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

Abstract

The electrical, optical and phase change properties of bismuth doped Sb₈Te₂ as-deposited and re-amorphised films have been characterised. Thin films of the material, with up to 15 atomic percent bismuth, have been synthesised by sputter deposition. As deposited amorphous films were stable at room temperature with a bismuth concentration upto 13 atomic percent. We show that effect of bismuth on the phase change properties of the films is to reduce the crystallization time by an order of magnitude. Both static and dynamic measurements of the as-deposited and reamorphised films have showed similar decreases of crystallisation time with bismuth increases. The crystallisation activation energy reduction appears unaffected by the bismuth atoms up to a concentration of 13 atomic percent. The structure of the films after annealing at 180ºC has been measured by X-ray diffraction; the material shows the same A7-type structure as that previously reported for the well known phase change film Ag_3.4In_3.7Sb_76.4Te_16.5. A reduction in the material viscosity with increasing bismuth is suggested as a means by which the reduction in crystallisation time is achieved while a negligible change in activation energy and structure is possible. The effect of bismuth dopants on the Sb₈Te₂ materialʼs physical properties and the consequent performance of optical media and electrical devices will be discussed.

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ORCID for D.W. Hewak: orcid.org/0000-0002-2093-5773

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