Role of surface stoichiometry in the Cl2/GaAs(001) reaction

Simpson, W. C.; Shuh, D. K.; Hung, Wei Hsiu; Håkansson, M.C.; Kanski, J.; Karlsson, Ulf O.; Yarmoff, J. A.

doi:10.1116/1.580342

Cited by 23 publications

(25 citation statements)

References 18 publications

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“…Furthermore, the film growth method should be a simple, inexpensive chemical process that is similar in procedure to SiO 2 growth on Si via exposure to O 2 . Recently, it was shown that a 10 eV band gap insulator, GaF 3 , can be grown on GaAs via exposure to various fluorine-based compounds (30,34,35,38,107,108,120,(123)(124)(125)(126). Operational devices have been constructed from GaF 3 -GaAs structures (124,125,(127)(128)(129), which demonstrates that the interface state density can be reduced to a sufficiently low level that GaF 3 may be a suitable insulator for GaAs-based devices.…”

Section: Fluorinementioning

confidence: 99%

“…Thus, chlorine simply bonds to whichever element is present at the surface. Mokler et al (138), using thermal desorption spectroscopy (TDS) and AES, and Simpson et al (120), using SXPS, found that the initial rate of Cl uptake is greater on Ga-rich surfaces. Mokler et al (138) further showed that a surface capped with 50Å of As was entirely unreactive to Cl 2 .…”

Section: Chlorinementioning

confidence: 99%

“…From core-level photoelectron spectroscopy investigations, it was found that the etching reaction occurs in a step-wise manner (89,97,116,120).…”

Section: Chlorinementioning

confidence: 99%

“…Namely, Ga-rich GaAs(001)-c(8 × 2) is passivated by a layer of GaCl, but As-rich GaAs(001)-c(2 × 8) exhibits continuous Cl 2 uptake, which is indicative of etching. Using SXPS, Simpson et al (120) determined that following room-temperature chlorination, As-rich GaAs(001) surfaces initially form more As chlorides, whereas Ga-rich surfaces initially form more Ga chlorides. Thus, chlorine simply bonds to whichever element is present at the surface.…”

Section: Chlorinementioning

confidence: 99%

“…The principal products on the surface following room-temperature reaction are AsCl and GaCl 2 (89,116,120), so either Step 7b or Step 8a is rate limiting. Since comparable amounts of both AsCl and GaCl 2 build up on the surface, the slow rate of removal of one of them must be limiting the other.…”

Section: Chlorinementioning

confidence: 99%

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Fundamental Studies of Halogen Reactions With Iii-v Semiconductor Surfaces

Simpson

Yarmoff

1996

Annu. Rev. Phys. Chem.

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It is technologically important to understand how halogens react with semiconductor surfaces because halogen compounds are commonly used to etch semiconductor wafers in the microelectronics industry. Halogens are also model adsorbates for studying chemisorption on covalently bonded materials, such as semiconductors, owing to the simple nature of the bonds that they form. The growing use of III-V materials in the manufacture of optoelectronic devices has prompted investigations of the reactions of molecular halogens (XeF 2 , Cl 2 , Br 2 , and I 2 ) with III-V semiconductor surfaces (GaAs, GaSb, InP, InAs, and InSb). This review examines the more fundamental of these investigations, which involve model systems in ultra-high vacuum, focusing on the chemistry of the halogen surface reactions and the physical and electronic structure of the reacted surfaces.

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Section: Fluorinementioning

confidence: 99%

Section: Chlorinementioning

confidence: 99%

“…From core-level photoelectron spectroscopy investigations, it was found that the etching reaction occurs in a step-wise manner (89,97,116,120).…”

Section: Chlorinementioning

confidence: 99%

Section: Chlorinementioning

confidence: 99%

Section: Chlorinementioning

confidence: 99%

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Fundamental Studies of Halogen Reactions With Iii-v Semiconductor Surfaces

Simpson

Yarmoff

1996

Annu. Rev. Phys. Chem.

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Constructing Graphitic‐Nitrogen‐Bonded Pentagons in Interlayer‐Expanded Graphene Matrix toward Carbon‐Based Electrocatalysts for Acidic Oxygen Reduction Reaction

Liu

Zheng

et al. 2021

Advanced Materials

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large-scale application of proton-exchange membrane fuel cells (PEMFCs). [1,2] However, most nonmetallic materials (e.g., organic compounds and ceramics) are not active for ORR in acid electrolytes due to their poor conductivity. Meanwhile, most metal-based materials are not acid-resistant, hindering their practical application in acid media. Despite great efforts devoted to the development of alternative materials, the activity of current non-Pt catalysts is still much inferior to Pt and its alloys. [3] Among the nonmetallic materials, carbon nanomaterials (CNMs), especially graphene, are an appropriate candidate with a host of merits, including high electrical conductivity, stable anticorrosion performance even under acidic condition, tunable physical and chemical properties. [3,4] However, the pristine graphene with symmetric local sp 2 -hybridized electronic structure is inert for electrocatalysis due to its electroneutrality. Surface functionalization (e.g., heteroatom doping such as N [5] ) is a good strategy to break the electroneutrality and induce asymmetry of charge distribution at neighbor carbon sites in graphene, [4,6] enhancing the electron donation to activate molecular oxygen. For example, the carbon π electrons in nitrogen-doped carbon materials are activated by conjugating with the lone-pair electrons from adjacent pyridinic-N (Py-N) [7][8][9] or graphitic-N (G-N), [10][11][12] which is proved to be active toward ORR. Besides, the nitrogen-doped carbon nanotube array also shows significantly improved activity than its intrinsic structure. [13] Other strategies including geometric structuring (increase specific surface area [14] and create porous structure [15] ) could also enhance the catalytic activity. The CNMs synthesized by these strategies are proved efficient in alkaline electrolytes, but far inferior to that of Pt/C catalyst in an acid medium. For example, Liang et al. reported the CNM named meso-PoPD [16] (total N content: 9.5 at%, Py-N content: 3.6%, with large mesopores) shows the half-wave potential of about 0.76 V in 0.1 m KOH, but only 0.42 V in 0.5 m H 2 SO 4 ; Parvez et al. reported a N-doped graphene [17] with the half-wave potential of 0.77 V in 0.1 m KOH, but only about 0.52 V of that in 0.5 m H 2 SO 4 . Therefore, it is a great challenge to further improve the ORR performance of CNMs in acidic electrolytes.The inferior activity for CNMS toward acidic ORR can be ascribed to two main reasons: 1) The intrinsic activity of Metal-free carbon-based materials with high electrocatalytic activity are promising catalysts for the oxygen reduction reaction (ORR) in several renewable energy systems. However, the performance of carbon-based materials is far inferior to that of Pt-based catalysts in acid electrolytes. Here, a novel carbonbased electrocatalyst is reported toward ORR in 0.1 m HClO 4 with half-wave potential of 0.81 V and better durability (100 h reaction time) than commercial 20 wt% Pt/C. It is achieved by constructing graphitic-nitrogen (GN)-bonded pentagons in graphitic carb...

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