Impact of Premetallization Surface Preparation on Nickel-based Ohmic Contacts to Germanium Telluride: An X-ray Photoelectron Spectroscopic Study

Haila M. Aldosari, Hamed Simchi, Zelong Ding, Kayla A. Cooley, Shih Ying Yu, Suzanne E. Mohney

Research output: Contribution to journalArticle

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Abstract

Surfaces of polycrystalline α-GeTe films were studied by X-ray photoelectron spectroscopy (XPS) after different treatments in an effort to understand the effect of premetallization surface treatments on the resistance of Ni-based contacts to GeTe. UV-O3 is often used to remove organic contaminants after lithography and prior to metallization; therefore, UV-O3 treatment was used first for 10 min prior to ex situ treatments, which led to oxidation of both Ge and Te to GeOx (x < 2) and TeO2, respectively. Then the oxides were removed by deionized (DI) H2O, (NH4)2S, and HCl treatments. Additionally, in situ Ar+ ion etching was used to clean the GeTe surface without prior UV-O3 treatment. Ar+ ion etching, H2O, and (NH4)2S treatments create a surface richer in Ge compared to the HCl treatment, after which the surface is Te-rich. However, (NH4)2S also oxidizes Ge and gradually etches the GeTe film. All treated surfaces showed poor stability upon prolonged exposure to air, revealing that even (NH4)2S does not passivate the GeTe surface. The refined transfer length method (RTLM) was used to measure the contact resistance (Rc) of as-deposited Ni-based contacts to GeTe as a function of premetallization surface preparation. HCl-treated samples had the highest Rc (0.036 ± 0.002 ω·mm), which was more than twice that of the other surface treatments. This increase in Rc is attributed to formation of the Ni1.29Te phase at the Ni/GeTe interface due to an abundance of Te at the surface after HCl treatment. In general, treatments that resulted in Ge-rich surfaces offered lower Rc.

Original languageEnglish (US)
Pages (from-to)34802-34809
Number of pages8
JournalACS Applied Materials and Interfaces
Volume8
Issue number50
DOIs
StatePublished - Dec 21 2016

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Germanium
Ohmic contacts
Photoelectrons
Nickel
X rays
Surface treatment
Etching
Ions
Contact resistance
Metallizing
Oxides
Lithography
X ray photoelectron spectroscopy
Impurities
Oxidation

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Cite this

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title = "Impact of Premetallization Surface Preparation on Nickel-based Ohmic Contacts to Germanium Telluride: An X-ray Photoelectron Spectroscopic Study",
abstract = "Surfaces of polycrystalline α-GeTe films were studied by X-ray photoelectron spectroscopy (XPS) after different treatments in an effort to understand the effect of premetallization surface treatments on the resistance of Ni-based contacts to GeTe. UV-O3 is often used to remove organic contaminants after lithography and prior to metallization; therefore, UV-O3 treatment was used first for 10 min prior to ex situ treatments, which led to oxidation of both Ge and Te to GeOx (x < 2) and TeO2, respectively. Then the oxides were removed by deionized (DI) H2O, (NH4)2S, and HCl treatments. Additionally, in situ Ar+ ion etching was used to clean the GeTe surface without prior UV-O3 treatment. Ar+ ion etching, H2O, and (NH4)2S treatments create a surface richer in Ge compared to the HCl treatment, after which the surface is Te-rich. However, (NH4)2S also oxidizes Ge and gradually etches the GeTe film. All treated surfaces showed poor stability upon prolonged exposure to air, revealing that even (NH4)2S does not passivate the GeTe surface. The refined transfer length method (RTLM) was used to measure the contact resistance (Rc) of as-deposited Ni-based contacts to GeTe as a function of premetallization surface preparation. HCl-treated samples had the highest Rc (0.036 ± 0.002 ω·mm), which was more than twice that of the other surface treatments. This increase in Rc is attributed to formation of the Ni1.29Te phase at the Ni/GeTe interface due to an abundance of Te at the surface after HCl treatment. In general, treatments that resulted in Ge-rich surfaces offered lower Rc.",
author = "Aldosari, {Haila M.} and Hamed Simchi and Zelong Ding and Cooley, {Kayla A.} and Yu, {Shih Ying} and Mohney, {Suzanne E.}",
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Impact of Premetallization Surface Preparation on Nickel-based Ohmic Contacts to Germanium Telluride : An X-ray Photoelectron Spectroscopic Study. / Aldosari, Haila M.; Simchi, Hamed; Ding, Zelong; Cooley, Kayla A.; Yu, Shih Ying; Mohney, Suzanne E.

In: ACS Applied Materials and Interfaces, Vol. 8, No. 50, 21.12.2016, p. 34802-34809.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Impact of Premetallization Surface Preparation on Nickel-based Ohmic Contacts to Germanium Telluride

T2 - An X-ray Photoelectron Spectroscopic Study

AU - Aldosari, Haila M.

AU - Simchi, Hamed

AU - Ding, Zelong

AU - Cooley, Kayla A.

AU - Yu, Shih Ying

AU - Mohney, Suzanne E.

PY - 2016/12/21

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AB - Surfaces of polycrystalline α-GeTe films were studied by X-ray photoelectron spectroscopy (XPS) after different treatments in an effort to understand the effect of premetallization surface treatments on the resistance of Ni-based contacts to GeTe. UV-O3 is often used to remove organic contaminants after lithography and prior to metallization; therefore, UV-O3 treatment was used first for 10 min prior to ex situ treatments, which led to oxidation of both Ge and Te to GeOx (x < 2) and TeO2, respectively. Then the oxides were removed by deionized (DI) H2O, (NH4)2S, and HCl treatments. Additionally, in situ Ar+ ion etching was used to clean the GeTe surface without prior UV-O3 treatment. Ar+ ion etching, H2O, and (NH4)2S treatments create a surface richer in Ge compared to the HCl treatment, after which the surface is Te-rich. However, (NH4)2S also oxidizes Ge and gradually etches the GeTe film. All treated surfaces showed poor stability upon prolonged exposure to air, revealing that even (NH4)2S does not passivate the GeTe surface. The refined transfer length method (RTLM) was used to measure the contact resistance (Rc) of as-deposited Ni-based contacts to GeTe as a function of premetallization surface preparation. HCl-treated samples had the highest Rc (0.036 ± 0.002 ω·mm), which was more than twice that of the other surface treatments. This increase in Rc is attributed to formation of the Ni1.29Te phase at the Ni/GeTe interface due to an abundance of Te at the surface after HCl treatment. In general, treatments that resulted in Ge-rich surfaces offered lower Rc.

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