Application of High Throughput Methods to the Development of Materials For Non-Magnetic Storage
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Application of High Throughput Methods to the Development of Materials For Non-Magnetic Storage C. Eric Ramberg, Y. Wang, Q. Fan, E. McDermott, J. Wang, K. Kenyon, M. Field, M. Hornbostel, S. Guan, S. Nguyen Symyx Technologies, Inc., 3100 Central Expressway, Santa Clara, CA 95051. ABSTRACT High throughput, thin film synthesis methods have been used to make libraries of diverse metallic and metal-chalcogenide compositions. These libraries have been subject to a variety of screening protocols, including X-ray diffraction (XRD) after repeated annealing steps, and the measurement of temperature dependent electrical properties. The application of these methods for the development of materials for non-magnetic storage media is presented. INTRODUCTION “Combinatorial” or “High Throughput” methods have been applied in a variety of fields for the discovery of new materials. These methods are based on a hierarchy of information quality. Coarse, but rapid measurements are typically used to differentiate between good and bad samples. More detailed (expensive) measurements are subsequently performed on the better samples. Thus, experimental efficiency is maximized. TECHNOLOGY A workflow for the discovery and development of novel metallic and metal-based compounds has been developed at Symyx Technologies. This workflow begins with thin film synthesis of diverse compositions using physical vapor deposition (PVD). Samples are then screened to examine phase stability vs. temperature using sequential rapid thermal annealing (RTA) combined with x-ray diffraction (XRD) to examine phase stability. Additionally, a high throughput tool for measuring the temperature dependence of the sample resistance has been developed, which yields a rich set of thermodynamic and kinetic data on phase transformation rates and stabilities of different phases. High throughput synthesis has been carried out using a proprietary combinatorial physical vapor deposition (PVD) system [1]. Samples are synthesized in “library” format, in which a plurality of discrete samples is made on a single substrate for ease of synthesis and measurement. Each discrete sample is defined with a contact mask, as shown in Figure 1. Dynamic shutters either block or expose different parts of the wafer to the deposition plume, thus controlling the sputtered amount on each sample. This system has been used for metals, nitrides, Te, Sb, Sn, Bi, and C, as shown in Figure 2. Chemistry is modified by the sequential deposition of different components; each sample’s stoichiometry is determined by the relative thickness of each component deposited, using the molar densities of the respective components.
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To ensure mixing, the components are deposited periodically, such that the continuous thickness of any given component is always less than 3-4 nm. Each “period” is repeated as many times as required to achieve the desired total thickness. Typical thicknesses used in this study are of the order 200-300nm. Samples (in prior studies on binary and ternary compounds) containing
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