Understanding crystallization in undoped and nitrogen doped GeTe thin films using substrate curvature measurements

Jagtap, Piyush Vijay (2023) Understanding crystallization in undoped and nitrogen doped GeTe thin films using substrate curvature measurements. Materialia, 28. p. 101738. ISSN 2589-1529

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Abstract

Herein, we study the crystallization of undoped and nitrogen doped amorphous GeTe thin films (slightly rich in Ge) obtained by sputtering using substrate curvature measurements to understand the underlying mechanisms controlling stress evolution in the film throughout the phase transformation. At temperatures below crystallization temperature, amorphous films showed stress relaxation and the stress gradually became tensile with annealing time. The GeTe samples show a two-step crystallization wherein amorphous GeTe crystallized first (at the crystallization temperature Tx) followed by crystallization of excess Ge (Ge precipitation) at -Tx+50 °C. Upon GeTe crystallization, a sharp increase in the tensile stress is explained using a coalescence mechanism. This interpretation resolves the issue of the discrepancy between the measured stress buildup reported by several authors and the predicted stress jump from elastic accommodation of density change. The precipitation of excess Ge (from amorphous to crystalline) along grain boundaries in GeTe leads to compressive stress build-up. Nitrogen doping affects both the GeTe and Ge crystallization events leading to lesser tensile and compressive stress. The models for stress relaxation in the amorphous phase, stress build-up due to GeTe, and excess Ge crystallization are discussed.

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IITH Creators:

IITH Creators	ORCiD
Jagtap, Piyush Vijay	UNSPECIFIED

Item Type:

Article

Uncontrolled Keywords:

Crystallization; GeTe; Nitrogen doping; Phase-change materials; Stress; Amorphous films; Crystallization; Germanium; Germanium compounds; Grain boundaries; Nitrogen; Phase change memory; Precipitation (chemical); Semiconductor doping; Stress relaxation; Thin films; Annealing time; Crystallization temperature; Curvature measurement; Nitrogen-doped; Nitrogen-doping; Phases transformation; Stress build-ups; Stress evolution; Substrate curvature; Thin-films; Phase change materials

Subjects:

Others > Crystallography
Others > Metallurgy Metallurgical Engineering
Materials Engineering > Materials engineering

Divisions:

Department of Material Science Engineering

Depositing User:

Mr Nigam Prasad Bisoyi

Date Deposited:

28 Sep 2023 11:26

Last Modified:

28 Sep 2023 11:28

URI:

http://raiithold.iith.ac.in/id/eprint/11713