Comparative Study of Surface Energies of Native Oxides of Si(100) and Si(111) via Three Liquid Contact Angle Analysis
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.473
Comparative Study of Surface Energies of Native Oxides of Si(100) and Si(111) via Three Liquid Contact Angle Analysis 1
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Saaketh R. Narayan , Jack M. Day , Harshini L. Thinakaran , Nicole Herbots , 1,4 1,4 1,4 Michelle E. Bertram , Christian E. Cornejo , Timoteo C. Diaz , Karen L. 2 1 1 1 3 Kavanagh , R. J. Culbertson , Franscesca J. Ark , Sukesh Ram , Mark W. Mangus , 1,4 Rafiqul Islam 1
Arizona State University, Dept. of Physics
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Simon Fraser University, Vancouver
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LeRoy Eyring Center for Solid State Physics, ASU
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Cactus Materials, Inc.
ABSTRACT
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The effects of crystal orientation and doping on the surface energy, γ , of native oxides of Si(100) and Si(111) are measured via Three Liquid Contact Angle Analysis T (3LCAA) to extract γ , while Ion Beam Analysis (IBA) is used to detect Oxygen. During 3LCAA, contact angles for three liquids are measured with photographs via the “Drop and Reflection Operative Program (DROP™). DROP™ removes subjectivity in image analysis, and yields reproducible contact angles within < ±1°. Unlike to the Sessile Drop Method, DROP can yield relative errors < 3% on sets of 13 3 20-30 drops. Native oxides on 5 x 10 B/cm p doped Si(100) wafers, as received in sealed, 25 wafer teflon boats continuously stored in Class 100/ISO 5 conditions at T 24.5°C in 25% controlled humidity, are found to be hydrophilic. Their γ , 52.5 ± 1.5 2 mJ/m , is reproducible between four boats from three sources, and 9% greater than T 2 γ of native oxides on n doped Si(111), which averages 48.1 ± 1.6 mJ/m on four 4” 16 Si(111) wafers. IBA combining O nuclear resonance with channeling detects 30% T more oxygen on native oxides of Si(111) than Si(100). While γ should increase on LW thinner, more defective oxides, Lifshitz-Van der Waals interactions γ on native 2 LW 2, oxides of Si(100) remain at 36 ± 0.4 mJ/m , equal to γ on Si(111), 36 ± 0.6 mJ/m LW 18 3 + since γ arises from the same SiO2 molecules. Native oxides on 4.5 x 10 B/cm p T 2 doped Si(100) yield a γ of 39 ± 1 mJ/m , as they are thicker per IBA. In summary, 3LCAA and IBA can detect reproducibly and accurately, within a few %, changes in the surface energy of native oxides due to thickness and surface composition arising from doping or crystal structure, if conducted in well controlled clean room conditions for measurements and storage.
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INTRODUCTION The electronic defect-density at the surfaces and interfaces of semiconductors and their oxides is key to electronic devices such as solar cells [1, 2], transistors [3], and cutting-edge particle detectors. Electronic defects trap charges, adding noise to carrier transport and impacting device performance. Forming an ideal semiconductor-oxide interface commonly starts with a
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