Electronic passivation of GaP surfaces using (NH<sub>4</sub>)<sub>2</sub>S treatment

Jȩdral, L.; Ruda, H. E.; Sodhi, Rana N.S.; Ma, Hongmei; Mannik, L.

doi:10.1139/p92-169

Cited by 14 publications

(6 citation statements)

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“…On average, the typically expected adventitious C layer was estimated to be ∼0.7 nm by using a single-overlayer model with I 0 Ox (43%) for Ga. This value of thickness is consistent with the one (0.3–0.9 nm) measured on Al 2 O 3 /Al by Piao and McIntyre .…”

Section: Resultssupporting

confidence: 87%

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

et al. 2012

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Tunneling junctions having the structure Ag TS −S(CH 2 ) n−1 CH 3 // Ga 2 O 3 /EGaIn allow physical−organic studies of charge transport across selfassembled monolayers (SAMs). In ambient conditions, the surface of the liquid metal electrode (EGaIn, 75.5 wt % Ga, 24.5 wt % In, mp 15.7°C) oxidizes and adsorbs-like other high-energy surfaces-adventitious contaminants. The interface between the EGaIn and the SAM thus includes a film of metal oxide, and probably also organic material adsorbed on this film; this interface will influence the properties and operation of the junctions. A combination of structural, chemical, and electrical characterizations leads to four conclusions about Ag TS −S(CH 2 ) n−1 CH 3 // Ga 2 O 3 /EGaIn junctions. (i) The oxide is ∼0.7 nm thick on average, is composed mostly of Ga 2 O 3 , and appears to be self-limiting in its growth. (ii) The structure and composition (but not necessarily the contact area) of the junctions are conserved from junction to junction. (iii) The transport of charge through the junctions is dominated by the alkanethiolate SAM and not by the oxide or by the contaminants. (iv) The interface between the oxide and the eutectic alloy is rough at the micrometer scale. ■ INTRODUCTIONWe, and others, are developing procedures with which to study charge transport across self-assembled monolayers (SAMs). 1−32We have explored two systems, both based on electrodes made of liquid metals (Hg, and a eutectic alloy of gallium and indium, which we abbreviate as EGaIn) and focused on the latter. The latter system has two major components: (i) a SAM supported by a template-stripped silver (Ag TS ) electrode and contacted by (ii) a "top" electrode of EGaIn (75.5 wt % Ga, 24.5 wt % In, mp 15.7°C 33 ) that is a liquid at room temperature and covered with a thin metal oxide film; we refer to these junctions by a nomenclature defined earlier 1 as Ag TS −SR//Ga 2 O 3 /EGaIn, where R is an organic group (which may range in structure from simple n-alkyl groups to more complex functionalities, e.g., aromatics 28 or ferrocenes 13,34,35 ). These junctions are typically formed, characterized, and used in contact with ambient laboratory atmosphere. In these conditions, the surface of EGaIn oxidizes rapidly and spontaneously (for convenience we indicate the composite structure-oxide skin and metal electrode-as "Ga 2 O 3 / EGaIn") and it-as do all other surfaces-adsorbs adventitious contaminants (e.g., water, organic molecules, particles). The electrical resistance, thickness, and heterogeneity of the composite films of metal oxide and contaminants on the surface (and their variability from electrode to electrode, and from junction to junction) have not been characterized: the most serious ambiguity affecting the measurement of charge transport through Ag TS −SR//Ga 2 O 3 /EGaIn junctions is currently the effect of the oxide skin and adventitious contaminants.

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Section: Resultssupporting

confidence: 87%

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

et al. 2012

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“…In a similar manner, Lau et al calculated the overlayer thickness of polysulphide‐treated InP surface assuming a uniform layer‐by‐layer structure. This is in contrast to calculations performed on (NH 4 ) 2 S passivated of GaP surfaces where a dramatic increase in estimated thickness was observed with angle when a uniform coverage was assumed. Following work of McKeown et al, f was varied until a consistent average value was obtained with angle.…”

Section: Introductioncontrasting

confidence: 97%

Surface and buried interface layer studies on challenging structures as studied by ARXPS

