An analytical model for nanoscale electrothermal probe recording on phase-change media
Aziz, Mustafa M.
Wright, C. David
Journal of Applied Physics
American Institute of Physics
Scanning probe memories are now emerging as a means of achieving nanoscale resolution data storage. The use of microscopic conductive tips in contact with a phase-change material to record data as amorphous and crystalline marks is one such approach, making use of the large difference in electrical conductivity between the two phases to distinguish between two binary states on replay and hence provide a memory function. The writing process is complex and involves electronic, thermal, and phase-change processes that are difficult to model and study except using numerical techniques. A simplified analytical model of electrothermal writing by probe on a basic two-layer phase-change structure is developed here, and used to predict the required voltage levels for recording and the expected diameters of recorded crystalline and amorphous marks. A simplified model of cooling and solidification was also developed to study the cooling rates during amorphization. The predictions are shown to be in agreement with published experimental measurements and numerical simulations. The developed analytical models were extended to investigate the effects of introducing coating layers on recording voltage levels, to study the depth profiles of recorded marks, and to derive expressions for the capacitance and resistance of the phase-change layer that contribute to the transient behavior of the recording system.
notes: This paper presents comprehensive mathematical models for understanding the writing (recording) processes in new, ultra-high density, probe-based electrical storage. The analytical models address practical implementation issues in this technology, and allow parametric testing and optimisation of practical storage media structures. It provides a theoretical understanding and confirmation of system dependencies and practical writing conditions observed experimentally by researchers at Tohoku University in Japan. The work led to an invited presentation on probe-based storage by Aziz at the prestigious Seagate Research Conclave held in June 2007 at Sprintown, Northern Ireland. Contact: Dr Alan Johnson, Research Director, Seagate Technology (Ireland), (firstname.lastname@example.org)
Copyright © 2006 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 99 (2006) and may be found at http://link.aip.org/link/?JAPIAU/99/034301/1
Vol. 99 (3), article 034301