TY - JOUR
T1 - Understanding gaas Native Oxides by Correlating Three Liquid Contact Angle Analysis (3LCAA) and High Resolution Ion Beam Analysis (HR-IBA) to X-Ray Photoelectron Spectroscopy (XPS) as Function of Surface Processing
AU - Ram, Sukesh
AU - Chow, Amber A.
AU - Khanna, Shaurya
AU - Suresh, Nikhil C.
AU - Ark, Franscesca J.
AU - Narayan, Saaketh R.
AU - Gurijala, Aashi R.
AU - Day, Jack M.
AU - Karcher, Timothy
AU - Culbertson, Robert J.
AU - Whaley, Shawn D.
AU - Kavanagh, Karen L.
AU - Herbots, Nicole
N1 - Funding Information:
The authors acknowledge the use of facilities within the Eyring Materials Center at Arizona State University. The authors also wish to acknowledge financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) (Conseil de recherches en sciences naturelles et en genie du Canada) for its research grant, to support HR-IBA and XPS and acquiring GaAs wafers from different sources.
Publisher Copyright:
© Materials Research Society 2019.
PY - 2019
Y1 - 2019
N2 - Chemical bonding in native oxides of GaAs, before and after etching, is detected by X-Ray Photoelectron Spectroscopy (XPS). It is correlated with surface energy engineering (SEE), measured via Three Liquid Contact Angle Analysis (3LCAA), and oxygen coverage, measured by High Resolution Ion Beam Analysis (HR-IBA). Before etching, GaAs native oxides are found to be hydrophobic with an average surface energy, γT, of 33 ± 1 mJ/m2, as measured by 3LCAA. After dilute NH4OH etching, GaAs becomes highly hydrophilic and its surface energy, γT, increases by a factor 2 to a reproducible value of 66 ± 1 mJ/m2. Using HR-IBA, oxygen coverage on GaAs is found to decrease from 7.2 ± 0.5 monolayers (ML) to 3.6 ± 0.5 ML. The 1.17 ratio of Ga to As, measured by HR-IBA, remains constant after etching. XPS is used to measure oxidation of Ga and As, as well as surface stoichiometry on two locations of several GaAs(100) wafers before and after etching. The relative proportions of Ga and As are unaffected by adventitious carbon contamination. The 1.16 Ga:As ratio, measured by XPS, matches HR-IBA analysis. The proportions of oxidized Ga and As do not change significantly after etching. However, the initial ratio of As2O5 to As2O3, within the oxidized As, significantly decreases after etching from approximately 3:1 to 3:2. Absolute oxygen coverage, as a function of surface processing, is determined within 0.5 ML by HR-IBA. XPS offers insight into these modifications by detecting electronic states and phase composition changes of GaAs oxides. The changes in surface chemistry are correlated to changes in hydro-affinity and surface energies measured by 3LCAA.
AB - Chemical bonding in native oxides of GaAs, before and after etching, is detected by X-Ray Photoelectron Spectroscopy (XPS). It is correlated with surface energy engineering (SEE), measured via Three Liquid Contact Angle Analysis (3LCAA), and oxygen coverage, measured by High Resolution Ion Beam Analysis (HR-IBA). Before etching, GaAs native oxides are found to be hydrophobic with an average surface energy, γT, of 33 ± 1 mJ/m2, as measured by 3LCAA. After dilute NH4OH etching, GaAs becomes highly hydrophilic and its surface energy, γT, increases by a factor 2 to a reproducible value of 66 ± 1 mJ/m2. Using HR-IBA, oxygen coverage on GaAs is found to decrease from 7.2 ± 0.5 monolayers (ML) to 3.6 ± 0.5 ML. The 1.17 ratio of Ga to As, measured by HR-IBA, remains constant after etching. XPS is used to measure oxidation of Ga and As, as well as surface stoichiometry on two locations of several GaAs(100) wafers before and after etching. The relative proportions of Ga and As are unaffected by adventitious carbon contamination. The 1.16 Ga:As ratio, measured by XPS, matches HR-IBA analysis. The proportions of oxidized Ga and As do not change significantly after etching. However, the initial ratio of As2O5 to As2O3, within the oxidized As, significantly decreases after etching from approximately 3:1 to 3:2. Absolute oxygen coverage, as a function of surface processing, is determined within 0.5 ML by HR-IBA. XPS offers insight into these modifications by detecting electronic states and phase composition changes of GaAs oxides. The changes in surface chemistry are correlated to changes in hydro-affinity and surface energies measured by 3LCAA.
KW - III-V
KW - Rutherford Backscattering (RBS)
KW - oxidation
KW - surface chemistry
KW - x-ray photoelectron spectroscopy (XPS)
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U2 - 10.1557/adv.2019.320
DO - 10.1557/adv.2019.320
M3 - Article
AN - SCOPUS:85085679600
SN - 2059-8521
VL - 4
SP - 2249
EP - 2263
JO - MRS Advances
JF - MRS Advances
IS - 41-42
ER -