Phase transformation kinetics—the role of laser power and pulse width in the phase change cycling of Te alloys

Rubin, K.; Barton, Roger; Chen, M.; Jipson, V. B.; Rugar, D.

doi:10.1063/1.97808

Cited by 20 publications

(8 citation statements)

References 8 publications

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“…8,9 A 658 nm diode laser was focused to a diffraction limited spot, through a 0.65 NA objective, and used to locally heat the sample. The incident power was incremented from 5 to 58 mW, and for each power setting, the pulse duration was varied from 10 to 500 ns in steps of 10 ns.…”

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confidence: 99%

Reduction in crystallization time of Sb:Te films through addition of Bi

Simpson

Hewak

Fons³

et al. 2008

Applied Physics Letters

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The electrical, optical, and phase change properties of bismuth doped Sb 8 Te 2 films have been characterized. Thin films of the material, with up to 15 at. % percent Bi, have been synthesized; amorphous films were stable at room temperature with a Bi concentration of up to 13 at. %. The effect of Bi on the phase change properties of the film is shown to reduce the crystallization time by an order of magnitude while the crystallization activation energy reduction is minimal; 0.2 eV. Over the last 30 years, 1 phase change materials have been extensively investigated for optical data storage applications. Phase change recording is based on the reversible switching between the crystalline and amorphous states. The rate that data can be erased and directly overwritten is reliant on the crystallization time of the material; thus, understanding the effect of compositional variations on the crystallization times of these materials is of key importance.The effect of Bi doping, in the well researched Ge 2 Sb 2 Te 5 ͑GST͒ phase change alloy, has been reported by a number of groups. [2][3][4] Experimental results demonstrate that the use of Bi as a dopant could play an important role in the demonstration of improved data storage materials. When doped in GST, Bi is known to reduce the transition temperatures without affecting the crystal structure or its lattice parameters. 2In addition to the well known GST composition, the Sb:Te binary compositions are also known phase change materials. 5The appreciation of bismuth's mechanism in Sb:Te compounds could aid the understanding in the somewhat more complex Bi doped ternary systems. The Sb 2 Te phase shows a wide compositional tolerance with Sb content ranging from 63 to 81 at. %. 6 In this work, samples containing 80% Sb have been doped with Bi; close to the maximum Sb concentration at which the Sb 2 Te phase is formed. Since this crystal can form over a wide Sb compositional range, it is anticipated that it will show some acceptance of the Bi atom. The crystallization, optical, and electrical properties have been investigated.The Bi content was varied between 0 and 15 at. % by attaching pure Bi pieces to a Sb 8 Te 2 sputtering target. Sputtering was performed in an argon atmosphere, controlled at 0.5 Pa, with a rf power of 100 W. Films, with thickness of 100 nm, were deposited onto Si and SiO 2 substrates. The film composition was measured by x-ray fluorescence spectroscopy using a Rigaku RIX 2100 system. The crystallization temperature and its activation energy were measured by monitoring the reflection as a function of temperature, using a Linkam microscope furnace in conjunction with a broad visible source and a monochromator-detector setup. Measurements of the crystallization temperature were made at heating rates of 5, 10, 15, 20, and 25°C min −1 in an Ar atmosphere. These heating rates are many orders of magnitude lower than that of laser or joule heating. However, for the purpose of comparing samples measured in the same fashion, these heating rates were deemed suffici...

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mentioning

confidence: 99%

Reduction in crystallization time of Sb:Te films through addition of Bi

Simpson

Hewak

Fons³

et al. 2008

Applied Physics Letters

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“…The transformation kinetics during pulsed laser heating can be estimated from the isothermal TTT diagram by integrating the fraction transformed along the thermal path. In actual pulsed laser heating experiments, the transformation kinetics have not been directly observed and a diagram of the resultant phase fields as a function of the laser power and pulse duration is often more useful, 6 as shown in Fig. 3͑b͒.…”

Section: Crystallization Kinetics Of Phase Change Mediamentioning

confidence: 99%

Modeling of laser pulsed heating and quenching in optical data storage media

Volkert¹,

Wuttig

1999

Journal of Applied Physics

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In order for rewritable optical data storage to compete with other storage technologies, it is crucial to increase the data transfer rate and storage capacity. Near-field recording should enable considerable progress in these areas, however, currently available near-field light sources are limited by their low output powers. This puts severe constraints on the thermal properties of the phase change media. This article addresses how rewritable optical data storage media can meet data transfer rate and storage capacity requirements. In particular, the required laser power for writing and erasing submicron ''bits'' is calculated. It is shown using modeling how the power and the write and erase times depend on the structure and thermal properties of the media, as well as on the crystallization kinetics of the recording layer. Guidelines for media optimization and areas that presently pose the most serious limitations are presented.

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“…12 ' 13 However, less emphasis has been placed on searching for significantly different alternative materials systems for use as the active medium in phasechange memory. 6 " 11 Unfortunately, these materials undergo degradation during cycling.…”

Section: Introductionmentioning

confidence: 99%

Copper vanadates as candidate materials for phase change optical memory

1992

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Several copper vanadium oxide melts were tested for possible application as the active medium in phase-change optical data storage devices. These materials were melted in the bulk and then quenched. Their phase development was characterized to help determine their applicability to optical data storage. It was found that they satisfy many of the criteria necessary for successful phase-change data storage; further studies of their behavior in thin film geometry would be warranted.

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Phase transformation kinetics—the role of laser power and pulse width in the phase change cycling of Te alloys

Cited by 20 publications

References 8 publications

Reduction in crystallization time of Sb:Te films through addition of Bi

Reduction in crystallization time of Sb:Te films through addition of Bi

Modeling of laser pulsed heating and quenching in optical data storage media

Copper vanadates as candidate materials for phase change optical memory

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