Atomic force microscope (AFM) induced nanolithography has been successfully utilized on perovskite manganite thin films by several groups to create nanoscale patterns for various fundamental mesoscopic-scale transport studies. However, the chemical and physical processes involved have not been understood. This work presents possible microscopic mechanisms for AFM induced nanolithography in La2/3Ba1/3MnO3-δ films induced by an AFM tip, which is negatively biased with respect to the sample in a humid environment. A self-consistent conceptual framework, which accounts for the previously reported observations of changes in the nanomodified regions such as volume increases, selective acid etching, as well as changes in the chemical composition detected by energy dispersive spectroscopy, is reported. Microscopic mechanisms delineated in this work are based on the following: existence of known compounds composed of the available elements (La, Ba, Mn,O, and H) resulting in equal or higher formal oxidation states, postulated electrochemical half reactions resulting in these compounds, reference density and solubility data for these compounds, incorporation of environmental H2O and CO2 by the postulated product solids, electromigration, and electrochemical migration.

Dry etching of polystyrene (PS) with oxygen, using ion beams or plasmas is found to affect the diffusion characteristics of molten PS. Four different techniques, reactive ion beam etching (RIBE), reactive ion etching (RIE), and plasma etching in barrel and downstream reactors are used. Polymer molecules lying near the surface of an etched sample are found to have been immobilized, and thus unable to diffuse. The quantity of material affected in this manner is found to increase with polymer molecular weight, and to be greater in samples etched by RIBE and RIE than in the pure plasma methods. Etching is also found to reduce the permeability of the sample surface to diffusion by unetched polymers. The permeability is found to decrease with the penetrant polymer’s molecular weight, and to decrease more drastically in RIBE and RIE treated samples than the plasma treated samples. Surface wrinkling of RIBE samples upon annealing above the glass transition temperature is also seen. The results are found to yield a consistent picture of polymer damage during dry etching consisting of crosslinking and chain scission. These experiments demonstrate the utility of polymer diffusion in the characterization of topological damage to polymer molecules.

The diffusion of deuterated polystyrene (d-PS) in a polystyrene matrix was used to probe the damage to the polymer surface caused by reactive ion beam etching (RIBE). Diffusion was seen to be hindered in a d-PS film treated by RIBE, an immobilization apparently due to crosslinking of the surface monolayer of the polymer sample.

Reactive ion beam etching of polyimide thin films was investigated using x-ray photoelectron spectroscopy (XPS) and etch rate measurements. The etching mechanism and the near surface damage produced in polyimide by exposure to argon and oxygen ion beams were compared. The etch rate of polyimide by oxygen ions was studied as a function of ion current density and neutral oxygen molecular flux, and the results were found to match a model for the contribution of neutral fluxes to the etch process. Ion beam etching with inert argon ions was found to produce a graphitelike layer on polyimide. Reactive ion beam etching with oxygen ions resulted in much faster etching than for argon ions, and did not produce a graphitized layer.

Surface fluorination of polyimide thin films during CF4 + O2 reactive ion beam etching (RIBE) was investigated. The removal of the fluorinated layer by a subsequent oxygen ion beam etch was also studied. Electron spectroscopy for chemical analysis (ESCA) and Rutherford backscattering spectrometry (RBS) detected a fluorinated surface layer on the order of 100 A thick. Fluorine atom concentration in the surface of the film (as measured by RBS) and the etch rate of the film were measured as a function of several experimental parameters: ion energy, ion current density, etch time, and gas composition. The results are compared with theoretical predictions of the total number of fluorine atoms retained in the film after etching.

Polyimide layers approximately 10 μm thick on Si wafers were ion beam etched (IBE) by Ar. Ion energies up to 1000 eV and beam current densities as high as 0.3 mA/cm2 were used to a total dose of 54 mC/cm2. After etching, the samples were exposed to iodine vapor for fixed periods of time. The diffusion of iodine into the samples was used to probe for ion induced changes in the polyimide structure. The concentration of the diffused iodine was measured as a function of depth by Rutherford backscattering spectrometry. For the IBE samples the surface concentration of iodine was markedly decreased. The iodine diffusivity in the near surface region of thickness 0.2 μm was reduced by two orders of magnitude. These results indicate that etching appears to cause modification of the polyimide film at depths far greater than the range of the incident ions or their secondary electrons in polyimide.