Microstructure and noise characteristics of Co-Cr-Ta films on ultraflat glass substrates for longitudinal recording disks

Abstract

Co–Cr–Ta/Cr bilayered films for longitudinal recording disks were deposited by facing targets sputtering (FTS) on 2.5 in. and ultraflat disk substrates of durable single-crystal silicon at temperature Ts of 100 °C and Ar pressure PAr of 0.2 mTorr. TEM observation of the films revealed ultrafine microstructures, and grain boundaries were unclear. The noise and recording characteristics of those disks were comparable with those of very high-performance disks with Co–Cr–Pt films, with coercivity Hc of 2.4 kOe, employed as a reference, even though the Co–Cr–Ta films exhibited macroscopic Hc of only 800 Oe. In this study, Co85Cr13Ta2/Cr bilayered films with the same composition as the above-mentioned disks were deposited by plasma-enhanced (PEFTS) on 2.5 in. and glass–ceramic substrates with ultraflat surface and tough durability at Ts of 100 °C to obtain better microstructure, signal-to-noise ratio (SNR), and surface flatness, with consequent lower flying height, than those on Si substrates, thus making it possible to fabricate ultrahigh-density recording disks. The PEFTS apparatus has several outstanding advantages such as plasma-free substrates, low background pressure of 5×10−7 Torr, low PAr of 0.1 mTorr, and higher mobility of the adatoms than in conventional FTS because of the proximity of the substrate to the central axis of the targets, indicating uniform plasma distribution, with up to six target units in a vacuum chamber. The film’s surface roughness Ra of 0.7 nm and the high mobility of the adatoms result in narrow grain boundaries without pores and inclusions, which were observed by TEM, and better overwrite performance than that of Si substrates and the same SNR as Si substrates, which were measured with a read/write test stand. These results will allow practical application in ultrahigh-density recording systems, including 1 in. microdrives.

Interface-directed sol-gel: direct fabrication of the covalently attached ultraflat inorganic oxide pattern on functionalized plastics

“…We consider that the precise tailoring of chemical structures on substrate surfaces is especially important, because it has been demonstrated that functionalized surface often plays a key role in determining the surface morphology [46][47][48][49][50][51][52][53][54], pattern formation [41] and adhesion strength [42][43][44][45] of inorganic coating. Recently, our lab successfully achieved precise tailoring of chemical structures on a polymer surface at molecular level by an extremely simple "confined photocatalytic oxidation" (CPO) reaction [77].…”

“…The controlled depositions of high quality inorganic oxides on polymeric substrates are often necessary to provide key functions for the devices through themselves, interactions with metals [31] and other oxides [32,33], as well as surface chemical derivations [5,12,13]. For achieving satisfactory applications, such organic/inorganic hybrid materials should possess at least five characters: stable interface adhesion [34][35][36][37], tunable coating thickness [34], the ability of large-area patterning [38,39], low surface roughness [40,41] and high optical transparency [34]. However, polymer surfaces usually have low surface energy and reactivity, irregular molecular orientation and high roughness, and poor thermal and mechanical stabilities, which thus make it difficult to fabricate high quality oxide films upon them [30].…”

Perpendicular Magnetic Anisotropy in the CoFeB/Pt Multilayers by Extraordinary Hall Effect

“…Magnetic anisotropy is the foundation to study the appearance of spontaneous magnetization, the mechanism of magnetic reversals and related process. The total anisotropy energy comes from many aspects that closely related to the structure of the materials, such as the shape of the materials, crystalline phase, and elastic strain in material, and so on [12][13][14][15]. Here, a strong PMA is observed only when the t CoFeB is thin because PMA is mainly attributed to interface effects [14].…”

Effect of Magnetic Field Arrangement of Facing Targets Sputtering (FTS) System on Controlling Plasma Confinement

“…Therefore, a model that not only provides insight into magnetron operation but also practical criteria for designing a magnetron is required. Originally, facing targets sputtering (FTS) method was proposed for growing magnetic materials such as Co-Cr, Co-Cr-Ta, and Co-ferrite for perpendicular recording media [6][7][8].…”