Sodhi

Brodersen

Cademartiri

et al. 2017

Surface & Interface Analysis

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Previous extensive studies were performed at Surface Science Western on the treatment of III-V semiconductors to produce surfaces suitable for subsequent epitaxial growth. X-ray photoelectron spectroscopy (XPS) was used to study oxide formation and capping techniques, and to monitor changes that would occur upon thermal desorption. The effects of a remote plasma on these surfaces were studied as well as to apply thin dielectric films of Si 3 N 4 in order to study interfacial properties. Angleresolved XPS (ARXPS) was performed in many cases to ascertain oxide layer thickness, uniformity, and structure. For the types of surfaces studied-mirror finished semiconductors, ARXPS is straightforward, and the angular dependence is obtained by physically altering the surface orientation with respect to the analyser. While the sample can be repositioned with care to analyse the same spot, changing the angle will effectively change the sampling area, further, surface topography can preclude the use of ARXPS. Use of parallel PARXPS, now available on recent instrumentation, can alleviate these problems. In this case, photoelectrons are collected simultaneously from a large angle. A multichannel detector allows this to be split into smaller angles thereby giving the PARXPS spectra without physically tilting the sample. Further, because the sample is not tilted, topographical effects are minimised allowing meaningful data to be extracted from not so perfect samples. To illustrate this, a detailed PARXPS study on a gallium Indium eutectic (EGaIn) will be presented. Various methods of extracting the depth information from these spectra will be discussed. Finally, the application of using PARXPS to study buried interfaces will be briefly discussed.

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“…For surface features desirable in photo-electrochemical applications, i.e., lowering the density of surface-specific electrical defects or inhibiting corrosion, wet chemical treatments are attractive. Simple immersion of GaP substrates in solutions containing sulfur-based reagents ͓e.g., ͑NH 4 ͒ 2 S or alkanethiols͔ [7][8][9] can initially alter the surface wetting properties, surface energetics of GaP, and surface recombination processes. However, methods based on solutions of inorganic sulfides/organic thiols have not yet produced well-defined, chemically resilient GaP interfaces with optimal interfacial properties.…”

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confidence: 99%

Physicochemical and Electrochemical Properties of Etched GaP(111)A and GaP(111)B Surfaces

Mukherjee¹,

Erickson

Maldonado³

2010

J. Electrochem. Soc.

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The observable chemical, electrochemical, and morphological features of GaP͑111͒ surfaces after wet chemical etching have been assessed using X-ray photoelectron spectroscopy, atomic force microscopy, and electrochemical impedance spectroscopy. HF͑aq͒, NH 4 F͑aq͒, H 2 SO 4 ͑aq͒, HCl͑aq͒, HCl-HNO 3 ͑aq͒, and dilute Br 2 in CH 3 OH ͑with and without a follow-up alkaline etch͒ are all potent etchants for GaP͑111͒ but yield distinctly different GaP͑111͒A and GaP͑111͒B surface conditions. Freshly etched GaP͑111͒B interfaces show higher residual oxide coverages and are generally rougher than similarly treated GaP͑111͒A surfaces. Differential capacitance measurements of n-GaP͑111͒A and n-GaP͑111͒B electrodes show that various etchants result in a wide range of apparent values for the conduction bandedge potentials, spanning approximately 700 mV in acetonitrile. These data show that these etched surfaces are not equivalent and that the observable physicochemical and electrochemical properties of GaP͑111͒ are strongly influenced by the choice of wet chemical etchant. Additionally, X-ray photoelectron spectra show that adsorption of ͑4-fluorophenyl͒methanethiol onto GaP͑111͒ is insensitive to surface orientation or etching method, indicating no dominant covalent interaction between organic thiols and GaP͑111͒ interfaces.

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Electronic passivation of GaP surfaces using (NH₄)₂S treatment

Cited by 14 publications

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Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

Surface and buried interface layer studies on challenging structures as studied by ARXPS

Physicochemical and Electrochemical Properties of Etched GaP(111)A and GaP(111)B Surfaces

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Electronic passivation of GaP surfaces using (NH4)2S treatment

Cited by 14 publications

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Electrical Resistance of AgTS–S(CH2)n−1CH3//Ga2O3/EGaIn Tunneling Junctions

Electrical Resistance of AgTS–S(CH2)n−1CH3//Ga2O3/EGaIn Tunneling Junctions

Surface and buried interface layer studies on challenging structures as studied by ARXPS

Physicochemical and Electrochemical Properties of Etched GaP(111)A and GaP(111)B Surfaces

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Electronic passivation of GaP surfaces using (NH₄)₂S treatment

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions

Electrical Resistance of Ag^TS–S(CH₂)_n−1CH₃//Ga₂O₃/EGaIn Tunneling Junctions