Amorphous carbon nitride coatings of thickness of 5 and 30 nm were deposited onto 65 and 95 mm magnetic thin-film rigid disks surfaces using single-cathode and dual-cathode magnetron sputtering systems containing nitrogen-argon plasmas. Under optimum deposition conditions, amorphous carbon nitride coatings can be synthesized on ultrasmooth thin-film disks with no significant pinholes at thickness down to 5 nm, with hardness 22–28 GPa (compared to 7–12 GPa for amorphous carbon), and r.m.s. roughness as low as 0.25 nm. These amorphous carbon nitride coatings were shown to have better contact-start-stop performance and three-to-four times better pin-on-disk contact durability compared with amorphous carbon overcoats under identical testing conditions. Amorphous carbon nitride appears to be a promising candidate overcoat material for replacing amorphous carbon in the next-generation magnetic thin-film rigid disk systems.

Nanoindentation and nanoscratching experiments have been performed to assess the mechanical and tribological behavior of three thin film materials with potential application as wear resistant coatings for magnetic disk storage: (1) hydrogenated-carbon (CHx); (2) nitrogenated-carbon (CNx); and (3) boron suboxide (BOX). The hardness and elastic modulus were measured using nanoindentation. Ultra-low load nanoscratching tests were performed to assess the relative scratch resistance of the films and measure their friction coefficients. The mechanical and tribological performance of the three materials are discussed and compared. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or impled, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, , manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Gas-induced conductance changes were measured on palladium-dosed single-crystal tin oxide (SnO2) thin films having well-characterized surface properties. Films were fabricated using two methods: reactive sputtering and chemical vapor deposition. Film orientation and crystal structure were determined by x-ray diffraction, while surface morphology was characterized using atomic force microscopy. Conductance changes were measured continuously on film surfaces during alternating exposure and evacuation cycles to partial pressures of H2, O2, and CO in a vacuum chamber. The conductance change was found to be proportional to the square root of the initial film conductance and was interpreted in terms of gas-induced changes in the width of a near-surface space-charge layer. The variation of conductance as a function of gas pressure during alternating exposure and evacuation cycles of H2 and O2 is consistent with a model that involves surface reactions between coadsorbates.