of the monomer molecules is a key process in film deposition using this technique. The method shows promise and versatility for the fabrication of a wide range of amorphous films, including, for example, a-C:H and a-C:H:O.

Optical Properties of Thin Films of Polymerized Acetylene Deposited by dc and rf Glow Discharge

By glow discharge polymerization [1], organic thin films having promising important technolqgycal applications [2,3,4,5,6] can be obtained. These materials can be obtained in a range of physical and chemical properties, depending on the starting monomer and on the deposition parameters.